不同施氮水平纽荷尔脐橙叶绿素含量的季节变化

以1年生盆栽枳砧纽荷尔脐橙为试材,研究不同施氮水平对叶片氮含量,春梢、夏梢和秋梢落叶率,以及春梢、夏梢和秋梢叶绿素含量季节变化的影响。结果显示,施氮植株当年萌发的春梢和夏梢的落叶率在次年5月有减少的趋势,秋梢落叶率则有增加的趋势,其余时期施氮量与落叶率关系不明显;叶片氮含量与施氮量极显著正相关(r=0.97);施氮在大多数时期可显著或极显著提高不同枝梢叶片的叶绿素含量,在整个测定时期内保持较为稳定,在单株施氮量6.5g范围内这种效应随施氮量增加而显著增强,对照(不施氮)植株不同枝梢叶片的叶绿素含量从当年10月开始明显下降且次年4月锐降。由此可见,充足的氮肥不仅可提高纽荷尔脐橙叶片叶绿素含量且可减少其季节性变化幅度。

Seasonal Variation in Leaf Chlorophyll Content of Newhall Navel Orange Seedlings Applied with Different Levels of Nitrogen

One-year-old potted Newhall navel orange(Citrus sinensis Osbeck cv.Newhall) seedlings on trifoliate orange(Poncirus trifoliata(L.) Raf.) rootstock were applied with different levels of nitrogen(N),and the effects of N application levels on leaf abscission,leaf N content and the seasonal changes in leaf chlorophyll content of spring,summer and autumn shoots were studied.Results showed that leaf abscission rates of spring and summer shoots on trees applied with N tended to decrease in the following May,while that of autumn shoots tended to increase.There was no significant correlation between N application level and leaf abscission during other seasons.A significantly positive correlation existed between N content in leaves and per tree N application level(r=0.97).The chlorophyll content in leaves of spring,summer and autumn shoots on trees treated with application of N was significantly increased and was relatively steady in the whole studied period.No further increase in leaf chlorophyll content was observed as the application rate exceeded 6.5 g of N.However,higher rate of N application was beneficial to the maintenance of a steady chlorophyll level.The chlorophyll content in leaves of all shoots of control trees decreased obviously in October and sharply in the following April.These results suggested that N application could increase chlorophyll content in leaves of Newhall navel orange and reduce the seasonal changes in chlorophyll level.