摘要:为阐明米槁光合作用对干旱胁迫的响应规律与适应机制，以一年生米槁幼苗为研究对象，进行盆栽试验研究设置3种不同土壤含水量梯度，利用Li-6400便携式光合作用系统测定干旱胁迫下的光合生理指标及光响应过程，光响应曲线模拟采用直角双曲线模型、非直角双曲线模型、指数模型和直角双曲线修正模型进行拟合并对比，以期选出适用于干旱环境下的光响应模型。结果表明（1）光响应曲线模型对干旱胁迫下米槁幼苗的光合作用拟合中直角双曲线、非直角双曲线和指数模型适用于低光合有效辐射（PAR），但拟合光响应参数与实测值相差大，只有直角双曲线修正模型能够很好的拟合各个处理且拟合参数比较精确米槁幼苗。（2）光合作用的表观量子效率（Φ）小于一般植物的光合量子效率，则其对弱光的光能利用效率相对较低。（3）在较强的光合有效辐射条件下，严重干旱胁迫下的米槁净光合速率P_n显著下降，出现了明显的光抑制现象；中度胁迫下净光合速率（P_n）、最大净光合速率（P_nmax）、光补偿点（LSP）最大，米槁具有较宽的抗旱适应范围，有一定的抗旱性；严重胁迫下P_n、P_nmax、LSP降低，蒸腾速率（T_r）与气孔导度（G_s）下降幅度更大，但仍具有较高的水分利用效率（WUE），米槁在严重的干旱胁迫下光合机构受到一定的损伤，但自身可以通过生理调节来积极适应不良环境，减少光合机构伤害。（4）综合来看，在人工管理或种植米槁时，为了适应米槁生长发育，建议土壤含水量保持在23.05%到14.92%之间。



Abstract:The objective of this study was to elucidate the response and adaptation mechanisms of Cinnamomum migao seedlings to drought stress. Using pot experiments, we examined the effects of three relative water levels on the growth of 1-year-old C. migao seedlings by measuring photosynthetic physiological indices and light responses under drought stress. The responses were analyzed in terms of four different light response curve models:rectangular hyperbola, non-rectangular hyperbola, exponential, and modified rectangular hyperbola. The following results were obtained. (1) According to the values of photosynthetic parameters calculated using the four models, the rectangular hyperbola, non-rectangular hyperbola, and exponential models were suitable for low photosynthetically active radiation. However, only the modified rectangular hyperbola model provided a good fit for each treatment and the fitting parameters were more accurate. (2) The apparent quantum efficiency (Φ) of photosynthesis of drought-stressed plants was smaller than that of normal plants, and therefore the utilization efficiency of these plants is lower. (3) The net photosynthetic rate (P_n) of severely stressed C. migao plants decreased significantly under strong photosynthetically active radiation, whereas values for the net photosynthetic rate (P_n), maximum net photosynthetic rate (P_nmax), and light compensation point were the highest under conditions of moderate stress. C. migao has a wide range of stress tolerance. Under severe stress, P_n, P_nmax, and LSP decreased, and transpiration rate (T_r) and stomatal conductance (G_s) decreased more significantly; however, the plants still had a higher water-use efficiency. Although C. migao plants suffer damage under severe drought stress, they can adjust to the adverse environments through physiological modification and by reducing damage to their photosynthetic apparatus. (4) In order to facilitate growth and developmental adaptation in C. migao during management, it is recommended that the soil moisture content be maintained at levels between 23.05% and 14.92%.





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