MECHANICALLY ISOLATED PHOTOSYNTHETIC CELLS FROM ASPARAGUS CLADOPHYLLSORIGINATE FROM 2 DISTINCT TISSUE LOCATIONS

Photosynthetically competent cells from cladophylls of Asparagus densi florus (Kunth) Jessop, previously called Asparagus sprengeri Regel, ar e readily isolated using mechanical disruption of tissue. They have be en used in many physiological and biochemical studies. Light microscop y indicates an apparently homogeneous population of cells. However, th e tissue locations of the isolated cells is not clear, and more than o ne cell type may be present. A light microscope examination of fresh a nd cleared cladophyll tissue revealed a complex articulated network of photosynthetic cells between the epidermal and vascular tissues. Thre e types of photosynthetic cell were identified. The first type, referr ed to as the spongy mesophyll cells, had a shape distinct from that of the isolated cells; they were elongated and often branched. The two o ther types of cells were similar in shape to the isolated cells and we re 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 phot osynthetic cells indicated an overall ratio of 2.4 (+/- 0.7) and that only the last two cell types were represented. The elongated spongy me sophyll cells were therefore excluded during the isolation procedures; because of their elongated irregular shape they were probably elimina ted during cell filtration to remove debris. Consequently, isolated ce lls represent two distinct cell types that may respond differently to experimental treatments.