Morphogenesis in endosperm cultures

Numerous attempts have been made to culture the immature and mature endosperm tissues under aseptic conditions. Callus formation has been reported in more than a dozen species, but rarely organogenesis. There is not much difference in nutritional requirements of different taxa. Mature endosperm tissue of about half-a-dozen species of parasitic angiosperms and only three of autotrophs have been induced to differentiate organs. When the differentiation of organs is directly from the endosperm, i.e. without the intervention of callus, vascularization is not a pre-requisite; however, when organogenesis follows callus formation, vascular tissue differentiation precedes organogenesis. Though, root and shoot differentiation occur invariably from the callus, formation of a complete plantlet is rare (reported only in an autotrophic member, Putranjiva roxburghii). For obtaining a successful culture of mature endosperm tissue, association of embryo in situ is necessary, at least, initially. In some systems, this embryo-effect can be replaced by pre-soaking the endosperm pieces in GA3 solution. In most of the species a source of reduced nitrogen such as CH or YE is essential for callusing and differentiation; this has been replaced in part, by an amino acid, valine, in Putranjiva. In continuously-growing callus the capacity for differentiation of organs is lost with a concurrent increase in the ploidy of the cells. Like androgenic haploids, the production of triploids through endosperm culture would also be very rewarding.