元江元谋干热河谷土壤氮磷水平对酸角叶片氮磷含量及光合的影响

Effects of soil nitrogen and phosphorus levels on leaf nitrogen and phosphorus contents and photosynthesis of Tamarindus indica L. in Yuanjiang and Yuanmou dry-hot valley

为了解元江及元谋干热河谷人工栽培酸角的土壤氮磷含量对酸角叶片氮磷含量及光合作用的影响,本研究测定了两个干热河谷区酸角人工林土壤、叶片氮磷含量及光合参数,并使用4种常用的光响应曲线拟合模型(直角双曲线模型、非直角双曲线模型、直角双曲线修正模型、二项式拟合模型)对其进行拟合。结果表明:元江、元谋干热河谷酸角人工林土壤氮磷含量及氮磷比存在显著差异,两地土壤氮含量分别为1.205和0.881 g·kg-1,磷含量分别为0.481和0.177 g·kg-1,氮磷比分别为2.61和5.49;两地酸角叶片氮含量存在显著差异,元江、元谋干热河谷酸角叶片的氮含量分别为17.28和13.51 g·kg-1,而叶片磷含量没有显著差异,分别为1.51和1.18 g·kg-1,叶片氮磷比也没有显著差异,分别为11.80和11.66; 4个光响应曲线拟合模型对两个干热河谷酸角的光响应曲线都有较高的拟合度,但直角双曲线修正模型在低光合有效辐射情况下拟合度最高,而二项式拟合模型在高光合有效辐射情况下拟合度最高,因此表观量子效率(α)、光补偿点(LCP)、暗呼吸速率(Rd)取直角双曲线修正模型的拟合数值,元江、元谋两地酸角的数值分别为0.055和0.060、38.921和8.019μmol·m-2·s-1、1.377和0.404μmol·m-2·s-1;最大净光合速率(Pnmax)、光饱和点(LSP)取二项式拟合模型的拟合数值,两地分别为11.073和6.331μmol CO2·m-2·s-1、3223.2和2532.4μmol·m-2·s-1;元江干热河谷的酸角光合作用显著高于元谋干热河谷,两地土壤磷含量和叶片磷含量是影响酸角光合作用的关键因子。

Field experiments were carried out to examine the effects of different soil nitrogen and phosphorus concentrations on leaf nitrogen and phosphorus concentrations and photosynthesis of tamarind( Tamarindus indica L.) in the Yuanjiang and Yuanmou dry-hot valleys. Soil nitrogen and phosphorus concentrations,leaf nitrogen and phosphorus concentrations,and the photosynthetic parameters were measured. We used four kinds of common light response curve fitting models,including rectangular hyperbola model,non-rectangular hyperbola model,modified rectangular hyperbola model,and quadratic regression model. The results showed that soil nitrogen and phosphorus concentrations,and ratio of nitrogen to phosphorus were significantly different between Yuanjiang and Yuanmou dry-hot valleys. Soil nitrogen concentrations were 1.205 and 0.881 g·kg-1,soil phosphorus concentrations were 0.481 and 0.177 g·kg-1,soil nitrogen to phosphorus ratios were 2.61 and 5.49,respectively in Yuanjing and Yuanmou dry-hot valleys. Leaf nitrogen concentrations of tamarinds were 17. 28 and 13. 51 g · kg-1 in Yuanjing and Yuanmou dry-hot valleys,respectively,being significantly different. There was no significant difference in leaf phosphorus concentrations( 1.51 vs. 1.81 g·kg-1) between Yuanjiang and Yuanmou valleys. The ratio of nitrogen to phosphorus in leaf had no significant difference between the two sites( 11.80 vs. 11.66). The four light response curve fitting models all had a high degree of fitting for the light response curves of the tamarind in the two sites. The modified rectangular hyperbola model under the condition of low photosynthetically active radiation( PAR) was the best one,while the quadratic regression model under the condition of high PAR fitting degree was the most suitable model. The apparent quantum efficiency( α),light compensation point( LCP),dark respiration rate( Rd) were calculated with the modified rectangular hyperbola model,with corresponding values of 0.055,38.921 μmol·m-2·s-1 and 1.377 μmol·m-2·s-1 in Yuanjiang valley,and 0.060,8.019 μmol·m-2·s-1 and 0.404 μmol·m-2·s-1 in Yuanmou valley,respectively. The maximum net photosynthetic rate( Pnmax) and light saturation point( LSP) were calculated with the quadratic regression model,with corresponding values of 11.073 and 3223.2 μmol CO2·m-2·s-1 in Yuanjiang valley,and 6.331 and 2532.4 μmol CO2·m-2·s-1 in Yuanmou valley,respectively. In conclusion,photosynthetic rate of tamarind in Yuanjiang dry-hot valley was significantly higher than that in Yuanmou dry-hot valley. Soil phosphorus and leaf phosphorus concentrations were the key influencing factors for the photosynthesis of tamarind.