干热河谷车桑子光合生理特性对氮磷添加的响应

氮磷养分是限制干热河谷植物生长的重要元素，不同土壤上植物受到的养分限制类型不同。光合作用作为植物生长发育的基础，不同土壤上氮磷养分添加对干热河谷植物光合生理特征的影响还没有报道。因此，以干热河谷优势植物——车桑子为研究对象，在元谋县不同海拔处采集土壤，设置加氮（+N）、加磷（+P）、氮磷同时添加（+NP）和不添加（CK）四个处理，研究车桑子光合响应曲线、叶绿素含量和叶绿素荧光特性对氮、磷添加的响应规律，并探讨光合响应特征与车桑子生长的关系：研究结果显示：1）不同海拔土壤上，车桑子光合生理特性对氮磷添加具有不同的响应。在低海拔燥红土上，氮添加处理（+N和+NP）提高了车桑子净光合速率、叶绿素含量和PSII活性；中海拔紫色土上，+NP促进了车桑子光合速率和叶绿素含量的提高；高海拔黄棕壤上，+N处理降低了车桑子净光合速率和PSII活性，而磷添加处理（+P和+NP）提高了车桑子净光合速率。2）车桑子光合特性对养分添加的响应取决于土壤的养分限制类型，限制性养分添加可以提高车桑子的净光合速率。3）燥红土上+P以及黄棕壤上+N对PSⅡ最大光化学效率（Fv/Fm）的降低更大程度上归于可变荧光Fv的减少而不是最小荧光F₀的增加，可减少养分限制对光系统II造成的伤害。4）三种土壤类型上车桑子的叶绿素含量和组成差异极显著，相比于燥红土和紫色土，黄棕壤上车桑子的叶绿素含量显著更高，而叶绿素a/b显著更低。综上，本研究结果表明，车桑子光合能力受到氮和磷的共同调节，不同土壤上光合生理特性的响应可增强植物对限制性养分的适应性，影响植物生长发育。

Responses of photosynthetic characteristics of Dodonaea viscosa to nitrogen and phosphorus addition in a dry-hot valley

Plant growth is limited by nitrogen and/or phosphorus in the dry-hot valley, and the nutrient limitations may differ across soil types. Photosynthesis is the basis of plant growth and development. However, the effects of nitrogen and phosphorus on plant photosynthetic characteristics in dry-hot valley have not been reported. In this study, we planted Dodonaea viscosa, the dominate species in the dry-hot valley in different soils with different elevations in Yuanmou county and fertilized them factorially with nitrogen and phosphorus. The effects of nitrogen and phosphorus addition on photosynthetic response curve, chlorophyll content and chlorophyll fluorescence were studied, and the relationship between photosynthetic response and D. viscosa growth was discussed. The results showed that:1) photosynthetic characteristics of D. viscosa in different soils responded to nitrogen and phosphorus addition differently. The net photosynthetic rate, chlorophyll content, and PSII activity of D. viscosa were increased by nitrogen addition (+N and +NP) in dry red soil. +NP promoted the photosynthetic rate and chlorophyll content of D. viscosa in purple soil. +N reduced photosynthetic rate and PSII activity of D. viscosa in yellow brown soil, where P addition treatment (+P and +NP) increased the photosynthetic rate. 2) The responses of photosynthetic characteristics of D. viscosa to nutrient addition were depended on the type of nutrient restriction in soil. The addition of the limited nutrient could improve the net photosynthetic rate of D. viscosa. 3) The reductions of Fv/Fm caused by +P in dry red soil and +N in yellow brown soil were attributed to the reduction of Fv rather than the increase of F₀, which could relieve the damage of PSII. 4) Chlorophyll content and chlorophyll composition of D. viscosa in the three soils were significantly different. Compared with dry red soil and purple soil, chlorophyll content in yellow brown soil was significantly higher, while chlorophyll a/b was significantly lower. To sum up, the results showed that the photosynthetic capacity of D. viscosa was co-regulated by nitrogen and phosphorus, and the responses of photosynthetic characteristics of D. viscosa in different soils could enhance their adaptability to restricted nutrients and affect their growth.