Effect of Light Conditions on the Resistance of Current-year Fagus Crenata Seedlings Against Fungal Pathogens Causing Damping-off in a Natural Beech Forest: Fungus Isolation and Histological and Chemical Resistance
Effect of Light Conditions on the Resistance of Current-year Fagus Crenata Seedlings Against Fungal Pathogens Causing Damping-off in a Natural Beech Forest: Fungus Isolation and Histological and Chemical Resistance
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DOI：
10.1007/s10886-009-9687-4
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发表时间：
2009-09
影响因子：
2.3
通讯作者：
Y. Ichihara;K. Yamaji
中科院分区：
文献类型：
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作者：
Y. Ichihara;K. Yamaji
林窗动态影响林下光照强度，进而影响林木幼苗的防御和存活。当年度毛茛幼苗在冠层下表现出很高的死亡率，这是由立枯病引起的。相比之下，它们在间隙中经受住了病原体的攻击。然而，防御机制对猝倒尚未完全理解。为了确定影响当年幼苗死亡率的抗性因素，我们比较了幼苗的存活率和幼苗下胚轴的化学和组织学特征。当年生苗木的立枯病主要发生在6月下旬至7月，林缘样地苗木成活率高于郁闭样地。通过幼苗下胚轴接种试验，鉴定出炭疽菌（Colletotrichum dematium）和大果刺盘孢（Drocarponsp.）仅在低光照下才能作为致病病原体。在7月初，只有幼苗下胚轴从森林边缘情节表现出周壁形成。从6月中旬至7月，从林缘地块的幼苗下胚轴积累的总酚量的两倍左右的那些积累的幼苗下胚轴从封闭的立场情节。下胚轴甲醇提取物的乙酸乙酯相具有抑菌活性。我们的结论是，从森林边缘情节幼苗可以抵抗病原菌的攻击，通过peridendum形成和增加苯酚的合成。在林隙动态中，受光强控制的植物防御机制可能对促进幼苗更新具有重要意义。
Forest gap dynamics affects light intensity on the forest floor, which in turn may influence defense and survival of tree seedlings. Current-yearFagus crenataseedlings show high mortality under the canopy caused by damping-off. In contrast, they survive pathogen attacks in gaps. However, defense mechanisms against damping-off have not been fully understood. In order to determine the resistance factors that affect mortality in current-year seedlings, we compared seedling survival and chemical and histological characteristics of the hypocotyls of seedlings from closed-stand and forest-edge plots. Damping-off occurred in the current-year seedlings mainly from the end of June to July; survival rate of the seedlings was higher in the forest-edge plot than in the closed-stand plot. By performing an inoculation test on the seedling hypocotyls, we identifiedColletotrichum dematiumandCylindrocarponsp. as the causative pathogens under low illumination only. In the beginning of July, only seedling hypocotyls from the forest-edge plot exhibited periderm formation. From mid-June to July, seedling hypocotyls from the forest-edge plot accumulated approximately twice the amount of total phenols as those accumulated by seedling hypocotyls from the closed-stand plot. The ethyl acetate phase of methanol extracts of hypocotyls showed antifungal activity. We conclude that seedlings from the forest-edge plot may resist pathogenic attack via periderm formation and increased phenol synthesis. Plant defense mechanisms that are controlled by light intensity may be important for promoting seedling regeneration in forest gap dynamics.