Pinkard Elizabeth, Gill Warwick, Mohammed Caroline
Cooperative Research Centre for Forestry, Private Bag 12, Hobart, Tasmania 7001, Australia.
Tree Physiol. 2006 Aug;26(8):989-99. doi: 10.1093/treephys/26.8.989.
Intumescences or abnormal, non-pathogenic, blister-like protuberant growths, form on Eucalyptus globulus Labill. and, to a much lesser extent, Eucalyptus nitens (Deane and Maiden) Maiden leaves when plants are grown in a high relative humidity environment. We examined the histology of intumescences and their effects on leaf photosynthetic processes. Intumescences were induced by placing E. globulus and E. nitens seedlings in a relative humidity of 80% in a greenhouse for 5 days. Symptomatic and asymptomatic leaves of plants with intumescence development were compared with leaves of control plants. Light-saturated carbon dioxide (CO(2)) assimilation (A(max)) and responses of CO(2) assimilation (A) to varying intercellular CO(2) partial pressure (C(i)) were measured. Symptomatic and asymptomatic leaf samples were fixed and sectioned and cellular structure was examined. Intumescences greatly reduced the photosynthetic capacity of E. globulus leaves and were associated with reduced electron transport rate and ribulose bisphosphate (RuBP) regeneration capacity. Tissue necrotization and cellular collapse of the palisade mesophyll and deposition of phenolic compounds in the affected areas, probably reduced light penetration to photosynthesizing cells as well as reducing the amount of photosynthesizing tissue. Photosynthetic capacity of E. nitens was unaffected. The intumescences resembled simple lenticels, both morphologically and developmentally. To our knowledge, this is the first time that lenticel-like structures developed in response to environmental conditions have been described on leaves.
当蓝桉（Eucalyptus globulus Labill.）以及在较小程度上的尼氏桉（Eucalyptus nitens (Deane and Maiden) Maiden）植株生长在高相对湿度环境中时，叶片上会形成肿大或异常的、非致病性的、水泡状突出生长物。我们研究了肿大的组织学及其对叶片光合过程的影响。通过将蓝桉和尼氏桉幼苗置于温室中相对湿度80%的环境下5天来诱导肿大。将出现症状和未出现症状的有肿大发育的植株叶片与对照植株的叶片进行比较。测量了光饱和二氧化碳（CO₂）同化率（A(max)）以及二氧化碳同化率（A）对不同细胞间二氧化碳分压（C(i)）的响应。对出现症状和未出现症状的叶片样本进行固定、切片并检查细胞结构。肿大极大地降低了蓝桉叶片的光合能力，并与电子传递速率降低和核酮糖二磷酸（RuBP）再生能力降低有关。栅栏叶肉组织的坏死和细胞塌陷以及受影响区域酚类化合物的沉积，可能减少了光合细胞的光穿透率以及光合组织的数量。尼氏桉的光合能力未受影响。这些肿大在形态和发育上类似于简单的皮孔。据我们所知，这是首次描述叶片上因环境条件而形成的类似皮孔的结构。
