Effect of three brassinosteroids on morphological and physiological parameters of in vitro plantlets of potato Solanum tuberosum L. c.v. Desireé in vitro and in the greenhouse

Abstract

The brassinosteroids MH5, Biobras-6 and Biobras-16 were applied to the culture medium in concentrations ranging from 0.1 to 0. 001 mg.l-1. The plantlets were then transplanted into the greenhouse. Brassinosteroids tended to diminish morphologic characters such as fresh and dry weight, plant height and node number, both, in vitro and at acclimatization. Brassinosteroids influenced physiologic parameters such as waterloss after cutting, dry matter content, internode length and root shoot ratio of acclimatized microplants. The adverse effect on biomass production diminished with decreasing concentration of the brassinosteroid in the culture medium, at the same time maintaining positive effects on physiological parameters. Application of 0. 005 mg.l-1 Biobras 6 or MH 5 in vitro led to increased tuber production in the greenhouse, in a magnitude of 50%, both, tuber number and tuber yield. A similar effect could be achieved with foliar application in the greenhouse, though the increase in yield and tuber number was however lower. Key words: acclimatization, biomass, biobras, Brassinosteroids, dry weight, fresh weight.