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The impact of seasonal short-term drought on plant physiology and resilience is crucial for conservation and management strategies. This study investigated drought stress effects on growth, photosynthetic capacity, and physiological responses of Camphor (Cinnamomum camphora) seedlings in Guangxi province, China. Fertilized potted plants underwent continuous drought treatments to assess varying water supply effects. Treatments included normal water supply (CK), light drought (D1), moderate drought (D2), and severe drought (D3). Physiological indicators including net photosynthetic rate (Pn), stomatal conductance (Gs), transpiration rate (Tr), and intercellular CO2 concentration (Ci) were measured. Additionally, the stomatal limitation value (Ls) was calculated using the formula Ls = 1-Ci/Ca, and water use efficiency (WUE) was computed as Pn/Tr. Furthermore, parameters such as PIABS (Performance Index based on absorbed light energy), WK (the ratio of variable fluorescence FK at the K point to the amplitude FO-FJ), VJ (the ratio of variable fluorescence FJ at the J point to the amplitude FO-FP), ΔI/I0 (the relative amplitude of the 820 nm light absorption curve), superoxide dismutase (SOD), peroxidase (POD), catalase (CAT), and malondialdehyde (MDA) were measured to evaluate the impact of drought stress on various physiological processes and antioxidant enzyme activities. Results showed significant decreases in base diameter growth (GD) and seedling height growth (GH) with increasing drought stress. Notably, moderate (D2) and severe (D3) drought treatments led to negative GD values. GD decreased by 23.79%, 114.85%, and 175.50% for D1, D2, and D3 treatments, respectively, while reductions of 40.00%, 73.33%, and 90.00% in GD were observed compared to the control (CK). Pn decreased significantly across treatments, with D1CK>D2>D3. Light energy transmission to PSI by the unit reaction center (REo/RC) initially increased then decreased, significantly smaller in D3 compared to D1. Conversely, heat dissipation absorbed by the unit reaction center (DIo/RC) increased notably in D3 compared to D1 and CK. PIABS, WK, VJ, and ΔI/I0 decreased over time, while Rubisco enzyme activity decreased, while proline (Pro) levels increased. Superoxide dismutase (SOD), peroxidase (POD), catalase (CAT), and malondialdehyde (MDA) levels significantly increased during D1 treatment but decreased with D2 and D3 treatments. Overall, drought severity had varying impacts on Cinnamomum camphora growth and photosynthetic structure, with D1 treatment maintaining normal growth and metabolic activities, while D2 and D3 treatments resulted in severe membrane damage, rendering seedlings essentially unable to survive. These findings provide a theoretical basis for implementing water management practices and conservation strategies for camphor seedlings.

季节性短期干旱对植物生理特性与抗逆性的影响，对于植物保护与管理策略的制定至关重要。本研究以中国广西省的香樟（Cinnamomum camphora）实生苗为试验材料，探究干旱胁迫对其生长、光合能力及生理响应的调控效应。将经施肥处理的盆栽植株实施持续干旱处理，以评估不同供水条件的影响效应。试验设置正常供水对照组（CK）、轻度干旱（D1）、中度干旱（D2）及重度干旱（D3）4组处理。
测定了净光合速率（net photosynthetic rate, Pn）、气孔导度（stomatal conductance, Gs）、蒸腾速率（transpiration rate, Tr）及胞间CO₂浓度（intercellular CO₂ concentration, Ci）等多项生理指标。此外，通过公式Ls=1-Ci/Ca计算得到气孔限制值（stomatal limitation value, Ls），并以Pn与Tr的比值计算水分利用效率（water use efficiency, WUE）。同时，还测定了基于吸收光能的性能指数（Performance Index based on absorbed light energy, PIABS）、K点可变荧光FK与FO-FJ振幅的比值（WK）、J点可变荧光FJ与FO-FP振幅的比值（VJ）、820nm光吸收曲线的相对振幅ΔI/I0、超氧化物歧化酶（superoxide dismutase, SOD）、过氧化物酶（peroxidase, POD）、过氧化氢酶（catalase, CAT）及丙二醛（malondialdehyde, MDA）等参数，以全面评估干旱胁迫对各类生理过程及抗氧化酶活性的影响。
研究结果显示：随着干旱胁迫程度加剧，香樟的地径生长量（GD）与苗高生长量（GH）均出现显著下降。其中，中度（D2）与重度（D3）干旱处理组的地径生长量呈现负值。与对照组（CK）相比，D1、D2、D3组的地径生长量分别降低23.79%、114.85%与175.50%。各处理组的净光合速率均显著降低，整体表现为D1>CK>D2>D3。单位反应中心传递至光系统I的光能（REo/RC）呈先升高后降低的变化趋势，且D3组的该指标显著低于D1组。与之相反，单位反应中心吸收的热能耗散（DIo/RC）在D3组中较D1组与对照组显著升高。PIABS、WK、VJ及ΔI/I0随处理时长增加而下降，核酮糖二磷酸羧化酶/加氧酶（Rubisco）活性亦呈下降趋势，而脯氨酸（proline, Pro）含量则显著升高。在D1处理组中，超氧化物歧化酶（SOD）、过氧化物酶（POD）、过氧化氢酶（CAT）活性及丙二醛（MDA）含量均显著上升，但在D2与D3组中则出现下降。
总体而言，干旱严重程度对香樟的生长与光合结构具有差异化影响：轻度干旱（D1）处理可维持植株正常生长与代谢活动，而中度与重度干旱处理则会造成严重的膜系统损伤，致使实生苗基本无法存活。本研究结果可为香樟实生苗的水分管理实践与保护策略制定提供理论依据。