Phenology, morphology and reproductive biology of the tuberous sundew, Drosera erythrorhiza Lindl

Abstract

The seasonal growth cycle of Drosera erythrorhiza was examined in native habitat near Perth, W.A. Vegetative growth was from autumn to late spring (March to October), aestivation by underground tubers from November to February. Each germinating tuber produced an upward growing stem terminated at the soil surface by a rosette of glandular leaves. Light was required to initiate the rosette. New tubers formed during July and August. A positively geotropic axillary shoot (dropper) developed from the stem base and penetrated the epidermal sheath(s) of the parent tuber to form a replacement tuber within the emptying storage tissues of its parent. Diageotropic axillary shoots (rhizomes), produced higher up the stem, extended radially, each swelling terminally to produce a daughter tuber. Plants flowered profusely only after fire, and were not observed to reproduce from seed. Reproduction of clones was analysed in terms of number and depth of placement of parent and daughter tubers. Age structure of clones was studied by counting epidermal sheaths surrounding tubers. Clones appeared to undergo cyclic rejuvenation, periods of intensive daughter tuber production alternating with periods of minimal reproduction. Soil type, fire history and season modified this reproductive behaviour by affecting the intensity of daughter tuber production and the growth and survival of tubers.