Letteratura scientifica selezionata sul tema "Barley Physiology"

Barley (Hordeum vulgare L.) is the most susceptible cereal species to excess moisture stress. Waterlogging-induced hypoxia causes major morphological, physiological, and metabolic changes, some of which are regulated by the action of plant growth regulators and signal molecules including nitric oxide. Recent studies have evidenced the participation of phytoglobins in attenuating hypoxic stress during conditions of excessive moisture through their ability to scavenge nitric oxide and influence the synthesis and response of growth regulators. This review will highlight major cellular changes linked to plant responses to waterlogging stress with emphasis on phytoglobins.

AbstractModern hulless wheats, Triticum aestivum L., are more susceptible to the wheat midge, Sitodiplosis mosellana (Géhin), than the hulled, wild, ancestral species. Hulless cultivars of barley, Hordeum vulgare L., are becoming more widely grown in western Canada than in the past. Hulled and hulless cultivars of two-rowed and six-rowed barleys were tested for their susceptibility to wheat midge, to determine if this midge might become a serious pest of barley and to assess which plant traits might affect host suitability. In the field, larval populations on 10 barley cultivars were much lower than on wheat. In the laboratory, when the flag leaf sheath was peeled back to expose preflowering spikes, female midges readily oviposited on spikes of barley, although less so on younger spikes. Few larvae were able to develop on barley when eggs were laid after spikes had flowered. All barleys completed flowering, or nearly so, before spikes emerged from the flag leaf sheath, with two-rowed cultivars flowering earlier than six-rowed barleys. No differences in larval densities were found between hulless and hulled barleys, and therefore, factors other than the hulled trait must account for reduced susceptibility of barley. Because barley flowers within the flag leaf sheath, its period of susceptibility to infestation is much shorter than for wheat, as evidenced by reduced infestation of earlier-flowering two-rowed cultivars compared with later-flowering six-rowed cultivars. Also, the tight closure of the leaf-like glumes that form the florets of barley probably makes access to young seeds more difficult for newly hatched larvae than is the case for wheat. At comparable crop growth stages, larval densities on all the barleys were < 10% of those on spring wheat. The introduction of hulless barley for production in Canada is unlikely to increase wheat midge damage on barley to an economic level.

Background. Barley is the second cereal crop in Russia in terms of its importance and production volume. It is used for food, feed, and industrial purposes. The production of malting barley in Russia exceeds 1.5 million tons; each year the area under this crop increases by 10–15%, reaching 600,000– 800,000 hectares. Barleys suitable for brewing must have certain physicochemical and technological properties. The main requirements for raw materials are presented in GOST 5060-86 (state standard for malting barley). An important condition for obtaining sustainable harvests is the development and utilization of cultivars resistant to a set of edaphic stressors. The purpose of this work was searching for resistant cultivars for use in targeted breeding.Materials and methods. The material for the study included 161 spring barley cultivars for brewing from the collection of plant genetic resources held by VIR. The laboratory assessment of aluminum tolerance in barley accessions was carried out at the initial phases of plant growth and development, using the method of calculating root and shoot length indices. The tested malting barley was classified into five resistance groups.Results and conclusions. Cultivars resistant to Al3+ ions were identified among different ecogeographic groups of malting barleys. The trait had a wide range of variability in terms of both the root length index (0.17–0.95) and shoot length index (0.47–0.99). Accessions with high resistance to ionic (Al3+) stress can be used in barley breeding targeted at the development of high-yielding malting cultivars most adapted to harmful environmental factors.

Climate change from elevated [CO2] may reduce water availability to crops through changes in precipitation and higher temperatures. However, agriculture already accounts for 70% of human consumption of water. Stomata, pores in the leaf surface, mediate exchange of water and CO2 for the plant. In crops including barley, the speed of stomatal response to changing environmental conditions is as important as maximal responses and can thus affect water use efficiency. Wild barleys and landraces which predate modern elite lines offer the breeder the potential to find unexploited genetic diversity. This study aimed to characterize natural variation in stomatal anatomy and leaf physiology and to link these variations to yield. Wild, landrace and elite barleys were grown in a polytunnel and a controlled environment chamber. Physiological responses to changing environments were measured, along with stomatal anatomy and yield. The elite barley lines did not have the fastest or largest physiological responses to light nor always the highest yields. There was variation in stomatal anatomy, but no link between stomatal size and density. The evidence suggests that high photosynthetic capacity does not translate into yield, and that landraces and wild barleys have unexploited physiological responses that should interest breeders.

Abstract The potential to increase barley grain yield lies in the indeterminate nature of its inflorescence meristem, which produces spikelets, the basic reproductive unit in grasses that are linked to reproductive success. During early reproductive growth, barley spikes pass through the maximum yield potential—a stage after which no new spikelet ridges are produced. Subsequently, spikelet abortion (SA), a phenomenon in which spikelets abort during spike growth, imposes a bottleneck for increasing the grain yield potential. Here, we studied the potential of main culm spikes by counting potential spikelet number (PSN) and final spikelet number (FSN), and computed the corresponding SA (%) in a panel of 417 six-rowed spring barleys. Our phenotypic data analyses showed a significantly large within- and across-years genotypic variation with high broad-sense heritability estimates for all the investigated traits, including SA. Asian accessions displayed the lowest SA, indicating the presence of favourable alleles that may be exploited in breeding programs. A significantly negative Pearson’s product–moment correlation was observed between FSN and SA. Our path analysis revealed that PSN and FSN explain 93% of the observed phenotypic variability for SA, with PSN behaving as a suppressor trait that magnifies the effect of FSN. Based on a large set of diverse barley accessions, our results provide a deeper phenotypic understanding of the quantitative genetic nature of SA, its association with traits of high agronomic importance, and a resource for further genetic analyses.

Climate change is a major threat to most of the agricultural crops grown in tropical and sub-tropical areas globally. Drought stress is one of the consequences of climate change that has a negative impact on crop growth and yield. In the past, many simulation models were proposed to predict climate change and drought occurrences, and it is extremely important to improve essential crops to meet the challenges of drought stress which limits crop productivity and production. Wheat and barley are among the most common and widely used crops due to their economic and social values. Many parts of the world depend on these two crops for food and feed, and both crops are vulnerable to drought stress. Improving drought stress tolerance is a very challenging task for wheat and barley researchers and more research is needed to better understand this stress. The progress made in understanding drought tolerance is due to advances in three main research areas: physiology, breeding, and genetic research. The physiology research focused on the physiological and biochemical metabolic pathways that plants use when exposed to drought stress. New wheat and barley genotypes having a high degree of drought tolerance are produced through breeding by making crosses from promising drought-tolerant genotypes and selecting among their progeny. Also, identifying genes contributing to drought tolerance is very important. Previous studies showed that drought tolerance is a polygenic trait and genetic constitution will help to dissect the gene network(s) controlling drought tolerance. This review explores the recent advances in these three research areas to improve drought tolerance in wheat and barley.

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.

In the Event of Women outlines the stakes of what Tani Barlow calls “the event of women.” Focusing on the era of the late nineteenth century through the mid-twentieth century's Cultural Revolution, Barlow shows that an event is a politically inspired action to install a newly discovered truth, in this case the mammal origins of human social evolution. Highbrow and lowbrow social theory circulating in Chinese urban print media placed humanity's origin story in relation to commercial capital's modern advertising industry and the conclusion that women's liberation involved selling, buying, and advertising industrial commodities. The political struggle over how the truth of women in China would be performed and understood, Barlow shows, means in part that an event of women was likely global because its truth is vested in biology and physiology. In so doing, she reveals the ways in which historical universals are effected in places where truth claims are not usually sought. This book reconsiders Alain Badiou's concept of the event; particularly the question of whose political moment marks newly discovered truths.

The variability of quantitative traits (plant height, spike length, apical internode length, number of spikelets and grains per spike, number of productive tillers per plant) in barley calcaroides mutant of cv. Sonor induced by gamma rays (250 Gy) has been studied. The analysis of variance showed that year condi-tions were mainly responsible (10.59 to 46.96%) for variation of studied traits, followed by the genotype (1.48 to 20.5%) and the interaction of these factors (1.94 to 8.64%), with only one exception for number of grains per spike. Variation of this trait depends mostly on genotype factors. The mean values of all studied traits of mutant form were lower than of Sonor variety. This morphological mutant has a scientific importance.