Pollen and anther development in Nelumbo (Nelumbonaceae)
Pollen and anther development in Nelumbo (Nelumbonaceae)
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DOI：
10.2307/2656664
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发表时间：
1999-12-01
影响因子：
3
通讯作者：
Osborn, JM
中科院分区：
文献类型：
--
作者：
Kreunen, SS;Osborn, JM
莲科（Nelumbonaceae）是水生被子植物的一个小科，包括莲（Nelumbo nucifera）和黄莲（Nelumbo lutea）。历史上，该属被认为与睡莲目（Nymphaeales）密切相关，然而新的系统研究将莲与低等真双子叶植物，特别是悬铃木属（Platanus）联系在一起。近年来，花粉发育的研究大大有助于了解系统发育关系，但很少有人知道这些事件在莲。本文首次从形态学上描述了花粉和花药的发育过程。lutea一个全面的个体发育序列记录，包括造孢组织，小孢子母细胞，四分体，游离孢子，成熟花粉粒阶段。沉积的小孢子母细胞外套和胼胝质壁，四面体和tetraximus四分体的共同发生，形成的primexine在四分体，和primexine持久性到后期的自由孢子阶段。大多数外壁的发展发生在游离孢子阶段的沉积覆盖层柱的exexexine，一个片状endexine，和一个不寻常的颗粒层下面，并与endexine lamellae混合。在最早的成熟花粉阶段，两层内壁迅速形成。记录的花粉发育的主要事件包括自由孢子阶段分泌型绒毡层的降解和成熟花粉粒阶段U形药室内壁增厚的快速形成。大多数成熟的花粉粒是三沟的，但也有不太常见的单沟和双孔的花粉粒。莲的气孔类型是被子植物气孔数目的一个重要转变。然而，莲的孔径变异可能与该属中孔径个体发育的晚相关，其发生在早期的游离孢子阶段。这一特点，以及其他细节的花粉和花药发育莲，比较那些睡莲目和悬铃木，努力提供额外的洞察系统和系统发育关系。虽然莲属与这两个类群在某些性状上相似，但莲属的个体发育序列在许多方面是不同的。
The Nelumbonaceae are a small family of aquatic angiosperms comprising Nelumbo nucifera and Nelumbo lutea. Historically, the genus has been considered to be closely related to Nymphaeales, however new systematic work has allied Nelumbo with lower eudicots, particularly Platanus. In recent years, studies of pollen development have contributed greatly to the understanding of phylogenetic relationships, but little has been known about these events in Nelumbo. In this paper, pollen and anther development are morphologically described for the first time in N. lutea. A comprehensive ontogenetic sequence is documented, including the sporogenous tissue, microspore mother cell, tetrad, free spore, and mature pollen grain stages. The deposition of a microspore mother cell coat and callose wall, the co-occurrence of both tetrahedral and tetragonal tetrads, the formation of a primexine in tetrads, and primexine persistence into the late free spore stage are shown. The majority of exine development occurs during the free spore stage with the deposition of a tectate-columellate ectexine, a lamellate endexine, and an unusual granular layer below and intermixed with the endexine lamellae. A two-layered intine forms rapidly during the earliest mature pollen stage. Major events of anther development documented include the degra dation of a secretory-type tapetum during the free spore stage and the rapid formation of U-shaped endothecial thickenings in the mature pollen grain stage. The majority of mature pollen grains are tricolpate, however less common monosulcate and diaperturate grains also develop. Go-occurring aperture types in Nelumbo have been suggested to be an important transition in angiosperm aperture number. However, aperture variability in Nelumbo may be correlated with the lateness of aperture ontogeny in the genus, which occurs in the early free spore stage. This character, as well as other details of pollen and anther ontogeny in Nelumbo, are compared to those of Nymphaeales and Platanus in an effort to provide additional insight into systematic and phylogenetic relationships. Although Nelumbo is similar to both groups in several characters, the ontogenetic sequence of the genus is different in many ways.