遮阴对油用牡丹叶片衰老生理指标的影响

为揭示轻度遮阴提高牡丹种籽产量和品质的生理机制,明确最佳遮阴时间,以凤丹牡丹为研究对象,分析了不同遮阴处理下叶片的瞬时净光合速率(Pn)、最大净光合速率(P_max)、叶绿素含量(Chl),丙二醛(MDA)、过氧化氢(H₂O₂)和脯氨酸(Pro)的积累,过氧化氢酶(CAT)、过氧化物酶(POD)和超氧化物歧化酶(SOD)活性,以及生长素(IAA)、赤霉素(GA₃)和脱落酸(ABA)含量的动态变化规律。结果表明,轻度遮阴下,油用牡丹叶片Pn在70 d前低于对照,70 d后高于对照,平均较对照提高16.7%;P_max仅在56 d时较对照降低6.5%,平均较对照提高78.1%;Chl含量始终高于对照,平均较对照增加63.1%;H₂O₂、MDA、Pro的积累均低于对照,且平均分别较对照降低25.2%、22.9%、19.0%;整个过程中,与对照相比,CAT、POD、SOD活性平均增加11.4%、19.5%、12.5%,IAA、GA₃含量平均增加25.1%、6.0%,ABA含量平均降低9.6%。中度遮阴下,Pn仅在成熟期高于对照;重度遮阴下,Pro的积累始终高于对照。综上所述,在缓慢生长期和成熟期改善叶片光合性能、延缓叶片衰老是轻度遮阴提高牡丹籽产量和品质的生理学基础。本研究结果为油用牡丹最佳遮阴时间的选择提供了理论参考。

Effects of Shading on Leaf Senescence and Physiological Characteristics of Oilseed Peony

To reveal the physiological mechanism of light shading on seed yield and quality improving, and to determine the optimum shading time, the following physiological indexes of P. ostii Feng Dan were investigated such as the dynamic changes of net photosynthetic rate (Pn), maximum net photosynthetic rate (P_max), chlorophyll content (Chl), the content of malondialdehyde (MDA), hydrogen peroxide (H₂O₂), and proline (Pro), the activity of catalase (CAT), peroxidase (POD), superoxide dismutase (SOD), as well as the content of auxin (IAA), gibberellic acid (GA₃), abscisic acid (ABA). The results showed that under light shading environment, Pn was significantly lower than the control before 70 DAP(days after pollination), but significantly higher after 70 DAP. The average Pn increased by 16.7% than the control. P_max decreased by 6.5% only at 56 DAP, and the average increased by 78.1%. Chl content was higher than control during the process, and the average increased by 63.1%. The accumulation of H₂O₂, MDA and Pro content were significantly lower than control, and the average decreased by 25.2%, 22.9% and 19.0%, respectively. During seed filling period, the average of CAT, POD and SOD activities increased by 11.4%, 19.5% and 12.5%, respectively; the contents of IAA and GA₃ increased by 25.1% and 6.0%, and the ABA decreased by 9.6%, respectively. In moderate shading, Pn was higher than the control only at the maturity stage. In severe shading treatment, the accumulation of Pro was always higher than that of control. This indicated that improved photosynthetic performance and delayed senescence of leaves during slow growth and maturity period were the physiological basis for light shading improving the seed yield and quality. The findings provided a theoretical reference for selection of optimum shading time of oilseed peony.