The Growth, Anatomy and Morphogenetic Potential of Callus and Cell Suspension Cultures of Hevea brasiliensis

Abstract

Callus cultures have been initiated from stem expiants of young plants of Hevea brasiliensis and maintained over long periods at 30 °C by serial subculture in Murashige and Skoog medium containing 2 mg l-1 2,4-D and 0-5 mg l-1 kinetin. Newly-initiated cultures spontaneously initiated roots but, on serial subculture, this property was lost and the cultures became heterogeneous (consisting of proliferating light segments and darker compact non-growing segments). Serially propagated cultures continued to differentiate a few scattered latex vessels containing particulate material similar to that in the root laticifers. This callus (O callus) did not yield a growing cell suspension when transferred to agitated liquid medium. However, the large cell aggregates which could be recovered after two passages in liquid medium, when again grown on solid medium yielded a highly friable light-coloured fast-growing homogeneous callus (R callus) which retained its distinctive character on subculture. This callus when transferred back to agitated liquid medium yielded a fine rapidly growing cell suspension culture which could be serially propagated at 30 °C in the same medium as that used for callus culture. Both the O and R cultures were 2,4-D dependent, but differed in their responses to 2,4-D. Both retained their diploid character when serially propagated. Serially-propagated suspensions came to contain a proportion of polyploid cells. When the suspensions were maintained for several months without subculture the larger cell aggregates which developed gave rise to embryo-like structures. Attempts to promote the further development of these embryo-like structures into plantlets were unsuccessful.