叶面肥对‘巨峰’葡萄光氧化胁迫的缓解效应

Protective effects of foliar fertilizer on ‘Kyoho’ grape under photooxidation

【目的】探究光氧化胁迫条件下叶面肥对葡萄叶片的保护及缓解效应。【方法】以设施栽培的‘巨峰’葡萄为试材,叶面喷施CaCl_2、NaHSO_3、氨基酸钙叶面肥、氨基酸钙叶面肥+NaHSO_3,然后叶片涂抹甲基紫精(MV)模拟光氧化胁迫,研究叶面肥对光氧化条件下葡萄叶片的光合、荧光参数、超氧阴离子(O_2~)产生速率、H_2O_2含量及MDA含量等的影响。【结果】叶片涂抹MV后发生光氧化胁迫,各处理的相关指标均发生改变,其指标表现均不如仅喷清水的对照,但与喷清水+MV处理相比,喷施叶面肥处理指标变化幅度均变小,不同程度地缓解了光氧化对葡萄叶片的伤害。喷清水+MV处理的净光合速率(P_n)下降幅度最大,比清水对照下降了47.9%,喷施氨基酸钙肥600倍液以及氨基酸钙肥600倍液+NaHSO_3的效果好,P_n下降幅度小,分别比喷清水+MV处理的低34.8个百分点和33.7个百分点,差异显著;气孔导度(G_s)变化趋势同P_n。初始荧光(F_0)指标,喷清水+MV处理增幅最大,为22.0%;喷施氨基酸钙600倍液+NaHSO_3处理的增幅最小,为5.1%,比前者低16.9个百分点;最大荧光F_m、PSⅡ最大光化学效率F_v/Fm、F_v/F_0、实际光化学效率Φ_(PSⅡ),喷施叶面肥处理下降幅度均小于喷清水+MV处理。各处理的超氧阴离子(O_2~)产生速率、H_2O_2含量、MDA含量增加幅度不同,其中喷清水+MV处理增加幅度最大,分别为56.0%、83.8%、34.8%;喷施叶面肥处理增加幅度均变小,其中喷施氨基酸钙600倍液+NaHSO_3处理的增加幅度最小,分别为19.4%、15.1%、0.99%,明显减轻了光氧化胁迫。【结论】综合各项指标,喷施叶面肥对葡萄光氧化胁迫有明显的缓解效应,以喷施氨基酸钙600倍液+NaHSO_3效果最好,建议在生产中选择应用。

【Objective】Photooxidative stress is one of the important factors that affect crop yield. Light oxidation or inhibition can cause up to 10% or more crop losses even without other stress factors. In the Tai＇an area, the plastic film of protected culture is usually removed in the middle of July after the grape harvest. At this time light intensity in the natural field is 1 400 to 1 782 μmol·m（-2）·s（-1）from 11：00 to 15：00,which far exceeds the light saturation point of grape leaves（576 to 972 μmol·m（-2）·s（-1））. Drastic increases of light intensity after the plastic film removal can cause light inhibition symptoms in grape trees such as leaf function decline, poor flower bud differentiation and photooxidative damage. Therefore, to explore effective measures of reducing the high light injurys and yield losses, the effects of foliar fertilizer on protecting grape leaves from photo oxidation damage were studied.【Methods】‘Kyoho＇grapes under protected cultivation were chosen as the experimental material. The grapes were cultivated using a vertical trellis systemand with spacing of 1.5 m×3 m. The healthy mature leaves in the middle of the new shoots of three yearold‘Kyoho＇grape trees were treated with water（control, T1）, 600-fold calcium amino acid＋200 mg·L（-1）NaHSO_3（T2）, 600-fold calcium amino acid（T3）, 0.3% Ca Cl_2（T4）, 200 mg·L（-1）NaHSO_3（T5） respectively on July 3, 2015. The whole plant and both sides of the leaves were sprayed. Then methyl viologen（MV）was applied on leaves for all treatments except control to induce photooxidative stress at 8 am on July 5.The plastic film of the greenhouse was then removed. Two hours later, photosynthetic and chlorophyll fluorescence parameters were measured using a CIRAS-2 photosynthetic instrument and FMS-2 pulse modulated fluorometer respectively（PPSystems and Hansatech, England）, and photosynthetic parameters which included the net photosynthetic rate（P_n） and the stomatal conductance（G_s）; fluorescence parameters which included initial fluorescence（F_0）, maximum fluorescence（F_m）, maximal photochemical efficiency（F_v/F_m）and actual photochemical efficiency（Φ_（PSⅡ））. After determing the photosynthetic parameters, the leaves used for the determination of the photosynthetic parameters were quickly saved in liquid nitrogen and taken back to the laboratory; several light inhibition indexes, including the production rate of superoxide aninradical（O_2）, H_2O_2 and malondialdehyde（MDA） contents were measured using the hydroxylamine oxida-tion method, spectrophotometric method and the thiobarbituric acid method respectively.【Results】The photosynthetic indexes and light inhibition indexes of all MV treatments were worse than the no MV control. However, when MV was applied, compared with only spraying water（T1）, spraying foliar fertilizer（T2, T3, T4, T5） could alleviate the photooxidative stress damage of the grape leaves to a certain extent.Compared with the no MV control, the Pnof T1 declined 47.9%, and that of T2 and T3 declined13.1% and 14.2%, respectively. The difference between the two groups was significant, and G_s had the same change trend, which illustrated that the application of foliar fertilizer could keep the grape leaves at a high level of photosynthesis. Chlorophyll fluorescence parameter F_0 represented the fluorescence yield when the PSⅡ reaction center was completely opened, and the rise of F_0 indicated that the PSⅡ reaction center was damaged or reversible inactivation occured. F_0 of all MV treatments increased, that of T1 increased the most, up to 22%, while that of spraying foliar fertilizer treatments increased much less than T1, that of T2 increased 5.1%, with the smallest increase and 16.9 percentage points lower than that of T1. Fmwas the fluorescence level when the PSⅡ reaction center completely closed and the decrease of Fm under strong light was a characteristic of the photoinhibition. F_v/F_m represented the primary light energy conversion efficiency of the PSⅡ reaction center, and the decline of F_v/F_m indicated that photoinhibition occurred in the plant leaves. Φ_（PSⅡ）reflected the actual light energy capture efficiency. F_m, F_v/F_m and Φ_（PSⅡ）for all MV treatments decreased, and that of T1 decreased by 15.7%, 22.7%, and 31.2%, respectively.And all spraying foliar fertilizer treatments decreased less than T1. Photooxidative damage could cause the accumulation of the reactive oxygen species（ROS） and MDA in the leaves, and when it reached a certain degree, it will cause the reduction of the photosynthetic efficiency. Compared to the no MV control,the light inhibition indexes（production rate of O_2, the content of H_2O_2 and MDA） of all treatments increased differently. The MV treatment significantly increased the production rate of O_2 and the accumulation of H_2O_2, MDA, and the three indexes of T1 increased 56.0%, 83.0% and 34.8% respectively, with the biggest increase; those of T2 increased 19.4%, 15.1% and 0.99% respectively, with the smallest increase.This indicated that spraying foliar fertilizer could obviously alleviate the light oxidative stress and the accumulation of the reactive oxygen species（ROS） and MDA in the leaves.【Conclusion】In general, foliar fertilizer could effectively alleviate the damage of grape leaves caused by light oxidative stress, and keep thehigh level of photosynthesis and damage to the PSⅡ system. Calcium amino acid＋NaHSO_3 has the best ef-