东北红豆杉幼苗对不同水分条件的光合和生理响应

以盆栽4年生东北红豆杉扦插苗为试验材料，研究了在不同水分条件下，东北红豆杉幼苗叶片的叶绿素含量和保护酶活性的变化以及光合特性对光强的响应。结果表明:土壤含水量80%±5%与土壤含水量50%±5%处理下的东北红豆杉幼苗叶片的叶绿素含量、光合特性以及保护酶活性均无明显差异，而土壤含水量在20%±5%时，东北红豆杉幼苗前14 d内叶绿素含量、保护酶活性和丙二醛含量没有明显变化，14 d后幼苗叶片的叶绿素含量显著降低，保护酶SOD和POD活性下降，MDA含量增加，与土壤含水量80%±5%和50%±5%条件下差异显著。从光合响应曲线中可以看出，较高的水分条件对东北红豆杉幼苗影响不大，但干旱胁迫使表观量子效率、最大净光合速率和光饱和点降低，光补偿点升高，使东北红豆杉光能利用效率降低，光合作用受到抑制，叶肉细胞利用CO2的能力降低，光合碳同化和有机物的积累受阻。 

Physiological and photosynthetic response to different water conditions of Taxus cuspidate seedlings

A total of 30 individuals of potted 4-year-old Taxus cuspidata cutting seedlings were selected as the experimental materials.We studied the response of leaf chlorophyll content,protective enzyme activities and photosynthetic characteristics to light intensity in different water conditions of T.cuspidata seedlings,and the results showed that there was no significant difference between middle soil moisture conditions (water content was 50%±5%) and relatively high moisture conditions (water content was 80%±5%) in chlorophyll content,photosynthetic characteristics and the protection of enzyme activity.When the soil moisture content was relative drought(water content was 20%±5%),in early 14 days of potting,leaf chlorophyll content,protective enzyme activities and MDA content did not change significantly;after 14 days,leaf chlorophyll content of seedlings reduced significantly,and the protective enzyme activities of SOD and POD decreased,but the MDA content increased.There was a significant difference between middle soil moisture conditions and relatively high moisture conditions.From light response curves,we can know that relatively high moisture conditions had little influence on T.cuspidata,but drought stress reduced apparent quantum yield(AQY),maximum net photosynthetic rate(Pmax)and light saturation point(LSP),and increased light compensation point(LCP),which decreased light use efficiency of T.cuspidata,inhibited photosynthesis,reduced the ability of mesophyll cells making use of CO2,and then hindered photosynthetic carbon assimilation and accumulation of organic obstruction of T.cuspidata seedlings.