Intense Water Deficit Research Articles

Early water-deficit effects on seminal roots morphology in barley

In order to study seminal roots morphology in barley grown under different water treatments, experiments were carried out under glasshouse-controlled conditions. Eight genotypes were cultivated under four water treatments (100, 75, 50 and 25% of field capacity). Seminal root length and root-to-shoot dry matters' ratio were measured. Root volume was assessed at three soil depths. Results showed broad genotypic differences for all traits. The effect of low and moderate water deficit was slight. In contrast, the impact of severe water treatment was strongly marked on all traits. The impact of water deficit intensity on root traits at different soil depths is discussed. To cite this article: M. Sahnoune et al., C. R. Biologies 327 (2004).

Using the CERES-Maize model in a semi-arid Mediterranean environment. New modelling of leaf area and water stress functions

The CERES-Maize model does not simulate satisfactorily the productivity under soil water scarcity. In a previous paper by Ben Nouna et al. (Eur. J. Agron. 13 (2000) 309), this poor performance was attributed to an inaccurate leaf surface simulation and to the water stress function. This paper proposes the introduction of two new modules in the original version of CERES-Maize model. For the LAI module, an analytical approach is followed, consisting of simulating the leaf area of each individual leaf, by the calibration of different functions (leaf appearance, leaf area growth, end of leaf growth, leaf senescence). The new stress function expresses the ratio of actual to maximum evapotranspiration rate as a function of an indicator of the plant water status (pre-dawn leaf water potential). The two modules have been separately introduced into the CERES model and the output compared with the observed values and those simulated by the CERES model in its original version. The results of validation showed that the revised LAI module improved the LAI prediction compared with the one of the original model. Moreover, for the purpose of generalising the new LAI module, its predictions were also compared with the LAI simulated by the Muchow et al. model (Agron. J. 87 (1990) 338), which has been calibrated at several latitudes with different maize varieties. As compared with the original version of CERES, the new water stress function gave a different prediction in terms of the timing and intensity of soil water deficit during the cropping cycle. The stress intensity, as calculated by the new function, was generally less severe than that simulated by the original version.

Reproductive Development of White Clover (Trifolium repens L.) is Not Impaired by a Moderate Water Deficit That Reduces Vegetative Growth: I. Inflorescence, Floret, and Ovule Production

Field experiments have shown that water deficit can either increase or decrease white clover (Trifolium repens L.) seed yield depending on its intensity. In order to explain this behavior, we evaluated the effect of water deficit intensity on the components of plant reproductive potential: number of reproductive stolons produced per plant (NSr), inflorescences per reproductive stolon (NI), viable florets per inflorescence (NFv) and ovules per floret (NO). Four experiments were conducted in greenhouse or growth chamber on white clover plants grown in large or small soil columns, or in small pots with vermiculite. Water supply was managed to maintain relatively constant values for predawn soil water potential and midday leaf relative water content (RWC) during the deficit period (20 to 68 d). Water deficit treatments were classified as moderate (M) or severe (S) on the basis of the reduction of RWC compared with the well‐watered plants (C) and of previously established relationships between RWC, soil water potential and vegetative growth. The development of inflorescences, florets and ovules were largely unaffected in M plants, while vegetative growth was depressed by reductions in leaf number per stolon (up to 30%), leaf area (30 to 40%), and by inhibition of stolon branching. Moderate water deficits induced an increase in the percentage of reproductive stolons per plant and reproductive phytomers per stolon. Although this positive effect on the reproductive to vegetative balance was generally observed with S water deficit, the reproductive potential of S plants was strongly depressed relative to C and M plants because of reduced stolon branching, phytomer production, and increased inflorescence and floret abortion. These results show that inflorescence, floret and ovule development of white clover were not impaired by a moderate water deficit that reduced vegetative growth, and suggest good prospects to manage optimal soil‐plant status to maximize potential of seed production.

Effects of water deficit on Mediterranean and temperate cultivars of tall fescue

Two glasshouse experiments were carried out to evaluate the morphological and physiological responses to water deficit of Mediterranean and temperate tall fescue (Festuca arundinacea Schreb.) cultivars. In Expt 1, 3 cultivars were studied: 2 temperate cultivars, Grasslands Advance (GA) and El Palenque (EP); and a Mediterranean cultivar, Maris Kasba (MK). Water deficit was induced in containers of 4 plants of a single cultivar by withholding water. In Expt 2, plants of EP and MK were grown together in the same container and received water daily with gradation in intensity of water deficit achieved by varying the daily water ration per container. All cultivars in each experiment exhibited commonly reported responses to water deficit, characterised by diminished evaporative surface area and increased root : shoot ratio. The response of MK was primarily morphological and MK plants had smaller plant size, higher root : shoot ratio, and a lower growth rate compared with temperate cultivars. By contrast, response of temperate cultivars was primarily physiological; stomatal conductance of temperate cultivars was lower and these cultivars had a greater tendency for leaf lamina osmotic adjustment than MK under the most stressful water deficit conditions studied. The morphological adaptations of MK were very effective in delaying the onset of water deficit in Expt 1 when plants were grown with others of the same cultivar, but rendered MK plants uncompetitive and more susceptible to water deficit in Expt 2 where plants of MK where interspersed with plants of a temperate cultivar.

Genetic purity analysis of hybrid broccoli (Brassica oleracea var. italica) seeds using RAPD PCR

Determination of genetic purity of F1-hybrid seeds is aquality control requirement in the production of hybrid Brassica vegetableseeds. Hybrid varieties of these vegetable crops have arisen from a limitedgermplasm base, making discrimination of parental and hybrid lines verylaborious and troublesome. The use of RAPD PCR for evaluating seed purity in acommercial F1-hybrid broccoli a single cultivar bywithholding water. In Expt 2, plants of EP and MK were grown together in thesame container and received water daily with gradation in intensity of waterdeficit achieved by varying the daily water ration per container.All cultivars in each experiment exhibited commonly reported responses towater deficit, characterised by diminished evaporative surface area andincreased root : shoot ratio. The response of MK was primarily morphologicaland MK plants had smaller plant size, higher root : shoot ratio, and a lowergrowth rate compared with temperate cultivars. By contrast, response oftemperate cultivars was primarily physiological; stomatal conductance oftemperate cultivars was lower and these cultivars had a greater tendency forleaf lamina osmotic a

The production and storage of a fermentor-grown bacterial culture containing Synergistes jonesii, for protecting cattle against mimosine and 3-hydroxy-4(1H)-pyridone toxicity from feeding on Leucaena leucocephala

The leguminous shrub Leucaena leucocephala (leucaena) iswidely used as a forage species for cattle in tropical agriculture. However,leucaena contains the toxic amino acid mimosine. Both mimosine and its primaryruminal degradation product 3-hydroxy-4(1H)-pyridone (DHP) are toxic and theiraccumulation in the animal’s system results in hair loss, reducedliveweight gain, and goitre. The ruminal bacteriumngle cultivar bywithholding water. In Expt 2, plants of EP and MK were grown together in thesame container and received water daily with gradation in intensity of waterdeficit achieved by varying the daily water ration per container.All cultivars in each experiment exhibited commonly reported responses towater deficit, characterised by diminished evaporative surface area andincreased root : shoot ratio. The response of MK was primarily morphologicaland MK plants had smaller plant size, higher root : shoot ratio,

Reproductive Development of White Clover ( L.) is Not Impaired by a Moderate Water Deficit That Reduces Vegetative Growth

Field experiments have shown that water deficit can either increase or decrease white clover (Trifolium repens L.) seed yield depending on its intensity. In order to explain this behavior, we evaluated the effect of water deficit intensity on the components of plant reproductive potential: number of reproductive stolons produced per plant (NSr), inflorescences per reproductive stolon (NI), viable florets per inflorescence (NFv) and ovules per floret (NO). Four experiments were conducted in greenhouse or growth chamber on white clover plants grown in large or small soil columns, or in small pots with vermiculite. Water supply was managed to maintain relatively constant values for predawn soil water potential and midday leaf relative water content (RWC) during the deficit period (20 to 68 d). Water deficit treatments were classified as moderate (M) or severe (S) on the basis of the reduction of RWC compared with the well-watered plants (C) and of previously established relationships between RWC, soil water potential and vegetative growth. The development of inflorescences, florets and ovules were largely unaffected in M plants, while vegetative growth was depressed by reductions in leaf number per stolon (up to 30%), leaf area (30 to 40%), and by inhibition of stolon branching. Moderate water deficits induced an increase in the percentage of reproductive stolons per plant and reproductive phytomers per stolon. Although this positive effect on the reproductive to vegetative balance was generally observed with S water deficit, the reproductive potential of S plants was strongly depressed relative to C and M plants because of reduced stolon branching, phytomer production, and increased inflorescence and floret abortion. These results show that inflorescence, floret and ovule development of white clover were not impaired by a moderate water deficit that reduced vegetative growth, and suggest good prospects to manage optimal soil-plant status to maximize potential of seed production.

Efeitos de potenciais de água no solo, em diferentes estádios fenológicos da cultura da cevada (Hordeum vulgare L.)

Objetivando avaliar os efeitos de défices hídricos, em três estádios fonológicos da cultura da cevada (Hordeum vulgare L.), foi conduzido experimento em vasos, com delineamento em blocos ao acaso. Foram utilizados nove tratamentos decorrentes da combinação dos potenciais mínimos de água no solo de -0,05, -0,20 e -1,50 MPa, com os estádios fenológicos de máximo perfilhamento, florescimento e grão leitoso, permanecendo uniformizados durante o restante do ciclo, entre os potenciais de -0,01 a -0,05 MPa. Os resultados de produção, peso e teor de proteína dos grãos, tamanho de espigas, número total e número de espigas chochas, mostraram que os efeitos de défices hídricos variaram com a intensidade, duração e estádio fenológico da cultura, onde o estádio de florescimento mostrou-se mais sensível ao défice de água. A ocorrência de défice hídrico intenso, em cada um dos estádios, bem como ciclos repetidos de défices moderados ou intensos, levaram à diminuições significativas na produção de grãos, além de ocorrer tendência ao aumento do teor de protema dos grãos. O manejo da irrigação na cultura da cevada, quando se busca a máxima eficiência no uso da água, deve levar em conta os diferentes estádios fenológicos.

Timing and Intensity of Water Deficits During Flowering and Grain‐Filling in Pearl Millet

AbstractYields of pearl millet [Pennisetum americanum (L.) Leeke]–a rainfed crop grown mainly on light soils in the semiarid and arid regions–are often reduced by water deficit when rains end early. The comparative response of this crop to varying intensity and timing of water deficit during flowering and grain‐filling was investigated in field experiments using a line‐source sprinkler system. The soil was an Alfisol (Udic Rhodustalf) with approximately 60 mm of plantextractable moisture. Genotypes differing in maturity were used to simulate differing timings of terminal stress. Grain yields were linearly reduced with increasing intensity of stress in all genotypes. Yield reduction rate was dependent on the time of stress onset in relation to time of flowering, as earlier‐flowering genotypes partially escaped stress. Grain number per unit area and grain size were reduced by intensity of water deficit. Grain yield and grain number, but not grain size, were affected by the time of stress onset at all intensities. Across the entire data set, stress intensity and timing accounted for 75% of the variation in measured grain yield. An advance in time of onset of stress by a day caused a 0.9% reduction in relative grain yield, compared to a 0.7% reduction in relative grain yield for each 1% additional irrigation deficit. Effects of timing of stress increased significantly with increase in stress intensity. The results emphasize the importance of timing and intensity of stress when comparing genotypes of different maturity groups using linesource gradient system, or when selecting genotypes for droughtprone environments

A Large-Area, Lightweight Rainshelter with Programmable Control

ABSTRACT IN order to implement water stress studies in the field where the probability of rain is significant, some type of rain excluding device must be used to assure the timeliness and intensity of plant water deficits. A rainshelter facility, which covers 0.13 ha (0.33 acres), has been constructed at the Kellogg Biological Station of Michigan State University for the study of plant growth response to soil water deficit. The facility consists of two buildings which run on a single drive system. The buildings are located at opposite ends of a set of tracks and move toward each other during rainfall. The ends of the buildings which face one another are open so that when the buildings meet in the center, they enclose the entire test plot. Once the buildings cover the plot, ventilation is provided by openings at the base of the walls and by a 17.8 cm (7 in.) wide lateral opening that runs the full length of the ridge of each building's roof. A programmable controller governs the movement of the buildings and performs constant checks on the system's status. This facility incorporates many features from other rainshelter designs that have performed satisfactorily. To our knowledge, it covers a larger area than any other previously constructed.

Moisture Deficits and Grain Sorghum Performance: Evapotranspiration‐Yield Relationships1

AbstractKnowledge of evapotranspiration‐yield (ET‐Y) relationships is fundamental in evaluating strategies for managing limited irrigation. The work reported here was done to develop ET‐Y functions for grain sorghum [Sorghum bicolor (L.) Moench], to provide base data for a water management improvement study in Nebraska. A field experiment was conducted using a modified line source sprinkler system to establish treatments that resulted in several different ET levels during each growth stage. The system was installed on a Valentine very fine sand (Typic Ustipsament) in west central Nebraska.The specific objectives of the study were: 1) to determine the crop evapotranspiration‐yield relationships for grain sorghum in this location, 2) determine how the timing and intensity of water deficits affect this relationship, 3) compare the evapotranspiration‐yield response of selected genotypes, and 4) to determine whether crop water use efficiency can be increased by judicious limited irrigation.In two seasons the relationship between evapotranspiration (ET) and grain yield (Y) or dry matter was linear. Evapotranspiration reduction under all conditions tested incurred some yield reduction. For a given genotype the slope of the ET‐Y relationship varied greatly depending on the growth period treatment. The lowest slopes were associated with a treatment in which stress built up steadily over the entire growing season. The slope was generally much steeper when irrigation was restricted to varying degrees for only a portion of the growing season. With greater yield reductions per unit of ET deficit, the latter treatments were considered suboptimal irrigation strategies compared to a gradual stress buildup.One hybrid had a lower slope of the ET‐Y relationship than the other genotypes for the treatment that provided water stress of gradually increasing severity. The percentage yield reductions were similar for all hybrids, however. The yield reduction ratios of the genotypes were different for the two growing seasons.Water use efficiency consistently decreased as ET declined below the maximum. It appeared that water stress, regardless of timing, tended to reduce water use efficiency. The reductions were smallest when stress increased gradually throughout the growing season.

Variação do regime de umidade do solo durante o ciclo fenológico de plantas de batata

Neste trabalho foram analisadas as relações entre a produção, o desenvolvimento vegetativo e a evapotranspiração de uma cultura de batata (Solanum tuberosum L.) submetida à três regimes de umidade, definidos pelos valores assumidos pelo potencial matricial da água do solo antes de se proceder as irrigações (-0,5; -1,0 e -5,0 bares) em três estádios de desenvolvimento das plantas. Com respeito à produção de tubérculos, ficou evidenciado que por ocasião da tuberização e desenvolvimento de um grande número de tubérculos, as plantas revelaram uma maior sensibilidade à redução da umidade do solo. Assim, ocorrendo deficits moderados (-1,0 bar) no período inicial de desenvolvimento, a produção não foi significativamente afetada. Isto foi atribuído, em parte, à recuperação parcial do crescimento vegetativo no estádio subseqüente, quando foram restabelecidas condições mais adequadas de umidade no solo. O mesmo não se verificou no tratamento submetido a deficits mais severos (-5,0 bares) no estádio inicial. Neste caso, o crescimento foi quase irreversivelmente reduzido, contribuindo para diminuir a produção e a eficiência de utilização de água pelas plantas. A redução da umidade do solo, a partir dos 60 dias após a emergência das plantas, não afetou a produção de tubérculos. Este procedimento concorreu para aumentar significativamente a eficiência de utilização de água. Além disso, havendo suspensão total da irrigação neste período, a senescência foi antecipada em 16 dias, em relação aos tratamentos submetidos a níveis de umidade mais elevados. O desenvolvimento vegetativo e a produção não foram igualmente afetados pela redução da umidade do solo. Conseqüentemente, o crescimento das plantas não parece se constituir em um índice absoluto da produção de tubérculos de batata.