苯嗪草酮对苹果坐果和光合生物学特征的影响

Effects of metamitron on fruit set and photosynthetic biological characteristics of apples

为解决苹果人工疏果费时费工、效率低等问题,以矮化中间砧红富士苹果为试材,以清水为对照(CK),研究了幼果期喷施化学疏果剂苯嗪草酮200、300和400 mg·L^(-1)的疏果效应及对叶片光合生物学特征的影响。结果表明:与CK相比,喷施苯嗪草酮可显著降低花序和花朵坐果率,降幅分别为16.5%~22.8%和50.9%~53.9%,其中300 mg·L^(-1)苯嗪草酮疏果作用最强,单果率为46.6%,双果率为18.3%。苯嗪草酮作为光系统抑制剂,在降低叶片叶绿素含量的同时对光合作用也产生了较大影响,其中对叶绿素含量的抑制作用在处理15 d后消失,对净光合速率的抑制作用在处理11 d后逐渐消失。叶绿素荧光测定结果显示,苯嗪草酮处理显著降低了叶片开放的PSⅡ反应中心的能量捕捉效率(Fv/Fm)、实际光化学效率(ΦPSⅡ)、光化学猝灭系数(qP)和非光化学猝灭系数(NPQ),其抑制作用持续至处理后15 d。OJIP分析显示,苯嗪草酮使苹果叶片放氧复合体受到了伤害,尤其限制了PSⅡ反应中心电子从QA到QB的传递;苯嗪草酮处理使Wk提高,ψo、RC/CSm和PIabs显著降低,以300 mg·L^(-1)影响最显著。说明苯嗪草酮处理破坏了苹果叶片PSⅡ反应中心的结构,阻碍了电子从PSⅡ供体侧向受体侧的传递,进而影响了光合速率,使幼果因缺少光合产物积累而脱落。

With dwarfing interstock Fuji apples as the test materials and water treatment as the control(CK), we examined the fruit thinning effect and its influences on leaves’ photosynthesis by spraying 200, 300, and 400 mg·L^(-1) metamitron during the young fruit period to solve artificial fruit thinning problems(time-consuming, much labor, and low efficiency). The results showed that metamitron application could significantly reduce the inflorescence and flowers’ fruit-setting rate by 16.5%-22.8% and 50.9%-53.9%, respectively. The treatment of 300 mg·L^(-1) metamitron had the strongest fruit thinning effect, with a single fruit rate of 46.6% and a double fruit rate of 18.3%. As a photosynthesis inhibitor, metamitron application reduced the chlorophyll content of leaves and strongly affected photosynthesis. The inhibitory effect on chlorophyll content disappeared after 15 days of the treatment, while that on the net photosynthetic rate disappeared gradually after 11 days of the treatment. The application of metamitron significantly reduced the maximum quantum yield of PSⅡ reaction center(Fv/Fm), actual photochemical efficiency(ΦPSⅡ), photochemical quenching coefficient(qP) and non-photochemical quenching coefficient(NPQ), with such inhibitory effect having been lasted for 15 days. OJIP analysis showed that metamitron caused damage to the apple leaves’ oxygen-evolving complex, especially limiting the transfer of electrons in the PSⅡ reaction center from QA to QB. Metamitron treatment increased Wk, and significantly decreased ψo, RC/CSm, and PIabs. Besides, 300 mg·L^(-1) metamitron had the most significant effect. Our results showed that metamitron destroyed the structure of the PSⅡ reaction center of apple leaves and hindered the transfer of electrons from the donor to the receptor of PSⅡ. Consequently, the photosynthetic rate was affected, and the young fruits fell off due to the lack of accumulation of photosynthetic products.