Effects of nitrogen nutrition on photosynthesis and fruit production in Japanese pear, apple and grape trees.

以日本梨、苹果和葡萄为试材，研究了生长期氮素营养对果实净光合速率、光合产物积累、氮素吸收、产量和品质的影响。本研究以<^（15）N>和<^（13）C>为示踪元素，结果表明：高氮处理下，新梢生长期的光合活性高于中氮处理和无氮处理。果实生长期以中氮水平最高，4月上旬施入的氮素大部分被吸收并转移到细根和芽中。6月中旬施入的氮肥主要向地上部和地上部转移。在果实生长期和成熟期，中氮和无氮处理下，果实中~（13）C>的运转量增加，高氮处理下，果实中~（13）C>的运转量减少，而中氮和无氮处理下，果实中~（13）C>的运转量主要在糖果中增加，但有机酸和氨基酸含量没有增加。在高氮水平下，有机酸和氨基酸类果实中的<^（13）C>含量高于糖类果实。

The effects of nitrogen nutrition during the growth season on net photosynthesis, photosynthate accumulation, nitrogen absorption, yield and fruit quality in Japanese pear, apple and grapes were investigated. In this studies, <^(15)N> and <^(13)C> were used as tracer elements.Photosynthetic activities in the shoot growth period were higher at high N levels than that both medium N levels and none N levels. While, in the fruit growth period, it were highest at medium N levels.Most of the nitrogen which had been applied on early April, were absorbed and translocated into fine roots and buds. The nitrogen applied on mid June were mainly translocated into leves and shoots. On the other hand, the nitrogen absorbed on early September were mainly transelocated into older shoots and roots.In the fruit growth and mature periods, the amount of <^(13)C> translocated into fruit increased at both medium N levels and none N levels, and decreased at high N levels.The <^(13)C> incorporated into fruit increased mainly in the sugar fruction at medium N levels and none N levels, but did not increased in both organic acid and amino acid fructions. In high N levels, more <^(13)C> was found in the organic acid and amino acid fructions than in the sugar fruction.