泡桐叶片的水分特征研究

Water Characteristics of Paulownia Leaves

该文从水势和水量两个角度,在正常水分状况下,对泡桐叶片的水分特征进行研究.结果表明:泡桐序列叶片绝对含水量(Wd)呈抛物线变化,即嫩叶>老叶>成熟叶,叶片间相对含水量(Wr)无差别.在叶片的吸水过程中,成熟叶和老叶具有明显的稳定期,嫩叶却不明显,吸水速率为成熟叶>老叶>嫩叶.从开始浸泡至拐点的时间嫩叶为3h54min,成熟叶3h42min,老叶3h48min.在失水过程中,老叶和成熟叶之间无差别,嫩叶的失水速度却明显快于成熟叶和老叶,但到达拐点的时间最短为成熟叶(3h24min),嫩叶和老叶无差别(3h34min,3h33min).泡桐序列叶片水势变化的一个主要特点是在成熟的功能叶片处有明显的拐点,其后叶水势较为稳定.泡桐成熟叶片的水势日变化呈双峰型,分别在9:00左右和14:00左右达到最低值,日变幅约0.8MPa.叶水势与绝对含水量和相对含水量均呈显著的指数相关关系(Rd=0.95,Rr=0.96).在水分亏缺情况下,水势指标比含水量指标更敏感,更易于准确反映叶片水分亏缺状况.

Data of water potential and content of paulownia leaves under normal water condition are analyzed. Results are showed as follows:①the absolute water contents of the sequential leaves, based on dry weight, vary in a parabola (\%R\%=0.71), and the sequences of those contents is as followed: tender leaf>old leaf>mature leaf, but the relative water contents among these leaves are not remarkably different. ②During the process of water absorption of leaves, the mature leaf and the old leaf have an apparent smooth stage but the tender leaf has not. The order of the velocity of water absorption is: mature leaf>old leaf>tender leaf. It took 3 hours and 54 minutes for the tender leaf to arrive the inflection point, 3 hours and 42 minutes for the mature leaf, 3 hours and 48 minutes for the old leaf. ③During the process of water desorption, there is not apparent difference between the old leaf and the mature leaf, and the velocity of water desorption of the tender leaf is apparently faster than that of the mature leaf and the old leaf. But it is the mature leaf that spends the least time (3 h 24 min)to arrive the inflection point, and there is not remarkable difference between the tender leaf(3 h 34 min) and the old leaf(3 h 33 min). ④A main characteristic of water potential variation of sequential leaves of paulownia is: there is an apparent inflection point in the process of variation of water potential, and then the variation tends to be smooth. Variation tendency of water potential in a day shows a form of double peak value, and the two peak values appear at approximate 9:00am and 2:00pm, its amplitude of variation in a day is approximate 0.8 MPa. ⑤With the development of water deficit of paulownia leaf, the leaf water potential shows a remarkable index and logarithmic interrelation with both the absolute water content (\%R\%\-d=0 95) and the water saturation deficit (\%R\%\-\{WSD\}=-0 96) under room conditions, and index of water potential is more sensible and accurate than that of water content to reflect the state of water deficit of paulownia leaf.