短期黑暗对矮牵牛幼苗叶片光合结构及功能的影响

Effects of short-term darkness on leaf photosynthetic structure and functions of Petunia hybrida seedlings

以矮牵牛(Petunia hybrida)为试验材料,常温黑暗条件处理1、4 d和15 d,后两种处理在光照(PFD=150μmol·m^(-2)·s^(-1))下恢复4、8 d和12 d,对幼苗叶片显微结构、叶绿体超微结构及光合功能进行了研究。结果表明:(1)与0 d相比,黑暗处理1、4 d和15 d叶片厚度分别下降9.9%、16.9%和36.2%;栅栏组织厚度黑暗处理1 d有显著减小,海绵组织厚度黑暗处理4 d后有显著下降。黑暗处理1 d的幼苗叶片,叶绿体片层排列紧密但方向稍紊乱;黑暗处理4 d,叶绿体片层排列扭曲变形,叶绿体内有空洞;黑暗处理15 d,叶绿体内布满空洞,趋于解体。恢复光照,黑暗处理4 d幼苗叶片显微结构及叶绿体超微结构完全恢复,15 d幼苗基本恢复。(2)黑暗处理后叶绿素、Pn、Gs、Ci、Fv/Fm和F/Fo均显著下降,Fo显著上升。恢复光照,以上光合特性各值均基本恢复到正常水平。黑暗及恢复光照过程中叶绿素含量的变化主要取决于Chl a,而Chl b保持相对稳定;黑暗处理4 d幼苗光合作用的下降主要是由气孔限制所致,而15 d幼苗光合作用的下降主要是非气孔因素造成。

Petunia hybrida seedlings were used as test materials and treated under normal atmospheric temperature and darkness for 1,4 d and 15 d,and then the seedlings treated for 4 and 15 d were exposed to normal light（PFD = 150 μmol.m^-2. s^-1）for 4,8 and 12 d in order to study the changes in the leaf microstructure, chloroplast ultrastructure and photosynthesis. The results showed that compared with the leaves of seedlings treated for 0 d,those treated for 1,4 d and 15 d decreased by 9.9%, 16.9% and 36.2% in thickness, respectively; the palisade tissue of 1 d darkness treatment and the spongy tissue of 4 d darkness treatment significantly reduced in thickness. The leaf chloroplasts were close in lamella arrangement but slightly disordered in direction after 1 d darkness treatment,twisted in lamella arrangement and had some cavities after 4 d darkness treatment, and tended to disintegration after 15 d darkness treatment. When exposed to normal light,the leaf microstructure and chloroplast ultrastructure could completely recover for the seedlings of 4 d darkness treatment and basically recover for the seedlings of 15 d darkness treatment. After darkness treatment the net photosynthetic rate（Pn）, stomatal conductance（Gs）, intercellular CO2 concentration （Ci） and chlorophyll fluorescence parameters-Fv/Fm and Fv/Fo decreased significantly,while the Fo significantly increased due to darkness. When the seedlings were exposed to normal light, all the above values basically returned to their normal levels. The variation of chlorophyll content mainly depended on Chl a while Chl b kept relatively stable during the darkness treatment and light recovery. The photosynthesis decline of the seedlings of 4 d darkness treatment was mainly limited by the stomas while that of the seedlings of 15 d darkness treatment was caused by non-stoma factors.