水分胁迫对龙眼光合作用的影响

Effect of Water Stress on Photosynthesis of Longan

以一年生实生盆栽苗为试材,用红外线 CO_2气体分析器研究了水分胁迫对龙眼光合作用的影响。结果表明,幼龄叶片对水分胁迫的反应比较敏感,老龄叶片反应迟钝;叶片光合速率(Pn)的下降与叶片含水量的下降基本同步,都明显滞后于土壤相对含水量的下降;Pn 下降的原因,既有气孔因素,也有非气孔因素;严重的水分胁迫改变了叶片光合速率的日进程;复灌后其光合作用恢复较慢,且不能恢复到胁迫前的最高水平;龙眼生长的最适土壤相对含水量为62%～84%,灌水临界期约为38%～42%。

One-year-old potted seedling trees were used to study the effects of water stress on photosynthesis of Longan(Dirnocarpus longana Lour.),with an infrared gas analyzer.Response of net photosynthetic rate (Pn)to water stress in young leaves was more sensitive than that in old leaves.The decline of Pn under wa- ter stress was concurrent with the decline of leaf water content(LW),they were both lag behind that of rela- tive soil water content(SW),and were induced by both stomatal factors and non-stomatal factors.Severe drought stress changed the diurnal variation curve of Pn.Pn went up,but more slowly,after re-irrigation, and could not return to the highest level of Pn before drought treatment.The optimum SW of Pn varied from 62%～84%.The critical level of SW,at which the plant needs irrigation,was about 38%.