Zhang Yongqiang, Li Juan, Xu Qijiang, Chen Chuanxin, Nie Shihui, Lei Junjie, Duan Liusheng
College of Agronomy and Biotechnology, China Agricultural University, Beijing, China.
Research Institute of Grain Crops, Xinjiang Academy of Agricultural Sciences, Urumqi, Xinjiang, China.
Front Plant Sci. 2024 Nov 28;15:1498123. doi: 10.3389/fpls.2024.1498123. eCollection 2024.
Agroforestry intercropping is an effective way to optimize land use and ensure food security. However, the physiological mechanism by which the shading of dominant plants inhibits the yield of non-dominant plants in this mode remains to be investigated. A two-year location experiment of walnut-winter wheat intercrop combined with exogenous 6-benzyladenine (6-BA, the first synthetic cytokinin) treatment was conducted to reveal the mechanism of 6-BA in inhibiting wheat growth and yield formation under shade stress by measuring the photosynthetic characteristics, antioxidant capacity, hormone homeostasis of wheat flag leaves and yield. The results showed that compared with far canopy area (FCA), antioxidant enzyme activity [e.g. superoxide dismutase (SOD), peroxidase (POD)], zeatin (ZT) and abscisic acid (ABA) content and photosynthesis of wheat flag leaves were significantly reduced in below canopy area (BCA) treatment during flowering and grain filling stages, thereby inhibiting wheat dry matter accumulation and yield formation. Exogenous 6-BA significantly increased hormone [i.e. indoleacetic acid (IAA), ZT and gibberellin (GA)] levels, antioxidant enzyme activities and photosynthesis in flag leaves, thereby increasing dry matter and yield, especially in the FCA condition. Furthermore, net photosynthetic rate (Pn), stomatal conductance (Gs), intercellular CO concentration (Ci), activities of ribulose bisphosphate carboxylase (RuBPCase) and phosphoenolpyruvate carboxylase (PEPCase), ABA and ZT concentrations of flag leaves at flowering and filling stages had a significant contribution to yield formation under 6-BA and shade treatments. Overall, cytokinin regulates the inhibitory effects of shade stress on wheat photosynthesis, antioxidant capacity and hormone homeostasis to reduce wheat yield loss.
农林间作是优化土地利用和确保粮食安全的有效途径。然而，在这种模式下，优势植物遮荫抑制非优势植物产量的生理机制仍有待研究。通过测量小麦旗叶的光合特性、抗氧化能力、激素稳态和产量，进行了为期两年的核桃 - 冬小麦间作并结合外源6 - 苄基腺嘌呤（6 - BA，第一种合成细胞分裂素）处理的定位试验，以揭示6 - BA在遮荫胁迫下抑制小麦生长和产量形成的机制。结果表明，与远冠层区域（FCA）相比，在开花期和灌浆期，冠层下方区域（BCA）处理的小麦旗叶抗氧化酶活性[如超氧化物歧化酶（SOD）、过氧化物酶（POD）]、玉米素（ZT）和脱落酸（ABA）含量以及光合作用显著降低，从而抑制了小麦干物质积累和产量形成。外源6 - BA显著提高了旗叶中的激素[即吲哚乙酸（IAA）、ZT和赤霉素（GA）]水平、抗氧化酶活性和光合作用，从而增加了干物质和产量，尤其是在FCA条件下。此外，开花期和灌浆期旗叶的净光合速率（Pn）、气孔导度（Gs）、细胞间CO浓度（Ci）、核酮糖二磷酸羧化酶（RuBPCase）和磷酸烯醇式丙酮酸羧化酶（PEPCase）活性、ABA和ZT浓度对6 - BA和遮荫处理下的产量形成有显著贡献。总体而言，细胞分裂素调节遮荫胁迫对小麦光合作用、抗氧化能力和激素稳态的抑制作用，以减少小麦产量损失。
