鸭梨不同枝类叶片光合速率在生长期的变化趋势

Change Tendency in the Photosynthetic Rate of Ya Pear Leaves on Different Branches at Different Developing Stages

用改进半叶法测定鸭梨不同部位叶片和不同枝类叶片不同时期的光合速率。结果表明，９年生密植鸭梨外围新梢叶和短枝叶的光合速率分别为１６．７３～３３．７３和１３．５６～２５．７４ｍｇＣＯ２ｄｍ－２ｈ－１，内膛短枝叶的光合速率为４．５５～９．９０ｍｇＣＯ２ｄｍ－２ｈ－１。５月下旬至８月下旬的两年连续测定表明，盛果期大树外围新梢叶的光合速率高于外围短枝叶。短枝叶的光合速率在５月份呈现最高值，６月份及以后有所降低，至８月底下降幅度不显著。

The photosynthetic rate of Ya pear leaves on different branches and location was tested using improved half leaf method at different developing stages.The results indicated that the net photosynthetic rates were 16.73-33.73 and 13.56-25.74mg CO2.dm-2.h-1 respectively in leaves on the outside shoots and on the outside spurs and 4.55-9.90mg CO2.dm-2.h-1 in leaves on the inside spurs for nine year-old densely planted Ya pear trees.Continued measurements made from the late May to the late August in 2 years showed that the photosynthetic rate of the leaves on the outside shoots was higher than that of leaves on the outside spurs in large and mature trees.The photosynthetic rate of the spur leaves reached its peak in May,then decreased a little in June, and levelled off till the end of August.