Maize Hybrid Variability for Transpiration Decrease with Progressive Soil Drying

Abstract

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.

Is the Stay‐Green Trait in Sorghum a Result of Transpiration Sensitivity to Either Soil Drying or Vapor Pressure Deficit?

“…Br.) genotypes, that the threshold ranged from 0.30 to 0.47, and Gholipoor et al (2012b) found, in a comparison of 36 maize ( Zea mays L.) hybrids, a threshold range of 0.33 to 0.60. Those genotypes with a high threshold seemingly have the capacity to conserve soil water during soil‐drying events early in the growing season so that soil water remains during grain filling to allow sustained growth and expression of the stay‐green phenotype.…”

“…Similar results were demonstrated in pearl millet, in that a genotype tolerant to drought expressed limited‐transpiration trait at high VPD (>2.0 kPa) (Kholova et al, 2010). Gholipoor et al (2012b) examined the response to increasing VPD of 35 maize hybrids and found 11 expressed the maximum transpiration trait with the breakpoint for the limitation on transpiration occurring at 1.7 to 2.5 kPa.…”

The expression of dehydrin genes and the intensity of transpiration in drought-stressed maize plants

“…In a study by Gholipoor et al (2013), sap flow measurements proved an accurate indicator of the water flow and transpiration rates relative to abiotic stress parameters (drought and intensity of light) for maize. With increased evapotranspiration requirements (depending on the daily variation in global solar radiation and air temperature), the transpiration rate was higher compared with the rates under water-stressed conditions.…”

“…The transpiration of plants decreased during both daily and seasonal periods with decreasing soil water content in relation to the evapotranspiration conditions of the environment. The sensitivity threshold of maize transpiration to the availability of soil moisture may also be influenced by the genotype (Gholipoor et al 2013;Leitner et al 2014). Compared with the soil moisture content at full field capacity, an AWHC decrease of 20% resulted in a statistically significant decrease in the amount of transpired water by maize plants (Wu et al 2011b).…”

“…Benešová et al (2012) reported that the more tolerant genotype showed a slower closing of stomata, which resulted in a greater loss of water from the tissues; however, this genotype yielded a greater efficiency of photosynthesis for a longer time and a related higher level of synthesis of protective proteins, including DHN1, under mild stress than in the more sensitive genotype. According to results published by Gholipoor et al (2013), drought-tolerant genotypes exhibited decreased transpiration rates at an earlier stage in the soil drying cycle than other less water-conserving genotypes, thereby conserving more water for later use if the drought persisted.…”