木薯叶形与光合特性、SPAD值的相关性研究

Correlation of leaf shape of cassava with SPAD value and photosynthetic characteristics

[目的]研究木薯叶片形态与光合特性、SPAD值之间的相关性,为木薯高产品种选育提供理论依据.[方法]以5个叶形差异较大的木薯品种（系）为材料,测定不同叶位叶片形态指标、净光合速率、气孔导度、胞间CO2浓度、蒸腾速率和SPAD值,通过方差分析和相关性分析,探讨叶形对光合特性、SPAD值的影响.[结果]中间裂叶长度与光合生理指标呈显著正相关,中间裂叶长度与净光合速率、气孔导度、胞间CO2浓度、蒸腾速率的相关系数分别达到0.946、0.981、0.810和0.816;木薯SPAD值与叶形指标、光合生理指标之间相关性不显著;相同品种（系）不同叶位之间叶形指标和SPAD值均差异不明显,SPAD值在第6个叶位（最上部全展叶第23片叶）时较高;净光合速率值总体上随叶位从上到下呈逐渐降低的趋势,木薯最上部全展叶第3～11片叶光合效率最高.[结论]木薯的中间裂叶长度越长,其净光合速率、气孔导度、胞间CO2浓度、蒸腾速率值越大,品种（系）光合效率越高;保持木薯中上部叶片的光合作用功能对提高木薯产量有重要意义.

[Objective]The correlation of leaf shape of cassava with SPAD value and photosynthetic characteristics was studied to provide references for breeding high-yield variety of cassava. [Method]Five cassava genotypes with various shapes of leaves were used as materials. Their leaf index, SPAD value, net photosynthetic rate, stomatal conductance, intercellular CO2 concentration and transpiration rate were measured. The effects of leaf shape on photosynthetic characteristics and SPAD value were discussed through variance and correlation analysis. [ Result ]The results showed that the length of middle lobes had significant positive correlation with photosynthetic indexes. Its correlation coefficient with net photosynthetic rate, stomatal conductance, intercellular CO2 concentration and transpiration rate was 0.946, 0.981, 0.810, 0.816, respectively. The correlation of SPAD values with leaf index and photosynthetic indexes was not significant. SPAD value and different leaf positions had no significant difference, and the relative higher value was in the sixth leaf position （the 23 nd full spreading up- per leaf）. The net photosynthetic rate reduced from the top to down gradually, and the uppermost fully expanded leaves （from 3nd to 11th） had the highest photosynthetic efficiency. [ Conclusion ]Net photosynthetic rate, stomatal conductance, intercellular CO2 concentration, transpiration rate and photosynthetic efficiency increased with the length increase of cassava middle lobes. Maintaining photosynthetic characteristics of cassava upper-middle leaves has important implications for improving cassava yield.