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1.
A challenge to breeding drought‐tolerant barley in the Middle‐East is that precipitation and evaporative demand patterns dictate opposite water use strategies (conservative vs. risk‐taking). To characterize these strategies, we examined high‐resolution, whole‐plant transpiration rate (TR) responses to increasing vapour pressure deficit (VPD) and nocturnal TR (TRN) dynamics among 25 local barley genotypes, using a novel phenotyping system. These traits were specifically selected because they exist under modalities enabling the expression of both strategies. The genotypes were selected from locations spread across a large aridity gradient represented by temperature and precipitation data spanning 30 years. Here, we uncovered a substantial diversity in TR responses to VPD where slopes of the linear responses correlated negatively with local maximal temperatures, pointing to opposite drought tolerance strategies. Low canopy conductance (low slopes) was associated with higher aridity, likely to enable water‐saving, while higher conductance was associated with wetter areas, likely to enable a more aggressive water use to maximize physiological activity. TRN was highly diverse and represented up to 15% of maximal daytime TR, pointing to the possibility of increasing water‐saving by reducing TRN. Furthermore, we detected pre‐dawn variation in TRN that negatively correlated with local precipitation, indicating that a tighter circadian control is associated with adaptation to drought, consistently with a circadian resonance mechanism. These findings indicate that canopy conductance and TRN are potentially beneficial to design drought‐tolerant barley germplasm adapted to different drought regimes taking place in the Middle‐East.  相似文献   

2.
Maize (Zea mays L.) yield is often restricted by low soil water availability, particularly late in the growing season. To increase yields, genetic options for more effective use of available soil water are being explored. One option is to select genotypes that have restricted transpiration rate under high vapour pressure deficit (VPD) conditions so that soil water is conserved for use later in the growing season. While genetic variation for this trait has been identified within several crop species, such variation has never been explored in maize. The objective of this study was to examine transpiration rate of 35 single‐cross hybrids to determine whether hybrids can be identified that express limited transpiration under high VPD. Two sets of experiments were undertaken in which plants were exposed to a range of VPD in chambers. A two‐phase transpiration response was observed in 11 hybrids in which there was a threshold VPD above which transpiration rate was restricted. The VPD threshold varied from 1.7 to 2.5 kPa among these hybrids. Eight hybrids were included in both sets of experiments, and the same results were obtained in both experiments, indicating that expression of the trait was consistent.  相似文献   

3.
Historically, wheat yields in drought‐prone Australian environments have been consistently increasing for over a century. There is currently an agreement that approximately half of that increase is attributable to breeding programmes, but their physiological basis remains poorly documented. In this investigation, we hypothesized that limited whole‐plant transpiration rate (TR) under high atmospheric vapour pressure deficit (VPD) could result in advantageous water conservation and crop yield increase under south Australian conditions. Therefore, TR response to VPD was measured in the 0.9–3.2 kPa range for a group of 23 wheat cultivars that were released from 1890 to 2008. Consistent with a water‐conservation hypothesis, all genotypes displayed a VPD break point (BP) in TR with increasing VPD such that TR was limited at VPD above a BP of about 2 kPa. The BP and slope of TR with increasing VPD above the break point were correlated with the year of release, although the changes were in different directions. Such changes in these transpiration parameters were independent of plant leaf area and only marginally correlated with Zadok's stages. These results indicated that selection over 120 years by breeders for yield increase unconsciously resulted in genotype selection for the expression of the limited‐TR trait.  相似文献   

4.
The rise of atmospheric CO2 concentration ([CO2]) affects stomatal conductance and thus transpiration and leaf temperature. We evaluated the effect of elevated [CO2] levels under different water supply on daily sap flow and canopy microclimate (air temperature (Tc) and vapour pressure deficit (VPD)) of maize. The crop was cultivated in circular field plots under ambient (AMB, 378 μmol mol?1) and elevated [CO2] (FACE, 550 μmol mol?1) using free‐air CO2 enrichment with sufficient water in 2007, while in 2008 a DRY semicircle received only half as much water as compared to the WET semicircle from mid of July. In 2007, sap flow was measured in WET simultaneously under AMB and FACE conditions and was significantly decreased by elevated [CO2]. In 2008, sap flow was measured in all four treatments but not simultaneously. Therefore, data were correlated with potential evaporation and the slopes were used to determine treatment effects. Drought reduced whole‐plant transpiration by 50 % and 37 % as compared to WET conditions under AMB and FACE, respectively. Moreover, CO2 enrichment did not affect sap flow under drought but decreased it under WET by 20 % averaged over both years. The saving of water in the period before the drought treatment resulted in a displacement of dry soil conditions under FACE as compared to AMB. Under WET, CO2 enrichment always increased Tc and VPD during the day. Under DRY, FACE plots were warmer and drier most of the time in August, but cooler and damper short after the start of drought in July and from the end of August onwards. Thus, the CO2 effect on transpiration under drought was variable and detectable rather easy by measuring canopy microclimate.  相似文献   

5.
An accurate estimation of stomatal resistance (rS) also under drought stress conditions is of pivotal importance for any process‐based prediction of transpiration and the energy budget of real crop canopies and quantification of drought stress. A new model for rS was developed and parameterized for winter wheat using data from field experiments accounting for the influences of net radiation (RNet), air temperature (TAir) and vapour pressure deficit of the atmosphere (VPD) interacting with an average water potential in the rooted soil (ψRootedSoil). rS is simulated with a limiting factor approach as maximum of the metabolic (related to photosynthesis) and hydraulic (related to drought stress) acting influences assuming that, if drought stress occurs, it will dominate stomatal control: rS = max(rS(TAir), rS(RNet), rS(VPD, ψRootedSoil)). This transitional approach is suited to reproduce measured daily time courses of rS with a varying accuracy for the single measurement dates but performed satisfactorily for the whole data set (r2 = 0.63, RMSE = 59 s m?1, EF = 0.60). This new semi‐empiric approach calculates rS directly from external environmental conditions. Therefore, it can be easily implemented in existing model frameworks as link between operational crop growth models that use the concept of radiation use efficiency instead of mechanistic photosynthesis modelling and soil–vegetation–atmosphere transport models.  相似文献   

6.
The relationship between biomass production and N2 fixation under drought‐stress conditions in peanut genotypes with different levels of drought resistance is not well understood. The objective of this study was to determine the effect of drought on biomass production and N2 fixation by evaluating the relative values of these two traits under well watered and water‐stress conditions. Twelve peanut genotypes were tested under field conditions in the dry seasons of 2003/2004 and 2004/2005 in north‐east Thailand. A split‐plot design with four replications was used. Main‐plot treatments were three water regimes [field capacity (FC), 2/3 available soil water (AW) and 1/3 AW], and sub‐plot treatments were 12 peanut lines. Data were recorded on biomass production and N2 fixation under well watered and water‐stress conditions. Genotypic variations in biomass production and N2 fixation were found at all water regimes. Biomass production and N2 fixation decreased with increasing levels of drought stress. Genotypes did not significantly differ in reductions for biomass production, but did differ for reductions in N2 fixation. High biomass production under both mild and severe drought‐stress conditions was due largely to high potential biomass production under well‐watered conditions and, to a lesser extent, the ability to maintain high biomass production under drought‐stress conditions. High N2 fixation under drought stress also was due largely to high N2 fixation under well‐watered conditions with significant but lower contributions from the ability to maintain high nitrogen fixation under drought stress. N2 fixation at FC was not correlated with the reduction in N2 fixation at 2/3 AW and 1/3 AW. Positive relationships between N2 fixed and biomass production of the tested peanut genotypes were found at both levels of drought stress, and the relationship was stronger the more severe the drought stress. These results suggested that the ability to maintain high N2 fixation under drought stress could aid peanut genotypes in maintaining high yield under water‐limited conditions.  相似文献   

7.
Quinoa (ChenopodiumquinoaWilld.) is a highly nutritious Andean seed crop which shows great potential to grow under a range of hostile environments. The objective of this study was to investigate the differences of drought tolerance of a Bolivian (Achachino) and a Danish (Titicaca) variety, and especially drought‐related adaption strategies. Soil water status was expressed as the fraction of transpirable soil water (FTSW). Relative stomatal conductance (RSC), relative transpiration (RT) and relative leaf water potential (RLW) were calculated by determining stomatal conductance, transpiration rate and leaf water potential of the drought‐treated plants relative to those of fully irrigated plants. The responses of RSC, RT and RLW to decreasing FTSW were described by a linear‐plateau model. The critical value of FTSW was the threshold of FTSW where the parameters studied decreased. The thresholds increased CS for stomatal conductance, CT for transpiration and CLfor leaf water potential. Achachino showed significantly lower CT and CL when compared with Titicaca, implying that transpiration and leaf water potential were less affected under mild drought conditions in the Bolivian variety. CS in Achachino was significantly higher than CL and CT, which indicated that stomatal conductance declined before transpiration and leaf water potential were reduced. Such difference was found in Titicaca where reduction of leaf area had more effect on transpiration than stomatal closure. Slower growth rate and smaller leaf area in combination with a lower stomatal conductance was found to contribute to drought resistance in Achachino. ABA concentration in the xylem sap tended to increase in both varieties after 2 days onset of drought, prior to decline in leaf water potential. Titicaca showed significantly (P < 0.05) higher ABA concentration when compared with Achachino under both fully irrigated and drought conditions. Titicaca had higher xylem nutrient concentration in comparison with Achachino in both fully‐watered and drought plants at day 2 after onset of soil drying. It was concluded that Titicaca was more sensitive to progressive drought than Achachino which avoided water loss by means of lower growth rate and smaller leaf area.  相似文献   

8.
This study investigated the relationship between osmotic potential at full hydration (π100) and turgor loss point (ΨTLP) in wheat (Triticum aestivum) to determine the potential of using π100 to predict ΨTLP under well‐watered (WW) and drought (WS) conditions. Two methods for determining π100 were tested: pressure–volume (PV) analysis and freezing point osmometry. The study also measured π100 in a range of 38 field‐grown wheat cultivars to determine whether there is genetic variation in π100 under field conditions. π100 correlated with ΨTLP using both methods under both water treatments, particularly WS. Genetic variation of π100 in the field, under rainfed conditions, was greater than controlled conditions and ranged from ?0.94 to ?1.95 MPa. Overall, the evidence supports development of π100 as a novel tool for plant breeders to screen large populations of wheat and identify genotypes with lower ΨTLP, an integrative trait that is related to drought tolerance.  相似文献   

9.
This study was conducted to evaluate the types of gene action governing the inheritance of resistance to peanut bud necrosis disease (PBND) in populations derived from three crosses involving two resistant (ICGV 86388 and IC 10) and one susceptible (KK 60–1) peanut lines. Populations were composed of P1 P2, F1 F2, BC11, BC12, BC11S and BC12S. These populations were evaluated for PBND incidence in a farmer's field in Kalasin province in north‐east Thailand, where PBND is a recurring problem. Results showed variations between crosses in the relative contributions of different types of gene effect. The results indicate that multiple genes control the PBND resistance trait, and that the two resistant lines differ in some of these genes. As non‐additive gene effects are important in all three crosses, selection for low PBND incidence in these crosses would be more effective in later generations.  相似文献   

10.
The ability of a plant to modify its root distribution to exploit deeper stored soil water may be an important mechanism to avoid drought. This study aimed at assessing root distributions, variations in root length density (RLD) and percentage of root distribution, and the relevance of root traits for yield of drought‐resistant peanut genotypes under different available soil water levels. The experiment was conducted in the dry season during the years 2003/04 and 2004/05. Eleven peanut genotypes (ICGV 98300, ICGV 98303, ICGV 98305, ICGV 98308, ICGV 98324, ICGV 98330, ICGV 98348, ICGV 98353, Tainan 9, KK 60‐3 and Tifton‐8) and three soil moisture levels [field capacity (FC), 2/3 available soil water (AW) and 1/3 AW] were laid out in a split‐plot design with four replications. Roots were sampled by a core sampler at 37, 67 and 97 days after sowing (DAS). Root length was determined by a scanner and the WINRHIZO Pro 2004a software. RLD was calculated as the ratio of root length (cm) and soil volume (cm3). Graphical illustration of root distribution was constructed by merging RLD in the first and second soil layers (0–40 cm) as upper roots and pooling RLD at the third, fourth and fifth layers (40–100 cm) as lower roots. Pod yield, biomass and harvest index (HI) were recorded at harvest. A drought tolerance index (DTI) was calculated for each parameter as the ratio of the parameter under stress treatment to that under well‐watered conditions. Variations in RLD in 40 to 100 cm layer (RLD40 to 100 cm) were found under well‐watered conditions, and the peanut genotypes could be readily identified as high, intermediate and low for this trait. Changes in RLD in the 40 to 100 cm soil layer were found at 2/3 AW and were more evident at 1/3 AW. ICGV 98300, ICGV 98303, ICGV 98305, ICGV 98308 and KK 60‐3 were classified as drought responsive as they increased RLD in the deeper subsoil level in response to drought. In general, RLD under drought conditions was not related to biomass production. The ability to maintain the percentage of RLD (DTI for %RLD) was related to pod yield, DTI for pod yield and DTI for HI. ICGV 98300, ICGV 98303, ICGV 98305 exhibited high DTI (RLD40 to 100 cm) which may explain their high pod yield, DTI (PY) and DTI (HI). Based on these observations we classified them as drought‐avoiding genotypes.  相似文献   

11.
Drought adaptation strategies of two bambara groundnut landraces, Uniswa Red and S19‐3, collected from contrasting environments in Africa, were compared. Our objectives were to investigate the relative significance of effective stomatal control induced by the abscisic acid (ABA) signalling and osmotic adjustment in regulating plant water relations in general for this legume species. The ABA concentration [ABA] in the leaf increased linearly with declining relative leaf water content, and there were significantly higher [ABA] in Uniswa Red compared with S19‐3 at the final harvest in the drought‐stressed plants. Estimated by a linear‐plateau model, S19‐3 initiated the reduction in transpiration at a significantly lower soil water threshold (FTSW = 0.50 ± 0.024) than Uniswa Red (FTSW = 0.69 ± 0.023) indicating that the latter was more sensitive in reducing plant water use in response to soil drying. A similar trend was found for stomatal closure during soil drying, although the soil water thresholds at which relative stomatal conductance (gs) started to decline were not significantly different between the two landraces. By an early closure of stomata and hence an early reduction in transpiration rate during soil drying, Uniswa Red could be defined as a ‘water‐saver’ such that it maintains leaf water status to a great extent of soil water deficit. This strategy is important for survival during intermittent drought. While S19‐3 could be defined as a ‘water‐spender’ with a late closure of stomata, hence a late declining of transpiration rate during soil drying allowed the landrace to maximize its water use despite giving up its leaf water relations. Such drought response together with a fast phenological development of S19‐3 indicates that the landrace is capable of escaping from terminal drought while maximizing its water use and productivity when soil water is available.  相似文献   

12.
Phenoxy herbicides such as 2,4‐dichlorophenoxy acetic acid (2,4‐D) and 4‐chloro‐2‐methylphenoxy acetic acid (MCPA) are selective herbicides used extensively in agriculture for weed control. Wild radish (Raphanus raphanistrum) is a problem weed across the globe and heavily infests crop fields in Australia. Phenoxy herbicides are used to selectively control dicot weeds, including wild radish. As a result of selection, phenoxy‐resistant wild radish populations evolved in Western Australia. In this research, introgression of phenoxy resistance from wild radish to cultivated radish (Raphanus sativus) was investigated following classical breeding procedures. F1 progeny were generated by crossing MCPA‐resistant R. raphanistrum and MCPA‐susceptible R. sativus. F1 hybrids were screened for MCPA resistance. The MCPA‐resistant F1 hybrids were used to produce three generations of backcross progeny. Genetic analyses of F1 and backcross progeny demonstrated introgression of the MCPA‐resistant trait from wild radish to cultivated radish. Implications of phenoxy resistance introgression into cultivated radish include potential development of herbicide‐tolerant radish cultivars or other members of the Brassicaceae family.  相似文献   

13.
Beet mosaic virus (BtMV) is an aphid transmitted, viral disease of beet found worldwide. The Bm gene, a resistance gene effective against BtMV, was identified in the sugar beet line 8500 and backcrossed into a C37 background to produce line C719. Three populations were developed from the cross of line C719 with the susceptible line C37 with the intent of developing markers for use in marker‐assisted selection. The F2 progeny of three crosses were scored for resistance. Two of the three populations conformed to a 3 : 1 ratio, indicating a single gene trait. Sequence characterized amplified region (SCAR) markers were developed by using bulked segregant analysis combined with random amplified polymorphic DNA type markers. The markers showed close association to the Bm resistance gene and were effective in all three populations. The A1 allele for genetic male sterility also was found to be associated with Bm and the SCAR marker. Development of a single‐nucleotide polymorphism marker from the SCAR sequence was used to validate linkage to chromosome 1 using separate mapping populations. This marker will be useful for the introgression of the Bm gene into germplasm.  相似文献   

14.
Carbon isotope discrimination (Δ) has been proposed as an indirect selection criterion for transpiration efficiency and grain yield in wheat. However, because of high cost for Δ analysis, attempts have been made to identify alternative screening criteria. Ash content (ma) has been proposed as an alternative criterion for Δ in wheat and barley. A pot experiment was conducted to analyse the relationship between Δ, mineral content and gas exchange parameters in seedlings and leaves of bread wheat (Triticum aestivum L.). Plants of 10 genotypes were cultivated under three different water regimes corresponding to moderate (T3), intermediate (T2) and severe drought (T1) stress obtained by maintaining soil humidity at 75 %, 55 % and 45 % of the humidity at field capacity respectively. Δ and ma in seedlings and leaves showed significant differences among the three water treatments. Significant positive correlations were found between Δ and ma in seedlings and leaves at elongation and anthesis stages in severe drought stress (T1). Δ was negatively associated with potassium (K) content in intermediate drought stress (T2) and positively with magnesium (Mg) content in T2 and T3 (moderate drought stress) in flag leaf at anthesis. There were negative correlations between Δ and single‐leaf intrinsic water‐use efficiency (WT) in T2 and T3 at anthesis stage. Stronger positive associations were noted between Δ and stomatal conductance (gs) in T1 and T2 than in T3 at anthesis. These results suggested that Δ is a good trait as an indirect selection criterion for genotypic improvement in transpiration efficiency, while ma is a possible alternative criterion of Δ in wheat vegetative organs, especially in stressed environments. Significant association was found between Δ and K, Mg and Ca contents that would merit being better investigated.  相似文献   

15.
Environmental stresses such as chilling temperatures can decrease germination, emergence, flower and fruit development, marketable yield, and postharvest fruit storage longevity in cucumber (Cucumis sativus L.). While response to chilling injury in cucumber is controlled by simple plastidic (maternal) and nuclear (paternal) factors, no chilling tolerant U.S. processing varieties are commercially available. Furthermore, even though three single nucleotide polymorphic sites have been identified as plastid components associated with chilling tolerance in cucumber, it is not known how these factors interact with nuclear factors controlling economically important traits. Therefore, an experiment was designed to evaluate the rate of recovery of the chilling susceptible (cytoplasm) genotype during introgression backcrossing (IB), where it was used as a recurrent parent after the initial mating to a line possessing chilling tolerant cytoplasm (donor parent). Phenotypic yield and quality trait data were collected on processing type backcross progeny (BC1–5 and BC2S3) derived from an initial ‘Chipper’ (tolerant) × line M 29 (susceptible) mating, and rate of progression to the recurrent parent was determined by simple sequence repeat marker and morphological trait analyses. Substantial degrees of the recurrent parent phenotype and nuclear genome were recovered by the BC2 generation (P = 0.001), with nearly complete recovery of recurrent parental traits and its nuclear genome occurring by the BC3. General combining ability (GCA) of derived BC2S3 lines was significant for yield, yield/plant, length (L), diameter (D), and L:D ratios. The BC2S3 line GCA and rate of progression towards the recurrent parent for economically important traits suggests that elite chilling tolerant cucumber germplasm can be developed rapidly through IB and marker genotyping.  相似文献   

16.
Drought is ubiquitous in rainfed cropping systems and often limits maize yields. The sensitivity of transpiration response early in progressive soil drying is a trait with potential to improve crop drought resistance. Simulation studies demonstrated that increased sensitivity to drying soil leading to restricted transpiration rates results in conservation of soil water during vegetative stages for possible use during grain filling. In contrast to other crops, there have been no studies characterizing genotypic variability for this trait in maize. Experiments in controlled environments were conducted to characterize the fraction of transpirable soil water (FTSW) threshold on drying soil for 36 hybrids selected for variation in the field for drought resistance, regions of adaptation and stay green. While FTSW thresholds varied among hybrids from 0.60 to 0.33, these thresholds were not uniformly associated with level of drought resistance in the field. Nevertheless, this study demonstrated a high FTSW threshold corresponded with drought resistance observed in some modern maize germplasm (hybrids #7, 17, 24, 27 and 32). This knowledge can enable breeding work seeking to exploit this adaptive trait to improved drought tolerance in low threshold FTSW germplasm.  相似文献   

17.
In temperate regions, perennial forage-based cropping systems are expected to face an increasing frequency of summer droughts over the next decades prompting the need for more resilient cultivars. However, most efforts mainly focus on Mediterranean-type environments where the plant survival is often engaged. Under temperate environments, vapor pressure deficit (VPD) is a key component of drought, because its variation alters the crop transpiration rate (TR) and therefore its ability to fix carbon even in well-watered conditions. Despite this knowledge, there is no available data about the diversity of whole-plant TR responses to VPD and soil moisture among key forage crops such as alfalfa, red clover, cock’s foot and perennial ryegrass. Further, field-based evidence is lacking regarding the links between TR responses to VPD and yield under drought. Here, we combined experimental approaches characterizing gas exchange responses to VPD and soil moisture at scales that ranged from the growth chamber to the field, where yields were characterized both quantitatively and qualitatively over the course of 2 years on 8 genotypes from the 4 above species. A significant variability in TR responses to increasing VPD and soil water deficit was found among locally-adapted cultivars. More importantly, TR responses to VPD – but not to decreasing soil moisture – were found to be consistently correlated to relative yield performances under drought, in a way indicating that conservative water use under high evaporative demand promoted higher yield outputs. In contrast, yields under drought were unrelated to canopy temperature and leaf gas exchange measured in the field. Further, no link was found between TR responses to VPD and qualitative yield traits such as digestibility indicating that the hypothesized water saving strategy does not improve yield at the expense of forage quality. This study opens the way for future forage breeding and management strategies taking advantage of the diversity of TR responses to drought to implement climate-change resilient forage-based systems.  相似文献   

18.
Water deficit is a major factor responsible for soybean yield gap in Southern Brazil and tends to increase under climate change. An alternative to reduce such gap is to identify soybean cultivars with traits associated to drought tolerance. Thus, the aim of this study was to assess soybean adaptive traits to water deficit that can improve yield under current and future climates, providing guidelines for soybean cultivar breeding in Southern Brazil. The following soybean traits were manipulated in the CSM-CROPGRO-Soybean crop model: deeper root depth in the soil profile; maximum fraction of shoot dry matter diverted to root growth under water stress; early reduction of transpiration under mild stress; transpiration limited as a function of vapor pressure deficit; N2 fixation drought tolerance; and sensitivity of grain filling period to water deficit. The yields were predicted for standard and altered traits using climate data for the current (1961–2014) and future (middle-century) scenarios. The traits with greater improvement in soybean yield were deeper rooting profile, with yield gains of ≈300 kg ha−1, followed by transpiration limited as a function of vapor pressure deficit and less drought-induced shortening of the grain filling period. The maximum fraction of shoot dry matter diverted to root and N2 fixation drought tolerance increased yield by less than 75 kg ha−1, while early reduction of transpiration resulted in a small area of country showing gains. When these traits were combined, the simulations resulted in higher yield gains than using any single trait. These results show that traits associated with deeper and greater root profile in the soil, reducing transpiration under water deficit more than photosynthesis, creating tolerance of nitrogen fixation to drought, and reducing sensitivity of grain filling period to water deficit should be included in new soybean cultivars to improve soybean drought tolerance in Southern Brazil.  相似文献   

19.
Post‐flowering drought tolerance is referred to as the stay green trait in sorghum. Plants with stay green resist drought‐induced premature plant senescence. In breeding programmes, stay green is evaluated under limited irrigation, post‐flowering moisture‐stress field conditions and visually scored at or soon after physiological grain maturity. The objective of this study was to investigate the relationship between the stay green rating and total leaf chlorophyll content. The parents B35 and Tx7000, and their 98 F, recombinant inbred lines were evaluated in replicated field trials under limited (post‐flowering stress) and full‐irrigation (non‐stress) conditions. After scoring the stay green trait of stressed plants, total leaf chlorophyll contents were measured with a chlorophyll meter (SPAD values) and a spectrophotometer method. The SPAD value had a significant linear relationship with total leaf chlorophyll (R2= 0.91) and with visual stay green rating (with R2= 0.82). Relative water content in top leaves of the stay green lines was about 81%, much higher than non‐stay green lines (38%), indicating that the stay green lines kept the stalk transporting system functioning under severe drought conditions, The results indicate that visual stay green ratings were a reliable indicator of leaf senescence an should be useful to sorghum breeders in evaluating progeny when breeding for drought tolerance.  相似文献   

20.
During the vegetative phase of growth of two field bean and two field pea cultivars of different drought tolerance, the effect of short and prolonged soil drought on gas exchange (CO2 i H2O), leaf water potential (ψ), stomatal diffusive resistance (rS), uptake of CO2, and the distribution and accumulation of 14C was studied. Differences in the response to drought conditions between resistant and susceptible cultivars were marked. After 5 days of soil drought, the decrease in net photosynthesis and transpiration rate and the increase of stomatal resistance were greater in the drought-resistant cultivars than in the drought-susceptible ones. In contrast, after 10 days of drought the decrease of leaf PN (CO2 assimilation rate), E (rate of transpiration) and ψ (water potential) was greater in the susceptible cultivars than in the resistant ones. Significant differences between the resistant and the susceptible cultivars were also observed in the assimilation and translocation of 14C by the green parts of the plant. The amount of carbon accumulation in roots in drought-susceptible cultivars increased less than in the drought-resistant cultivars. For treatments in which optimal soil watering was resumed after 5 or 10 days of drought there was no evidence of effects of drought on the majority of measurements, but the drought-resistant cultivars showed a general tendency for a more rapid recovery. Our results confirm the existence of genetic variability in drought tolerance among the cultivars of field bean and field pea. The recorded differences in the response to drought of experimental cultivars may indicate that, under water deficit in the soil and in plant tissues, they may use different strategies to avoid the damaging effects of temporary limitation of water supply; for example, the drought-resistant cultivars may more effectively conserve tissue hydration through effective stomatal closure. Also, the observed changes in carbon assimilation and accumulation might be the reason for their different responses to drought. The change in radioactivity losses in the control and stressed plants may result from the differences in demand for energy to maintain cell structure and function. Similarly, the less intense carbon accumulation in the roots of the sensitive cultivars could be caused by more harmful effects of drought on root growth.  相似文献   

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