不同光照条件下东北红豆杉幼苗光合特性日变化

Diurnal changes of photosynthetic characteristics of Taxus cuspidata seedlings under different light conditions

为了解东北红豆杉的光适应特性以达到高效培育的目的,以5年生东北红豆杉幼苗为研究对象,研究3种光照条件下(全光照FL、60%全光照F1和30%全光照F2)东北红豆杉幼苗光合特性的日变化规律,明确其幼苗随光温变化的生理响应特点。结果显示:3组幼苗的净光合速率(Pn)均呈现双峰变化趋势,9:00时Pn的峰值显著高于15:00时的峰值,且F2条件下的Pn最高,F1次之,FL最低;显然增加光照强度后,幼苗的Pn受到了强光的抑制。气孔导度(Gs)和蒸腾速率(Tr)的日变化规律与Pn相似,呈现出明显的双峰趋势,F2条件下幼苗的Gs变化幅度要小于其他2组幼苗的Gs;上午F2条件下幼苗的Tr最高,下午FL条件下的Tr最高。胞间CO2浓度(Ci)呈现V型变化趋势,上午F2条件下幼苗的Ci最高,下午最低,且与FL条件下的幼苗差异显著。气孔限制值(Ls)的变化趋势与Ci完全相反。总体而言,幼苗增加光照强度后,在1 d内,从外观上幼苗生长状态正常,但净光合速率明显下降。

In order to understand the characteristics of light adaptation of Taxus cuspidata for efficient cultivation,we selected 5-year-old seedlings to study the diurnal changes of photosynthetic characteristics under three different light conditions,i. e.,full light（ FL）,60% FL（ F1） and 30% FL（ F2）,and measured the physiological responses of the seedlings to the change of light and temperature. The results showed that the photosynthetic rate（ Pn） of all three groups had a double-peaked curve,and Pnof seedlings at 9： 00 am was significantly higher than that at 15： 00 pm. Pnunder F2 light condition was the highest,and the Pnvalue under the F1 light condition was higher than that under the full light condition.It was clear that Pnof seedlings was restrained by the increase of light intensity. The diurnal changes of stomatal conductance（ Gs） and the transpiration rate（ Tr） showed a similar double-peaked pattern of the Pnvalues. The variations of Gsvalues of the seedlings under F2 light condition was lower than the other two groups; the Trunder F2 light condition reached the highest value in the morning,and the Trunder FL condition was the highest in the afternoon. The intercellular carbon dioxide concentration（ Ci）showed a ＂V＂curve trend. The Ciof seedlings under F2 had the highest value in the morning,and the Cireached the opposite trend in the afternoon,significantly different from the FL trend. The trend of thediurnal variation of stomatal limitation（ Ls） was opposite to that of Cicompletely. In general,the net photosynthetic rate of the seedlings decreased with the increase of light intensity during the daytime obviously.