Department of Botany, Faculty of Science, Kasetsart University, Bangkok, 10900, Thailand.
Division of Biological Science, Faculty of Science, Prince of Songkla University, Songkhla, 90110, Thailand.
Protoplasma. 2024 Nov;261(6):1281-1295. doi: 10.1007/s00709-024-01969-4. Epub 2024 Jul 16.
Garcinia dulcis (Roxb.) Kurz (Clusiaceae) is a medicinal plant native to Southeastern Asia, with a peculiar, precocious pollenkitt production in early microspore development. We aimed to find out whether different secretory activities of the tapetum or a premature sporoderm development provides additional evidence for our recent hypothesis for the precocious pollenkitt production. Histology, histochemistry and ultrastructure of tapetum and sporoderm development during pollenkitt secretion in Garcinia dulcis were conducted, based on light and electron microscopy analysis. The results showed that Garcinia dulcis possesses normal pollen development. The presence of two different pollen coating types, precocious pollenkitt (L1) and common pollenkitt (L2), in the anther tapetum indicate that they are produced in two different active stages of the secretory tapetum. The precocious pollenkitt production and transport to the locule takes place in early active tapetal cells at early tetrad to early microspore stage and is ongoing until late microspore stage. The production of the second type of pollenkitt (L2) starts shortly after the first active tapetum stage together with the formation of sporopollenin precursors. The sporoderm formation was completed at late microspore stage, when the tapetal cell walls start to disintegrate. Orbicules are lining the inner tapetum wall at middle to late microspore stage. ER (during early microspore stage) and plastids (during late microspore stage) were the two main sources of pollenkitt, which finally fused to pollenkitt droplets when the tapetal cells degenerated at mature bicellular pollen stage.
甜藤（藤黄科）是一种原产于东南亚的药用植物，其花粉粒在早期小孢子发育时具有独特的早熟花粉粒分泌现象。我们旨在探讨绒毡层不同的分泌活动或过早的花粉壁发育是否为我们最近提出的早熟花粉粒分泌假说提供了额外的证据。我们基于光镜和电镜分析，对甜藤绒毡层和花粉壁发育过程中的组织学、组织化学和超微结构进行了研究。结果表明，甜藤具有正常的花粉发育过程。在花药绒毡层中存在两种不同的花粉涂层类型，早熟花粉粒（L1）和普通花粉粒（L2），这表明它们是在绒毡层分泌的两个不同活跃阶段产生的。早熟花粉粒的产生和向腔室的运输发生在早期四分体到早期小孢子阶段的活跃绒毡层细胞中，并持续到小孢子晚期。第二种花粉粒（L2）的产生在第一活跃绒毡层阶段之后不久开始，同时形成花粉壁前体。在小孢子晚期，当绒毡层细胞壁开始解体时，花粉壁形成完成。在小孢子中期到晚期，球体排列在内绒毡层壁上。内质网（在小孢子早期）和质体（在小孢子晚期）是花粉粒的两个主要来源，当绒毡层细胞在成熟的二细胞花粉期退化时，它们最终融合成花粉粒液滴。
