scholarly journals Lower soil moisture threshold for transpiration decline under water deficit correlates with lower canopy conductance and higher transpiration efficiency in drought-tolerant cowpea

2012 ◽  
Vol 39 (4) ◽  
pp. 306 ◽  
Author(s):  
Nouhoun Belko ◽  
Mainassara Zaman-Allah ◽  
Ndiaga Cisse ◽  
Ndeye Ndack Diop ◽  
Gerard Zombre ◽  
...  
Keyword(s):  
Growth Parameters ◽  
Canopy Temperature ◽  
Vapour Pressure Deficit ◽  
Canopy Conductance ◽  
Genotypic Differences ◽  
Transpiration Efficiency ◽  
Severe Stress ◽  
Water Regimes ◽  
Terminal Drought ◽  
Canopy Temperature Depression

As water availability is critical for reproduction, terminal drought tolerance may involve water-saving traits. Experiments were undertaken under different vapour pressure deficit (VPD) and water regimes (water stress (WS) and well watered (WW)) to test genotypic differences and trait relationships in the fraction of transpirable soil water (FTSW) at which transpiration declines, canopy conductance (proxied by transpiration rate (TR, g H2O cm–2 h–1)), canopy temperature depression (CTD, °C), transpiration efficiency (TE, g kg–1) and growth parameters, using 15 contrasting cowpea (Vigna unguiculata (L.) Walp.) genotypes. Under WW conditions at the vegetative and early podding stages, plant mass and leaf area were larger under low VPD, and was generally lower in tolerant than in sensitive genotypes. Several tolerant lines had lower TR under WW conditions and restricted TR more than sensitive lines under high VPD. Under WS conditions, transpiration declined at a lower FTSW in tolerant than in sensitive lines. Tolerant lines also maintained higher TR and CTD under severe stress. TE was higher in tolerant genotypes under WS conditions. Significant relationships were found between TR, and TE, CTD and FTSW under different water regimes. In summary, traits that condition how genotypes manage limited water resources discriminated between tolerant and sensitive lines. Arguably, a lower canopy conductance limits plant growth and plant water use, and allows tolerant lines to behave like unstressed plants until the soil is drier and to maintain a higher TR under severe stress, as lower TR at high VPD leads to higher TE.

Genotypic variation in whole-plant transpiration efficiency in sorghum only partly aligns with variation in stomatal conductance

2019 ◽  
Vol 46 (12) ◽  
pp. 1072 ◽  
Author(s):  
Geetika Geetika ◽  
Erik J. van Oosterom ◽  
Barbara George-Jaeggli ◽  
Miranda Y. Mortlock ◽  
Kurt S. Deifel ◽  
...  
Keyword(s):  
Stomatal Conductance ◽  
Photosynthetic Capacity ◽  
Genotypic Variation ◽  
Vapour Pressure Deficit ◽  
Genotypic Differences ◽  
Transpiration Efficiency ◽  
Plant Transpiration ◽  
Leaf Chlorophyll ◽  
Residual Variation ◽  
Whole Plant

Water scarcity can limit sorghum (Sorghum bicolor (L.) Moench) production in dryland agriculture, but increased whole-plant transpiration efficiency (TEwp, biomass production per unit of water transpired) can enhance grain yield in such conditions. The objectives of this study were to quantify variation in TEwp for 27 sorghum genotypes and explore the linkages of this variation to responses of the underpinning leaf-level processes to environmental conditions. Individual plants were grown in large lysimeters in two well-watered experiments. Whole-plant transpiration per unit of green leaf area (TGLA) was monitored continuously and stomatal conductance and maximum photosynthetic capacity were measured during sunny conditions on recently expanded leaves. Leaf chlorophyll measurements of the upper five leaves of the main shoot were conducted during early grain filling. TEwp was determined at harvest. The results showed that diurnal patterns in TGLA were determined by vapour pressure deficit (VPD) and by the response of whole-plant conductance to radiation and VPD. Significant genotypic variation in the response of TGLA to VPD occurred and was related to genotypic differences in stomatal conductance. However, variation in TGLA explained only part of the variation in TEwp, with some of the residual variation explained by leaf chlorophyll readings, which were a reflection of photosynthetic capacity. Genotypes with different genetic background often differed in TEwp, TGLA and leaf chlorophyll, indicating potential differences in photosynthetic capacity among these groups. Observed differences in TEwp and its component traits can affect adaptation to drought stress.

scholarly journals Suitability of Canopy Temperature Depression, Specific Leaf Area, and SPAD Chlorophyll Reading for Genotypic Comparison of Peanut Grown in a Sub-humid Environment

2014 ◽  
Vol 41 (2) ◽  
pp. 100-110 ◽  
Author(s):  
D. Singh ◽  
M. Balota ◽  
T. G. Isleib ◽  
E. Collakova ◽  
G. E. Welbaum
Keyword(s):  
Leaf Area ◽  
Water Deficit ◽  
Specific Leaf Area ◽  
Canopy Temperature ◽  
Physiological Characteristics ◽  
Growth Stages ◽  
Pod Yield ◽  
Humid Environment ◽  
Canopy Temperature Depression ◽  
Temperature Depression

ABSTRACT Peanut (Arachis hypogaea L.) is mostly grown under rainfed production with water deficit being the major limiting factor. Several physiological characteristics have been proposed as surrogates for yield and genotypic selection under water deficit in arid climates, but their suitability for selection under sub-humid rainfed production where water deficit can also occur is not clear. Canopy temperature depression (CTD), specific leaf area (SLA), and SPAD chlorophyll reading of eight virginia-type peanut genotypes were evaluated at three growth stages in field trials involving rainfed and irrigated plants in sub-humid environments in northeastern Virginia-Carolina (VC) region in 2011 and 2012. Significant (p≤0.05) variation in pod yield and all physiological characteristics was observed in response to water regime in both years. Rainfed plants had warmer (CTD 2.2 vs. 3.1 °C) and greener canopies in 2011 but cooler (CTD 3.9 vs. 2.2 °C) and less green canopies in 2012 than the irrigated plants. Compared to irrigated plants, rainfed plants had slightly increased SLA in 2011 (135 vs. 131 cm2 g−1), but decreased SLA in 2012 (133 vs. 144 cm2 g−1). Differences (p≤0.05) among genotypes were observed for pod yield, SLA, and SPAD chlorophyll reading, but not for CTD. Among the physiological characteristics, only SPAD chlorophyll readings were significantly correlated to pod yield in all water regimes and growth stages in 2012, but not in 2011. Based on these results, CTD, SLA, and SPAD chlorophyll reading appear to be unsuited for genotypic selection for yield and water-deficit tolerance for peanut grown in sub-humid environment of the Virginia-Carolina region in part due to unpredictable rainfall amount and distribution. For reproducible field evaluations, additional methods will have to be used such as use of rain exclusion shelters.

scholarly journals Evidence for genotypic differences among elite lines of common bean in the ability to remobilize photosynthate to increase yield under drought

2016 ◽  
Vol 155 (6) ◽  
pp. 857-875 ◽  
Author(s):  
I. M. RAO ◽  
S. E. BEEBE ◽  
J. POLANIA ◽  
M. GRAJALES ◽  
C. CAJIAO ◽  
...  
Keyword(s):  
Drought Stress ◽  
Grain Yield ◽  
Common Bean ◽  
Harvest Index ◽  
Genotypic Differences ◽  
Area Index ◽  
Wild Bean ◽  
Terminal Drought ◽  
Terminal Drought Stress ◽  
Pod Harvest Index

SUMMARYCommon bean (Phaseolus vulgaris L.) is the most important food legume for human consumption. Drought stress is the major abiotic stress limitation of bean yields in smallholder farming systems worldwide. The current work aimed to determine the role of enhanced photosynthate mobilization to improve adaptation to intermittent and terminal drought stress and to identify a few key adaptive traits that can be used for developing drought-resistant genotypes. Field studies were conducted over three seasons at Centro Internacional de Agricultura Tropical, Palmira, Colombia to determine genotypic differences in adaptation to intermittent (two seasons) and terminal (one season) drought stress compared with irrigated conditions. A set of 36 genotypes, including 33 common bean, two wild bean and one cowpea were evaluated using a 6 × 6 lattice design under irrigated and rainfed field conditions. Three common bean elite lines (NCB 226, SEN 56, SER 125) were identified with superior levels of adaptation to both intermittent and terminal drought stress conditions. The greater performance of these lines under drought stress was associated with their ability to remobilize photosynthate to increase grain yield based on higher values of harvest index, pod harvest index, leaf area index and canopy biomass. Two wild bean germplasm accessions (G 19902, G 24390) showed very poor adaptation to both types of drought stress. One small-seeded black line (NCB 226) was superior in combining greater values of canopy biomass with greater ability to mobilize photosynthates to grain under both types of drought stress. Two small-seeded red lines (SER 78, SER 125) seem to combine the desirable traits of enhanced mobilization of photosynthates to seed with effective use of water through canopy cooling under terminal drought stress. Pod harvest index showed significant positive association with grain yield under both types of drought stress and this trait can be used by breeders as an additional selection method to grain yield in evaluation of breeding populations for both types of drought stress.

scholarly journals Physiological Efficiency of Sugarcane Clones under Water-Limited Conditions

2020 ◽  
Vol 63 (1) ◽  
pp. 133-140
Author(s):  
Raja Arun kumar ◽  
Srinivasavedantham Vasantha ◽  
Arjun S. Tayade ◽  
Sheriff Anusha ◽  
Ponmani Geetha ◽  
...  
Keyword(s):  
Chlorophyll Fluorescence ◽  
Irrigation Water ◽  
Canopy Temperature ◽  
Water Security ◽  
Physiological Traits ◽  
Cane Yield ◽  
Leaf Rolling ◽  
Sugarcane Production ◽  
Canopy Temperature Depression ◽  
Temperature Depression

Highlights`Significant reductions in canopy temperature depression (CTD), chlorophyll fluorescence (Fv/Fm), SPAD index, and leaf rolling index were observed under limited irrigation during the grand growth stage of sugarcane.This study highlights the significance of CTD and Fv/Fm as useful physiological tools for selecting sugarcane clones suitable for production under water-limited conditions.Clones Co 10026, Co 13006, Co 85019, Co 62175, Co 86010, and Co 1148 performed better under limited irrigation, and these clones can reduce the amount of irrigation water required for sugarcane production, ensuring water security.Abstract. Sugarcane is one the most important commercial crops in India and globally. The annual water requirement for sugarcane ranges from about 1000 to 2900 mm, and this variation mainly depends on the agro-ecological conditions, cultivation practices, and crop cycle. In a changing climate, the delay or failure of monsoons will have a direct effect on the water available for irrigation in India. Given these constraints, sustaining sugarcane production is challenging. The ICAR-Sugarcane Breeding Institute (ICAR-SBI) in Coimbatore, India, has developed sugarcane genotypes that are resilient to drought stress. To study the role of physiological traits in identifying sugarcane varieties suitable for water-limited conditions, an experiment was conducted at ICAR-SBI with sugarcane clones in field conditions using irrigation at 100% cumulative pan evaporation (I0) and with 50% reductions in the volume and frequency of irrigation (I2). Physiological traits, including canopy temperature depression (CTD), chlorophyll fluorescence (Fv/Fm), soil plant analysis development (SPAD) index, leaf rolling index (LRI), and cane yield, were recorded for sugarcane clones grown under I0 and I2. Significant reductions of 85.9%, 15.4%, 4.9%, 44.9%, and 56.0%, respectively, in CTD, Fv/Fm, SPAD index, LRI, and cane yield were found for water-limited conditions (I2) compared to I0. Fv/Fm showed a decreasing trend in I2 compared to I0 and also showed a significant positive correlation (r = 0.43) with cane yield. CTD varied significantly between the two treatments and also showed a significant positive correlation with cane yield (r = 0.45). Both Fv/Fm and CTD are adaptive traits for water-limited conditions and are useful for screening sugarcane clones suitable for water-limited conditions. Clones Co 10026, Co 13006, Co 85019, Co 62175, and Co 86010 had superior cane yields under water-limited conditions (I2) and better physiological traits. Water deficit is one of the most critical abiotic stresses that affect sugarcane productivity. By growing clones that are water use efficient (Co 10026, Co 13006, Co 85019, Co 62175, and Co 86010), the irrigation water requirement can be reduced for sugarcane production in India. In addition, new sugarcane clones can be developed for water-limited conditions by using the identified clones in breeding programs for water use efficiency, and water security can be achieved for sugarcane grown tropical and sub-tropical areas of India. Keywords: Canopy temperature, Chlorophyll fluorescence, Global water security, Irrigation, Water productivity

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