Timing of Water Deficit Limits Maize Kernel Setting in Association With Changes in the Source-Flow-Sink Relationship

Abstract

The kernel setting of maize varies greatly because of the timing and intensity of water deficits. This variation can limit leaf productivity (source), the translocation of assimilated sugars (flow), and yield formation (sink). To explain the decline in kernel setting of maize under water deficits from the perspective of source-flow-sink, a 3-year experiment was conducted under a rain shelter. Five water regimes were studied. One regime included well-irrigated (CK) treatment. Four regimes involved water deficits: irrigation was withheld during the 6- to 8-leaf stage (V6−8), the 9- to 12-leaf stage (V9−12), the 13-leaf stage to tasseling stage (V13−T), and the silking stage to blister stage (R1−2). Water deficit effects on kernel setting began when the water deficit occurred at V9 and became more significant with time. Kernel weight was reduced by 12 and 11% when there were water deficits during V9−12 and V13−T, respectively. This was the result of reduced leaf area (limited source) and an altered vascular bundle in the ear peduncles (limited assimilate flow). The reduced vascular bundle number, rather than the ear peduncle cross-sectional area, significantly affected the final kernel weight when exposed to a water deficit prior to the silking stage. The water deficits prior to and close to the flowering stage significantly reduced ear kernel number; that is, 14 and 19% less during V13−T and R1−2, respectively, compared with the kernel number during the CK treatment. This reflects a smaller sink under water deficit conditions. Additionally, ovary size was reduced the most in the V13−T water deficit compared with other treatments. After rewatering, the water deficit before or during flowering stage continued to have residual effects on grain-filling in the late growth period. The grain-filling rate decreased under the V9−12 water deficit; the grain-filling duration shortened under the R1−2 water deficit; and both negative effects occurred under the V13−T water deficit. This study clearly indicated that (1) the water deficit during the vegetative organ rapid growth period both limited leaf source development and assimilate flow and slowed down kernel development, and (2) the water deficit just before and during flowering reduced kernel sink. Deficits at both times could retard grain-filling and reduce maize yield. The results of the present study might guide irrigation practices in irrigated maize or inform the management of sowing time in rainfed maize, to desynchronize the water deficit and the plant’s reactions to such deficits at different stages.

Effect of Irrigation Intervals on Growth, Productivity and Quality of Some Yellow Maize Genotypes

“…Many investigators found the growth and productivity of maize were increased by the application of adequate water irrigation every 10 days (Gomaa et al, 2014;El-Sobky & Desoky, 2017;Abo El-Ezz & Haffez, 2019) or 12 days (Yasin, 2016), 14 days (Solieman et al, 2019) and 15 days (Gomaa et al, 2015) as compared with prolonging irrigation intervals more than those periods. On the other hand, exposing maize plants to water stress condition by skipping one or more irrigations caused a depression in the yield and its components of maize as reported by Ashraf et al (2016), El-Sobky & El-Naggar (2017), Mohammed et al (2017) and Li et al (2018). Under the minimum water conditions, the best option for maize production, yield improvement and yield stability is growing varieties are more tolerant for drought stress (Gabr et al, 2018;Hategekimana et al, 2018).…”

Comparative Study on Leaf Gas Exchange, Growth, Grain Yield, and Water Use Efficiency under Irrigation Regimes for Two Maize Hybrids

“…In our study, under rainfed conditions, the number of kernels decreased by 17.7% in 2017 and 21.1% in 2018, compared with RI. Other studies observed a significant decrease in number of kernels by 31.13% [27], and 19% [28] under drought stress during flowering period. Maize crops were found to be particularly susceptible to drought at the flowering stage [29].…”

Stacking Tolerance to Drought and Resistance to a Parasitic Weed in Tropical Hybrid Maize for Enhancing Resilience to Stress Combinations

“…Gurney et al (2002) found that a tolerant maize cultivar that produced high grain yield in the presence of Striga asiatica infection maintained higher rates of photosynthesis in the field in comparison to a susceptible cultivar. As drought stress reduces leaf area, accelerates leaf senescence, decreases leaf source activity, and changes numerous physiological and biochemical processes (Zaidi et al, 2004;Wahid et al, 2005;Li et al, 2018), the retention of green leaf area in the DTSTR hybrids under parasite infection may promote high rates of photosynthesis leading to increased kernel setting and grain yield under drought stress (Li et al, 2018;Tani et al, 2019). At the same time, the emphasis on enhanced vegetative growth, less visible leaf senescence, and synchronized male-female flowering of lines during the second stage of selection under managed drought stress may further accentuate photosynthetic activity to boost performance of the DTSTR hybrids under both drought stress and Striga infestation.…”