The 'inch flora': Some observations on the morphology and seed biology of annual plant species common in semi-arid woodlands of western Victoria

摘要

Annual plants are an under-studied component of the Victorian flora. We describe the morphology and seed biology of ten species common to semi-arid woodlands in far western Victoria: Actinobole uliginosum, Blennospora drummondii, Calandrinia granulifera, Centrolepis strigosa, Millotia tenuifolia, Podotheca angustifolia, Pogonolepis muelleriana, Quinetia urvillei, Rhodanthe pygmaea, Triptilodiscus pygmaeus. Two forms of growth morphology were observed- 'erect' and 'branched'. Tree species were found to have myxospermous seeds. Here, the seed coat contains a mass of dry mucilage which hydrates and swells rapidly on contact with water. Eight species appear to have dormant seed at the time of dispersal, presumably a strategy to avoid germination in summer. This dormancy was overcome when seed was heated to 35°C for 4 weeks. Our preliminary studies conform that annuals are a fascinating group of plants which warrant much better ecological understanding. Further quantitative investigation of the seed biology (particularly the extent and role of myxospermy), seed germination requirements (including dormancy-breaking mechanisms) and developmental anatomy are clearly necessary.