Combined effects of high temperature and waterlogging on yield and stem development of summer maize

The purpose of this study was to identify the physiological mechanism underlying the effects of high temperature and waterlogging on summer maize.The stem development and yield of the maize hybrid Denghai 605 in response to high-temperature stress,waterlogging stress,and their combination applied for six days at the third-leaf,sixth-leaf,and tasseling stages were recorded.The combined stresses reduced lignin biosynthetic enzyme activity and lignin accumulation,leading to abnormal stem development.Reduction of the area and number of vascular bundles in stems led to reduced dry matter accumulation and allocation.Decreased grain dry weight at all three stages reduced grain yield relative to a control.In summary,high temperature,waterlogging,and their combined stress impaired stem development and grain yield of summer maize.The combined stresses were more damaging than either stress alone.

氮素水平对甜菜干物质积累、分配和产糖量的影响

论述了不同氮素水平下，甜菜植株干物质积累与分配的规律，及其与产量形成的关系。指出了施氮量与块根含糖率呈极显著的负相关，r＝－0．993；而施氮量与块根产量和单位面积产糖量均呈二次曲线相关。本项研究中最高产糖量的最适施氮量为N120（120kg／hm2）。