嫁接对低温弱光下甜椒幼苗光合作用的影响

以‘卫士’和‘部野丁’为砧木，以‘赤峰特选’为接穂进行嫁接，在光照培养箱内对甜椒自根苗和嫁接苗进行低温(8 ℃/ 5℃)弱光(100 μmol·m^-2·s^-1)处理，处理7 d后在正常条件（25 ℃/18 ℃，PFD 550～600 μmol·m^-2·s^-1）下恢复3 d，研究低温弱光下甜椒嫁接苗和自根苗气体交换参数、羧化效率和荧光参数等的变化.结果表明：低温弱光胁迫3 d时，甜椒幼苗叶片的光合速率（P_n）、气孔导度（G_s）和羧化效率（CE）均下降50%以上，之后P_n、G_s趋于平稳，CE持续下降;胞间CO₂浓度（C_i）呈先下降后上升趋势.低温弱光下，甜椒幼苗的暗下最大光化学效率(F_v/F_m)、光下实际光化学效率（Ф_PSⅡ）及电子传递速率（ETR）显著降低，初始荧光(F_o)有所升高，表明其光合机构受到一定伤害，但处理结束3 d后基本恢复.与自根苗相比，嫁接苗在各处理阶段的P_n、G_s、CE、Ф_PSⅡ、F_v/F_m和ETR都有不同程度的提高，F_o明显降低.可见，嫁接可显著提高甜椒幼苗的光合功能，减轻低温弱光对其光合作用的影响.

Effects of grafting on photosynthesis of sweet pepper seedlings under low temperature and weak light intensity.

Sweet pepper ‘Chifengtexuan’ seedlings were grafted onto ‘Weishi’ and ‘Buyeding’ rootstocks, treated with low temperature (8 ℃/ 5 ℃) and weak light intensity (100 μmol·m-2·s-1) for 7 days, and then recovered under normal conditions (25 ℃/18 ℃, PFD 550〖KG-*2〗-〖KG-*7〗600 μmol·m-2·s-1) for 3 days to study the variations of their gas exchange parameters, carboxylation efficiency, and fluorescence parameters, with the own-rooted ‘Chifengtexuan’ seedlings as the control. The results showed that on the 3rd day of low temperature and weak light intensity stress, the photosynthetic rate (Pn), stomatal conductance (Gs), and carboxylation efficiency (CE) of both own-rooted and grafted seedling leaves decreased more than 50%, and after then, the Pn and Gs tended to stable while CE decreased continually. The intercellular CO2 concentration (Ci) declined first, but enhanced after the 4th day of the stress. Low temperature and weak light intensity decreased the maximal photochemical efficiency of PSⅡ in darkness (Fv/Fm), actual photochemical efficiency of PSⅡ during illumination (ФPSⅡ) and electron transport rate (ETR), but increased the initial fluorescence (Fo), which implied that the stress caused definite damage of photosynthetic apparatus. However, the damage diminished after 3 days of recovery. Comparing with those of own-rooted seedlings, the Pn, Gs, CE, ФPSⅡ, and Fv/Fm of grafted seedlings increased to various degrees, and Fo decreased markedly during the stress. It was concluded that grafting could promote the photosynthetic function, and alleviate the effects of low temperature and weak light intensity on the photosynthesis of sweet pepper seedlings.