In order to improve the management of nitrogen(N) fertilization in pear orchards, we investigated the effects of application timing on the distribution, storage, and remobilization of N in mature pear trees in a field...In order to improve the management of nitrogen(N) fertilization in pear orchards, we investigated the effects of application timing on the distribution, storage, and remobilization of N in mature pear trees in a field experiment at Jingtai County, Gansu Province, China. Nine trees were selected for the experiment and each received equal aliquots of 83.33 g N in the autumn, spring, and summer, with ^(15)N-labeled(NH_4)_2SO_4 used in one of the aliquots each season. Results showed that the(^(15)NH_4)_2SO_4 applied in the autumn remained in the soil during the winter. In the following spring this N was absorbed and rapidly remobilized into each organ, especially new organs(leaves, fruit and new shoots). The ^(15)N supplied in spring was rapidly transported to developing fruit between the young fruit and fruit enlargement stages. ^(15)N from the summer application of fertilizer was mainly stored in the coarse roots over the winter, then was mobilized to support growth of new organs in spring. In conclusion, for pear trees we recommend that the autumn application of N-fertilizer be soon after fruit harvest in order to increase N stores in fine roots. Spring application should be between full bloom and the young fruit stages to meet the high N demands of developing fruit. Summer application of fertilizer at the fruit enlargement stage does not contemporaneously affect the growth of pears, but increases the N stored in coarse roots, and in turn the amount available for remobilization in spring.展开更多
Cherry tomatoes （Lycopersicon esculentura Mill., cv. hongyangli） were hydroponically cultivated in a greenhouse to determine the effect of different nitrogen （N） forms on organic acid concentration and the activit...Cherry tomatoes （Lycopersicon esculentura Mill., cv. hongyangli） were hydroponically cultivated in a greenhouse to determine the effect of different nitrogen （N） forms on organic acid concentration and the activities of related enzymes involved in nitrogen and organic acid metabolism during cherry tomato fruit development. The results showed that fruit nitrate reductase （NR） activity was much higher following treatment with 100% NO3 and 75% NO3 ＋ 25% NH＋ than with 100% NH＋ except at maturity. Glutamine synthetase （GS） activity trended downward during fruit development under all three treatments. Plants fed 100% NH＋ had the lowest fruit citrate and malate levels at maturity, with the highest malate concentration at an early stage. The activity of phosphoenolpyruvate carboxylase （PEPC） was found to be in accord with the malate concentration with every N source. Under all three N forms, the citrate synthase （CS） activity peaked one week before the citrate concentration.展开更多
基金funded by the earmarked fund of China Agriculture Research System(CARS-29-10)。
文摘In order to improve the management of nitrogen(N) fertilization in pear orchards, we investigated the effects of application timing on the distribution, storage, and remobilization of N in mature pear trees in a field experiment at Jingtai County, Gansu Province, China. Nine trees were selected for the experiment and each received equal aliquots of 83.33 g N in the autumn, spring, and summer, with ^(15)N-labeled(NH_4)_2SO_4 used in one of the aliquots each season. Results showed that the(^(15)NH_4)_2SO_4 applied in the autumn remained in the soil during the winter. In the following spring this N was absorbed and rapidly remobilized into each organ, especially new organs(leaves, fruit and new shoots). The ^(15)N supplied in spring was rapidly transported to developing fruit between the young fruit and fruit enlargement stages. ^(15)N from the summer application of fertilizer was mainly stored in the coarse roots over the winter, then was mobilized to support growth of new organs in spring. In conclusion, for pear trees we recommend that the autumn application of N-fertilizer be soon after fruit harvest in order to increase N stores in fine roots. Spring application should be between full bloom and the young fruit stages to meet the high N demands of developing fruit. Summer application of fertilizer at the fruit enlargement stage does not contemporaneously affect the growth of pears, but increases the N stored in coarse roots, and in turn the amount available for remobilization in spring.
基金Supported by the National Natural Science Foundation of China (No. 30600382)the foundation of the Institute of Soil Science,Chinese Academy of Sciences (No. 055131)
文摘Cherry tomatoes （Lycopersicon esculentura Mill., cv. hongyangli） were hydroponically cultivated in a greenhouse to determine the effect of different nitrogen （N） forms on organic acid concentration and the activities of related enzymes involved in nitrogen and organic acid metabolism during cherry tomato fruit development. The results showed that fruit nitrate reductase （NR） activity was much higher following treatment with 100% NO3 and 75% NO3 ＋ 25% NH＋ than with 100% NH＋ except at maturity. Glutamine synthetase （GS） activity trended downward during fruit development under all three treatments. Plants fed 100% NH＋ had the lowest fruit citrate and malate levels at maturity, with the highest malate concentration at an early stage. The activity of phosphoenolpyruvate carboxylase （PEPC） was found to be in accord with the malate concentration with every N source. Under all three N forms, the citrate synthase （CS） activity peaked one week before the citrate concentration.
