Tesi sul tema "Barley Physiology"

The protein concentration of cereal grains is low and the production of cereal crops with increased grain protein concentrations is desirable. This work investigates the physiological aspects of protein accumulation potential in barley grain. A recently developed perfusion system was used in four experiments conducted in 1993 and 1994. In the field experiment, plants were allowed to take up urea at 15 or 30 mM N, or ethephon at 15 $ mu$ M. Abscisic acid and 2,4-D decreased total seed weight spike$ sp{-1}$. Gibberellic acid and 2,4-D increased seed protein concentration and content, while ABA decreased both of these. Kinetin and abscisic acid treatments resulted in the highest and lowest levels, respectively for flag leaf photosynthesis, stomatal conductance, transpiration and intercellular CO$ sb2$ concentration. Both protein content spike$ sp{-1}$ and seed protein concentration were elevated in plants fertilized with 10.7 mM N via the soil and plants perfused with 30 mM N via the peduncle. Plants receiving treatments of 10.7 mM N from the soil and mixture of 30 mM N and GA$ sb3$ or 2,4-D through the peduncle had increased protein content seed$ sp{-1}$, and the highest seed weight spike$ sp{-1}$, respectively. Peduncle perfusion with 30 mM N increased spike protein concentration and content and grain protein concentration without affecting seed weight spike$ sp{-1}$. Grain protein concentration was increased by peduncle perfusion with ethephon. The perfusion technique worked well under field conditions. (Abstract shortened by UMI.)

Plant growth regulator(s) (PGR) can be used as lodging inhibitors and/or yield promoters for spring barley (Hordeum vulgare L.). From 1987 to 1990 four field experiments were conducted to monitor barley main-stem apical development and to determine the effects of chlormequat (CCC) and ethephon on the development, physiology and yield of spring barley. Our data provide a description of barley apical development and the general pattern of leaf and spikelet primordium production under field conditions. In general, PGR treatment reduced the apical dominance of dominant sinks allowing the survival and greater development of more subordinate sinks. Early application of either CCC or ethephon retarded development of the main-stem apex from shortly after application to the awn elongation stage and reduced the number of aborted spikelet primordia, thus increasing the potential number of grains per spike and sometimes grain yield. Ethephon applied at ZGS 39 reduced plant height and lodging. Early application (ZGS 30) of ethephon, alone or in combination with CCC increased the number of spikes m$ sp{-2},$ but not grain yield. The number of spike-bearing shoots per unit area or per plant was increased by early PGR treatment, primarily by enhancement of tiller number rather than tiller survival. Early application of CCC or ethephon to spring barley is not justified, and caution must be taken when using ethephon at the currently recommended rate and stage for lodging control. Post-anthesis application of ethephon can efficiently enhance grain fill and yield of spring barley.

The development of new and novel polymorphic assay methods represents one of the most significant developments in plant and animal biology. The exploitation of these genetic markers is of relevance to both applied and fundamental research. Recombinant DNA technology provides the opportunity to develop phenotypically neutral genetic markers in any organism from which DNA can be extracted. The research described in this thesis has focused on the development, evaluation and exploitation of genetic markers in barley. Both protein and DNA based molecular markers were evaluated as a means of detecting polymorphism in H. vulgare and H. spontaneum. New methods for detecting polymorphisms based on the Polymerase Chain Reaction (PCR) were assessed and successfully applied to barley. The segregation of alleles at morphological, isozyme and RFLP loci were monitored in doubled haploid (DH) populations of barley. In order to detect molecular variability, both clones of known function and anonymous clones were employed. Clones homologous to the- hordein gene complex on chromosome IH were used in conjunction with DHs to intra-chromosomally map various members of this multi-gene family. Allelic variation at the genetic loci segregating in the DH population was evaluated in relation to the expression of quantitative traits. This study established that several isozymes and RFLP loci were significantly associated with quantitative trait loci (QTL) of agronomic importance. Grain isozyme and ribosomal DNA (rDNA) variability was examined in Hordeum spontaneum populations sampled from 27 geographical sites in Israel. Considerable phenotypic variability was observed and isozyme and rDNA variants were identified that were not present in the H. vulgare gene pool. Furthermore, the variability detected was quantified and correlated with a range of ecogeographical factors. The distribution of grain isozyme and rDNA phenotypes was non-random with particular phenotypes being restricted to specific geographical areas of Israel. Information on the spatial distribution of diversity in H. spontaneum is a pre-requisite for the optimization of sampling and germplasm collecting strategies. Opportunities and limitations to the exploitation of genetic markers in barley improvement are considered.

This study was designed to explore correlations between flower and seed characters and the relationship of flower and seed characters to yield. Thirty six lines selected from Composite Cross XXXII material were planted in a randomized block design with four replications. At anthesis, spikes from each plot were collected and fixed in 70% alcohol. At the same time, an equivalent spike was tagged to be harvested at maturity. Measurements of flower characters were made on the preserved spikes and seed. Length, width and weight were obtained on the mature spikes. Flower volume was calculated by multiplying the area of lemma and palea by flower thickness. Correlations indicated that selection for flower characters at anthesis would be an effective selection technique for seed characters.

Small RNA are short, 18-25 nt molecules that regulate gene expression in plants and animals. Two main types, microRNA (miRNA) and short interfering RNA (siRNA) perform this regulation by transcript silencing, translation inhibition, DNA methylation and chromatin remodeling. This thesis is an investigation into small RNA activity in archaeological plant material, specifically barley grain from Qasr Ibrim, a multi-period archaeological site in southern Egypt. It is of particular interest due to its unusual phenotype, suggestive of stunted development that is unexpected in a staple, domesticated cultivar, and the unusual level of DNA and RNA preservation attributable to the extremely arid climate at the site. The research presented here is a comparative analysis of small RNA profiles and epigenetic states of Qasr Ibrim barley and modern, unstressed counterparts. It concludes that differential microRNA and epigenetic profiles are the result of stress response, adaptation, dormancy and / or viral infection unique to the archaeological grain. The primary method of investigation was generation of small RNA sequence data using the Illumina GAIIx platform. This was followed by extensive bioinformatic analysis (RNA diagenesis patterns, miRNA prediction, siRNA target prediction and small genome in silico reconstruction) the results of which were in turn validated experimentally (genomic methylation states, locus-specific methylation analysis and direct miRNA detection). The research represents a twofold contribution to knowledge: first, proof-of-principle that biologically meaningful archaeological RNA can be extracted despite its relative instability to DNA, and second that a unique miRNA profile and epigenetic state is detectable in this particular cultivar of archaeological barley.

L'ordi (Hordeum vulgäre L.) és un cereal de zones temperades conreat extensament en
climes mediterranis. Es desenvolupa favorablement en àrees de pluviometria mitjana anual
superior a 250 mm. Durant les darreres dècades, els increments en rendiment deguts a activitats
de millora genètica han estat poc importants a causa, probablement, de la limitació que la sequera
i altres estressos abiòtics exerceixen sobre el creixement. Futurs increments poden veure's
accelerats per un millor coneixement dels processos que controlen el creixement i
desenvolupament i que limiten la product! vi tat dels genotips en situacions de manca d'aigua. Dins
d'aquest contexte, les activitats d'investigació en fisiologia vegetal haurien de tenir un fort
impacte, en un futur proper, en l'increment de l'eficiència dels programes de millora tradicionals.
Aquesta tesi pretén ampliar el coneixement actual d'aquells factors que redueixen el creixement,
la productivitat i la qualitat de l'ordi en ambients mediterranis. Amb aquesta finalitat, s'han
avaluat en assajos localitzats a la província de Lleida (nordest d'Espanya) i, ocasionalment, a les
províncies de Navarra (nord d'Espanya) i Valladolid (centre d'Espanya), un conjunt de deu
genotips d'ordi (incloent-hi dos i sis carreres) que difereixen en adaptació a ambients semiàrids.
Inicialment, un conjunt de tres genotips moderns i altament productius (Barberousse,
Orria i Plaisant) va ésser utilitzat per examinar l'efecte que una reducció de l'embomal
reproductiu (nombre de grans per espiga) provocava sobre el pes i el creixement del gra,
l'acumulació de carbohidrats i el transport de nitrogen en condicions semiàrides (Capítols I i II).
Els increments en pes de gra obtinguts en resposta a una reducció del 50% de l'embornal van ser
progressivament superiors en aquells ambients amb grans testimoni de menor pes. Pel contrari,
el nitrogen es va acumular uniformement en tots els ambients en resposta a una reducció de
l'embornal. Aquests resultats suggereixen que el rendiment final es troba fortament limitat, en
ambients productivament pobres, per la disponibilitat de carbohidrats durant l'omplenat del gra,
en tant que l'acumulació de proteïnes en el gra sembla independent de les condicions ambientals
en que té lloc l'omplenat del gra. El grau de limitació exercit per la font es va manifestar més
elevat en els grans situats en espigúeles laterals de l'espiga, amb independència de la
disponibilitat d'assimilats per l'omplenat del gra. Aquest desavantatge dels grans laterals de
l'espiga es va poder atribuir principalment a taxes d'acumulació de matèria seca inferiors durant
l'omplenat.
La influència d'estressos abiòtics com ara la sequera o les altes temperatures en el procés
d'omplenat dels grans es va examinar en detall utilitzant el conjunt dels deu genotips assajats en
dotze ambients (Capítols III i IV). L'objectiu final va consistir a detectar variabilitat genètica així
com determinar possibles mecanismes morfofisiològics de tolerància als esmentats estressos. Els
possibles factors causants d'interacció genotip-ambient (G*E) en el pes del gra, tasa i duració
d'omplenat es van estudiar mitjançant l'ús de models estadístics biadditius. Es van detectar
sensibilitats genotípiques diferencials en tolerància a sequera i a elevades temperatures de postantesi
pel pes final del gra, que varen atribuir-se parcialment a diferències entre els grups d'ordis
de dos i sis carreres. La presència de GxE per a la taxa d'omplenat es va explicar per l'efecte
conjunt de variables climàtiques de pre-antesi, la qual cosa va suggerir que les diferències
genotípiques podrien ser degudes parcialment a diferències en el balanç font/embornal entre ordis
de dos i sis carreres en antesi. L'existència de GXE per a la duració d'omplenat va poder-se
atribuir principalment a diferències en data d'antesi entre genotips, indicant l'existència d'una
estratègia d'escapament causant d'un allargament del période d'omplenat d'alguns genotips a
finals del cicle de cultiu.
La relació entre rendiment i discriminació isotòpica del carboni (A) en grans va avaluar-se
extensament en un grup de 22 ambients (Capítol VI), i també va examinar-se la possibilitat
d'utilització de la concentració de cendres en teixits aeris com a substitut de A (Capítol VII).
L'expressió genotipica del rendiment va estar condicionada per l'ambient d'una forma més
important que la de A. L'existència de GxE pel rendiment va suggerir la presència d'una
interacció qualitativa amb un punt de creuament aproximat situat en productivitats mitjanes
inferiors a 3 t ha"1. Pel contrari, la classificació de genotips per a A no va variar substancialment
amb l'ambient. En general, aquells genotips amb valors baixos de A i, per tant, amb elevades
eficiències de transpiració, van ésser superiors en ambients poc productius (ambients per sota de
3 t ha"1), en tant que valors genotípics de A elevats van mostrar-se com avantatjosos en ambients
de rendiment mig i alt. És probable que, quan la sequera sigui moderada, un important embornal
reproductiu forci la planta a incrementar la seva conductancia estomàtica i, com a conseqüència,
l'aigua total utilitzada. Aquest fenomen probablement capgira la relació negativa esperada entre
A i biomassa o rendiment quan la disponibilitat d'aigua és factor limitant. Per altra banda, la
concentració mineral en grans va trobar-se relacionada freqüentment i de forma negativa amb A,
en tant que no va trobar-se relació entre la concentració mineral en palla i A. Aquests resultats
suggereixen que l'acumulació mineral en teixits aeris mostrejats a finals del cicle de cultiu és
independent de l'eficiència de transpiració durant l'omplenat del gra. La concentració de cendres
en grans podria emprar-se com a criteri de selecció complementari a A en ambient semiàrids, si
bé es fa necessari un coneixement fisiologie més profund dels mecanismes que afecten
l'acumulació de minerals en el gra.
La sequera esdevé el principal factor limitant del creixement i la productivitat de l'ordi
en els secans semiàrids mediterranis. En el present estudi, les diferències en productivitat en un
conjunt de 22 ambients van poder atribuir-se, en gran part, a diferències paral·leles en
disponibilitat hídrica des de sembra fins a antesi, période en el qual es determina el nombre de
grans per m2. La presència d'una interacció GXE de tipus qualitatiu pel rendiment, així com les
relacions fluctuants entre rendiment i A, depenent de la intensitat de l'estrès hídric, suggereixen
que la tolerància a la sequera i l'elevat potencial de rendiment son conceptes antagònics en ordi.
La cebada (Hordeum vulgäre L.) es un cereal de zonas templadas ampliamente cultivado
en climas mediterráneos. Se desarrolla favorablemente en zonas de pluviometría media anual
superior a 250 mm. Durante las últimas décadas, los incrementos en rendimiento debidos a
actividades de mejora genética han sido poco importantes probablemente a causa de la limitación
que la sequía y otros estreses abióticos ejercen sobre el crecimiento. Futuros incrementos pueden
verse acelerados por un mejor conocimiento de los procesos que controlan el crecimiento y
desarrollo y que limitan la productividad de los genotipos en situaciones caracterizadas por la
falta de agua. En este contexto, las actividades de investigación en fisiología vegetal deberían
tener un fuerte impacto, ya en un futuro próximo, en el incremento de la eficiencia de los
programas de mejora tradicionales. La presente tesis pretende ampliar el conocimiento actual de
aquellos factores que reducen el crecimiento, la productividad y la calidad de la cebada en
ambientes mediterráneos. Con este fin se ha evaluado en ensayos situados en la provincia de
Lérida (nordeste de España) y, ocasionalmente, en las provincias de Navarra (norte de España)
y Valladolid (centro de España), un conjunto de diez genotipos de cebada (incluyendo dos y seis
carreras) que difieren en adaptación a ambientes semiáridos.
Inicialmente, un conjunto de tres genotipos modernos y altamente productivos
(Barberousse, Orria y Plaisant) fue utilizado para examinar el efecto que una reducción del
sumidero reproductivo (número de granos por espiga) provocaba sobre el peso y el crecimiento
del grano, la acumulación de carbohidratos y el transporte de nitrógeno en condiciones semiáridas
(Capítulos I y II). Los incrementos en peso del grano obtenidos en respuesta a una reducción del
sumidero del 50% fueron progresivamente superiores en aquellos ambientes con granos testigo
de menor peso. Por el contrario, el nitrógeno se acumuló uniformemente en todos los ambientes
en respuesta a una reducción del sumidero. Estos resultados sugieren que el rendimiento final se
encuentra fuertemente limitado, en ambientes productivamente pobres, por la disponibilidad de
carbohidratos durante el llenado del grano, mientras que la acumulación de proteínas en el grano
parece independiente de las condiciones ambientales en las que el llenado del grano tiene lugar.
El grado de limitación ejercido por la fuente fue más elevado para los granos situados en
espiguillas laterales de la espiga, con independencia de la disponibilidad de asimilados durante
el llenado del grano. Esta desventaja de los granos laterales de la espiga pudo atribuirse
principalmente a tasas inferiores de acumulación de materia seca durante el llenado.
La influencia de estreses abióticos tales como la sequía o las altas temperaturas en el
proceso de llenado de los granos se examinó en detalle utilizando el conjunto de los diez
genotipos ensayados en doce ambientes (Capítulos III y IV). El objetivo final perseguido
consistió en detectar variabilidad genética así como en determinar posibles mecanismos
morfofisiológicos de tolerancia a dichos estreses. Los posibles factores causantes de interacción
genotipo-ambiente (G*E) en el peso del grano, la tasa y la duraoión de llenado se estudiaron
mediante el uso de modelos estadísticos biaditivos. Se detectaron sensibilidades genotípicas
diferenciales en la tolerancia a la sequía y a las elevadas temperaturas de post-antesis para el peso
final del grano, que se atribuyeron parcialmente a diferencias entre los grupos de cebadas de dos
y seis carreras. La presencia de G*E para la tasa de llenado se explicó por el efecto conjunto de
variables climáticas de pre-antesis, lo que sugirió que las diferencias genotípicas pudieran deberse
parcialmente a diferencias en el balance fuente/sumidero entre cebadas de dos y seis carreras en
antesis. La existencia de G*E para la duración del llenado pudo atribuirse principalmente a
diferencias en fecha de antesis entre genotipos, indicando la existencia de cierta estrategia de
escape causante de un alargamiento del periodo de llenado de algunos genotipos al final del ciclo
de cultivo.
La relación entre rendimiento y discriminación isotópica del carbono (A) en granos se
evaluó extensamente en un grupo de 22 ambientes (Capítulo V), y también se examinó la
posibilidad de utilizar la concentración de cenizas en tejidos aéreos como substituto de A
(Capítulo VI). La expresión genotipica del rendimiento fue condicionada por el ambiente de una
forma más acusada que la de A. La existencia de GXE para el rendimiento sugirió la presencia
de una interacción cualitativa cuyo punto de cruce cabría situarlo aproximadamente en
productividades medias inferiores a 3 t ha"1. Por el contrario, la clasificación de genotipos para
A no cambió substancialmente con el ambiente. En general, aquellos genotipos con bajos valores
de A y, por tanto, con elevadas eficiencias de transpiración, fueron superiores en ambientes poco
productivos (ambientes por debajo de 3 t ha"1), mientras que valores genotípicos de A elevados
se revelaron como ventajosos en ambientes de rendimientos medios y altos. Es probable que,
cuando la sequía es moderada, un importante sumidero reproductivo, típico de cultivares
modernos, fuerce la planta a incrementar su conductancia estomática y, en consecuencia, el agua
total utilizada. Este fenómeno probablemente invierte la relación negativa esperada entre A y
biomasa o rendimiento cuando la disponibilidad de agua es un factor limitante. Por otra parte,
XVll
la concentración mineral en granos estuvo relacionada frecuentemente y de forma negativa con
A, mientras que no se encontró relación entre la concentración mineral en paja y A. Estos
resultados sugieren que la acumulación mineral en tejidos aéreos muestreados al final del ciclo
de cultivo es independiente de la eficiencia de transpiración durante el llenado del grano. La
concentración de cenizas en granos podría utilizarse como criterio de selección complementario
a A en ambientes semiáridos, si bien es necesario un conocimiento fisiológico más profundo de
los mecanismos que afectan a la acumulación de minerales en el grano.
La sequía representa el principal factor limitante del crecimiento y la productividad de la
cebada en los secanos semiáridos mediterráneos. En el presente estudio, las diferencias en
productividad en un conjunto de 22 ambientes pudieron atribuirse en gran medida a diferencias
paralelas en disponibilidad hídrica desde siembra hasta antesis, período en el cual se determina
el número de granos por m2. La presencia de una interacción G*E de tipo cualitativo para el
rendimiento, así como las relaciones fluctuantes entre rendimiento y A, dependiendo de la
intensidad del estrés hídrico, sugieren que la tolerancia a la sequía y el elevado potencial de
rendimiento son conceptos antagónicos en cebada.
Barley (Hordeum vulgäre L.) is an important temperate cereal extensively cultivated in
Mediterranean climates. It can be grown successfully where the average annual rainfall exceeds
250 mm. Yield improvement for Mediterranean areas during the last decades has been slow
probably due to the limitation that drought and other abiotic stresses exert on plant growth. Future
increases in productivity may be accelerated by a better understanding of processes that control
growth and development and limit genotypic performance of barley provided water is scarce.
Thus, physiological research should have a considerable impact in the near future in increasing
the efficiency of traditional breeding programs. This thesis focusses on widening current
physiological knowledge of factors that curtail growth, productivity and quality of barley in
Mediterranean environments. To that end, a set often genetically diverse barley cultivare, which
includes two- and six-rowed types differing in adaptation to semiarid environments, has been
extensively evaluated in rainfed environments located in the province of Lleida (Northeastern
Spain) and, occasionally, in the provinces of Navarra (Northern Spain) and Valladolid (Central
Spain).
A subgroup of three high yielding, modern six-rowed genotypes (Barberousse, Orria and
Plaisant) was used initially to examine the effect of a decrease in the reproductive sink (i.e.,
number of grains per spike) on individual grain weight and growth, carbohydrate accumulation
and N uptake under semiarid conditions (Chapters I and II). Grain weight increases in response
to a 50% sink-reduction were progressively greater in environments with smaller control grains.
On the contrary, N accumulated uniformly across environments in response to sink manipulation.
These results suggest that grain yield is largely limited by carbohydrate supply (i.e., source
limited) during grain filling in poor rainfed environments, whereas protein accumulation into
growing grains seems independent of the environmental conditions in which grain filling
develops. The degree of such limitation to grain growth was consistently higher for those grains
placed in lateral spikelets of the barley ear, irrespective of the availability of assimilates for grain
filling. Such disadvantage of lateral grains could be ascribed mainly to lower dry matter
accumulation rates during grain filling.
The influence of abiotic stresses such as drought or high temperature in the context of the
grain filling process was further examined for the complete set often genotypes grown in 12
environments (Chapters III and IV). The final objective was to detect genetic variability and to
determine possible morphophysiological mechanisms for tolerance to these abiotic constraints.
Possible factors underlying genotype by environment interaction (GxE) for individual grain
weight (IGW), grain filling rate (GFR) and grain filling duration (GFD) were explored by means
of biadditive models. Differential genotypic sensitivities for IGW were found with respect to
post-anthesis drought and elevated temperatures, which could be partially attributed to the
difference between two- and six-rowed barleys. GXE for GFR could be partially explained by the
joint effect of pre-anthesis climatic variables, suggesting that variation in genotypic behaviour
for this trait may be caused by differences in source/sink balance between two- and six-rowed
genotypes at anthesis. In addition, GXE for GFD seemed to be driven mainly by differences in
anthesis date among genotypes, indicating the existence of an escape strategy lengthening the
grain filling period of selected culti vare at the end of the crop cycle.
The relationship between grain yield and carbon isotope discrimination (A) of mature
grains was thoroughly evaluated in a large set of 22 environments (Chapter V), and the feasibility
of using ash concentration in aboveground tissues as a surrogate of A explored (Chapter VI). The
genotypic expression for grain yield was considerably more affected by the environment than that
for A. GXE for grain yield suggested the existence of a crossover point at below 31 ha"1, whereas
genotypic ranking for A did not changed substantially across environments. Overall, genotypes
with lower A and, thus, with higher transpiration efficiency (TE), performed better in lowyielding
environments, i.e., those below the crossover point, while a high genotypic A was
advantageous in medium and high-yielding environments. It may be possible that, under
moderate drought, a large reproductive sink (typical of modern cultivars) force the plant to
increase its stomatal conductance and, consequently, its total water use. This phenomenon
probably overrides the expected negative relation between A and biomass or yield when water
is limiting. On the other hand, mineral concentration in mature grains was often negatively related
to A, and mineral accumulation in vegetative tissues was unrelated to A. Both results suggest that
mineral accumulation in aboveground tissues, sampled at maturity, is independent of the plant
TE during grain filling. Ash concentration in mature grains could be used as a complementary
criterion to A in semiarid environments, though a more accurate physiological understanding of
the mechanisms underlying mineral accumulation in grains is still needed.
Drought arises as the most limiting factor to barley growth and productivity in rainfed
Mediterranean environments. In the present study, differences in productivity in a set of 22
environments could be attributed largely to concomitant differences in water availability for
growth from sowing to anthesis, a period in which the number of grains m"2 is determined.
Presence of a crossover G*E interaction for grain yield, as well as changing relationships between
productivity and A depending on the intensity of water stress, suggest that drought tolerance and
yield potential are rather antagonistic concepts in barley.

The aim of this study was to characterise modern and historic barley varieties for agronomic and growth characteristics and to assess their resistance to Fusarium and mildew diseases. Barley is a major agricultural crop cultivated throughout the world providing an important source of energy and protein for humans and animals. To achieve its potential, however, it must be carefully managed to avoid diseases particularly those caused by fungi which can cause serious economic losses and affect food safety and quality. Contemporary barley varieties have been selected for yield and disease resistance. However, long term resistance to disease is increasingly difficult to achieve as microorganisms mutate and maintain their virulence. Investigating the potential of historic barley varieties as a genetic resource for future developments is one approach to obtaining novel attributes which may have been overlooked when breeding focused on yield rather than character of barley and on disease resistance. To examine the characteristics and disease resistance of historic barley varieties a series of investigations was conducted. Initially a screening was initiated by growing thirteen historic barley varieties and two modern barley varieties in a field trial in 2009. Growth features, yield and symptoms of mildew and Fusarium Head Blight (FHB) were scored and compared. This field experiment was repeated in 2010 with six of these varieties at the John Innes Centre by deliberately exposing the plants to F. culmorum Fu 42. A further experiment was conducted at the same time by growing seven varieties in glasshouse conditions at the University of Sunderland under inoculated and uninoculated conditions. From both growing seasons clear differences were found for the level of F. culmorum infection between the different barley cultivars with infection levels in heads ranging from 16% for Chevalier and 86.4% for Tipple barley varieties respectively. Nitrogen increased the level of FHB in all varieties possibly because ii of increased plant leaf number, tillers and humidity within the environment around the plant. Mycotoxin analysis showed that F. culmorum infection resulted in mycotoxin contamination of all varieties. However, levels of mycotoxin were significantly lower in Chevalier barley compared to other barley varieties including the two modern varieties, Tipple and Westminster. Observations using scanning electron microscopy indicated a different pattern of fungal growth in Chevalier barley with limited fungal development on both external and internal surfaces compared to other susceptible varieties. In general resistance against FHB disease depends on variable responses including plant physiology and morphology, antifungal compounds or resistance genes. Different flowering dates or flowering periods could be also considered reasons for different infection levels. However, in this study the duration of anthesis was not assessed and could be an important factor. Further experiments to identify the flowering times of different varieties could be considered for further research. The lower levels of disease associated with lower levels of mycotoxins and a reduced fungal development in Chevalier barley indicated that this variety has a strong resistance against FHB disease. This may be because of its late flowering and its tall height minimising colonisation from the soil. However, Chevalier barley was found to be very susceptible to powdery mildew disease, particularly in glasshouse studies. The potential of Chevalier barley to produce good malt was indicated when compared to modern varieties suggesting that Chevalier may be a valuable breeding stock for future developments.

Some physiological effects of freezing and flooding were studied on winter barley (Hordeum vulgare L.). The effects of freezing on plants grown under field conditions were determined by comparing plants exposed to naturally-occurring freezing temperatures with plants protected from such temperatures by thermostatically-controlled soil heating cables. The results from field trials in 1982/83 and 1983/84 showed the effects of freezing to include: (i) A reduction in the establishment of late-sown plants due to soil heaving. (ii) A retardation of plant and apical development. (iii) Occasional transient reductions in above ground dry matter and leaf area. (iv) Variable effects upon certain yield components. Attributes not greatly affected by such temperatures included cold hardiness and yield on a per plant basis. Controlled environment studies showed that non-lethal freezing temperatures ranging from -4 to -10oC significantly reduced shoot photosynthesis and dark respiration, the greater reductions being in photosynthesis. Factors involved in these reductions include damage to leaves and roots, neither of which were critical for plant survival. When a conductivity method was used to estimate the damage to different plant parts resulting from extracellular freezing, leaf laminae were found to be more freezing tolerant than roots, and young laminae were more tolerant than older laminae. Some effects of flooding were also studied using controlled environments, and cultivar differences in flooding tolerance were found. This tolerance was investigated by comparing the response to flooding of a tolerant cultivar (Athene) with a sensitive one (Maris Otter). Flooding sensitivity was shown as wilting in the leaves of Maris Otter, the onset of wilting being associated with the leakage of electrolytes and accumulation of ethanol in the leaf laminae. The results of exogenous application of ethanol to leaves, suggest the basis of this `tolerance' is ethanol exclusion. The production of aerenchyma was not associated with flooding tolerance.

Little is known about the crown system and its association with plant growth and development in spring cereals. This study investigated temperature, seeding depth and genotypic effects on crown development of barley; relationships between crown and seminal root systems; and classification and description of crown systems under deep seeding. Two greenhouse experiments were performed using PVC tubes. Low temperature and deep seeding reduced percentage and rate of emergence but increased crown number, crown depth, and crown weight in most genotypes. Crown number, crown depth and crown weight showed increased associations with seminal root, whole root, and shoot weight at low temperature and deep seeding in most genotypes. Deep plantings showed that crown systems of barley can be classified as unicrown, bicrown and multicrown types with some variants. One line produced plants with no subcrown internode under 12.5 cm planting. Our results suggested that the crown is a potential source of crown roots and tillers.

In this experiment, we used four male llamas that were three to four years of age from the Khara race. They were divided into two ad libitum feeding groups. The digestible energy (ED) was determined using samples that were sent to the laboratory. These samples were derived from a conventional in vivo assay using the method of total fecal collection in order to determine the difference between energy consumed and energy excreted. Metabolizable energy was calculated by deducting digestible energy, energy loss in the urine and energy loss in the gases (methane). Urinary energy was determined through the measurement of nitrogen in the urine as urea. Other studies have reported the energy values of alfalfa hay and barley as 414.05 Kcal/100g and 405.11 Kcal/100g, respectively. Additionally, alfalfa hay and barley have been recorded as having gross energy values of 6,973.92 Kcal/day and 4,373.65 Kcal/day, respectively. In this study, the energies excreted in the feces were 2,365.42 Kcal/day for alfalfa and 1,643.26 Kcal/day for barley. In order to determine the value of metabolizable energy, it is first necessary to obtain the urinary energy values (EU) by measuring the amount of nitrogen excretion as well as the energy of the gases (methane). Then, by deducting the energy calculated from the digestible energy, metabolizable energy may be estimated. The nitrogen content in urinary excretions from the llamas tested was highly variable from one treatment to another. With barley, the observed content was 0.59 g/day whereas with alfalfa hay it was 7.36 g/day. According to the data obtained for nitrogen content in urinary excretions, the amount of urea excreted each day was also obtained. It was also found to be variable from one food to another. Values of urea excretion for alfalfa and barley were 15.76 and 1.27 grams of urea/day respectively. By multiplying the daily amount of urea excreted by its caloric value (2.528 Kcal/g), the energy lost in the urine was determined to be 38.84 Kcal/day for alfalfa and 3.23 Kcal/day for barley. It was not possible to determine the energy of the gases. Instead, we used data obtained from llamas fed with forage (Engelhardt and Schneider, 1977). The data established that the energy loss as methane gas is approximately 7.1% of the gross energy. With this value as a reference for llamas, the energy losses as methane gas in this study were 495.08 Kcal/Kg/MS for alfalfa hay and 310.53 Kcal/Kg/MS for barley. By definition, the metabolic energy (EM) is the amount of energy from food that is calculated by determining the difference between the digestible energy (ED) and the energy lost in urine (EU) and gases (EG) according to the following equation (NRC, 1981): EM = ED - (EU + EG). Based on the equation, the metabolizable energy of alfalfa hay and barley are as follows: EB = 4140.49 Kcal/Kg/MS and EM = 2408.43 Kcal/Kg/MS for alfalfa compared to EB = 4051.20 Kcal/Kg/MS and EM = 2061.32 Kcal/Kg/MS for barley.

The main objective of this thesis dissertation is functionally characterizing the genes involved in biotic and abiotic stresses of plants at molecular level. Previously, upon pathogen attack Rad6 gene expression was found to be changed in wheat and barley plants. To functionally characterize the Rad6 gene, VIGS (Virus induced gene silencing) system was used. HR (Hypersensitive response) like symptoms was detected in every silenced barley and wheat plants. To figure out, transcriptomes and proteomes of Rad6 silenced plants were analyzed. 2-D PAGE analysis was also performed on silenced and control wheat plants. No pathogen growth was observed in Rad6 silenced barley lines. Additionally, the susceptible wild type Arabidopsis plants showed resistant phenotype when any of the Rad6 gene copies is mutated. This suggests that Rad6 gene has a negative regulatory role in plant disease resistance which was proved for the first time. Yeast two hybrid protein interaction study suggests that RAD6 carrying out its function by interacting with SGT1 protein and regulating resistance related genes. It has been first time reported in this thesis that E2 (Ubiquitin conjugating enzyme) takes role in plant disease resistance. Boron which is the other consideration in the scope of thesis as an abiotic stress factor at a very limited amount is necessary for the normal development of plants. This study is conducted on highly boron tolerant Gypsophila perfoliata L. collected from a location in the boron mining area. The plant samples were tested in the presence of high boron (35 mg/kg) concentrations. The transcriptomes of the plant samples treated with the excess levels of boron to that of the samples grown under normal concentration were compared using differential display PCR method. Thirty bands showing differential expression levels at varying time points were analyzed. 18 of them were confirmed via qRT-PCR.

Proposition d'un modele mecanique global du fonctionnement du canal semi-circulaire (csc) en considerant celui-ci comme une structure gonflable. Decomposition en un modele hydrostatique et un modele tenant compte des deplacements liquidiens sous l'action des contraintes internes et des variations de pression osmotique. Test sur un modele physique du csc et simulation sur ordinateur

博士
國立中興大學
植物學研究所
79
Water is one of the important environmental factors that effect plant growth. In Taiwan, the cultivations of field crops are often failed by the water stress due to the geographical and weather conditions. Therefore, it is necessary to understand the response of plants under water stress condition, and the relationship between drought-resistance and yield capacity for the purpose of improving the rotation system of cultivated crops. In the present experiment maize and barley were used as the materical. The following physiological and biochemical programs were studied: 1.The growth and physiology of photosynthesis of expanded leaves. 2.The significance of the changes in amount of sulutes inside expanding leaves and the growth functions under the condition water deficits and rewatering after water shortage. 3.The observations of the root/shoot ratio and the leaf size by using soil-sand culture under eaterstress condition. Moreover, to find out the possible factors which inhibited the leaf elongation 4.To search for the effects that water stress exerted on yield component of various crops. The results were summarized as follows: 1. The water potential and osmotic potential of expanded leaf of maize and barley displayed significant diurnal varivation under control and mild stress (-0.8 ~ -1.5 Mpa). The diurnal pattern of the osmotic potential of expanded leaf of all varienties, almost paralled to those of leaf water potential, thus maintaining the turgor level, thus because, the concentration of the major solutes of expanded leaf of all varieties, also exhibited a significant diurnal variations, and weren''t much changed by mild stress. The only change cuased by mild stress was starch/sucrose partitining ratio. 2. The photosynthetic rate, leaf conductance and leaf relative water content of each variety decreased with leaf water potential; and varied with varieties. The physiological responses could be used as indicators for selecting drought resistance. 3. Under moderate stress (-1.2 - -1.5 Mpa), the osmotic potential of expanded leaf of all varieties showed adjustable in various degree. The more drought-resitant strains, like maize TN11 and barley CB15, have much more solutes than those non-resisteant strains, like maize TNG351 and barley CH2. Therefore, osmoregulation can be maintaned and allowed to continue expansion growth under growth-inhibiting drought condition as well. 4. Leaf elongation is very sensitive to water shortage, and was inhibted under mild stress; For maize TN11, TNG351; barley CH2, CB15, leaf elongation ceased when predawn declined to -1.3 Mpa, -1.1 Mpa; -1.1 Mpa, -1.45 Mpa. Since the selongation of leaves os ,pre semsotove tp tje water supply, it gave a significant influence to the yield capacity, and it is so easily to dectate, so the response of LER (leaf elongation rate) to water stress, has become a useful indicator for screaring drought-resistant plants. 5. The Li+, Na+, K+ contents of the elongation leaves kept constant under the water stress condition. The orgainic compounds were accumulated significantly at early drought stage, and give a considerable influence to the osmotic adjustment. The earliest response to water deficits was the accumulation of soluble sugar content, then, the free amino acid. All these material were involved in osmotic adjustment. When the condition of water supply get worse, the extension growth of leaves had almost creased and metabolism of sugar and nitrogen compounds were also influenced. This showed that the necessity of growth is much related with the metabolism of feed back control. 6. As for the restoration of rewatering after water shortage, it give a corelation with crop varieties. The result showed, when the variety gave more drought-resistance, the leaves related with yield and physiological reactions, restored more healthy and stronger. 7. From the soil-sand culture, the result showed that the shoot growth of the plant under the water stress condition was reduced more than the root growth. This indicated that root-shoot ratio are increased by water stress. On the other hand, the cell wall extensibility were also decreased gradually after a long term of drought. Therefore, water deficits could also changed the leaf biophysical trait. 8. The important factors which effects the yield components are the time of water shortage and the degree of water stress. If the flower buds of plants were initaited under various water stress condition, then the grains per spike and panicle weight would be decreased, However, the plant height and panicle length were not influenad, consequently, the water are more short, the yield are more lower. When the period of plant internode elongation was under water shortage condition, the plant height was decreased significantly, the grains per spike and the weight of per 100 grains were also decreased. During the flowering stage, the water stress would influence the yield of grains per spike, the flowering date both barley and maize were delayed as well. In the milk-riping stage, the weight of per 100 graing would be effected by water stress, the seed filling period was also getting shorter. 水分為影響植物生長重要環境因子之一，但臺灣地理環境及氣象條件特殊，因此作物 仍常有缺水的危機，因此了解植物對缺水的反應、抗旱生理、缺水與產量構成因子之 關係，為推行稻田轉作之基礎工作之一． 本研究以生理學及生物化學為基礎，針對玉米、大麥進行下列四項探討： 1.輕中度缺水時，展開葉之生長、生理現象． 2.正展開葉片，於缺水、復水狀況下，其生長、容質消長情形及其所代表之意義． 3.利用盆栽砂土混合試驗，探討缺水時根／芽比，及葉面積變化，並進一步探討限制 伸長的可能原因． 4.探討缺水對產量構成因素之影響． 結果摘要如下： 1.供試材料玉米、大麥之對照植株及輕中度缺水植株（-0.8∼-1.5Mpa ），其展開葉 之葉片水分潛勢、滲透潛勢、均有日變化情形，且滲透潛勢日變化曲線，幾乎平行於 葉片水分潛勢日變化曲線線，而使葉片之膨至維持正值；此乃因葉內溶質含量亦有日 變化情形；輕中度缺水時，葉內溶質含量變化，未受嚴重影響，僅澱粉／蔗糖分配率 受影響． 2.各供試品種之淨光合率及葉片導度、葉片水分含量，均隨葉片水分潛勢下降而減小 ，且具品種間差異性存在，此差異性與品種之耐旱性有關；故缺水時，光合成機能之 持續力、及葉片水分含量，均可當耐旱性之重要指標， 3.中度缺水（-1.2∼-1.5Mpa ）時，各供試品種之展開葉均表現滲透調節象，且愈抗 旱之品種如玉米TN11、大麥CB15其葉內溶質累積量大於較不抗旱者，如玉米TNG351、 大麥CH2 ，因之較能發揮滲透調節作用，適當延緩缺水對葉片生長之影響． 4.葉片伸長速率，對植株水分狀況非常敏感．輕中度缺水時，葉片伸長已受抑制；玉 米TNG351；大麥CH2、CB15 分別於黎明前葉片水分潛勢（predawn ψ ） 為-1.3Mpa， -1.1Mpa；-1.1Mpa、-1.45Mpa時停止生長，由於葉片伸長對水分具高敏感性在加上 其測量容易及對產量具深遠影響，因此葉片伸長對缺水反應，為選擇抗旱之有效方法． 5.缺水時，各供試品種之正伸長葉，除 （圖表省略） 外，有機溶質累積現象明顯；且各種有機溶質對滲透調節貢獻各異，缺水初期，主要 由可溶性醣類，負責調節滲透潛勢，而後有游離胺基酸參與．但若缺水狀況持續惡化 ，則正伸長葉停止伸長，同時醣類代謝、氮素代謝亦受影響，因此生長需求與回饋性 抑制的代謝活動間有密切關係存在． 6.缺水後予以復水，其恢復能力，有品種間差異性存在．但愈抗旱之品種，復水後， 無論在生理反應上或與產量息息相關之葉面積上其恢復能力均較強． 7.盆栽砂土混合試驗顯示，斷水處理後，缺水植株，芽的生長要比根的生長易受缺水 影響，而導至根／芽比，產生顯著變化．且具品種差異性存在．除此而外，各供試品 種之葉片塑性變形值，亦因斷水處理而日益減少．因此很明顯地，缺水亦影響葉片之 生化物理特性． 8.缺水程度及缺水時期之不同，對產量及產量構成因子之影響各異．供試品種於幼穗 分化期，予以不同程度缺水時，產量構成因素中，以每穗粒數，穗重易受缺水影響． 而株高、穗長受缺水影響較小；缺水程度愈嚴重，產量降低愈明顯．節間快速伸長期 缺水，導致供試植株變矮，每穗粒數、百粒重均略為減少．開花期缺水，嚴重減少每 穗粒數，亦使玉米開花期至雌穗抽絲期、大麥之開花期延長．乳熟期缺水，常導致百 粒重減輕，並使各品種之榖粒充實期縮短．

Potassium (K+) is an essential nutrient and the most abundant cation in plant cells. Plants possess two transport systems for K+ acquisition: a high-affinity system (HATS), operating at external K+ concentrations ([K+]ext) below 1 mM, and showing reduced transport activity in the presence of ammonium (NH4+); and, a low-affinity system (LATS), operating at [K+]ext above 1 mM, that is not affected by NH4+. K+ transport and compartmentation were investigated in barley (Hordeum vulgare L.) and rice (Oryza sativa L.) using the non-invasive technique of compartmental analysis by tracer efflux (CATE), to simultaneously determine unidirectional membrane fluxes, ion concentrations, and exchange characteristics in subcellular compartments. These studies revealed striking differences in unidirectional K+ fluxes between HATS and LATS. It was found that flux measurements, using traditional direct influx (DI) protocols, accurately represented HATS influx, but underestimated LATS influx by as much as seven-fold. In both barley and rice, LATS K+ fluxes were found to undergo rapid, futile cycling, with the ratio of efflux:influx 3 to 5 times greater, and the cytosolic exchange rate 2 to 3 times faster than under HATS. Based upon plasma-membrane electrical potential measurements, efflux was found to be active under LATS conditions. LATS-mediated conditions for K+ were found to provide relief from NH4+ toxicity in barley by immediately reducing NH4+ influx by more than 50%, and significantly reducing NH4+ futile cycling. Employing the K+ channel inhibitors cesium, lanthanum, and tetraethylammonium, NH4+ was shown to have both K+-sensitive and –insensitive influx pathways at high [NH4+]ext. Based on current models of flux energetics, the combined uptake of K+ and NH4+ was found to utilize 60% of root oxygen consumption. Barley and rice both showed signs of NH4+ toxicity at low [K+]ext, but rice recovered at much lower [K+]ext, suggesting a crucial role of K+ in the NH4+-tolerance of rice. These experiments address fundamental aspects of K+ fluxes, and help provide a physiological framework for future studies of K+ transport and mineral nutrition.