磷素供给对米槁幼苗光合作用—CO_2响应的影响

【目的】探索不同磷素水平下米槁(C_innamomum migao H.W.Li)幼苗光合作用对CO_2的响应机制,为西南地区推广种植米槁及其科学施用磷肥提供参考依据。【方法】以0.5年生米槁幼苗为对象,设4个磷素(KH_2PO_4)供给浓度(CK为1.000 mmol/L,P_1、P_2和P_3处理分别为0.125、0.500和2.000 mmol/L)处理,测定各处理米槁幼苗的光合特性,利用直角双曲线模型、非直角双曲线模型及直角双曲线修正(P_n/C_i)模型拟合米槁幼苗的光响应曲线和参数。【结果】3种米槁幼苗光响应曲线拟合模型的拟合决定系数R~2均在0.9900以上,表达的效力趋势排序为P_n/C_i模型非直角双曲线模型直角双曲线模型,以P_n/C_i模型对米槁的光合作用—CO_2响应最实用,且不同磷素水平下模型拟合效力均符合此效力趋势。各磷素供给处理中,除胞间CO_2浓度(C_i)外,净光合速率(P_n)、气孔导度(G_s)和蒸腾速率(T_r)的排序均为CKP_3P_2P_1,且P_1处理的P_n、G_s和T_r均与其他处理差异显著(P0.05),表明1.000 mmol/L KH_2PO_4处理下米槁幼苗的光合作用效率最高。【结论】P_n/C_i模型最适宜进行米槁幼苗光合作用—CO_2响应拟合;施用适量磷素能促进米槁幼苗的光合作用,最适宜米槁幼苗生长的土壤磷含量为1.000 mmol/L。

Effects of phosphorus application on photosynthesis-CO2 response of Cinnamomum migao H. W. Li seedlings

Objective]This study was conducted to explore the response mechanism of photosynthesis to CO2 in Cin-namomum migao H. W. Li seedlings under different phosphorus levels,in order to provide reference for scientific phospho-rus application and cultivation of C. migao in southwestern China.Method]This study took half-year C. migao seedlings as experimental material. Four phosphorus(KH2PO4)supply concentrations(CK was 1.000 mmol/L,P1,P2 and P3 were 0.125,0.500 and 2.000 mmol/L respectively)were set. Photosynthetic characteristics of the C. migao seedlings under dif-ferent treatments were determinated,and light response curves and parameters were fitted by using right angle hyperbola model,non-right angle hyperbola model and modified right angle hyperbola model(Pn/Ci).Result]Determination coeffi-cients R2 of the three fitting models on C. migao seedlings photosynthesis response were above 0.9900,and the effective-ness trend was Pn/Ci model>non-right angle hyperbola model>right angle hyperbola model. Pn/Ci model was the most practical one for photosynthesis-CO2 response of C. migao seedlings,and fitting effectiveness of the model was in line with this trend under different phosphorus levels. Under all phosphorus treatments,except intercellular CO2 concentration (Ci),the rank of net photosynthetic rate(Pn),stomatal conductance(Gs),and transpiration rate(Tr)was CK>P3>P2>P1, and Pn,Gs and Tr under P1 treatment were significantly different from those under other treatments(P<0.05),which showed that the photosynthetic efficiency of C. migao seedlings was the highest under 1.000 mmol/L KH2PO4 treatment.Conclusion]The Pn/Ci model is the most suitable for photosynthesis-CO2 response fitting of C. migao seedlings. Appropri-ate application of phosphorus can promote C. migao photosynthesis. The most suitable content of phosphorus in soil for C. migao seedlings is 1.000 mmol/L.