Mechanically isolated photosynthetic cells from asparagus cladophylls originate from two distinct tissue locations

Abstract

Photosynthetically competent cells from cladophylls of Asparagus densiflorus (Kunth) Jessop, previously called Asparagus sprengeri Regel, are readily isolated using mechanical disruption of tissue. They have been used in many physiological and biochemical studies. Light microscopy indicates an apparently homogeneous population of cells. However, the tissue locations of the isolated cells is not clear, and more than one cell type may be present. A light microscope examination of fresh and cleared cladophyll tissue revealed a complex articulated network of photosynthetic cells between the epidermal and vascular tissues. Three types of photosynthetic cell were identified. The first type, referred to as the spongy mesophyll cells, had a shape distinct from that of the isolated cells; they were elongated and often branched. The two other types of cells were similar in shape to the isolated cells and were found attached to the epidermal and spongy mesophyll tissues. Those attached to the epidermis, the palisade cells, had a length to width ratio of 2.7 (± 0.5), while those attached to the spongy cells had a length to width ratio of 2.2 (± 0.5). Analysis of the isolated photosynthetic cells indicated an overall ratio of 2.4 (± 0.7) and that only the last two cell types were represented. The elongated spongy mesophyll cells were therefore excluded during the isolation procedures; because of their elongated irregular shape they were probably eliminated during cell filtration to remove debris. Consequently, isolated cells represent two distinct cell types that may respond differently to experimental treatments. Key words: asparagus, cladophyll, isolated photosynthetic cell, structure.