Density resistance evaluation of maize varieties through new "Density-Yield Model" and quantification of varietal response to gradual planting density pressure.

Increasing planting density is the main method and key management to enhance the grain yield. Preventing lodging and premature senescence in high planting density, and screening and enhancing the density-tolerance of maize variety is the main goal of agronomy. Differential response of maize hybrids to high plant density greatly affect the dry matter accumulation and its allocation to maize kernel, depending upon various traits responsible for crowding stress tolerance, of which ear characteristics are pivotal.

[Spectra characteristic effect of different density-resistant maize variety on planting density].

With Chlorophyll Meter SPAD-502 and Canopy Analyzer AccuPAR LP-80, the spectra characteristic effect of different density-resistant maize variety on planting density was studied, and the effect of planting density on photosynthetic performance of maize was discussed. The materials of the experiment were Yinong-103, Xianyu-335, Zhengdan-958 and Denghai-661, the row spacing was 80 cm X 40 cm, the plant spacing was gradually changed from Im to smaller spacing, the densities were 3.33, 3.

[Heterosis of photosynthetic performance of maize].

Taking four maize inbred lines with different photosynthetic rate and their two hybrids as test materials, the diurnal variations of their photosynthesis parameters in silking stage were measured to study the heterosis of photosynthetic performance. The results showed that the net photosynthetic rate (P), transpiration rate (Tr) and stomatal conductance (Gs) all presented obvious single-peaked curve in a day, with the peak value occurred at 10:00-12:00, 12:00 and 10:00-12:00, respectively, while water use efficiency (WUE) had a "V" type variation trend, with the lowest value appeared at 12:00. The diurnal variation of Pn and Tr correlated markedly with Gs, suggesting that Gs played an important role in regulating the diurnal variation of Pn and Tr.