A time course anatomical analysis of callogenesis from young leaf explants of oil palm (Elaeis guineensis Jacq.).

Histological and scanning electron microscopy analyses were employed to analyse callus development in oil palm at fortnightly intervals over a period of 28 weeks. The emergence of primary calli on the surface of the oil palm leaf explants was generally observed after 10 weeks of culture. Callus initiation was detected earlier, at six weeks, upon the division of perivascular cells within the leaf explant. This is the first report documenting the presence of a net-like structure termed as an extracellular matrix surface network (ECMSN) on the callus surface and the epidermal layer of the leaf explants of oil palm. We also observed peculiar ‘empty’ epidermal cells and small spherical particles on the surface of the epidermal cells of the leaf explants concomitant with the formation of a callus that have not been reported during callus initiation in other plants. These results may provide basic knowledge and facilitate our understanding of the biological processes involved during oil palm callogenesis. The anatomical changes and the presence of unique features like ECMSN may act as structural markers during callogenesis of oil palm. * Department of Cell and Molecular Biology, Faculty of Biotechnology and Biomolecular Sciences, Universiti Putra Malaysia, 43400 UPM Serdang,