辣椒不同紫色程度叶片的光合特性及光响应模型拟合研究

以紫色叶片辣椒‘CS3’与绿色叶片辣椒‘LS1’杂交F_2代分离群体为试验材料,比较研究了从浓紫到纯绿(Z-1、Z-2、Z-3、Z-4、Z-5、Z-6、Z-7)7个不同紫色程度辣椒的光合特性,同时运用直角双曲线模型、非直角双曲线模型、指数方程模型和直角双曲线修正模型等4种模型进行光响应拟合,并通过比较拟合优度决定系数(R~2)、表观量子效率(α)、最大净光合速率(P_(n,max))、光补偿点(LCP)、光饱和点(LSP)及暗呼吸速率(R_d)等参数,分析了4个模型的差异。结果表明:(1)当光合有效辐射(PAR)达到1 200μmol·m~(-2)·s~(-1)以后,紫色程度较高的辣椒(Z-1、Z-2、Z-3、Z-4、Z-5)的净光合速率—光响应曲线(P_n–PAR)仍然保持着上升趋势,没有出现光饱和或光抑制现象,且气孔导度(G_s)和蒸腾速率(T_r)迅速增大,胞间CO_2浓度(C_i)和水分利用效率(WUE)均维持在较高的水平;在PAR为2 000μmol·m~(-2)·s~(-1)时,Z-4的P_n最高,为(20.16±0.58)μmol·m~(-2)·s~(-1),Z-5的WUE(CO_2/H_2O)最高,为(2.02±0.01)μmol·μmol~(-1)。(2)4种模型均能较好地拟合不同紫色程度辣椒叶片P_n的光响应曲线,决定系数(R~2)在0.964~1.000之间。比较R~2得出,拟合效果优劣顺序为,直角双曲线修正模型非直角双曲线模型直角双曲线模型指数方程模型,仅直角双曲线修正模型获得了Z-2、Z-4、Z-5、Z-6、Z-7辣椒的LSP。根据直角双曲线修正模型,Z-4的LSP最大,为(2 958.41±923.48)μmol·m~(-2)·s~(-1)。得出结论,(1)紫色辣椒弱光利用能力属于中上水平,对强光具有一定的适应能力,不容易出现光饱和或光抑制现象,光合潜力较大,且暗呼吸消耗较小,有利于积累有机物,在选育耐强光的高产品种方面具有潜在的利用价值;(2)叶片紫色程度浅的辣椒有利于筛选节水型材料;(3)直角双曲线修正模型的拟合结果与实测值更为接近,且能获得更多的光合参数信息,较适用于拟合紫色辣椒光响应曲线。

Photosynthetic Characteristics and Light Response Model Fitting of Pepper Leaves in Different Degrees of Purple

A comparative study was conducted on the photosynthetic characteristics of seven peppers with different purple levels with CS3 hybrid F2 generation segregation population. The seven peppers were named as Z-1，Z-2，Z-3，Z-4，Z-5，Z-6 and Z-7，respectively，as the color changed from dark purple to green. Four models（i.e.，rectangular hyperbolic model，non-rectangular hyperbolic model，exponential model and modified rectangular hyperbolic model）were adopted to fit the light response curves for photosynthesis of the seven peppers. The difference among the four models was determined by comparing the parameters，such as determining coefficient（R2），apparent quantum efficiency（α），maximum net photosynthetic rate（Pn,max），light compensation point（LCP），light saturation point（LSP）and dark respiration rate（Rd）. The light response curves among the 7 types of peppers were significantly different under high photosynthetic effective radiation（PAR），i.e.，the light response of net photosynthetic rate（Pn） for the peppers with higher purple levels remained rising after PAR greater than 1 200 μmol · m-2 · s-1，without saturation and light inhibition phenomena. Meanwhile，stomata conductance（Gs）and transpiration rate（Tr）increased rapidly，the inter-cellular CO2 concentration（Ci）and water use efficiency kept in a high level. Under the photosynthetic effective radiation of 2 000 μmol · m-2 · s-1，the highest Pn value was （20.16 ± 0.58）μmol · m-2 · s-1 for Z-4，while the highest water use efficiency value（CO2/H2O）was（2.02 ± 0.01）μmol · μmol-1 for Z-5. Four models were applicable to fitting the Pn–PAR curve of multiple peppers varying in purple degree，with the R2 between 0.964 and 1.000. According to R2，the model performance decreased in the order of modified rectangular hyperbolic model，non-rectangular hyperbolic model，rectangular hyperbolic model and exponential function model. Nevertheless，the light saturation point（LSP）was only obtained by the modified rectangular hyperbolic model for the five types of purple peppers，i.e.，Z-2，Z-4，Z-5，Z-6 and Z-7. The maximum values of LSP were found in Z-4 through the modified rectangular hyperbolic model，valued（2 958.41 ± 923.48）μmol · m-2 · s-1. Our findings suggested that（1）purple pepper has an excellent weak light utilization capability，and could well adapt to strong light conditions without saturation or light inhibition phenomenon. At the same time，purple pepper has a lower dark respiration，which in turn benefits organism matter accumulation.（2）Purple pepper like Z-5 facilitates the selection of water-saving material.（3）The modified rectangular hyperbolic model is more suitable for fitting the purple pepper Pn–PAR curve as it could provide more parameters comparable to the measured ones.