Exine pattern determination in Angio sperm.

利用高分辨率扫描电镜研究了外阴发育，重点研究了保护膜形成和组成的初始发育过程。保护膜起源于四分体早期内陷质膜的突起部位。目前的研究表明，初始保护层是由不规则定向的纤维线组成的。纤维线在质膜上聚集形成网状。在四分体阶段，球状物质逐渐聚集在纤维线的网络中。随后，纤维线几乎被球状物质所掩盖。发育中的保护膜在胼胝质四分体包膜内具有粗糙的纹理。在游离小孢子期，颗粒状保护层变得均匀。目前的研究表明，保护层由纤维线和球状物质组成。纤维线可以作为受体和/或正在发育的外阴的骨架。

Exine development was studied using high resolution scanning electron microscopy, with attention to the initial developmental process of protectum formation and composition. The protectum is originated on the protuberant sites of the invaginated plasma membrane during the early tetrad stage. The present study shows that the initial protectum is composed of irregularly oriented fibrous threads. The fibrous threads accumulate and form a network on the plasma membrane. Globular materials gradually aggregate within the network of fibrous threads during the tetrad stage. Subsequently the fibrous threads are almost masked by the globular materials. The developing protectum has a coarse texture within the callosic tetrad envelope. At the free microspore stage the granular protectum becomes homogeneous. The present study suggests that the protectum consists of an association of fibrous threads and globular material. The fibrous threads may function as receptors and/or the skeleton of the developing exine.