干旱胁迫和化感作用对榄仁树幼苗生长、光合作用及生理生化的影响

该研究通过榄仁树幼苗的盆栽实验，用称重控水法设置3个水平的土壤水分含量(分别占田间持水量的75％~80％、50％~55％、30％~35％)和2个浓度水平的木麻黄凋落物浸提液，研究不同土壤干旱程度及不同浓度木麻黄凋落物浸提液对榄仁树生长、光合作用及生理生化的影响。结果表明：随着幼苗生长期的延长，土壤干旱和木麻黄凋落物浸提液对榄仁树幼苗存活率和株高增长有一定影响。60 d胁迫后显著减小了幼苗叶片数、叶面积、叶片含水量及叶片的生物量。15~60 d期间幼苗的净光合速率( Pn)、气孔导度( Ccond)、蒸腾速率( Tr)均显著减小，而幼苗叶片胞间CO2浓度( Ci)呈先减后增的变化。幼苗的水分利用率( WUE)和气孔限制值( Ls)显著增加，是导致光合作用降低的主要原因。干旱和木麻黄凋落物浸提液能显著增加榄仁树幼苗的叶片和根的细胞膜透性、Peroxidase(POD)活性及叶片Superoxide dismutase(SOD)活性。二元方差分析表明，土壤干旱和木麻黄凋落物浸提液对榄仁树的生长、光合作用及生理生化的影响有明显的交互作用且表现出一定的拮抗作用。该研究结果可为构建混交林型海防林提供参考。

Effects of drought stress and allelopathy on growth, photosynthesis and physio-biochemical characteristics of Terminalia catappa seedlings

We conducted a pot experiment with Terminalia catappa seedlings to study the impacts of drought and allelopathy on growth, photosynthesis and physio-biochemical characteristics of seedlings. In this case, we set three levels of soil moisture content(water supply range of 75%-80%, 50%-55% and 30%-35% water-holding capacity)controlled by weighing the pots with soil and seedlings and two concentration levels of leachates of Casuarina equisetifolia litter. The results showed that drought stress and litter leachates affected the survival rate and the height growth of Terminalia catappa with the seedlings growing. It significantly reduced numbers, areas, water content and biomass of leaves after 60 d dual stresses. It also significantly reduced the net photosynthesis(Pn), stomatal conductance(Ccond)and transpiration rate(Tr), but inter-cellular CO₂ concentration(Ci)decreased early and increased later. The water use efficiency(WUE)of the seedlings and the stomatal limitation value significantly increased, which might be the main reason to cause the decline of photosynthesis of seedlings. The dual stresses also increased the cell membrane penetrability and the activity of peroxidase(POD)in roots and leaves, as well as the activity of superoxide dismutase(SOD)in leaves. Analysis of variance indicated that there was interaction, which was antagonistic to certain extent, between the drought stress and allelopathy of Casuarina litter leachates on the growth, photosynthesis and physio-biochemical characteristics of Terminalia catappa seedlings. In short, this study will provide a reference for construction of mixed forest as windbreak.