玉米光合性能的杂种优势

以4个不同光合速率的玉米自交系及组配的2个杂交种为材料, 在吐丝期进行了光合速率(P_n)、蒸腾速率(T_r)、气孔导度(G_s)、水分利用效率(WUE)等光合性能指标日变化的测定,以探明玉米杂种优势光合性能的日变化规律.结果表明：光合性能中P_n、T_r和G_s 3项指标均呈明显的单峰曲线变化，峰值出现的时间分别为10:00—12:00、12:00和10:00—12:00，其中G_s、P_n早于T_r；WUE日变化规律与其它光合性能指标相反，呈现“V”趋势，低谷值出现在12:00点左右.P_n、T_r的日变化均与G_s密切相关，说明G_s在P_n、T_r日变化中起着重要的调节作用.对光合性能杂种优势率日变化进行分析表明，杂交种P_n、T_r、G_s具有午后优势现象，而WUE杂种优势率表现为上午高于下午,说明午后的环境条件更有利于杂交种抗性的发挥，为筛选高光效品种提供了一项可参考的指标.

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(Pn),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.Pn,Tr and Gs had higher heterosis in the afternoon than in the morning,while WUE was in reverse,indicating that maize hybrid had higher resistance to high temperature and dehydration in the afternoon,which provided a new path to select varieties with high net photosynthetic rate.