干旱胁迫对红皮柳光合特性日变化及生长的影响

Effect of drought stress on photosynthetic diurnal course and growth of Salix purpurea

红皮柳(Salix purpurea)是我国西北地区重要的乡土树种,生长快、适应性强,在水土保持、防护林和生物质能源等方面发挥重要作用。以红皮柳扦插苗为研究材料,通过盆栽试验,在4种不同程度干旱胁迫处理(对照、轻度干旱、中度干旱和重度干旱胁迫)下,测定叶片的光合作用参数及生长量,分析探讨干旱胁迫对红皮柳光合特性及生长的影响。结果表明:在轻度、中度和重度干旱胁迫下,红皮柳叶片净光合速率(Pn)日均值分别比对照下降10.4%(P>0.05)、17.9%(P<0.05)和58.2%(P<0.05),中度和重度干旱胁迫下Pn下降量达到显著水平;随着干旱胁迫程度的加剧,Pn的下降伴随着蒸腾速率(Tr)和气孔导度(Gs)的显著下降,水分利用效率(EWUE)逐渐升高,胞间CO_2浓度(Ci)先下降后上升;轻度干旱胁迫和中度干旱胁迫下Pn的降低是由于气孔限制引起,而重度干旱胁迫下受到气孔因素与非气孔因素的共同作用。而且,红皮柳生长受到干旱胁迫的显著影响,随着干旱胁迫程度的加重,株高和基径的相对增长率下降程度增大。

Salix purpurea, a native tree species in the northwestern China, grows fast and has strong adaptability. It plays important roles in water and soil conservation, shelter forest and bioenergy. In order to illustrate the photosynthetic mechanism and growth response of S. purpurea to soil drought stress, we studied the diurnal photosynthetic characteristics of the potted cutting plants under four different soil drougth stress （control, mild, moderate and severe drought stress）. The results showed that the diurnal means of the net photosynthetic rates （P,） reduced by 10.4% （P〉 0.05）, 17.9% （P〈0.05） and 58.2% （P〈0.05） under the mild, moderate and severe drought stress compared with con- trol, respectively. And the P, under moderate and severe drought stress reduced significantly. With the drought stress level increasing, the daily average of the net photosynthetic rates （Pn）, transpiration rates （ Tr） , stomatal conductance （ Gs ） also decreased significantly, while water utilization efficiency （ Ewur ） increased slightly. Unlike the above parame- ters, the intercellular CO2 concentration （ Ci ） decreased initially and then increased. These results suggested that the decrease of Pn under mild and moderate drought stress might be caused by stomatal limitation, while the decrease under severe drought stress might be caused by stomatal and non-stomata1 limitation. Furthermore, the relative growth ratio of height and ground diameter of S. purpurea cutting plants decreased significantly with the increased drought stress level.