EFFECT OF LIGHT AND GIBBERELLIC-ACID ON CHROMOSOME ENDOREDUPLICATION IN LEAF EPIDERMIS OF TRITICUM-DURUM DESF

The first foliage leaf of Triticum durum Deaf., cvs. Capelli and Creso , was studied for the action of light and gibberellic acid on differen t aspects of plant growth. Creso is a short-strawed cultivar carrying the Rht I gene, that influences both plant height and sensitivity to a pplied gibberellins. In this study, a cytophotometric analysis of chro mosome endoreduplication in bulliform cells of the leaf epidermis was undertaken. The bulliform cells are arranged in lone rows and comprise 4C, 8C, and 16C cells. The relative percentage of these cells was rec orded under different light regimes and in the presence or absence of gibberellic acid (GA(3)). Our data indicate that light strongly affect s the occurrence of chromosome endoreduplication. Although cvs. Cappel li and Creso show the same frequency of endoreduplicated cells in the dark, all light treatments induce lower endopolyploidy in cv. Creso wh ereas, in cv. Cappelli, a reduction in endopolyploidy is observed when plants are irradiated with blue-lacking fights. This indicates that t he action of a blue-light responsive photoreceptor determines high end opolyploidy. With respect to GA(3) treatment, cv. Creso is again shown to be insensitive to hormone application, whereas in cv. Cappelli, gi bberellic acid influences endopolyploidy level in the dark, causing Ve ry high frequencies of 8C cells and relatively high frequencies of 16C cells.