An Examination of the Reproductive Biology of Telopea speciosissima (Proteaceae) with Emphasis on the Nature of Protandry and the Role of Self‐Pollination in Fruit Set

Abstract

Aspects of the reproductive biology of the waratah Telopea speciosissima R.Br. were studied under controlled conditions using large, pot‐grown plants. One to 2 d prior to perianth opening, anthers dehisced in a circle of clumps onto the pollen presenter around the oval stigmatic groove (pollination chamber). This deposition pattern may lead to a degree of autogamous pollination. Pollen viability, measured by fluorescence microscopy (fluorescein diacetate), was at a maximum of 90% at perianth opening, decreasing to less than 50% after 8 d. Some viable pollen (ca. 10%) was detected up to 19 d after perianth opening. The timing of stigma receptivity was determined by esterase activity, by examination of pollen‐tube growth using fluorescence microscopy, and by visual inspection of the stigma using SEM. The stigma was receptive at perianth opening and up to ca. 9 d after. Although peak stigma receptivity occurred at 2 d and up to 7 d postperianth opening, this species may be considered only weakly protandrous and essentially homogamous, as pollen was generally viable throughout the entire period. Two days following self‐ or cross‐pollination, pollen tubes had grown through the pollination chamber and could be seen just entering the upper style. By 8 d, some pollen tubes were observed in the ovary area in self‐ and cross‐pollen treatments. Proportionally, more cross‐pollinated pistils had pollen tubes growing through to the ovary than self‐pollinated pistils. Manual pollen removal resulted in greater growth of self‐pollen tubes when compared with self‐pollen that was left intact on the flower. This indicates that either the stigma was stimulated by pollen removal or that pollen was pushed down into the stigmatic groove into closer contact with stigmatic surfaces. Despite the presence of pollen tubes in all parts of the pistil and the early growth of a small number of fruits in self‐pollinated treatments, only cross‐pollinated treatments resulted in mature fruits containing viable seeds. This evidence confirms late‐acting gametophytically controlled self‐incompatibility as the main nonvector mechanism for outbreeding in this species.