Wang Yadong, Zhang Qiuchi, Ju Mingxiu, Gao Kai, Han Liliang, Li Xingfu, He Jing, Su Derong
College of Grassland Science, Inner Mongolia Minzu University, Tongliao 028000, China.
Academy of Forestry Inventory and Planning, National Forestry and Grassland Administration of P.R. China, Beijing 100714, China.
Plants (Basel). 2025 May 22;14(11):1573. doi: 10.3390/plants14111573.
The effects of stomatal factors of plant leaves under partial root-zone drying (PRD) have been widely studied. However, the non-stomatal factors and the relationship between photosynthesis with soil moisture have not been explored. In this study, four treatments over-irrigation, full irrigation, moderate water deficit, and severe water deficit were investigated, aiming to evaluate the effects on the diurnal variation of alfalfa leaf photosynthesis under PRD and its relationship with stomatal and non-stomatal limitations, as well as soil moisture. The results showed that any levels of water deficit led to a decrease in the photosynthetic rate () of alfalfa leaves. Leaves under moderate and severe water deficit displayed a pronounced midday "photosynthetic lunch break," while those under over- and full irrigation did not display this phenomenon. Before 11:30 a.m., the reduction in was primarily due to stomatal limitations, as evidenced by reduced stomatal conductance () and decreased intercellular CO concentration (). After 11:30 a.m., non-stomatal limitations became the dominant factor, with both and transpiration rate () continuing to decrease, while increased, indicating a shift in the limiting factors. Under PRD with moderate water deficit, alfalfa experienced both stomatal and non-stomatal limitations within a single day, leading to a hay yield reduction of 18.6%. Additionally, over-irrigation helped to maintain higher and , increasing alfalfa yield and thus improving water productivity by 33.1%. The correlation coefficients between soil moisture content at 10 cm depths with alfalfa leaf , , and on the photosynthetic measurement day were 0.9864, 0.8571, and 0.8462, respectively. At 20 cm, the correlation coefficients were 0.8820, 0.6943, and 0.6951, respectively. The study concluded that both stomatal and non-stomatal mechanisms contributed to reduced alfalfa in water deficit of PRD. Furthermore, shallow soil moisture also played a crucial role in influencing photosynthetic performance.
植物叶片气孔因素在部分根区干旱（PRD）条件下的影响已得到广泛研究。然而，非气孔因素以及光合作用与土壤水分之间的关系尚未得到探讨。本研究调查了四种处理方式：过度灌溉、充分灌溉、中度水分亏缺和重度水分亏缺，旨在评估PRD对苜蓿叶片光合作用日变化的影响及其与气孔和非气孔限制以及土壤水分的关系。结果表明，任何程度的水分亏缺都会导致苜蓿叶片光合速率（）下降。中度和重度水分亏缺条件下的叶片呈现出明显的中午“光合午休”现象，而过度灌溉和充分灌溉条件下的叶片未出现此现象。上午11:30之前，光合速率的降低主要是由于气孔限制，这可通过气孔导度（）降低和细胞间CO浓度（）下降得到证明。上午11:30之后，非气孔限制成为主导因素，光合速率和蒸腾速率（）均持续下降，而细胞间CO浓度升高，表明限制因素发生了转变。在中度水分亏缺的PRD条件下，苜蓿在一天内同时经历了气孔和非气孔限制，导致干草产量降低了18.6%。此外，过度灌溉有助于维持较高的光合速率和蒸腾速率，提高苜蓿产量，从而使水分利用效率提高了33.1%。光合测定当天，10厘米深度土壤水分含量与苜蓿叶片光合速率、蒸腾速率和细胞间CO浓度的相关系数分别为0.9864、0.8571和0.8462。在20厘米深度，相关系数分别为0.8820、0.6943和0.6951。该研究得出结论，在PRD水分亏缺条件下，气孔和非气孔机制均导致苜蓿光合速率降低。此外，浅层土壤水分对光合性能也起着关键作用。
