长期水淹对‘中山杉118’幼苗呼吸代谢的影响

Effects of long-term flooding on respiratory metabolism of Taxodium ‘Zhongshansha 118' seedlings

中山杉(Taxodium‘Zhongshansha’)具有极强的耐淹性,但其耐淹机理仍没有明确。该研究以‘中山杉118’(Taxodium‘Zhongshansha 118’)幼苗为对象,在经过93天不同水淹处理(对照、水浸、浅淹、深淹)后测定中山杉叶片和根系的无氧呼吸酶活性、淀粉及可溶性糖含量、生物量以及根系活力,从能量消耗的角度初步探索了中山杉的耐淹性。结果表明:长期水淹使中山杉叶片与根系中3种无氧呼吸酶(乙醇脱氢酶、丙酮酸脱羧酶、乳酸脱氢酶)活性显著增加,且叶片与根系的乙醇脱氢酶活性均高于乳酸脱氢酶活性,中山杉的根系和叶片是通过加强以酒精发酵为主的无氧呼吸适应长期缺氧环境;不同水淹处理的叶片中3种无氧呼吸酶活性均高于根系,叶片对缺氧环境更加敏感;中山杉叶片和根系淀粉、可溶性糖含量均随水淹深度的增加显著增加,根系淀粉含量显著高于叶片,可溶性糖含量低于叶片;中山杉根系淀粉含量高是其能够长期忍受水淹的重要原因,且中山杉适应长期水淹的策略为忍耐型;经受长期水淹后中山杉根茎结合部长出气生根及茎基部膨大,同时根系外壁的木质化能将根系与外部水淹环境隔离,具有很强的耐淹性,可作为湿地生态修复、消落带生物治理的优良植物材料。

Aims Taxodium ‘Zhongshansha＇ had a strong submergence tolerance, but the biological mechanism is not clearly defined. The respiratory metabolism for the tolerance of Taxodium ‘Zhongshansha 118＇（（Taxodium distichum × Taxodium mucronatum） × Taxodium mucronatum） to long-term flooding was investigated through the measuring and analyzing the changes in root starch and soluble sugar as well as the contents of anaerobic respiration enzymes, including lactic dehydrogenase（LDH）, ethanol dehydrogenase（ADH） and pyruvate decarboxylase（PDC））, in the ‘Zhongshansha 118＇ seedling. The biomass and activities of the seedling roots were also measured and analyzed. Methods 24 1-year Taxodium ‘Zhongshansha 118＇ seedlings were randomly and equally divided into four groups and each group experienced one of four different levels of flooding（i.e., no flooding, waterlogging, partial submergence, deep submergence） from August 8 to November 8, 2014. Important findings The results showed that the contents of the anaerobic respiration enzymes in the seedling roots and leaves are increasing with the levels of severity of flooding, which indicated the roots and leaves adapt to long-term flooding by reinforcing their anaerobic respiration and activities of ADH that were higher than LDH for roots and leaves used in alcoholic fermentation mainly. The activities of anaerobic respiration enzymes in leaves were higher than that in roots, while leaves were more sensitive to flooding. The starch and soluble sugar in roots and leaves had similar trend with anaerobic respiration enzymes. However, roots starch was higher than leaves where soluble sugar was lower than roots. The higher content of starch were the important reason of strong submergence tolerance, and we consider the strategy to fit into long-term flooding is patience type. The paper demonstrate Taxodium ‘Zhongshansha 118＇ have the physiological and the morphological properties to adapt to long-term flooding, including aerial root and basal part of stem expanded and the outer wall of the root lignified to protect the roots from flooding.