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Annals of Botany 73: 225-230, 1994
© 1994 Annals of Botany Company
Pistil Structure and Pollen Tube Pathways in Leptospermum myrsinoides and L. continentale (Myrtaceae)
School of Botany, University of Melbourne, Parkville, Victoria 3052, Australia
Pistil structure and pollen tube growth were investigated in Leptospermum myrsinoides and L. continentale (Myrtaceae). Both L. myrsinoides and L. continentale pistils consist of an ovary with five locules, a style and a five-lobed dry, papillate stigma. A centrally located stigmatic cleft is present but extends only to the base of the stigma. Pollen germinates and grows intercellularly through the stigma into the central transmitting tissue of the style. Pollen tubes do not grow down the stigmatic cleft. At the base of the style the transmitting tissue separates into five, each tract leading through the placenta to one of the five locules. The pollen tubes continue to grow intercellularly through these five tracts entering the locules between the lobes of the placenta. Pollen tubes are smooth-walled and straight whilst in the transmitting tissue of the style but produce short lateral branches at regular intervals when in the locules. Branching continues until pollen tubes enter ovules. It is suggested that the observed branching in the locules is a result of pollen tubes following a chemotropic or thigmotropic pathway to the ovules. This behaviour was consistent in all pistils examined and no difference was observed in the behaviour of self- or cross-pollen tubes in the style or ovary.Copyright 1994, 1999 Academic Press
Leptospermum myrsinoides Schldl., Leptospermum continentale J. Thompson, pistil structure, pollen tube pathway, pollen tube branching