Genotypic variations in leaf and whole-plant water use efficiencies are closely related in bread wheat genotypes under well-watered and water-limited conditions during grain filling

Abstract

Wheat plants growing under Mediterranean rain-fed conditions are exposed to water deficit, particularly during the grain filling period, and this can lead to a strong reduction in grain yield (GY). This study examines the effects of water deficit after during the grain filling period on photosynthetic and water-use efficiencies at the leaf and whole-plant level for 14 bread wheat genotypes grown in pots under glasshouse conditions. two glasshouse experiments were conducted, one in a conventional glasshouse at the Universidad de Talca, Chile (Experiment 1), and another at the National Plant Phenomics Centre (NPPC), Aberystwyth, UK (Experiment 2), in 2015. Plants were grown under wellwatered (WW) and water-limited (WL) conditions during grain filling. The reductions in leaf water potential (Ψ), net CO 2 assimilation (An) and stomatal conductance (gs) due to water deficit were 79, 35 and 55%, respectively, during grain filling but no significant differences were found among genotypes. However, chlorophyll fluorescence parameters (as determined on dark-adapted and illuminated leaves) and chlorophyll content (Chl) were significantly different among genotypes, but not between water conditions. Under both water conditions, An presented a positive and linear relationship with the effective photochemical quantum yield of Photosystem II (Y(II)) and the maximum rate of electron transport (ETRmax), and negative with the quantum yield of non-photochemical energy conversion in Photosystem II (Y(NPQ)). The relationship between An and Chl was positive and linear for both water conditions, but under WL conditions An tended to be lower at any Chl value. Both, instantaneous (An/E) and intrinsic (An/gs) water-use efficiencies at the leaf level exhibited a positive and linear relationship with plant water-use efficiency (WUEp = plant dry weight/water use). Carbon discrimination (Δ 13 C) in kernels presented a negative relationship with WUep, at both WW and WL conditions, and a positive relationship with GY. Our results indicate that during grain filling wheat plants face limitations to the assimilation process due to natural senesce and water stress. the reduction in An and gs after anthesis in both water conditions was mainly due a decline in the chlorophyll content (non-stomatal limitation), whereas the observed differences between water conditions were mainly due to a stomatal limitation.In Mediterranean climatic regions, annual average temperatures have increased and precipitation decreased during the last century 1-3 , and this phenomenon has also affected Chile 4 . In addition, precipitation in Chile is strongly concentrated in winter and also manifests large inter-annual variability. Thus, wheat plants growing under rainfed conditions are exposed to a progressive water deficit starting from heading, leading to a 'terminal drought stress' , which reduces grain yield (GY). Therefore, enhancing crop resilience is a priority for Mediterranean environments and may also provide a better understanding of the physiological mechanisms ...

Investigation of Distinctive Morpho-Physio and Biochemical Alterations in Desi Chickpea at Seedling Stage Under Irrigation, Heat, and Combined Stress

“…For early stress detection in plants, chlorophyll fluorescence parameter Fv/Fm has been widely used because it revealed the maximum quantum efficiency of photosystem II (PSII) photochemistry (Sharma et al, 2015). Under irrigation, non-significant changes were observed for Fv/Fm for all genotypes, the same results were found in previous research on bread wheat under well-watered and water-limited conditions (Del Pozo et al, 2020). Earlier, a study revealed that two heat tolerant genotypes of chickpea depicted Fv/Fm value ranging 0.83-0.85, so CH104/06 could be a heat tolerant genotype because it depicted Fv/Fm 0.83 value (Makonya et al, 2019).…”

Root Architecture and Functional Traits of Spring Wheat Under Contrasting Water Regimes

“…Generally, plants subjected to cumulative water deficits (i.e., in tube and pot trials) may avert cell dehydration by decreasing the area of their transpiring AB and the rate of transpiration in the leaves (by decreasing stomatal conductance) and, thus, increasing WUE ( Elazab et al, 2012 ; del Pozo et al, 2020 ). Other mechanisms such as maintaining high relative water content in the leaves (by accumulating solutes such as proline and soluble sugars) at levels close to WW plants and/or decreasing the osmotic potential could avoid cell dehydration under the WL regime ( Acton, 2012 ).…”

“…Three glasshouse trials were carried out at the Plant Breeding and Phenomic Center (35 • 24 19 S; 71 • 37 59 W), Talca University, Talca, Chile, from 2015 to 2017. In 2015, a set of 13 advanced lines and two cultivars of spring wheat (Triticum aestivum L.) with contrasting performance under water deficit (Table 1) was chosen from a set of 384 genotypes (del Pozo et al, 2016(del Pozo et al, , 2020. Plants were sown in PVC tubes of 16 cm diameter and 160 cm length in a heated glasshouse ( Figure 1A) on 10 August.…”

“…Generally, plants subjected to cumulative water deficits (i.e., in tube and pot trials) may avert cell dehydration by decreasing the area of their transpiring AB and the rate of transpiration in the leaves (by decreasing stomatal conductance) and, thus, increasing WUE (Elazab et al, 2012;del Pozo et al, 2020). Other Data from the 2017 trial.…”

Leaf and Canopy Traits Associated with Stay-Green Expression Are Closely Related to Yield Components of Wheat Genotypes with Contrasting Tolerance to Water Stress

“…Two experiments were conducted in glasshouse and field conditions with a set of fourteen contrasting spring bread wheat ( Triticum aestivum L.) genotypes, listed in Table 6 . The genotypes were selected according to the yield tolerance index from a previous study [ 5 , 39 ]. Cultivars PANTERA-INIA and PANDORA-INIA feature a similar genetic background, but PANTERA-INIA is a Clearfield ® cultivar with resistance to the herbicide imidazolinone following the introduction of the Ser-Asn627 mutation into two acetolactate synthase (ALS) genes ( imi1 and imi2 ), located in wheat on chromosomes 6B and 6D, respectively, into cv.…”