Photocontrol of Shoot Regeneration from Hypocotyls of Tomato

Abstract

Thanks to the manipulation of hormone composition in the medium it has been possible to attribute morphogenic fonction to specific hormones and to separate spatially and in time the different hormone-dependent steps which are present in the morphogenic process (Christianson and Warnick 1988; Fambrini et al. 1996). By contrast, the role of the photomorphogenic pigments (if any) in the discrete steps characterizing the process of morphogenesis in vitro is still an open question despite a number of studies showing that light quantity, quality and duration influence both shoot and root formation (Hughes, 1981; Lercari et al. 1986; Economou and Read, 1987; Marcenaro et al, 1994). In the present paper we investigated the photocontrol of shoot regeneration from hypocotyl expiants of an au mutant of tomato and its isogenic wild type. The au mutant used in this study was isolated from tissue cultures as a result of somaclonal variation (Lipucci di Paola et al., 1988). The etiolated seedling of au mutant lacks spectrophotometrically detectable phytochrome, as a consequence of a excision in chromophore synthesis (Terry and Kendrick, 1996). In tomato plants at least five phytochrome genes are expressed (Hauser et al., 1997).