Effects Of Low-light Stress On The Growth And Development Of Two Different Genotypic Ear

Light is one of the most important environmental factor influecing the growth anddevelopment of maize (Zea mays L.). Sufficient light during the growing period is the basis ofhigh yield formation of maize. However, there are always prolonged rainy days during maizegrowing season in the Huang-huai-hai region, which are detrimental for maize yield formation.And prolonged rainy days at flowering stage bring more severe damage to maize production.Low-light environment leads to a decrease in photosynthetic rate, a reduction and redistribution ofbiomass, an extension of anthesis to silking interval, and a significant reduction of ear kernelnumber and grain yield. And there are significant differences in maize genotypes responses to lowlight stress. Previous studies have elucidated the effects of low-light stress on maize. However,whether the pollination and fructification ability, endogenous hormones or carbon and nitrogenmetabolism have influence on the whole ear development process and kernel set are not clear.A split plot experiment was conducted under field conditions during2010and2011, to studythe effects of shading and light recovery on the floral development, growth and development ofmaize ear, endogenous hormones of two maize hybrids, kernel setting and carbon and nitrogenmetabolism of different maize genotypes. The main plots are light treatment (natural light and50%shading) and sub-plots are cultivars (low light sensitive hybrid YY22and low light tolerancehybrid ZD958). In the low light treatment, maize plants were shaded with50%transmittanceshading nets from3days before tasselling to10days after silking. The main results are as follows:1. Low-light stress caused a slowdown of ear and tassel growth and development rate, delayedthe tasselling date, silking date and full flowering date, prolonged the anthesis-silking interval(ASI). Daily pollen quantity was higher under low-light stress than control at silking with a largerdifference of the low light sensitive hybrid. For the low light sensitive hybrid under low lightstress, reticulate and gaps between each reticulate in the surface of pollen were increased, pollenaperture and its near part were severely deformed with significantly retraction, nutrientsupplication were reduced by the reduction of starch grains in the pollen. While for the low lighttolerance hybrid under low light stress, pollen surface characters of the pollen were similar to thecontrol, with a little retraction of the pollen aperture and starch grain density in the pollen. Underlow light stress, pollen activity, pollen emergence rate and pollen tube growth rate of the low lightsensitive hybrid decreased while the low light tolerance hybrid increased. Silk elongation rate andsilks emerged from the husks were decreased more of the silks in the ear tip than in the ear base.Ear length and kernel number per ear decreased in both hybrids with the low light sensitive hybriddecreased more.2. The growth and development of maize ear was delayed, ear length, ear diameter, ear dry weight, ear row number, kernel number and kernel sink capacity were significantly decreasedwhile barren tip increased under low light conditions with low light sensitive maize hybridschanged more. Low-light stress delayed the growth and development of kernels, raised thenumber of abortive kernel, reduced kernel volume and dry weight. Spikelet ovary in ear apicalshowed signs of abortion at silking stage. The abortion progress of the kernel could not bedisrupted by the recovery of natural light.3. ABA and ZR content of both maize hybrids ears increased under low-light stress while GAcontent and GA/ABA ratio of both maize hybrids decreased. IAA content and IAA/ABA ratio ofZD958was increased while YY22decreased. The recovery of natural light in a short time hadlittle effect on the established hormone synthetic mechanisms.4. Contents of soluble sugar, sucrose and starch of apical kernel were increased while thecontent of nitrogen and C/N ratio decreased. Starch grain density in kernel endosperm cells ofYY22reduced while ZD958almost remained the same. Differences between treatments of YY22were greater than ZD958, apical was greater than middle. ZD958showed stronger compensatoryeffect after light recovery, differences between light treatments of kernel volume, dry weight,kernel carbon and nitrogen content and C/N ratio of ZD958were lower than YY22, The declinesof the starch synthesis and C/N ratio were the primary causes leading to kernel abortion.