The histopathology of Phaeocryptopus gaeumannii on Douglas-fir needles
The histopathology of Phaeocryptopus gaeumannii on Douglas-fir needles
复制标题
花旗松针上的褐隐藻的组织病理学
作者：
J. Stone;Bryan R. Capitano;J. Kerrigan
萌发的子囊孢子的Phaeocryptopus gaeumannii产生气孔上附着胞，穿透钉进入针。最初的感染发生在5月下旬和7月上旬，与萌芽和芽伸长相一致。针叶内的定植完全是细胞间的，并在7月至5月期间持续增加。没有观察到胞内菌丝或吸器，但菌丝紧密贴附叶肉和栅栏细胞壁丰富的3-5个月后首次感染。假囊原基开始形成于10月至4月，4-9月。在气孔上室中发育的假囊原基通过气孔下室中的特化细胞与内生叶状体连接，所述特化细胞具有加厚的顶壁并且类似瓶梗，但不参与无性生殖。顶端壁增厚，而不是出现的功能，加强对膨压的保卫细胞，允许细胞质的连续性，以保持之间的发展中的假囊和营养菌丝的针。在形成假囊壳原基的同时，附生菌丝从发育中的假囊壳的外围出现，在针叶表面生长，形成大量的附着胞，并通过在未占据的气孔上方产生附着胞而重新进入针叶。10月至1月期间，附生菌丝及其附属附着胞逐渐变得更加丰富。
Germinating ascospores of Phaeocryptopus gaeumannii produce suprastomatal appressoria from which penetration pegs enter needles. Initial infection occurs between late May and early Jul and coincides with budbreak and shoot elongation. Colonization within needles is exclusively intercellular and increases continuously during Jul–May. No intracellular hyphae or haustoria were observed, but hyphae closely appressed to mesophyll and palisade cell walls are abundant by 3–5 mo after initial infection. Pseudothecial primordia begin to form in epistomatal chambers Oct–Apr, 4–9 mo after initial infection. Pseudothecial primordia developing in the epistomatal chamber are connected to the endophytic thallus by specialized cells in the substomatal chamber that have thickened apical walls and resemble phialides but are not involved in asexual reproduction. The apical wall thickenings instead appear to function as reinforcement against the turgor pressure of the guard cells, allowing cytoplasmic continuity to be maintained between the developing pseudothecium and vegetative hyphae within the needle. Concurrent with the formation of pseudothecial primorida, epiphytic hyphae emerge from the periphery of developing pseudothecia, grow across the needle surface, form numerous anastomoses and reenter the needle by producing appressoria above unoccupied stomata. Epiphytic hyphae and their associated appressoria gradually become more abundant during Oct–Jan.