Biology of Australian seagrasses: Pollen development and submarine pollination in Amphibolis antarctica and Thalassodendron ciliatum (Cymodoceaceae)

Abstract

Development of the filiform pollen of the sea nymph Arnphibolis antarctica (Labill.) Sonder & Aschers. ex Aschers. has been characterized by high resolution light and electron microscopic methods. First pollen mitosis occurs at the end of the young spore period immediately preceding the vacuolate period, in contrast to many terrestrial pollens. Mature pollen is trinucleate, and is spirally coiled within the anther. The mature pollen wall shows a positive reaction for acid phosphatase like the intine of terrestrial pollens but is devoid of the outer exine layer, as judged by light and electron microscopic evidence. Development and arrangement of Thalassodendron ciliatum (Forssk.) Den Hartog pollen are similar. The adaptation of the pollen of aquatic plants for submarine pollination is reviewed in the light of evidence from 18th and 19th century work.

Genetic uniformity in Amphibolis antarctica, a dioecious seagrass

“…The seedlings themselves could be clonal as seedling formation has not been shown to be sexual by embryological studies and may be apomictic. However, pollination has been shown to be successful both in culture and in the field (Ducker et at., 1978;Verduin et at., 1996). In addition, high frequencies of male plants persist in some populations, and no evidence of fixed hybridity, as is characteristic of apomicts, was observed.…”

In situ submarine pollination in the seagrass Amphibolis antarctica: research notes

“…A similar submarine pollination mechanism is a feature of the unrelated freshwater species Lepilaena bilocularis Kirk (Cox 1993). Reference to the possibility that Amphibolis antarctica might exhibit submarine pollination is made by a number of authors such a s Ducker et al (1978) and Pettitt et al (1983). There appear to b e no in situ observations of submarine pollination of subtidal A. antarctica specimens to date.…”

“…results, see McConchie & Knox 1989). The mechanism of, and adaptations to, submarine pollination in A. antarctica in controlled seawater aquarlum conditions have been described in detail by Ducker et al (1978), Pettitt et al (1983) (Cox 1993). A similar submarine pollination mechanism is a feature of the unrelated freshwater species Lepilaena bilocularis Kirk (Cox 1993).…”

“…Pollen in hydrophilous angiosperms, including A. antarctica, is often filiform (e.g. Ducker et al 1978, McConchie et al 1982, Pettitt et dl. 1983) and has a reduced or no exine layer (e.g.…”

Germination of Pollen Inside Anthers in Some Non-Cleistogamous Species

“…Some pollen does not dehydrate, as in the case of submarine pollination (DucKER et al 1978;HESLOP-HARRISON 1979a, 1979c. Partially dehydrated pollen grains occur at shedding also in « certain species of Zingiberaceae and allied families » (HESLOP-HARRISON 1979c).…”