Effect of Gibberellic Acid on Genetically Controlled Tumour Formation and Vascularization in Tomato

Abstract

SEVERAL effects of gibberellic acid on plant growth and differentiation have been recognized^1–4, but there have been no previous reports of any effect on tumorous genotypes in vivo. This communication reports the effect of gibberellic acid on a genetically controlled condition resembling a tumour and on vascular development in a tomato hybrid. The tumour condition appears on the hybrid plants carrying the Frosty spot (Frs) gene from Lycopersicon chilense on the background of L. esculentum variety ‘Tiny Tim’, and is transmitted as a dominant trait⁵. Tumours consisting of groups of undifferentiated parenchymatous cells develop along the veins of the leaves, after which the affected tissues become chlorotic and necrotic^5,6. Plants with a tumour trait appear dwarfed and have poorly developed vascular tissue, which results in weak stems. The non-tumorous plants, however, are normal and show good vascular development. In the tumorous plants, differentiation of vascular tissue stops after three to six layers of secondary xylem have been formed (Fig. 1A). In contrast to this, the derivatives of cambium in the normal genotype are many and show relatively more lignification in the secondary xylem (Fig. 1B).