Influence of Carbohydrate Source on the In Vitro Flowering of Sturt's Desert Pea ('Swainsona formosa')

Abstract

'Swainsona formosa' (G. Don) J. Thompson (Sturt's desert pea) is an Australian native legume, which is used as an ornamental pot plant. It is also suitable for hanging baskets and cut flowers. One of the impediments to the commercialisation of 'S. formosa' as a pot plant is its inability to produce flowers under low light conditions. The possibility of using exogenous sugar application as a replacement for high light intensity conditions is considered with the objective of evaluating the effect of exogenous sugar application on the in vitro flowering of 'S. formosa'. Media containing different sugars (sucrose, fructose, and glucose) and concentrations (1.5, 3.0, 4.5, or 6.0% w/v) were used in both high and low light. In vitro flowering of 'S. formosa' depended on light conditions under which the stock plants were grown and on the sugar type and concentration in the culture medium. No flowers were observed in any cultures from low light grown stock plants after six weeks, whereas the explants from the high light grown stock plants cultured on Murashige and Skoog medium containing 3.0% and 4.5% sucrose developed flowers within four to six weeks. These results point to the possibility of an interaction between environmental conditions under which the explant source is grown and the types and concentrations of exogenous sugar used in the culture medium. The work presented here is the first report of 'S. formosa' producing flowers in vitro.