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【目的】揭示荔枝对低光照的响应和适应生理机制。【方法】以5 a生‘桂味’荔枝盆栽苗为材料,观测遮阴对新梢生长、叶片形态、光合作用和矿物质含量的影响。【结果】90%遮光率的全株遮阴处理显著抑制新梢伸长,导致新叶和老叶比重显著降低,成熟叶片净光合速率(Pn)、气孔导度(Gs)明显下降,而叶肉二氧化碳浓度(Ci)不降反略升,同时,使成熟叶片叶绿素指数(SPAD)及Fv/Fm显著增加。遮阴处理还使新、老叶片的矿质营养含量普遍提高,硝态氮:铵态氮的比值显著提高。持续遮阴导致叶片由老叶向新叶逐渐枯萎,遮阴45 d导致植株死亡。【结论】遮阴可引起荔枝叶片形态适应性变化和光能利用效率提高,其光合作用速率降低与气孔关闭及暗反应弱化等非气孔因素密切相关;遮阴导致矿质营养大量动员到叶片,但抑制硝酸还原;荔枝为不耐阴植物,长期遮阴可导致植株衰退死亡。
【Objective】 Reveal the response of litchi to low light and adapt to physiological mechanism. 【Method】 The effects of shading on shoot growth, leaf morphology, photosynthesis and mineral content of 5-year-old ’Gui-Wei’ litchi seedlings were studied. 【Result】 Shading treatment with 90% shading rate significantly inhibited shoot elongation, resulting in a significant decrease in the specific gravity of new leaves and old leaves. The net photosynthetic rate (Pn) and stomatal conductance (Gs) of mature leaves decreased significantly, while mesophyll The concentration of carbon dioxide (Ci) increased slightly without decreasing or decreasing while the chlorophyll index (SPAD) and Fv / Fm of mature leaves increased significantly. Shading treatment also makes the new and old leaves of mineral nutrition generally increased nitrate nitrogen: ammonium nitrogen ratio was significantly increased. Continuous shading led to the leaf from the old leaves to the new leaves gradually withered, shading 45 d led to plant death. 【Conclusion】 Shading can cause morphological changes of litchi leaves and the improvement of light energy utilization efficiency. The decrease of photosynthetic rate is closely related to the non-stomatal factors such as stomatal closure and dark reaction weakening. Shading leads to a large mobilization of mineral nutrients to the leaves, but inhibition Nitric acid reduction; litchi intolerance Yin plants, long-term shade can lead to plant decline and death.