遮荫对极小种群植物浙江安息香幼苗生长和光合特性的影响

Effects of Shading on Growth and Photosynthetic Characteristics of Extremely Small Populations Styrax zhejiangensis Seedlings

摘要:

浙江安息香(Styrax zhejiangensis)是浙江省特有的极小种群野生植物。该研究旨在探讨不同遮荫环境对其幼苗生长、养分及光合特性的影响，进而为其保护和人工栽培提供理论依据。研究对象为2 a生实生幼苗，设置3种光照强度: 全光照(L₀)、50% (L₅₀)和75%遮荫(L₇₅)，处理4个月，分析幼苗的生长特性、营养元素含量和光合参数。结果表明，不同遮荫条件下幼苗的株高、地径生长量及叶片结构有显著差异。50%遮荫下，幼苗通过优化叶片结构增强光能利用率；而在75%遮荫下，幼苗则通过进一步增加株高和地径以广布叶片的方式获取更多光能。遮荫促进浙江安息香叶片氮、钾含量上升，而磷、镁含量下降。随着遮荫强度增加，表观量子效率(AQY)和最大净光合速率(P_nmax)上升，光饱和点(LSP)、光补偿点(LCP)和暗呼吸速率(Rd)降低。叶绿素荧光参数表明，PSII潜在活性(F_v/F_o)和最大光化学量子效率(F_v/F_m)随遮荫程度增强均显著上升，而有效光量子产量(F_v′/F_m′)、光化学淬灭系数(qP)和电子传递效率(ETR)则先下降后回升。浙江安息香幼苗具有较强的耐荫性和光合调节能力，适度遮荫对其苗期生长、养分平衡和光合作用具有积极作用，合理遮荫管理和肥料施用可以为物种的保护和人工栽培提供重要支持。

Abstract:

Styrax zhejiangensis is an extremely rare wild plant endemic to Zhejiang Province. To explore the effects of different shading environments on seedling growth, the growth characteristics, nutrient element contents and photosynthetic parameters of two-year-old seedlings were analyzed under three light intensities: full light (L₀), 50% shading (L₅₀), and 75% shading (L₇₅), for 4 months. The results showed that the growth of height and ground diameter, as well as leaf structure of seedlings were significantly different under different shading conditions. Under L₅₀, seedlings enhanced their light energy utilization by optimizing leaf structure; while under L₇₅, seedlings increased their height and ground diameter to spread leaves more widely to obtain more light energy. Shading promoted the increase of nitrogen and potassium contents in the leaves of S. zhejiangensis, but decreased the contents of phosphorus and magnesium. With the increase of shading intensity, the apparent quantum efficiency (AQY) and maximum net photosynthetic rate (P_nmax) increased, while the light saturation point (LSP), light compensation point (LCP) and dark respiration rate (Rd) decreased. Chlorophyll fluorescence parameters indicated that the potential activity of PSII (F_v/F_o) and the maximum photochemical quantum efficiency (F_v/F_m) significantly increased with the increase of shading degree, while the effective photochemical quantum yield (F_v′/F_m′), photochemical quenching coefficient (qP) and electron transport rate (ETR) first decreased and then increased. The seedlings of S. zhejiangensis have strong shade tolerance and photosynthetic regulation ability. Therefore, moderate shading had a positive effect on their growth, nutrient balance and photosynthesis during the seedling stage. Reasonable shading management and fertilizer application could provide important support for the protection and artificial cultivation of the species.