Journal articles on the topic 'Midday stem water potential'
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1
Naor, Amos, Isaac Klein, and Israel Doron. "Stem Water Potential and Apple Size." Journal of the American Society for Horticultural Science 120, no. 4 (July 1995): 577–82. http://dx.doi.org/10.21273/jashs.120.4.577.
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The sensitivity of leaf (ψleaf) and stem (ψstem) water potential and stomatal conductance (gs) to soil moisture availability in apple (Malus domestics Borkh.) trees and their correlation with yield components were studied in a field experiment. Two drip irrigation treatments, 440 mm (H) and 210 mm (L), were applied to a `Golden Delicious' apple orchard during cell enlargement stage (55-173 days after full bloom). Data collected included ψstem, y leaf, gs, and soil water potential at 25 (ψsoil-25) and 50 cm (ψsoil-50). No differences in midday ψleaf's were found between irrigation treatments. Stem water potential was higher in the H treatment than in the L treatment in diurnal measurements, and at midday throughout the season. Stomatal conductance of the H treatment was higher than the L treatment throughout the day. Stomatal conductance between 0930 and 1530 hr were highly correlated with ψstem. The H treatment increased the percentage of fruit >65 mm, and increased the proportion of earlier harvested fruit reaching marketable size compared to the L treatment. Fruit size in the first harvest and the total yield were highly correlated with ψstem. The degree of correlation between plant water stress indicators and yield component decreased in the following order: ψstem>ψsoil-25,>ψsoil-50>ψleaf. The data suggest that midday ψstem may serve as a preferable plant water stress indicator with respect to fruit size.
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Naor, A., I. Klein, H. Hupert, Y. Grinblat, M. Peres, and A. Kaufman. "Water Stress and Crop Level Interactions in Relation to Nectarine Yield, Fruit Size Distribution, and Water Potentials." Journal of the American Society for Horticultural Science 124, no. 2 (March 1999): 189–93. http://dx.doi.org/10.21273/jashs.124.2.189.
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The interactions between irrigation and crop level with respect to fruit size distribution and soil and stem water potentials were investigated in a nectarine (Prunus persica (L.) Batsch. `Fairlane') orchard located in a semiarid zone. Irrigation treatments during stage III of fruit growth ranged from 0.62 to 1.29 of potential evapotranspiration (ETp). Fruit were hand thinned to a wide range of fruit levels (200 to 1200 fruit/tree in the 555-tree/ha orchard). Total yield did not increase with increasing irrigation rate above 0.92 ETp in 1996 and maximum yield was found at 1.06 ETp in 1997. Fruit size distribution was shifted towards larger fruit with increasing irrigation level and with decreasing crop level. The two highest irrigation treatments had similar midday stem water potentials. Our findings indicate that highest yields and highest water use efficiency (yield/water consumption) are not always related to minimum water stress. Total yield and large fruit yield were highly and better correlated with midday stem water potential than with soil water potential. This confirms other reports that midday stem water potential is an accurate indicator of tree water stress and may have utility in irrigation scheduling.
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Naor, A., H. Hupert, Y. Greenblat, M. Peres, A. Kaufman, and I. Klein. "The Response of Nectarine Fruit Size and Midday Stem Water Potential to Irrigation Level in Stage III and Crop Load." Journal of the American Society for Horticultural Science 126, no. 1 (January 2001): 140–43. http://dx.doi.org/10.21273/jashs.126.1.140.
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The interactions between irrigation and crop level with respect to fruit size distribution and midday stem water potential were investigated for 3 years in a nectarine (Prunus persica L. `Fairlane') orchard located in a semi-arid zone. Wide ranges of crop loads and irrigation rates in stage III were employed, extending from practically nonlimiting to severely limiting levels. Irrigation during stage III of fruit growth ranged from 0.63 to 1.29 of potential evapotranspiration (ETp). Fruit were hand thinned to a wide range of fruit levels (300 to 2000) fruit/tree in the 555-tree/ha orchard. The yields and stem water potentials from 1996, 1997 and 1998 were combined together and the interrelations among yield, crop load and stem water potential were examined. Fruit <55 mm in diameter growing at 400 fruit per tree were the only ones not affected by irrigation level. The yield of fruit of 60 to 75 mm in diameter increased with irrigation level, but only a slight increase was observed when the irrigation rate rose above 1.01 ETp. A significant decrease in the yields of 60 to 65, 65 to 70, and 70 to 75-mm size grades occurred at crop levels greater than 1000, 800, and 400 fruit per tree, respectively. Midday stem water potential decreased with increasing crop level, and it is suggested that midday stem water potential responds to crop load rather than crop level. Relative yields of the various size grades were highly correlated with midday stem water potential. It was suggested that the midday stem water potential integrates the combined effects of water stress and crop load on nectarine fruit size.
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Naor, A., R. Stern, M. Peres, Y. Greenblat, Y. Gal, and Moshe A. Flaishman. "Timing and Severity of Postharvest Water Stress Affect Following-year Productivity and Fruit Quality of Field-grown `Snow Queen' Nectarine." Journal of the American Society for Horticultural Science 130, no. 6 (November 2005): 806–12. http://dx.doi.org/10.21273/jashs.130.6.806.
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The effects of the timing and severity of postharvest water stress on the productivity and fruit quality of field-grown nectarine [Prunus persica (L.) Batsch cv. Snow Queen] were studied for two consecutive years. Three levels of postharvest water status (midday stem water potentials of -1.2, -2.0, and -2.8 MPa) were examined. They were designated as High, Med, and Low, respectively. In the second year two additional treatments were examined in which Low and Med water status were interchanged on 1 Sept. 2002, and these treatments were designated as Low/Med and Med/Low. The percentages of double fruits and of those having a deep suture increased with decreasing postharvest midday stem water potential during the previous year, and most of these defects were stimulated by water deficits that occurred prior to 1 Sept. Postharvest water stress led to decreased crop yield in the subsequent year because there were fewer fruits per tree. Flower buds with double pistils were first noticed in mid-September, and by mid-November the ranking of double pistils in the various treatments were similar to the ranking of double fruits measured a month after bloom in the subsequent season. Postharvest water stress delayed flower bud development. The percentage of double fruits increased from 10% in 2002 to 40% in 2003 and the higher percentage in 2003 was associated with higher air temperatures during the reproductive bud development stage in 2002 than in 2001. Our data and others suggest that high temperatures create a potential for the occurrence of double fruits, but that the fulfillment of that potential is highly dependent on postharvest tree water status. The occurrence of double and deep suture fruits were highly correlated with midday stem water potential in August of the previous year, i.e., during the initial stages of flower bud development. The occurrence of double fruits was observed to increase sharply as the midday stem water potentials fell below -2.0 MPa, which suggests that a midday stem water potential of -2.0 MPa could serve as a threshold for postharvest irrigation scheduling.
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Stern, R. A., M. Meron, A. Naor, R. Wallach, B. Bravdo, and S. Gazit. "Effect of Fall Irrigation Level in `Mauritius' and `Floridian' Lychee on Soil and Plant Water Status, Flowering Intensity, and Yield." Journal of the American Society for Horticultural Science 123, no. 1 (January 1998): 150–55. http://dx.doi.org/10.21273/jashs.123.1.150.
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The effect of fall irrigation level in `Mauritius' and `Floridian' lychee (Litchi chinensis Sonn.) on soil and plant water status, flowering intensity, and yield the following year was studied in a field during 2 consecutive years. At the end of the second vegetative flush after harvest (1 Oct. 1994 and 10 Oct. 1995), four irrigation treatments were initiated: 0.5, 0.25, 0.125, and 0 Class A pan evaporation coefficients designated 100%, 50%, 25%, and 0%. The three lower irrigation levels effectively stopped shoot growth, suggesting the 50% treatment to be the threshold for shoot growth cessation in both years. For both years, flowering intensity and yield in the 100% treatment were lower than those following the other three treatments. Soil and plant water-stress indicators responded to the water-stress irrigation treatments. However soil water-potential values were highly variable relative to plant water potentials. Stem water potential differed more markedly between treatments than leaf water potential. Midday stem water potential appeared to be the best water-stress indicator for irrigation control. Midday stem water potential in both years was correlated with midday vapor-pressure deficit, suggesting that the threshold for irrigation control should take into account evaporative demand.
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Tombesi, Sergio, Kevin R. Day, R. Scott Johnson, Rebecca Phene, and Theodore M. DeJong. "Vigour reduction in girdled peach trees is related to lower midday stem water potentials." Functional Plant Biology 41, no. 12 (2014): 1336. http://dx.doi.org/10.1071/fp14089.
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Stem or trunk girdling is a technique used in physiological studies and in horticultural practice for interrupting carbon flow through the phloem to other parts of the plant without influencing water flow in the xylem. Trunk girdling in peaches is practiced primarily to stimulate fruit growth but it also tends to decrease shoot vigour for a period of time after girdling. Water flow through the trunk or branches of peach trees is thought to be primarily dependent on the most recently formed ring of xylem and vegetative growth is closely related to stem water potential and stem hydraulic conductance. The aim of the present work was to determine whether vigour reduction due to girdling was correlated with a reduction in midday stem water potential during the period of time between girdling and the subsequent healing of stem tissue. ‘Springcrest’ peach trees were girdled on two different dates. Fruit yield and size, water sprout growth, proleptic shoot growth and stem water potential were measured. Early and late girdled trees yielded larger fruits and fewer and shorter water sprouts in comparison with control trees. Midday stem water potential declined significantly after girdling and gradually recovered until the time of fruit harvest. These results suggest that the vigour reduction of girdled trees is related to a decrease of midday stem water potential caused by girdling. Early tree girdling increased the reduction in midday stem water potential and shoot growth compared with the later girdling treatment. These results point out that even though girdling only removes bark and phloem tissue it can apparently affect water flow in xylem.
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Lampinen, Bruce D., Kenneth A. Shackel, Stephen M. Southwick, and William H. Olson. "Deficit irrigation strategies using midday stem water potential in prune." Irrigation Science 20, no. 2 (January 11, 2001): 47–54. http://dx.doi.org/10.1007/s002710000028.
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Shackel, K., S. Southwick, and B. Lampinen. "081 A PLANT-BASED MEASURE FOR DETERMINING TREE WATER NEEDS." HortScience 29, no. 5 (May 1994): 439f—439. http://dx.doi.org/10.21273/hortsci.29.5.439f.
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To be useful for indicating plant water needs, any measure of plant stress should be closely related to some of the known short and medium term plant stress responses, such as stomatal closure and reduced rates of expansive growth. Methods for the measurement of plant water potential (Ψ) are available, but conflicting results have led to disagreement as to whether any of these give an appropriate biological index of plant water stress. Some pressure chamber results may be attributed to an artifact of water loss following excision. Leaf and stem Ψ however, in addition to being numerically different, may not be equivalent indices of plant stress, and midday stem Ψ has proven to be a useful index of stress in a number of fruit trees. Day to day fluctuations in midday stem Ψ under well irrigated conditions is well correlated to midday Vapor Pressure Deficit, and hence can be used to predict a non-stressed baseline. A 50% decline in water use at both the leaf and canopy level were associated with relatively small reductions (0.5 to 0.6 MPa) in midday stem Ψ from this baseline in prune. In cherry, midday stem Ψ was correlated to both leaf stomatal conductance and rates of shoot growth, with shoot growth essentially stopping once midday stem Ψ dropped to between -1.5 to -1.7 MPa. In pear, increased fruit size, decreased fruit soluble solids and increased green color were all associated with increases in midday stem Ψ.
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Naor, A., and S. Cohen. "Sensitivity and Variability of Maximum Trunk Shrinkage, Midday Stem Water Potential, and Transpiration Rate in Response to Withholding Irrigation from Field-grown Apple Trees." HortScience 38, no. 4 (July 2003): 547–51. http://dx.doi.org/10.21273/hortsci.38.4.547.
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The sensitivity of water stress indicators to changing moisture availability, and their variability, determine the number of measurements that should be taken in order to represent properly plant water status in a certain orchard. In the present study we examined the sensitivity and variability of maximum daily trunk shrinkage, midday stem water potential, and daily transpiration rate in their responses to withholding irrigation from field-grown drip-irrigated `Golden delicious' apple trees in a commercial orchard. Irrigation was withheld from the stressed trees for 17 days starting in mid-July, and the control trees were irrigated daily at 100% of the “Class A” pan evaporation rate. The courses of daily transpiration rate, maximum trunk shrinkage, and midday stem water potential before and 10 days after the drying period were similar in the control and the stressed trees. Highly significant differences between the stressed and the control trees in their midday stem water potentials were apparent from the early stages of the stress period. Daily transpiration rate and maximum daily shrinkage were more variable than midday stem water potential, and differences between treatments became significant only after measurements were expressed relative to the initial values before irrigation was witheld. Differences between treatments (as percentages of the values obtained for the control trees) increased after irrigation stopped where these differences were greatest for maximum daily shrinkage, which reached 90%; moderate for stem water potential (60%); and least for daily transpiration rate, for which the differences remained below 20%. Our data show that the choice of a certain water stress indicator should be based on both the sensitivity to changing moisture availability and the degree of variability. Possible reasons for the different sensitivity to moisture availability and the different variability between the water stress indicators under study are discussed.
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Shackel, Kenneth A. "Water relations of woody perennial plant species." OENO One 41, no. 3 (September 30, 2007): 121. http://dx.doi.org/10.20870/oeno-one.2007.41.3.847.
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<p style="text-align: justify;"><strong>Aims</strong>: To describe the relation of various water status measures of woody perennial plants (predawn and midday stem and leaf water potential), to indices of physiological activity such as leaf conductance, vegetative growth and fruit growth and composition.</p><p style="text-align: justify;"><strong>Methods and results</strong>: Almonds were exposed to three levels of irrigation over three years, and midday stem water potential (SWP) and leaf conductance, collected at approximately weekly intervals, is reported for the third year of the study. A strong linear increase in both leaf conductance and trunk growth occurred with increasing SWP, and this relation was consistent both within and between treatments. A similarly positive linear relation was found between SWP and fruit size in pear, with a negative relation between SWP and fruit soluble solids and fruit color. In grapevine, SWP was found to be uniform across all lower canopy positions tested (trunk, cordon and near the base of current year shoots) and positively correlated to early season shoot growth even before irrigation treatments were applied. Midday SWP was found to be more sensitive than midday leaf water potential (LWP) for detecting treatment differences over the course of the season, but both were well correlated to average seasonal leaf conductance within and between irrigation treatments. Predawn SWP and LWP were not as well correlated to average seasonal leaf conductance, but the most important factor determining midday leaf conductance was wind speed, indicating that grape leaf stomatal responses are quite sensitive to this environmental factor.</p><p style="text-align: justify;"><strong>Conclusion</strong>: In a wide variety of woody crop species midday stem water potential (SWP) has been found to be a valuable tool for quantifying the degree of water stress experienced by the plant, and for understanding the physiological responses of the plant to water limited conditions. In grapevine, SWP detected irrigation differences over 1 month sooner than midday leaf water potential when the number of vines used and the number of samples taken were the same for both methods, and SWP had a higher correlation to leaf conductance than predawn leaf or stem water potential.</p><p style="text-align: justify;"><strong>Significance and impact of study</strong>: SWP as a standard method for quantifying water stress in grapevine and other crops will aid research in the development of reliable management practices to improve crop productivity and quality.</p>
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Milliron, L., A. Fulton, W. Krueger, and R. Rosecrance. "Midday stem water potential baseline for California ‘Manzanillo’ table olive orchards." Acta Horticulturae, no. 1335 (February 2022): 189–96. http://dx.doi.org/10.17660/actahortic.2022.1335.22.
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Deb, Sanjit K., Manoj K. Shukla, and John G. Mexal. "Estimating Midday Leaf and Stem Water Potentials of Mature Pecan Trees from Soil Water Content and Climatic Parameters." HortScience 47, no. 7 (July 2012): 907–16. http://dx.doi.org/10.21273/hortsci.47.7.907.
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Diurnal and temporal patterns of stem water potential (ψstem) and leaf water potential (ψleaf) were determined during June to Sept. 2010 and 2011 at lower (2.5 m tree height), mid- (4.6 m), and upper (7.6 m) canopy positions for two flood-irrigated, mature pecan [Carya illinoinensis (Wangenh.) K. Koch] orchards near Las Cruces, NM. Diurnal measurements of ψstem and ψleaf at three canopy heights were correlated under both dry and wet soil conditions. However, although soil water contents at Site 2 (silty clay loam texture) remained higher compared with Site 1 (sandy loam), ψstem and ψleaf values, particularly under dry soil conditions at Site 2, were consistently lower, showing the effect of clayey soil texture on pecan water stress. Diurnal patterns of ψstem and ψleaf indicated that measurements of ψstem and ψleaf should be made close to early afternoon (between 1400 and 1500 hr Mountain Standard Time) to evaluate mature pecan water stress, which also corresponded to maximum climatic stress conditions. Midday ψstem and ψleaf measured at three canopy heights over several irrigation cycles during the 2010 season were correlated with one another, midday soil water content at different depths, and atmospheric vapor pressure deficit (VPD). Multiple regression analysis [between midday ψstem or ψleaf and midday θavg (soil water content at 0 to 40 cm), air temperature (Tmd), and relative humidity (RHmd)] during the 2010 season revealed that two-parameter regression models [ψstem or ψleaf = f (midday θavg and Tmd)] were the most significant for the interpretation of midday ψstem or ψleaf at both sites. Using the two-parameter model, predictions of ψstem and ψleaf measured on the both shaded and sunlit sides of trees at three canopy heights for 2011 showed good agreement between measured and predicted ψstem and ψleaf (R2 ranged from 0.70 to 0.98). Two-parameter models derived in an earlier study generally underpredicted ψstem both in 2010 and 2011, which further supported the importance of the time of midday ψstem and ψleaf measurements suggested in this study.
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Buchner*, Richard P., Allan Fulton, Bruce Lampinen, Ken Shackel, Terry Prichard, Larry Schwankl, Sam Metcalf, and Cayle Little. "Effects of Three Levels of Midday Stem Water Potential on Chandler Walnut Growth and Yield in California." HortScience 39, no. 4 (July 2004): 814C—814. http://dx.doi.org/10.21273/hortsci.39.4.814c.
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Ninth leaf California Chandler Walnuts (Juglans regia) on Northern California Black (Juglans hindsii) or Paradox (English/black hybrid) rootstock were irrigated to achieve three levels of Midday Stem Water Potential (MSWP). Target potentials were: 1) low water stress (average MSWP of -3.2 bars); 2) mild water stress (average MSWP of -6.2 bars); and 3) moderate water stress (average MSWP of -7.3 bars). Stem Water Potential was measured midday (12-4 pm) by placing leaves inside water impervious, light blocking foil bags. Leaves remained bagged for at least ten minutes to achieve equilibrium. Bagged leaves were removed, placed inside a pressure chamber and stem water potential was measured at endpoint. Data are presented for the 2002 and 2003 seasons. Withholding irrigation water had a significant impact on `Chandler' growth, productivity, and profitability particularly on young, vigorously growing trees. Chandler/Black appears to be more tolerant to water stress compared to Chandler/Paradox For Chandler on Paradox, water stress significantly reduced growth, yield, price per pound, percent edible kernel, and resulted in darker kernels. In addition, water stress significantly increased the total percent offgrade. Withholding irrigation does not appear to be a good strategy in young, vigorously growing `Chandler' orchards. Mature trees and trees grafted onto Northern California black rootstock may be more tolerant of moisture stress.
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Shackel, Kenneth A., H. Ahmadi, W. Biasi, R. Buchner, D. Goldhamer, S. Gurusinghe, J. Hasey, et al. "Plant Water Status as an Index of Irrigation Need in Deciduous Fruit Trees." HortTechnology 7, no. 1 (January 1997): 23–29. http://dx.doi.org/10.21273/horttech.7.1.23.
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To be useful for indicating plant water needs, any measure of plant stress should be closely related to some of the known short- and medium-term plant stress responses, such as stomatal closure and reduced rates of expansive growth. Midday stem water potential has proven to be a useful index of stress in a number of fruit tree species. Day-to-day fluctuations in stem water potential under well-irrigated conditions are well correlated with midday vapor-pressure deficit, and, hence, a nonstressed baseline can be predicted. Measuring stem water potential helped explain the results of a 3-year deficit irrigation study in mature prunes, which showed that deficit irrigation could have either positive or negative impacts on tree productivity, depending on soil conditions. Mild to moderate water stress was economically beneficial. In almond, stem water potential was closely related to overall tree growth as measured by increases in trunk cross-sectional area. In cherry, stem water potential was correlated with leaf stomatal conductance and rates of shoot growth, with shoot growth essentially stopping once stem water potential dropped to between −1.5 to −1.7 MPa. In pear, fruit size and other fruit quality attributes (soluble solids, color) were all closely associated with stem water potential. In many of these field studies, systematic tree-to-tree differences in water status were large enough to obscure irrigation treatment effects. Hence, in the absence of a plant-based measure of water stress, it may be difficult to determine whether the lack of an irrigation treatment effect indicates the lack of a physiological response to plant water status, or rather is due to treatment ineffectiveness in influencing plant water status. These data indicate that stem water potential can be used to quantify stress reliably and guide irrigation decisions on a site-specific basis.
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Naor, Amos. "Irrigation and Crop Load Influence Fruit Size and Water Relations in Field-grown `Spadona' Pear." Journal of the American Society for Horticultural Science 126, no. 2 (March 2001): 252–55. http://dx.doi.org/10.21273/jashs.126.2.252.
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Interrelations between water potential and fruit size, crop load, and stomatal conductance were studied in drip-irrigated `Spadona' pear (Pyrus communis L) grafted on quince C (Cydonia oblonga L.) rootstock and growing in a semi-arid zone. Five irrigation rates were applied in the main fruit growth phase: rates of 0.25, 0.40, 0.60, 0.80, and 1.00 of “Class A” pan evaporation rate. The crop in each irrigation treatment was adjusted to four levels (200 to 1200 fruit per tree) by hand thinning at the beginning of June 1999. The crop was harvested on 1 Aug. 1999, and fruit size was determined by means of a commercial sorting machine. Soil, stem, and leaf water potentials and stomatal conductance were measured during the season. Crop yield was highly correlated with stem and soil water potentials. The highest midday stem water potential was lower than values commonly reported for nonstressed trees, and was accompanied by high soil water potential, indicating that the maximal water absorption rate of the root system under those particular soil conditions was limited. Stomatal conductance was highly correlated with leaf water potential (r2 = 0.54), but a much better correlation was found with stem water potential (r2 = 0.80). Stomatal conductance decreased at stem water potentials less than -2.1 MPa. Both stem water potential and stomatal conductance were unaffected by crop load under a wide range of irrigation rates.
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Fulton, Allan, Richard Buchner, Cyndi Gilles, Bill Olson, Nick Bertagna, Jed Walton, Larry Schwankl, and Ken Shackel. "Rapid Equilibration of Leaf and Stem Water Potential under Field Conditions in Almonds, Walnuts, and Prunes." HortTechnology 11, no. 4 (January 2001): 609–15. http://dx.doi.org/10.21273/horttech.11.4.609.
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Covering a plant leaf with a reflective, water impervious bag ensures that equilibrium is reached between the nontranspiring leaf and the stem, and appears to improve the accuracy of determining plant water status under field conditions. However, the inconvenience of covering the leaf for 1 to 2 hours before measuring stem water potential (SWP) has constrained on-farm adoption of this irrigation management technique. A second constraint has been that the requirement of midafternoon determinations limits the area that can be monitored by one person with a pressure chamber. This paper reports findings from field studies in almonds (Prunus dulcis),prunes (P. domestica), and walnuts (Juglans regia) demonstrating modified procedures to measure midday SWP, making it a more convenient and practical tool for irrigation management. For routine monitoring and irrigation scheduling, an equilibration period of 10 min or longer appears to be suitable to provide accurate SWP measurements. Based on the large sample sizes in this study, we estimate that measurement error related to equilibration time for SWP can be reduced to an acceptable level [0.05 MPa (0.5 bar)] with a sample size of about 10 leaves when using a 10-min equilibration period. Under orchard conditions where tree growth and health appears uniform, a sample of one leaf per tree and 10 trees per irrigation management unit should give an accurate mean indicator of orchard water status. Under more variable orchard conditions a larger sample size may be needed. Midmorning and midday SWP both exhibited similar seasonal patterns and responded alike to irrigation events. On some occasions, midday SWP was accurately predicted from midmorning SWP and the change in air vapor pressure deficit (VPD) from midmorning to midday, but both over- and underestimate errors [to 0.3 MPa (3.0 bar)] appeared to be associated with unusually low or high diurnal changes in VPD, respectively. Hence, direct measurement of SWP under midday conditions (about 1300 to 1500 hr) is still recommended.
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Naor, A. "MIDDAY STEM WATER POTENTIAL AS A PLANT WATER STRESS INDICATOR FOR IRRIGATION SCHEDULING IN FRUIT TREES." Acta Horticulturae, no. 537 (October 2000): 447–54. http://dx.doi.org/10.17660/actahortic.2000.537.52.
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Glass, V. M., D. C. Percival, and J. T. A. Proctor. "Tolerance of lowbush blueberries (Vaccinium angustifolium Ait.) to drought stress. II. Leaf gas exchange, stem water potential and dry matter partitioning." Canadian Journal of Plant Science 85, no. 4 (October 1, 2005): 919–27. http://dx.doi.org/10.4141/p03-028.
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A 2-yr field study examining the effect of soil moisture on plant water status, photosynthesis and gas exchange parameters in lowbush blueberry (Vaccinium angustifolium Ait.) was conducted at the Nova Scotia Wild Blueberry Institute (NSWBI), Debert, NS. Drought and irrigation treatments were applied over two years in either or both the vegetative and cropping years of production. Midday stem water potential values indicated that all treatments resulted in drought stress. Mean stem water potential values ranged from -1.41 to -1.45 MPa. Predawn stem water potentials in the vegetative growth season indicated that although some recharging and recovery of water loss occurred overnight, the drought-stressed plants did not fully return to pre-stress levels under the moisture-limiting conditions. Higher chlorophyll a and b levels were observed in the single-season drought treatment. Leaves of irrigated plants in both sprout and crop years had the highest stomatal density. There were no differences in photosynthetic rate (Pn) among treatments despite the lower stomatal conductance resulting from limited soil moisture. Key words: Photosynthesis, stomate, stem water potential
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Williams, Larry E. "Leaf water potentials of sunlit and/or shaded grapevine leaves are sensitive alternatives to stem water potential." OENO One 46, no. 3 (September 30, 2012): 207. http://dx.doi.org/10.20870/oeno-one.2012.46.3.1522.
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<p style="text-align: justify;"><strong>Aims</strong>: Leaf (Ψ<sub>l</sub>) and stem (Ψ<sub>stem</sub>) water potentials were measured on grapevines to determine the effects of shoot location on both methods to assess vine water status.</p><p style="text-align: justify;"><strong>Methods and results</strong>: Cabernet-Sauvignon and Merlot used in this study were grown at two locations in California. Measurements were taken at midday in July (Merlot) and at two times of the day (morning and afternoon), on two dates in August (Cabernet- Sauvignon). Measurements of Ψ<sub>l</sub> and Ψ<sub>stem</sub>, stomatal conductance and transpiration were taken on shoots entirely exposed to direct solar radiation or on shoots totally in the shade at the times of measurement. There were significant differences (<em>P</em> < 0.05) between Ψ<sub>l</sub> and/or Ψ<sub>stem</sub> measured on shoots exposed to direct solar radiation and those in the shade. Both Ψ<sub>l</sub> and Ψ<sub>stem</sub> were significantly greater on the shoots exposed to direct sunlight compared to those in the shade. There was no significant difference between Ψ<sub>l</sub> measured on shaded leaves and Ψ<sub>stem</sub> determined on the fully exposed shoots.</p><p style="text-align: justify;"><strong>Conclusions</strong>: Regardless of method used, water potentials were highly correlated with stomatal conductance measured on leaves in direct sunlight at the same time. All means of measuring grapevine water potential used in this study were highly correlated with one another.</p><p style="text-align: justify;"><strong>Significance and impact of the study</strong>: The data indicate that any of the techniques used in this study would be a sensitive indicator of vine water status and that the Ψ of shaded leaves would be an alternative to the measurement of Ψ<sub>stem</sub>.</p>
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McCutchan, Harold, and K. A. Shackel. "Stem-water Potential as a Sensitive Indicator of Water Stress in Prune Trees (Prunus domestica L. cv. French)." Journal of the American Society for Horticultural Science 117, no. 4 (July 1992): 607–11. http://dx.doi.org/10.21273/jashs.117.4.607.
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The relative sensitivity of plant- and soil-based measures of water availability were compared for prune trees subjected to a range of irrigation regimes under field conditions. Over the growing season, leaf- and stem-water potentials (ψ) measured at midday exhibited clear differences between frequently irrigated trees and unirrigated trees that were growing on stored soil moisture. Stem ψ was less variable than leaf ψ, and the daily variability in stem ψ was closely related to daily variability in evaporative demands, as measured by vapor pressure deficit (VPD). As a result of lower variability, stem ψ reflected the small stress effect of a moderate, 50% soil moisture depletion irrigation interval, whereas leaf ψ did not. The relation between soil water content and estimated orchard evapotranspiration (ET) was influenced by local differences in soil texture within the experimental plot. The relation between stem ψ and ET, however, was not influenced by soil texture and, in addition, was very similar to the relation between stem ψ and leaf stomatal conductance. Both relationships indicated that a 50% reduction in leaf and canopy level water loss characteristics was associated with relatively small reductions (0.5 to 0.6 MPa) in stem ψ. Stem ψ appears to be a sensitive and reliable plant-based measure of water stress in prune and maybe a useful tool for experimental work and irrigation scheduling.
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Williams, L. E., and F. J. Araujo. "Correlations among Predawn Leaf, Midday Leaf, and Midday Stem Water Potential and their Correlations with other Measures of Soil and Plant Water Status in Vitis vinifera." Journal of the American Society for Horticultural Science 127, no. 3 (May 2002): 448–54. http://dx.doi.org/10.21273/jashs.127.3.448.
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A study was conducted to compare three measurements of determining water status of grapevines (Vitis vinifera L.) in the field. Predawn leaf water potential (ΨPD), midday leaf water potential (Ψl), and midday stem water potential (Ψstem) were measured on `Chardonnay' and `Cabernet Sauvignon' grapevines grown in Napa Valley, California late in the 1999 growing season. Both cultivars had been irrigated weekly at various fractions (0, 0.5, and 1.0 for `Chardonnay' and 0, 0.5, 0.75, and 1.5 for `Cabernet') of estimated vineyard evapotranspiration (ETc) from approximately anthesis up to the dates of measurements. Predawn water potential measurements were taken beginning at 0330 hr and completed before sunrise. Midday Ψl and Ψstem measurements were taken only between 1230 and 1330 hr. In addition, net CO2 assimilation rates (A) and stomatal conductance to water vapor (gs) were also measured at midday. Soil water content (SWC) was measured in the `Chardonnay' vineyard using a neutron probe. Values obtained for ΨPD, Ψl, and Ψstem in this study ranged from about -0.05 to -0.8, -0.7 to -1.8, and -0.5 to -1.6 MPa, respectively. All three measurements of vine water status were highly correlated with one another. Linear regression analysis of Ψl and Ψstem versus ΨPD resulted in r2 values of 0.88 and 0.85, respectively. A similar analysis of Ψl as a function of Ψstem resulted in an r2 of 0.92. In the `Chardonnay' vineyard, all three methods of estimating vine water status were significantly (P < 0.01) correlated with SWC and applied amounts of water. Lastly, ΨPD, Ψl, and Ψstem were all linearly correlated with measurements of A and gs at midday. Under the conditions of this study, ΨPD, Ψl, and Ψstem represent equally viable methods of assessing the water status of these grapevines. They were all correlated similarly with the amount of water in the soil profile and leaf gas exchange as well as with one another.
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Crombie, D. Stuart, and J. T. Tippett. "A comparison of water relations, visual symptoms, and changes in stem girth for evaluating impact of Phytophthoracinnamomi dieback on Eucalyptusmarginata." Canadian Journal of Forest Research 20, no. 2 (February 1, 1990): 233–40. http://dx.doi.org/10.1139/x90-032.
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Water relations, stem girth, and crown vigour were measured in jarrah (Eucalyptusmarginata Donn ex Sm.) trees in adjoining areas of healthy and dieback-affected forest. The soil-borne fungus Phytophthoracinnamomi Rands was recovered from soils in the dieback areas, but not from neighbouring healthy forest. Trees on dieback sites were found to be more water stressed (with lower dawn water potentials and daytime stomatal conductances) than healthy trees on nearby areas free of P. cinnamomi. Severe water stress usually preceded crown deaths by several weeks to months. Dawn water potential and midday stomatal conductance were the most useful nondestructive indicators of dieback severity in declining trees. Subjective assessment of crown form was slightly less reliable than water relations as a separator of dieback and healthy trees. Changes in trunk girth were the least sensitive indicators of dieback severity. Midday stomatal conductance is recommended as a useful tool for monitoring short-term changes in vigour of dieback-affected trees.
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Shackel, Ken, and David Paige. "593 A Lightweight, Hand-operated Pressure Chamber for Determining Plant Water Status." HortScience 35, no. 3 (June 2000): 499B—499. http://dx.doi.org/10.21273/hortsci.35.3.499b.
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In a number of tree crops, we have found that the water potential of lower canopy, nontranspiring leaves, measured with the pressure chamber at midday (midday stem water potential), is an excellent index of plant water stress and can be used for irrigation scheduling. Because stem water potential is typically much higher than transpiring leaf water potential, a lower pressure is required for the measurement, allowing us to design and build a lightweight device that could be easily operated by hand. The prototype was designed for pressures up to 2 MPa, which is sufficient for most irrigation conditions. A number of design features were incorporated into the sealing gland to eliminate the need for retightening during the pressurization process, reduce the amount of tissue external to the pressure chamber, and allow a greater visibility of the petiole. Identical values to those obtained with the standard, compressed nitrogen pressure chamber were obtained over the entire 2-MPa range, and the time required using either device under field conditions was the same (about 1 min per measurement). A number of alternative protocols were tested, and we found that even substantial recutting of the petiole had no influence on the measured water potential, contrary to popular belief. We also found that the same sample could be remeasured multiple times (five), with no net change in the water potential, allowing the measurement to be checked if necessary. This device should be of great utility in field irrigation management.
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Brown, Kay F., M. McGowan, and M. J. Armstrong. "Response of the components of sugar beet leaf water potential to a drying soil profile." Journal of Agricultural Science 109, no. 3 (December 1987): 437–44. http://dx.doi.org/10.1017/s0021859600081648.
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SummaryFor many field-grown crops, including sugar beet, there is little information on the seasonal changes in leaf water potential and its components as the soil dries. Therefore, seasonal changes in leaf water, osmotic and turgor potentials of sugar beet were measured in two seasons, in crops that experienced differing degrees of soil moisture stress. In 1983 potentials of crops exposed to early and late droughts were compared with those of irrigated crops, and in 1984 measurements were made in a non-irrigated crop. In the irrigated crop the midday leaf water potential changed little during the season, except in response to fluctuating evaporative demand. In the drought and non-irrigated treatments there was a sharp fall in leaf water potential as soon as the soil water potential decreased. The size of the midday leaf water potential was primarily determined by soil dryness. However, the leaf water potential did not decrease below about — 1·5 MPa in either year. The leaf osmotic potential declined at the same time as the leaf water potential, but the extent to which this happened differed in the two years. Only in the 1984 non-irrigated crop did the osmotic potential continue to decrease as the soil dried, suggesting that osmotic adjustment had taken place in 1984 but not in 1983. Thus higher turgor was maintained in the 1984 crop than in the 1983 drought-affected crops. Some turgors were recorded as apparently negative in 1983.Since the leaf water potential declined to a minimum of about — 1·5 MPa, the soil water potential minima were also about — 1·5 MPa. However, deeper soil was not dried to this extent, suggesting that the extra resistance for water uptake from deep soil was limiting or the rooting density was too low.The pattern of recovery of leaf water potential overnight suggested that the rhizosphere resistance to water movement was small, even as the soil dried. However, measurement of stem water potentials in 1984 indicated that a significant resistance to water flow existed within the aerial part of sugar beet plants. This shows that the use of the water potential in leaves as an estimate of that in stems or roots can be misleading.
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Vega-Ibáñez, R., S. Ortega-Farías, F. Fuentes-Peñailillo, K. Gutter, and J. Albornoz. "Estimation of midday stem water potential in grapevine leaves (‘Cabernet Sauvignon’) using spectral reflectance indices." Acta Horticulturae, no. 1335 (February 2022): 325–30. http://dx.doi.org/10.17660/actahortic.2022.1335.40.
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Moriana, A., D. Pérez-López, M. H. Prieto, M. Ramírez-Santa-Pau, and J. M. Pérez-Rodriguez. "Midday stem water potential as a useful tool for estimating irrigation requirements in olive trees." Agricultural Water Management 112 (September 2012): 43–54. http://dx.doi.org/10.1016/j.agwat.2012.06.003.
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Othman, Yahia, Dawn VanLeeuwen, Richard Heerema, and Rolston St. Hilaire. "Midday Stem Water Potential Values Needed to Maintain Photosynthesis and Leaf Gas Exchange Established for Pecan." Journal of the American Society for Horticultural Science 139, no. 5 (September 2014): 537–46. http://dx.doi.org/10.21273/jashs.139.5.537.
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Demand for New Mexico’s limited water resources coupled with periodic drought has increased the necessity for tree water status monitoring to guide irrigation scheduling of pecan (Carya illinoinensis) orchards. The objectives of this study were to assess the impact of water status developed during the flood irrigation dry-down cycles on photosynthesis (Pn), and gas exchange [stomatal conductance (gS) to H2O (gH2O), transpiration (E), and intercellular CO2 (ci)] and to establish values of midday stem water potential (Ψsmd) that are needed to maintain Pn and gas exchange of pecan. We conducted the study simultaneously on two southern New Mexico mature pecan orchards from 2011 through 2013. Flood irrigation as determined by grower practice was used on both orchards and Pn, gH2O, E, and ci were assessed at Ψsmd of –0.4 to –2.0 MPa. Photosynthesis and gas exchange were higher in pecan trees shortly after irrigation than trees exhibiting water deficit near the end of a flood irrigation dry-down cycle. The decline in Pn was markedly noticeable when Ψsmd dropped below –0.9 MPa. We attributed the reduction in Pn mostly to stomatal limitation. The decline in Pn and gH2O exceeded 50% when Ψsmd ranged from –1.5 to –2.0 MPa. For those reasons, we recommended that pecan orchards be maintained at Ψsmd higher than –0.90 MPa to prevent significant reductions in carbon assimilation and gas exchange.
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Silva, Elizamar Ciríaco da, Marcos F. A. Silva, Rejane J. M. C. Nogueira, and Manoel B. Albuquerque. "Growth evaluation and water relations of Erythrina velutina seedlings in response to drought stress." Brazilian Journal of Plant Physiology 22, no. 4 (2010): 225–33. http://dx.doi.org/10.1590/s1677-04202010000400002.
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Erythrina velutina Willd. (common name: mulungu) is a deciduous, heliophyte found in the semi-arid region of northeastern Brazil. To evaluate the growth and water relations of mulungu seedlings in soils with different degrees of moisture content, an experiment was carried out under greenhouse conditions using four water treatments (100%, 75%, 50% and 25% of the field capacity- FC). Predawn (Ψpdw) and midday leaf water potential (Ψmdw), relative water content (RWC), plant height, number of leaves, stem diameter, leaf area (LA), specific leaf area (SLA), leaf area ratio (LAR), dry matter in different organs, biomass partitioning and root:shoot ratio were evaluated. No differences were detected between treatments for Ψpdw after 30 days; however, at midday, control plants and those under 75% FC underwent a greater reduction in Ψmdw than plants cultivated with 50% and 25% FC. After 90 days, only the plants under 50% FC exhibited a reduction in Ψmdw. RWC was reduced at midday, but there were no differences between treatments. Nearly all growth parameters were reduced due to water deficit, especially in the plants with 25% FC, as determined by the number of leaves, stem diameter, plant height, LA, SLA and dry mass in several organs. LAR and root:shoot ratio were not affected. Mulungu seedlings seem to have developed rusticity to overcome intermittent droughts with no change in the pattern of dry matter distribution. The maintenance of turgor pressure seems to be more associated to a reduction in the growth ratio than a reduction in leaf water potential.
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Egea, Gregorio, Ian C. Dodd, María M. González-Real, Rafael Domingo, and Alain Baille. "Partial rootzone drying improves almond tree leaf-level water use efficiency and afternoon water status compared with regulated deficit irrigation." Functional Plant Biology 38, no. 5 (2011): 372. http://dx.doi.org/10.1071/fp10247.
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To determine whether partial rootzone drying (PRD) optimised leaf gas exchange and soil–plant water relations in almond (Prunus dulcis (Mill.) D.A. Webb) compared with regulated deficit irrigation (RDI), a 2 year trial was conducted on field-grown trees in a semiarid climate. Five irrigation treatments were established: full irrigation (FI) where the trees were irrigated at 100% of the standard crop evapotranspiration (ETc); three PRD treatments (PRD70, PRD50 and PRD30) that applied 70, 50 and 30% ETc, respectively; and a commercially practiced RDI treatment that applied 50% ETc during the kernel-filling stage and 100% ETc during the remainder of the growth season. Measurements of volumetric soil moisture content in the soil profile (0–100 cm), predawn leaf water potential (Ψpd), midday stem water potential (Ψms), midday leaf gas exchange and trunk diameter fluctuations (TDF) were made during two growing seasons. The diurnal patterns of leaf gas exchange and stem water potential (Ψs) were appraised during the kernel-filling stage in all irrigation regimes. When tree water relations were assessed at solar noon, PRD did not show differences in either leaf gas exchange or tree water status compared with RDI. At similar average soil moisture status (adjudged by similar Ψpd), PRD50 trees had higher water status than RDI trees in the afternoon, as confirmed by Ψs and TDF. Although irrigation placement showed no effects on diurnal stomatal regulation, diurnal leaf net photosynthesis (Al) was substantially less limited in PRD50 than in RDI trees, indicating that PRD improved leaf-level water use efficiency.
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Shackel, K., B. Lampinen, S. Sibbett, and W. Olson. "THE RELATION OF MIDDAY STEM WATER POTENTIAL TO THE GROWTH AND PHYSIOLOGY OF FRUIT TREES UNDER WATER LIMITED CONDITIONS." Acta Horticulturae, no. 537 (October 2000): 425–30. http://dx.doi.org/10.17660/actahortic.2000.537.50.
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Lin, Yukun, Zhe Zhu, Wenxuan Guo, Yazhou Sun, Xiaoyuan Yang, and Valeriy Kovalskyy. "Continuous Monitoring of Cotton Stem Water Potential using Sentinel-2 Imagery." Remote Sensing 12, no. 7 (April 6, 2020): 1176. http://dx.doi.org/10.3390/rs12071176.
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Monitoring cotton status during the growing season is critical in increasing production efficiency. The water status in cotton is a key factor for yield and cotton quality. Stem water potential (SWP) is a precise indicator for assessing cotton water status. Satellite remote sensing is an effective approach for monitoring cotton growth at a large scale. The aim of this study is to estimate cotton water stress at a high temporal frequency and at a large scale. In this study, we measured midday SWP samples according to the acquisition dates of Sentinel-2 images and used them to build linear-regression-based and machine-learning-based models to estimate cotton water stress during the growing season (June to August, 2018). For the linear-regression-based method, we estimated SWP based on different Sentinel-2 spectral bands and vegetation indices, where the normalized difference index 45 (NDI45) achieved the best performance (R2 = 0.6269; RMSE = 3.6802 (-1*swp (bars))). For the machine-learning-based method, we used random forest regression to estimate SWP and received even better results (R2 = 0.6709; RMSE = 3.3742 (-1*swp (bars))). To find the best selection of input variables for the machine-learning-based approach, we tried three different data input datasets, including (1) 9 original spectral bands (e.g., blue, green, red, red edge, near infrared (NIR), and shortwave infrared (SWIR)), (2) 21 vegetation indices, and (3) a combination of original Sentinel-2 spectral bands and vegetation indices. The highest accuracy was achieved when only the original spectral bands were used. We also found the SWIR and red edge band were the most important spectral bands, and the vegetation indices based on red edge and NIR bands were particularly helpful. Finally, we applied the best approach for the linear-regression-based and the machine-learning-based methods to generate cotton water potential maps at a large scale and high temporal frequency. Results suggests that the methods developed here has the potential for continuous monitoring of SWP at large scales and the machine-learning-based method is preferred.
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McKenna, J. R., and E. G. Sutter. "The Effect of Stock Plant Water Potential, Auxin Application Method, and a Polyamines on Rooting Walnut Cuttings." HortScience 31, no. 4 (August 1996): 566e—566. http://dx.doi.org/10.21273/hortsci.31.4.566e.
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Experiments with field-grown hybrid Paradox (Juglans hindsii × J. Regia) walnut trees were conducted to assess the effects of stock plant water status, auxin application method, and the addition of spermine on adventitious root formation in stem cuttings. A 2-fold increase in rooting was noted when semihardwood cuttings were collected from dry (midday Ψw = –1.3 MPa) stock plants compared to the same trees six days later when fully hydrated (midday Ψw = –0.6 MPa). Spermine, when combined with potassium indolebutyric acid (KIBA) and applied as a quick dip, enhanced the rooting percentage in hardwood cuttings (54%) compared to controls treated with KIBA alone (18%). Spermine had no effect when it was applied together with KIBA using a toothpick application, producing 65% rooting compared to controls which had 75% rooting. By itself, spermine had no effect on rooting. The toothpick method for applying rooting compounds resulted in significantly higher rooting percentages for hardwood cuttings, but not for semihardwood cuttings. Combining spermine with KIBA had no effect on rooting of semihardwood cuttings.
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Chenafi, A., C. Carlen, A. Boudoukha, A. Hofer, and P. Monney. "EVALUATION OF REGULATED DEFICIT IRRIGATION FOR APPLE TREES CV. 'GALA' BASED ON MIDDAY STEM WATER POTENTIAL AND SOIL MATRIX POTENTIAL." Acta Horticulturae, no. 1038 (June 2014): 137–44. http://dx.doi.org/10.17660/actahortic.2014.1038.15.
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Shackel, Kenneth A., B. Lampinen, S. Southwick, D. Goldhamer, W. Olson, S. Sibbett, W. Krueger, and J. Yeager. "Deficit Irrigation in Prunes: Getting More with Less Water." HortScience 32, no. 3 (June 1997): 550D—550. http://dx.doi.org/10.21273/hortsci.32.3.550d.
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Prunes trees are believed to be relatively tolerant of water stress, and because prune fruit are dried, a low fresh to dry weight ratio of the fruit will reduce energy requirements for fruit drying and will represent an economic benefit to the grower. In previous research, we found that, under some orchard conditions, irrigation deprivation was associated with a number of economically beneficial effects, including a lower fresh to dry weight ratio of the fruit, increased return bloom, and final saleable crop yield. Analysis of these results was complicated by the effects of irrigation on alternate bearing, and the fact that tree water stress could be substantially different under different soil conditions for the same level of irrigation deprivation. Taking these factors into account, however, indicated that economic yield in prune could be maintained or increased by managing trees at a moderate level of water stress. An experiment was established to determine whether midday stem water potential could be used to guide irrigation and achieve a target level of water stress during the growing season, and whether a moderate level of water stress would be economically beneficial to prune production. By managing prune trees at a moderate level of water stress (midday stem water potential reaching about –1.5 Mpa by the end of the season) over 3 years, an average savings of 40% in applied irrigation water was obtained. Modest increases in return bloom, and an improved fruit dry to fresh weight ratio, occurred in moderately water stressed trees, although overall yield was not changed. The substantial savings in water, without reducing yield, should represent a net economic benefit to growers, depending on the price they pay for water.
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Mirás-Avalos, José Manuel, Emiliano Trigo-Córdoba, and Yolanda Bouzas-Cid. "Does predawn water potential discern between irrigation treatments in Galician white grapevine cultivars?" OENO One 48, no. 2 (June 30, 2014): 123. http://dx.doi.org/10.20870/oeno-one.2014.48.2.1566.
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<p style="text-align: justify;"><strong>Aims</strong>: To evaluate the usefulness of predawn water potential (<strong>Ψ</strong><sub>pd</sub>) to assess the water status of Galician grapevine cultivars for irrigation purposes.</p><p style="text-align: justify;"><strong>Methods and results</strong>: Three Galician white grapevine cultivars (Albariño, Godello and Treixadura) were subjected to rain-fed and irrigation conditions during the 2013 growing season. Diurnal changes in leaf water potential (<strong>Ψ</strong><sub>l</sub>) were measured using a pressure chamber on days with high evapotranspiration demand. Stem water potential (<strong>Ψ</strong><sub>s</sub>) was measured at midday. <strong>Ψ</strong><sub>pd</sub> was not able to discriminate between treatments, whereas <strong>Ψ</strong><sub>l</sub> and <strong>Ψ</strong><sub>s</sub> at midday were able to detect significant differences in water status among plants.</p><p style="text-align: justify;"><strong>Conclusion</strong>: <strong>Ψ</strong><sub>pd</sub> was not useful to evaluate vine water status under the Galician climatic conditions. In contrast, both <strong>Ψ</strong><sub>l</sub> and <strong>Ψ</strong><sub>s</sub> were effective for detecting differences between treatments and can thus be used for irrigation management purposes.</p><p style="text-align: justify;"><strong>Significance and impact of the study</strong>: This is the first study evaluating water status of Galician grapevine cultivars. It also provides useful information about the strategy for its control through measurements of midday <strong>Ψ</strong>l or <strong>Ψ</strong>s.</p>
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Wells, Lenny. "Mechanical Hedge Pruning Affects Nut Size, Nut Quality, Wind Damage, and Stem Water Potential of Pecan in Humid Conditions." HortScience 53, no. 8 (August 2018): 1203–7. http://dx.doi.org/10.21273/hortsci13217-18.
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Recent extensive pecan [Carya illinoinensis (Wangenh.) K. Koch] plantings coincided with a shift toward the planting of pecan trees at higher density by Georgia pecan producers in anticipation of maintaining these densities through hedge pruning. Initial studies of mechanical hedge pruning in the low-light environment of the southeastern United States have failed to show significant benefits to pecan production. The objectives of this study were to compare the effects of hedge pruning on pecan nut quality, yield, and midday stem water potential (ψ) of pecan trees in the temperate climate of the southeastern United States and to evaluate the effect of hedge pruning on windstorm damage to pecan trees. Treatments were arranged in a randomized complete block design with three blocks. Two treatments were evaluated; 1) Hedge-pruned; 2) Nonhedge-pruned (control). Midday stem ψ was 8.5%, 17.6%, and 16.6% higher (P ≤ 0.05), indicating less water stress, on hedged trees than on nonhedged trees during 2015, 2016, and 2017, respectively. Nut weight and percent kernel were increased (P ≤ 0.05) by hedge pruning 2 of 3 years of the study. Although no direct positive effect of hedge pruning on in-shell nut yield was observed, hedge pruning was not detrimental to pecan yield in the short term. Hurricane/Tropical Storm Irma brought damaging winds to the entire pecan-producing region of Georgia on 11 Sept. 2017, resulting in blown down trees, broken branches, and immature nuts blown from the trees. Hedged trees had 60% less wind damage in the form of major limb breakage and tree loss than did nonhedged trees.
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Goldhamer, David A., Elias Fereres, Merce Mata, Joan Girona, and Moshe Cohen. "Sensitivity of Continuous and Discrete Plant and Soil Water Status Monitoring in Peach Trees Subjected to Deficit Irrigation." Journal of the American Society for Horticultural Science 124, no. 4 (July 1999): 437–44. http://dx.doi.org/10.21273/jashs.124.4.437.
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To characterize tree responses to water deficits in shallow and deep rooted conditions, parameters developed using daily oscillations from continuously measured soil water content and trunk diameter were compared with traditional discrete monitoring of soil and plant water status in lysimeter and field-grown peach trees [Prunus persica (L.) Batsch `O'Henry']. Evaluation occurred during the imposition of deficit irrigation for 21 days followed by full irrigation for 17 days. The maximum daily available soil water content fluctuations (MXAWCF) taken at any of the four monitored root zone depths responded most rapidly to the deficit irrigation. The depth of the MXAWCF increased with time during the deficit irrigation. Differences relative to a fully irrigated control were greater in the lysimeter than the field-grown trees. Minimum daily trunk diameter (MNTD) and maximum daily trunk shrinkage (MDS) responded sooner than midday stem water potential (stem Ψ), predawn or midday leaf water potential (predawn leaf Ψ and leaf Ψ), or photosynthesis (A). Parameters based on trunk diameter monitoring, including maximum daily trunk diameter (MXTD), correlated well with established physiological parameters of tree water status. Statistical analysis of the differences in the measured parameters relative to fully irrigated trees during the first 10 days of deficit irrigation ranked the sensitivity of the parameters in the lysimeter as MXAWCF > MNTD > MDS > MXTD > stem Ψ = A = predawn leaf Ψ = leaf Ψ. Equivalent analysis with the field-grown trees ranked the sensitivity of the parameters as MXAWCF > MNTD > MDS > stem Ψ = leaf Ψ = MXTD = predawn leaf Ψ > A. Following a return to full irrigation in the lysimeter, MDS and all the discrete measurements except A quickly returned to predeficit irrigation levels. Tree recovery in the field-grown trees was slower and incomplete due to inadequate filling of the root zone. Fruit size was significantly reduced in the lysimeter while being minimally affected in the field-grown trees. Parameters only available from continuous monitoring hold promise for improving the precision of irrigation decision-making over the use of discrete measurements.
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Marsal, J., M. Gelly, M. Mata, A. Arbonés, J. Rufat, and J. Girona. "Phenology and drought affects the relationship between daily trunk shrinkage and midday stem water potential of peach trees." Journal of Horticultural Science and Biotechnology 77, no. 4 (January 2002): 411–17. http://dx.doi.org/10.1080/14620316.2002.11511514.
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Mirás-Avalos, José Manuel, Francisco Pérez-Sarmiento, Rosalía Alcobendas, Juan José Alarcón, Oussama Mounzer, and Emilio Nicolás. "Using midday stem water potential for scheduling deficit irrigation in mid–late maturing peach trees under Mediterranean conditions." Irrigation Science 34, no. 2 (February 5, 2016): 161–73. http://dx.doi.org/10.1007/s00271-016-0493-9.
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Sbraci, Sofia, Linda Salvi, Francesca Paoli, Eleonora Cataldo, Alessandra Zombardo, Sergio Puccioni, Paolo Storchi, and Giovan Battista Mattii. "Interactive effects of biostimulants and water stress on potted Pinot noir grapevines." BIO Web of Conferences 13 (2019): 03006. http://dx.doi.org/10.1051/bioconf/20191303006.
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Seaweeds extracts (SWE) are innovative and non-polluting tools that have become popular as biostimulants. Their effects on Pinot noir water potential, gas exchanges and fruit quality under drought stress and full irrigation were evaluated during the 2017 growing season. Differential irrigations were applied and Pinot Noir grapevines have been sprayed two times at label doses (3 g/L) during the vegetative growth, with the Ascophyllum nodosum exract, starting from veraison. During the season, measurements of single leaf gas exchange and stem water potential were made; moreover parameters of technological maturity (°Brix, acidity, pH) and phenological one were analyzed. The inhibition of gas exchange and increase of stomatal limitation induced by drought stress were not reduced by SWE where A.nodosum had positive effects on midday stem water potential. Under full irrigation SWE increased leaf gas exchange. No particular effect was observed on the technological parameters after the treatment. The application of the seaweed extract improved polyphenols accumulation in stressed theses, increasing wine grapes quality. A.nodosum can be useful to reduce negative effects of abiotic stress such lack of water and to improve polyphenols content in grapes, especially in genotypes with a limited phenolic profile like Pinot Noir variety.
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Blaya-Ros, Pedro José, Víctor Blanco, Roque Torres-Sánchez, and Rafael Domingo. "Drought-Adaptive Mechanisms of Young Sweet Cherry Trees in Response to Withholding and Resuming Irrigation Cycles." Agronomy 11, no. 9 (September 9, 2021): 1812. http://dx.doi.org/10.3390/agronomy11091812.
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The present work evaluates the main adaptive mechanisms developed by young sweet cherry trees (Prunus avium L.) to cope with drought. For this purpose, the young trees were subjected to two drought cycles with different water stress intensities followed by a recovery period. Three irrigation treatments were applied: control treatment (CTL) irrigated to ensure non-limiting soil water conditions; moderate water stress (MS) subjected to two drying cycles whose duration was dependent on the time elapsed until the trees reached values of midday stem water potential (Ψstem) of −1.3 and −1.7 MPa for the first and second cycle, respectively; and severe water stress (SS) similar to MS, but with reference values of −1.6 and −2.5 MPa. In-between drought cycles, MS and SS trees were irrigated daily as the CTL trees until reaching Ψstem values similar to those of CTL trees. The MS and SS trees showed an important stomatal regulation and lower vegetative growth. The decreasing leaf turgor potential (Ψturgor) during the drought periods accounted for 40–100% of the reduction in leaf water potential at midday (Ψmd). The minimum osmotic potential for mature leaves was about 0.35 MPa lower than in well-irrigated trees. The occasional osmotic adjustment observed in MS and SS trees was not sufficient to maintain Ψturgor values similar to the CTL trees or to increase the specific leaf weight (SLW). The leaf insertion angle increased as the water stress level increased. Severe water stress (Ψstem < −2.0 MPa) resulted in clear early defoliation as a further step in water conservation.
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Neilsen, Denise, Gerry Neilsen, Sunghee Guak, and Tom Forge. "Consequences of Deficit Irrigation and Crop Load Reduction on Plant Water Relations, Yield, and Quality of ‘Ambrosia’ Apple." HortScience 51, no. 1 (January 2016): 98–106. http://dx.doi.org/10.21273/hortsci.51.1.98.
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Uncertain water supplies resulting from changing climatic conditions in western North America led to this investigation of the role of crop load reduction in maintaining performance of high-density ‘Ambrosia’ apple (Malus ×domestica) on M.9 rootstock. A split-plot experimental design was imposed for three growing seasons (2007–09) with six replicates of four main plot irrigation treatments and three crop load subplots comprised of three trees. Four season-long irrigation (Irr) treatments were applied through 2 × 4 L·h−1 drip emitters per tree and included Irr1) control [100% evapotranspiration (ET) replacement], Irr2) 50% ET replacement, Irr3) 50% ET replacement to half the emitters, and Irr4) an increasingly severe treatment commencing at 50% ET replacement (once every 2 days) in 2007 and progressing to 25% and 18% ET replacement, 2008–09. Three target crop loads were established annually, 4–5 weeks after bloom as low (2.5, 3, and 3.75), medium (4.5, 6, and 7.5), and high (9, 12, and 15) fruit/cm2 trunk cross-sectional area (TCSA) 2007–09, respectively, by hand thinning around 4 weeks after bloom. Volumetric soil moisture contents generally reflected the amount of water applied and ranged from 20% for control (Irr1) to <10% for Irr4. Both irrigation and crop load treatments affected midday stem water potential more than leaf photosynthesis and stomatal conductance (gS). By the 2nd and 3rd year stem potential values for irrigation treatments ranged from a maximum of −1.0 to −1.3 MPa for Irr1 to minimums ≤-2.0 MPa for Irr4. gS decreased as midday stem potential decreased, but at any given stem potential value was greater at high crop loads, presumably in response to an increased demand for photosynthates. Fruit size decreased as crop load increased, but as irrigation deficits became more severe, fruit size was more closely correlated with stem water potential than gS. Consequently, fruit size was controlled by two mechanisms, competition for photosynthates and the effects of plant water status on gS. Negative linear relationships between crop load and average fruit size were used to determine the crop load required to produce an average fruit size of 200 g at different irrigation deficits. It was not possible to achieve adequate fruit size when applications were very low, as at 18% to 25% ET in Irr4. Crop load reduction around mid-June had no negative consequences for fruit quality, enhancing fruit color, and soluble solids concentration (SSC) and did not affect the incidence of sunburn, internal breakdown or bitter pit at harvest.
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O'Connell, Mark G., and Ian Goodwin. "Water stress and reduced fruit size in micro-irrigated pear trees under deficit partial rootzone drying." Australian Journal of Agricultural Research 58, no. 7 (2007): 670. http://dx.doi.org/10.1071/ar06306.
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Crop water relations, vegetative and reproductive growth, and soil water status were studied during 2 seasons to determine the effectiveness of partial rootzone drying (PRD) in a mature micro-irrigated pear orchard in the Goulburn Valley, Australia. PRD treatments were 50% (PRD50) and 100% (PRD100) of predicted crop water requirement (ETc) applied on one side of the tree alternated on a 14-day cycle compared with a Control treatment, which received 100% of ETc irrigated on both sides of the tree. Irrigation was applied daily by micro-jets to replace ETc estimated using reference crop evapotranspiration (ETo) and a FAO-56 crop coefficient of 1.15 adjusted for tree size. The PRD50 regime applied 174–250 mm for the season v. 347–470 mm for both the Control and PRD100 treatments. Irrigation maintained a well watered rootzone under the emitter compared with the drying profiles of the alternated wet/dry irrigated zones of the PRD treatments. There was no significant benefit of PRD100 compared with the Control irrigation regime. Similar vegetative growth (canopy radiation interception), reproductive growth (fruit growth rate, final fruit size, yield), fruit quality (total soluble solids, flesh firmness), and crop water relations (midday leaf conductance, midday leaf and stem water potential) were measured between the Control and PRD100. Trees under the PRD50 regime showed symptoms of severe water stress, that being greater fruit drop, reduced fruit size, lower yield, reduced leaf conductance, and lower leaf and stem water potential. The 50% water saving afforded by PRD50 led to a yield penalty of 16–28% compared with the Control and PRD100. PRD50 fruit failed to meet commercial cannery requirements due to poor fruit size. We conclude from an agronomic basis that deficit PRD irrigation management is not recommended for micro-irrigated pear orchards on fine-textured soils in the Goulburn Valley, Australia.
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Kulaç, Şemsettin, Pascal Nzokou, Deniz Guney, Bert Michael Cregg, and Ibrahim Turna. "Growth and Physiological Response of Fraser Fir [Abies fraseri (Pursh) Poir.] Seedlings to Water Stress: Seasonal and Diurnal Variations in Photosynthetic Pigments and Carbohydrate Concentration." HortScience 47, no. 10 (October 2012): 1512–19. http://dx.doi.org/10.21273/hortsci.47.10.1512.
Full textAbstract:
Four-year-old seedlings of Abies fraseri [(Pursh) Poir] (fraser fir) were grown in semicontrolled conditions in hoop houses with five watering regimes (0.00, 0.62, 1.25, 2.50, and 3.70 cm/week) with the goal of determining the seasonal variation in the physiological response to drought stress. Drought stress was monitored by measuring predawn (Ψpd) and midday (Ψmd) potentials in a subset of plants from each treatment. Physiological variables monitored were chlorophyll fluorescence (Fv/Fm), Chl a, Chl b, total carotenes, and total carbohydrate concentrations. Morphological characteristics including height growth, root collar diameter, and terminal shoot growth were also measured. Predawn stem water potential values were generally higher (–0.8 to –1.9 Mpa) than midday values (–1.3 to –2.9 Mpa). Irrigation consistently increased Ψpd and Ψmd compared with non-irrigated treatments. Photosynthetic pigments (Chl a, Chl b, and carotenes) decreased midseason (14 July) and increased toward the end of the season (25 Aug.) in predawn and midday measurements. There was a significant effect (P < 0.05) of drought stress on photosynthetic pigment concentrations in predawn and midday samples in the late-season measurements (25 Aug.). These results were accompanied with a similar significant difference in Fv/Fm between non-irrigated and irrigated trees. We concluded that significant effects observed on photosynthetic pigment concentrations in some of the treatments did not affect carbohydrate concentrations. Exposure of A. fraseri to water stress did not cause a reduction in supply of metabolic carbohydrates; consequently, the decline and mortality in water-stressed plants can only be the result of hydraulic failure caused by xylem cavitation leading to cessation of water flow in tissues, desiccation, and cellular death. Further studies are needed to confirm these preliminary conclusions.
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Shackel, Kenneth A. "Plant Water Status as an Index of Irrigation Needs in Deciduous Fruit Trees." HortScience 30, no. 4 (July 1995): 905B—905. http://dx.doi.org/10.21273/hortsci.30.4.905b.
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To be useful for indicating plant water needs, any measure of plant stress should be closely related to some of the known short- and medium-term plant stress responses, such as stomatal closure and reduced rates of expansive growth. Midday stem water potential (SWP) has proven to be a useful index of stress in a number of fruit trees. Day-to-day fluctuations in SWP under well-irrigated conditions is well-correlated to midday vapor pressure deficit, and hence can be used to predict a non-stressed baseline. Measurement of SWP helped to explain the results of a 3-year deficit irrigation study in mature prunes, which showed that deficit irrigation could have either positive or negative impacts on tree productivity, depending on soil conditions. Mild to moderate water stress was economically beneficial. In cherry, SWP was correlated to both leaf stomatal conductance and rates of shoot growth, with shoot growth essentially stopping once SWP dropped to between –1.5 to –1.7 MPa. In pear, increased fruit size, decreased fruit soluble solids, and increased green color were all associated with increases in SWP.
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Ortega-Farías, S., M. Duarte, A. Acevedo, Y. Moreno, and F. Córdova. "EFFECT OF FOUR LEVELS OF WATER APPLICATION ON GRAPE COMPOSITION AND MIDDAY STEM WATER POTENTIAL OF VITIS VINIFERA L. CV. CABERNET SAUVIGNON." Acta Horticulturae, no. 664 (December 2004): 491–97. http://dx.doi.org/10.17660/actahortic.2004.664.62.
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Arévalo, Jhon Jairo, Javier Enrique Vélez S., and Diego Sebastiano Intrigliolo. "Determination of an efficient irrigation schedule for the cultivation of rose cv. Freedom under greenhouse conditions in Colombia." Agronomía Colombiana 32, no. 1 (January 1, 2014): 95–102. http://dx.doi.org/10.15446/agron.colomb.v32n1.40160.
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An experiment on rose (Rosa sp.) cv. Freedom was performed in a greenhouse on the Bogota Plateau, Colombia, to identify an efficient irrigation regime for this crop. The tested treatments were based on three irrigation doses, applying different fractions of the estimated crop evapotranspiration (ETc), calculated using a class A evaporation tank: i) 100% ETc (ETc100), ii) 80% ETc (ETc80) and iii) 70% ETc (ETc70). During the entire experimental period, from mid-May to early September, the crop had a constant production of floral stems. In all of the irrigation treatments, the soil and plant water status were monitored using tensiometers and the midday stem water potential, respectively (ystem). In the fully irrigated roses, the actual water use was determined using a drainage lysimeter in order to obtain the local crop coefficients (Kc) by means of a water balance. From June to August, the obtained monthly Kc values varied between 1.10 and 1.26. Compared to the ETc100 treatment, 14.5 and 21.8% less water was applied in treatments ETc80 and ETc70, respectively. Despite this fact, no statistically significant differences were found among the treatments for rose production or quality. Finally, in the more irrigated roses, tight relationships between the stem water potential and vapor pressure deficit were obtained. The reported base-line equations can be used for predicting the optimum rose plant water status, depending on the environmental conditions. Overall, the reported results can be used for an efficient irritation schedule for rose crops under greenhouse conditions, using the local Kc and direct determinations of plant water status corrected for the evaporative demand.
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Ali, M., C. R. Jensen, and V. O. Mogensen. "Early signals in field grown wheat in response to shallow soil drying." Functional Plant Biology 25, no. 8 (1998): 871. http://dx.doi.org/10.1071/pp98061.
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The aim of the present work was to test under field condition earlier climate room findings that root-borne signals may control stomatal closure and leaf extension rate during mild soil drying. Stomatal conductance (g H2O) of flag leaves, leaf and stem extension rates, leaf water relations, leaf ABA content and predawn xylem [ABA] were measured daily in wheat grown in two soil types (sand and loam) in lysimeters in the field during a period of soil drying with high and low evaporative demands. At 3 days after withholding irrigation (DAI) on both soil types, when soil water potential (Ψsoil) in the upper soil profile of the droughted treatment had dropped to –70 kPa and with the lower layers still at field capacity, predawn xylem [ABA] increased. At 4 DAI the leaf extension rate decreased and midday leaf ABA content increased. Stem extension rates decreased at 5 DAI in loam and 7 DAI in sand. g H2O started to decrease 6 DAI in loam and 9 DAI in sand. These responses were observed before any detectable decrease in the midday leaf water status of the droughted plants had occurred relative to well- watered plants. The responses were closely related to Ψsoil and independent of evaporative demand. We conclude that, in wheat, root-borne signals probably control stomatal conductance and leaf extension rate during mild soil drying in the field.
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Rein, William H., Robert D. Wright, and John R. Seiler. "Propagation Medium Moisture Level Influences Adventitious Rooting of Woody Stem Cuttings." Journal of the American Society for Horticultural Science 116, no. 4 (July 1991): 632–36. http://dx.doi.org/10.21273/jashs.116.4.632.
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Stem cuttings of Blue Rug juniper (Juniperus horizontalis Moench `Wiltonii'), `Hino-Crimson' azalea [Rhododendron (Lindl.) P1anch `Hino-Crimson'], and `Helleri' holly (Ilex crenata Thunb. `Helleri') were propagated in 1 peat: 1 perlite (v/v) at one of five moisture levels based on medium dry weight (125%, 250%, 375%, 500%, or 625%). Cutting survival and percentage of rooted cuttings were highest at the highest medium moisture level in all three species. Incidence of cutting basal rot was not directly related to medium moisture level, but more to the growth stage of the stock plant. Midday xylem water potential (ψ) of cuttings for each species was highest in the wettest propagation medium and lowest in the driest medium. During propagation, stem cutting ψ below - 2.0 MPa occurred even in the wettest medium tested, and frequently reached - 4.0 MPa in cuttings in the driest treatment (125%). Basal water uptake by cuttings was highest in the wettest medium moisture level. Water uptake was highest during the first few days after insertion, and thereafter decreased until root emergence.
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Kjelgren, Roger. "Growth and Water Relations of Kentucky Coffee Tree in Protective Shelters during Establishment." HortScience 29, no. 7 (July 1994): 777–80. http://dx.doi.org/10.21273/hortsci.29.7.777.
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Growth and water relations of Kentucky coffee tree [Gymnocladus dioica (L.) K. Koch] whips in translucent tubelike shelters were investigated. In a container study, 1.2-m-high shelters were placed over whips following transplanting, then diurnal microclimate, water relations, and water use were measured. Shelter air temperature and vapor pressure were substantially higher, and solar radiation was 70% lower, than ambient conditions. Sheltered trees responded with nearly three-times higher stomatrd conductance than nonsheltered trees. However, due to substantially lower boundary layer conductance created by the shelter, normalized water use was 40910 lower. In a second experiment, same-sized shelters were placed on whips following spring transplanting in the field. Predawn and midday leaf water potentials and midday stomatal conductance (g,) were monitored periodically through the season, and growth was measured in late summer. Midday gs was also much higher in field-grown trees with shelters than in those without. Sheltered trees in the field had four times greater terminal shoot elongation but 40% less stem diameter growth. Attenuated radiation in the shelters and lower specific leaf area of sheltered trees indicated shade acclimation. Shelters can improve height and reduce water loss during establishment in a field nursery, but they do not allow for sufficient trunk growth.