光照强度对长春花叶片光合特性和叶绿素含量的影响

Effects of Light Intensity on Photosynthetic Characteristics and Chlorophyll Content of Leaves of Catharanthus roseus

摘要: 为筛选出长春花(Catharanthus roseus)幼苗进行光合作用的最佳光照强度，采用人工遮荫的方法，分别设置100% (CK)、70%、40%、10%透光率，处理15 d后，测定长春花幼苗叶片光合参数和叶绿素相对含量。结果表明：自然光下长春花光补偿点(LCP)、光饱和点(LSP)和净光合速率(P_n)均比70%、40%和10%透光光率大，分别为：LCP 16.22 μmol∙m⁻²∙s⁻¹，LSP 1000 μmol∙m⁻²∙s⁻¹，最大净光合速率(P_nmax)为18.56 μmol∙m⁻²∙s⁻¹，组间数值的差异随着光照强度的减弱逐渐增大。自然光下长春花叶绿素a (Chla)、叶绿素b (Chlb)的含量最小，分别为0.579 mg∙g⁻¹、0.324 mg∙g⁻¹，但Chla/Chlb的比值最大，为1.787。随着光照强度的减弱，长春花的LCP、LSP和P_n均呈现下降趋势，长春花叶绿素总量呈现上升趋势，Chla/Chlb的比值呈现下降趋势。

Abstract: To screen the best light intensity for photosynthesis in Catharanthus roseus seedlings, artificial shading was used to set light transmittance at 100% (CK), 70%, 40%, and 10%. After 15 days of treatment, photosynthetic parameters and relative chlorophyll content were measured in the leaves of C. roseus seedlings. The results showed that the light compensation point (LCP), light saturation point (LSP), and net photosynthetic rate (P_n) of C. roseus under natural light were higher than those under 70%, 40%, and 10% light transmittance, with LCP of 16.22 μmol∙m⁻²∙s⁻¹, LSP1000 μmol∙m⁻²∙s⁻¹. The maximum net photosynthetic rate (P_nmax) was 18.56 μmol∙m⁻²∙s⁻¹, and the differences in values between groups gradually increased as the light intensity decreased. Under natural sunlight, the content of chlorophyll a (Chla) and chlorophyll b (Chlb) in C. roseus leaves was the lowest, at 0.579 mg∙g⁻¹ and 0.324 mg∙g⁻¹, respectively, but the ratio of Chla/Chlb was the highest, at 1.787. As the light intensity decreased, the LCP, LSP, and P_n of C. roseus showed a downward trend, while the total chlorophyll content of C. roseus showed an upward trend, and the ratio of Chla/Chlb showed a downward trend.