遮荫与施硅对圆柏幼苗光合特性和生长的影响OA

To investigate how Juniperuschinensis seedlings respond and adapt to shading and to assess the mitigation effects of silicon application on shading stress,we studied the photosynthetic characteristics and growth of 5-year-old seedlings under four levels of shading and two silicon treatments.The results revealed that shading significantly increased the seedlings height while reducing the growth of basal diameter and first-order lateral branches.The height increased by up to 54.1%,whereas the growth in basal diameter,leafing intensity and first-order lateral branch length was reduced by as much as 65.6%,19.3%and 14.8%,respectively,under shad-ing.A significant negative correlation was observed between plant height and stem diameter,indicating that shading promoted vertical growth at the expense of radial growth and leaf and lateral branch development,aligning with the typical features of Shade Avoidance Syndrome.Under mild and moderate shading,there was an increase in net photosynthetic rate,total Chlorophyll,and leaf silicon con-tent,by as much as 118.3%,29.9%,and 62.7%,respectively.In contrast,stomatal conductance and transpiration rate decreased by up to 44.8%and 10.7%,improving shade tolerance.However,under heavy shading,the net photosynthetic rate fell by 36.0%,with stomatal conductance and transpiration rate increasing by 6.3%and 38.8%,respectively,indicating photosynthetic inhibition.Silicon application under shading conditions enhanced the net photosynthetic rate of the seedlings by up to 22.5%,reduced stomatal conduc-tance and transpiration rate by as much as 48.8%and 37.9%,respectively,thereby facilitating the accumulation of photosynthetic products.Additionally,the growth in basal diameter,first-order lateral branch length,and leafing intensity increased by as much as 143.7%,17.6%,and 33.1%,respectively,mitigating the effects of shade avoidance syndrome.Thus,silicon application alleviates the shade avoidance syndrome in Juniperuschinensis seedlings.