荷花玉兰休眠芽幼叶的形态和发育特征

Morphological and developing characteristics of the young leaves in dormant buds of Magnolia grandiflora

关键词:  木兰科  芽  幼叶  贴生  枯死

Key words:  Magnoliaceae  bud  young leaf  adnate  dead

摘要:

对荷花玉兰休眠芽的形态和发育特征进行了解剖观察。结果表明：幼叶多直立，个别旋抱状；叶片沿中脉向近轴面，在同株和异株的芽间随机性向左或向右纵向对折；叶芽内的外1～3层和花芽内的幼叶常枯死；花芽最内一层幼叶柄与其托叶贴生，并且叶片多完全退化，个别发育出较小的正常叶片。芽内幼叶枯死，是适应性的生理退化而非病害或营养不良现象，在演化上可能与其托叶替代幼叶作为芽鳞进行保护作用有相关性。

Abstract:

Morphological and developing characteristics of dormant buds of Magnolia grandiflora were observed with anatomical methods. The results are as follows:most of the young leaves are erecting，while a few are spiraling； leaf blades are all conduplicate longitudinally along its middle veil with the lateral edges inwards，and among the buds of a single tree and the different trees stochastically to the right or left；the outer 1-3 layer leaves in a leaf bud and all ones in a flower bud are mostly dead；the petioles of the inmost layer young leaves in flower buds，are adnate to its stipules，with their blades in most cases degenerated away and occasionally developing into normal and smaller ones. It’s considered that death of young leaves in the buds is physiologically degenerated for adaption，not caused by diseases or innutrition，which might have relevance to the substitution of stipules for young leaves as bud scales performing protectio in evolution.