[Ultracytochemical studies of aloin in Aloe arborescens leaves].

Lead acetate precipitation method was used for ultracytochemical localization of aloin. The processes of aloin production, transport and storage were studied by transmission electron microscope. Results showed that aloin was produced in the plastids of the assimilating tissue. The aloin was transported through the plastid membrane to the surrounding endoplasmic reticulum and enveloped in the vesicles by the endoplasmic reticulum elements, the vesicles approached and later fused with the plasmalemma. Some vesicles of the plastid membrane directly fused with the plasmalemma. The vesicles released their contents into the apoplast through exocytosis, and finally reached the vascular bundle sheath by apoplastic translocation. Aloin was transported to the internal tangential wall of vascular bundle sheath cell through endoplasmic reticulum vesicles, and reached the cytoplasm of aloin cell by means of plasmodesmata. Finally, aloin was stored in the vacuoles of aloin cell.

[Development of aloin cells and accumulation of anthraquinone in aloe leaf].

The development of aloin cells and its relationship with the accumulation of anthraquinone in aloe leaf were investigated with the methods of paraffin section, semi-thin section, histochemistry and fluorescent microscopy. The results showed: cells rounded the procambium bundle differentiated into bundle sheath at the initial stage of procambium bundle developing into vascular bundle. When the sieve tube members appeared in protophloem, there were a lay of procambium bundle cells reserved between the sieve tube members and bundle sheath. These cells began to devise, then developed into aloin cells through enlargement of volume and vacuolization with the differentiation of metaphloem and metaxylem. So the aloin cells were special phloem parenchyma cells because they shared the same origin with the other phloem cells. The investigation of histochemistry reflected that there were aloin precipitate in the central vacuole of aloin cells after the material was soaked in the liquid of 1% lead acetate [Pb (CH3COO)2]. In addition, the yellow fluorescence was observed in aloin cells when the section of fresh material was investigated under the fluorescent microscope with blue light, which suggested the aloin cells of vascular bundles were the mainly storage site of anthraquinone.