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在橡胶树受条溃疡菌(Phytophthora sp.)侵染后的某个时间,在受侵染组织周围会形成一个肉眼可见的深褐色层——褐变层。实验表明,(1)褐变层形成以后病斑即停止扩展;(2)形成褐变层后受侵染组织中的病原仍然是生活的;(3)原病斑形成褐变层后,在靠近它的地方进行再接种,结果新的病斑不能扩展到原病斑的褐变层。根据这些事实,我们认为褐变层在限制侵染扩展中起主要的作用。施用乙烯和限制侵染扩展的原因在于它使褐变层的形成较为迅速,所以能更有效地阻止病斑的扩展。
At some point after the rubber tree is infested by Phytophthora sp., A macroscopic dark brown layer called the browning layer is formed around the infected tissue. Experiments show that: (1) the formation of browning layer after the lesion stops expanding; (2) the formation of brown layer in the infected tissue is still living in the pathogen; (3) Near its place of re-vaccination, the results of the new lesion can not be extended to the brown spots of the original lesion. Based on these facts, we believe that the browning layer plays a major role in limiting the spread of the infection. The reason for the application of ethylene and to limit the spread of the infection is that it allows the formation of browning layers more rapidly, thereby preventing the spread of spots more effectively.