The Study Of Stay-green Trait Evaluation Index In Maize Leaf

In order to study the physiological and biochemical mechanisms and better understand the evaluation indexes of the stay-green trait in maize, the maize materials with different stay-green characteristics were used as the experimental material, which were studied though the field experiment conbined with laboratory analysis. In one hand, the physiological and biochemical mechanisms of stay-green trait were explored by detecting the changes of the green leaf area, photosynthetic pigments, photosynthetic parameters, protective enzyme activities, soluble protein and MDA contents in five different genotype maize. In the other hand,7 common Maize variety and 23 crosses were obtained by a incomplete diallel for field experiment. The stay-green trait of the 30 materials is described in terms of absolute green leaf area duration, relative green leaf area duration and stray-green degree at maturity. The experimental data were analysed by using statistical methods, which included correlation, path analysis. The relations of stay-green trait with the yield, anthesis period, mature period, photosynthetic parameters, growth stage and other agronomic traits were mainly reserached. Through the main component analysis and cluster analysis of the stay-green related traits, the mostly associated evaluation indexes of stay-green trait were ideterimined. The main results are as follows:1 The descent speed of number of green leaf, green leaf area, stay-green degree of non-stay green inbred line after anthesis were much faster than those of stay-green inbred line and hybrids materials. The absolute green leaf areas duration and relative green leaf areas duration of non-stay green inbred line were significantly lower than those of stay-green inbred.2 The content of photosynthetic pigments in different maize ear leaf had low-amplitude fluctuations on the 0-23th day after anthesis, and then declined. The content of photosynthetic pigments in stay-green inbred lines was more than that in non-stay green inbred lines. The net photosynthetic rate (Pn), stomatal conductance (Gs), transpiration rate (Tr) in stay-green inbred lines and hybrid materials after anthesis were slight change, and then rapid decline. But the non-stay green inbred lines gone directly into the rapid decline phase after anthesis, and the decline speed of Pn, Gs, Tr were faster than the stay-green phenotype.3 The SOD and POD activities of non-stay green phenotype inbred lines after anthesis were lower than that of stay-green phenotype inbred lines and hybrids materials. The content of CAT and soluble protein of all maize materials were decreased.4 The stay-green trait is very important to improve yield. Absolute leaf area duration and relative leaf area duration were extremely positive correlated with Panicle weight, grain yield per plant, and 100-seed weight.5 The close related agronomic traits with stay-green trait are green leaf area in anthesis, whole growth period, ear three leaves area in anthesis, days of emergence to silking, days of silking to maturity, net photo synthetic rate in the middle phase of senescence (Pnl). Absolute green leaf area duration was mainly direct affected by whole growth period, ear three leaves area in anthesis, days of emergence to silking, green leaf area in anthesis, while relative green leaf area duration was mainly direct affected by whole growth period, green leaf area in anthesis, ear three leaves area in anthesis and number of green leaf in anthesis. Stay-green degree at maturity was mainly direct affected by green leaf area in anthesis and maturity period. Evaluating the stay-green trait only by absolute and relative green leaf area duration was much affected by the growth period, it seems that stay-green phenotype tends to have a longer growth period, especially the lasting time of silking to maturity.6 In addition to absolute green leaf area duration, relative green leaf area duration and stay-green degree at maturity are offen used to evaluate the stay-green trait in maize. This research indicated that green leaf area in anthesis, days of silking to maturity and net photosynthetic rate in the middle phase of senescence also can be used as reference index to evaluate the stay-green trait.