Contractile growth of the hypocotyl of Lotononis bainesii seedlings in relation to some environmental factors.
Abstract
In a greenhouse experiment L. bainesii seeds were sown at 0, 10, 20 or 30 mm depth, covered with Digitaria decumbens straw (20 mm length) at 0, 70, 140 or 210 g/m2 and grown under shades giving 24, 47, 77 or 100% light transmission. Light negatively influenced the extension of the hypocotyl aboveground level and positively increased the contractile growth of the hypocotyl to produce a buried crown. Emergence from 10 and 20 mm depth and the absence of litter also favoured the development of a buried crown. In a field experiment at Queensland University's Mt. Cotton Research Station sheep were withdrawn from a D. decumbens dominated pasture containing L. bainesii. Five L. bainesii seedlings/quadrat (0.4 m × 0.4 m) were tagged and the height of the hypocotyl was measured as was the light received by the seedlings. The observations supported the findings from the greenhouse experiment. A buried crown did not develop in the absence of grazing. It was suggested that the maintenance of grazing pressure following seedling regeneration would promote L. bainesii density in mixed pastures.