Phenological development, shoot dry matter production, grain yield and yield components of rice were examined in relation to drought occurring at various stages of growth. Rice was sown three or four times at three-week intervals in the field in each of two years, and performance in three stress trials was compared with that in corresponding irrigation trials, with the aim of quantifying the response of the crop to water stress of 23–34 days' duration developing at different growth stages. When drought occurred during vegetative stages, it had only a small effect on subsequent development and grain yield. The reduction in yield of up to 30% was due to reduced panicle number per unit area in one trial, and reduced number of spikelets per panicle in another. The effect of water stress on yield was most severe when drought occurred during panicle development. Anthesis was delayed, the number of spikelets per panicle was reduced to 60% of the irrigated control and the percentage of filled grains decreased in one crop to zero. This decrease in grain yield to less than 20% of the control was associated with low dry matter production during the drought period as well as during the recovery period following the drought. When drought occurred during grain filling, the percentage of filled grains decreased to 40% and individual grain mass decreased by 20%. The effect of stress was also related to its severity during grain filling. Stress at this stage hastened maturity. The results suggest that variation in yield components due to water availability is related to the variation in dry matter production at particular growth stages. Results of a supplementary shading experiment show that the relationship between spikelet number per panicle or single grain mass and crop growth rate was the same, whether growth rate was varied by availability of soil water or solar radiation. Filled-grain percentage, however, was more sensitive to drought stress than shading when comparison was made at a similar crop growth rate.
"Several other researchers have also related SWP derived from volumetric water content to physiological responses during stress (Turner et al., 1986; Lilley and Fukai, 1994b; Boonjung and Fukai, 1996; Wopereis et al., 1996; Yang et al., 2007; Chu et al., 2013; Xangsayasane et al., 2014). In this study, we estimated SWP using a combination of tensiometric measurements and the mechanistic water flow model given by the Richards equation to examine if the SWP attained just before irrigation is resumed (i.e. "
[Show abstract][Hide abstract] ABSTRACT: We conducted a two-year field experiment to determine if water stress could be exploited to recover yield in one drought resistant (Vandana) and three susceptible (IR36, IR72 and Swarna) rice varieties. Stress was induced in active tillering, flowering and grain filling stages by suspending irrigation until the soil became sufficiently dry and plants began to show stress symptoms when irrigation was resumed, such that plants could recover from stress. We observed that terminal soil water potential (SWP) as low as −110 kPa in the active tillering stage was less detrimental to relative water content, proline content, and electrolyte leakage. A 27% rise in the level of stress led to ∼8%, 44% and 21% increase in yield in IR36, Vandana and Swarna. The possible causes are 23%, 39% and 10% increase in the corresponding root biomass of the varieties, resulting in higher water uptake in the vegetative stage treatment plots. This was further supported by high correlations between yield and terminal SWP in this treatment. Critical limits of SWP may be identified to exploit the potential of rice varieties to sustain or improve yield under water stress. Results also suggest an opportunity to design a water saving strategy in lowland rice production.
Agricultural Water Management 04/2015; 152:110-118. DOI:10.1016/j.agwat.2014.12.013 · 2.29 Impact Factor
"Feng et al. (2007) found UV-B and drought to have opposite effects on phenological timings in Triticum aestivum; therefore, there may be potential for interactive effects of drought and UV-B on plant phenology. Both drought and UV-B are further known to result in reproductive costs; for example, drought caused a significant reduction in yield of Oryza sativa (Boonjung and Fukai 1996), whereas UV-B caused a reduction in seed yield and an increase in the number of unseeded pods in Glycine max (Chimphango et al. 2007). Such loss of productivity can have considerable consequences, with drought alone estimated to cause $20 billion (US) in agricultural losses between 1980 and 2004 (Mittler 2006). "
[Show abstract][Hide abstract] ABSTRACT: Here, a factorial experiment was used to investigate the interactive effects of a UV-B episode and concurrent progressive drought on the growth, chemistry, and reproductive success of A. thaliana. Both drought and UV-B negatively affected rosette growth, although UV-B had the greater effect. Acclimation to UV-B involved adjustment of leaf morphology, while drought induced accumulation of soluble sugars and phenolics. All plants recovered from treatments, but the cost of recovery was a developmental delay resulting in alteration in phenological timings. Combined treatments interacted causing additive negative effects on growth following exposure. This may be linked with inhibition of soluble sugar accumulation by UV-B, restricting the capacity for osmotic adjustment in response to drought. Following cessation of treatments, relative growth rate (RGR) and net assimilation rate (NAR) were significantly stimulated in plants treated with combined drought and UV-B. This interaction alleviated subsequent impacts of elevated UV-B on silique yield and reproductive timings. This study demonstrates the potential for interaction between these two common environmental factors. Furthermore, it shows the changeable nature of these interactions over the course of exposure and recovery through to reproduction, highlighting the need for sustained assessment of such interactions over a plant's lifecycle.
Ecology and Evolution 11/2012; 2(11):2695-709. DOI:10.1002/ece3.387 · 2.32 Impact Factor
"Relative root growth has been used as a parameter to map QTLs for tolerance to boron toxicity in barley (Jefferies et al. 1999). A dramatic reduction in grain yield occurs when drought coincides with the irreversible reproductive processes, making the genetic analysis of reproductive stage drought tolerance crucially important (Cruz and O'Toole 1984; Price and Courtois 1999; Boonjung and Fukai 2000; Pantuwan et al. 2002). However, QTLs for root traits under reproductive stage drought stress have not yet been reported in wheat. "
[Show abstract][Hide abstract] ABSTRACT: Drought is a major constraint to maintaining yield stability of wheat in rain fed and limited irrigation agro-ecosystems. Genetic improvement for drought tolerance in wheat has been difficult due to quantitative nature of the trait involving multiple genes with variable effects and lack of effective selection strategies employing molecular markers. Here, a framework molecular linkage map was constructed using 173 DNA markers randomly distributed over the 21 wheat chromosomes. Grain yield and other drought-responsive shoot and root traits were phenotyped for 2 years under drought stress and well-watered conditions on a mapping population of recombinant inbred lines (RILs) derived from a cross between drought-sensitive semidwarf variety "WL711" and drought-tolerant traditional variety "C306". Thirty-seven genomics region were identified for 10 drought-related traits at 18 different chromosomal locations but most of these showed small inconsistent effects. A consistent genomic region associated with drought susceptibility index (qDSI.4B.1) was mapped on the short arm of chromosome 4B, which also controlled grain yield per plant, harvest index, and root biomass under drought. Transcriptome profiling of the parents and two RIL bulks with extreme phenotypes revealed five genes underlying this genomic region that were differentially expressed between the parents as well as the two RIL bulks, suggesting that they are likely candidates for drought tolerance. Syntenic genomic regions of barley, rice, sorghum, and maize genomes were identified that also harbor genes for drought tolerance. Markers tightly linked to this genomic region in combination with other important regions on group 7 chromosomes may be used in marker-assisted breeding for drought tolerance in wheat.
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