Beikircher B, Mayr S
Institute of Botany, University of Innsbruck, Sternwartestraße 15, 6020 Innsbruck, Austria.
Trees (Berl West). 2013 Jun;27(3):707-715. doi: 10.1007/s00468-012-0826-0. Epub 2012 Dec 14.
Lammas shoots are flushes formed by some woody species later in the growing season. Having less time to develop, tissue formation is suggested to be incomplete leading to a higher peridermal water loss during consecutive months. In this study, we analysed morphological and anatomical parameters, peridermal conductance to water vapour and the level of native embolism in mid-winter and late-winter of lammas shoots and normal spring shoots of the apple varieties 'Gala' and 'Nicoter'. Lammas shoots showed a significantly higher shoot cross-sectional area due to larger pith and corticular parenchyma areas. In contrast, phloem was significantly thicker in spring shoots. No pronounced differences were observed in xylem and collenchyma thickness or mean hydraulic conduit diameter. The phellem of spring shoots was composed of more suberinised cells compared to lammas shoots, which led to a significantly higher peridermal conductance in the latter. The amount of native embolism in mid-winter did not differ between shoot types, but in late-winter lammas shoots were more embolised than spring shoots. Data show that the restricted vegetation period of lammas shoots affects their development and, in consequence, their transpiration shield. This may also pose a risk for winter desiccation.
秋梢是一些木本植物在生长季后期形成的新梢。由于发育时间较短，其组织形成被认为不完整，导致在接下来的几个月中周皮水分损失更高。在本研究中，我们分析了苹果品种“嘎啦”和“烟富”的秋梢和正常春梢在仲冬和晚冬时的形态和解剖参数、周皮对水蒸气的导度以及天然栓塞水平。秋梢由于髓和皮层薄壁组织面积较大，其茎横截面积显著更大。相比之下，春梢的韧皮部明显更厚。木质部和厚角组织厚度或平均水力导管直径未观察到明显差异。与秋梢相比，春梢的木栓层由更多栓质化细胞组成，这导致秋梢的周皮导度显著更高。仲冬时不同新梢类型的天然栓塞量没有差异，但在晚冬时，秋梢比春梢栓塞更严重。数据表明，秋梢有限的生长时期会影响其发育，进而影响其蒸腾屏障。这也可能带来冬季干燥的风险。
