Annuals with transient seed banks: the population biology of indigenous Sorghum species of tropical north-west Australia

Andrew, M.H. and Mott, J.J. (1983) Annuals with transient seed banks: the population biology of indigenous Sorghum species of tropical north-west Australia. Australian Journal of Ecology, 8 (3). pp. 265-276.

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Indigenous Sorghum species are a prominent feature of the seasonally-dry tropics of north-west Australia. Studies of the dormancy characteristics of these species were undertaken, and measurements of seedling emergence, of plant survival, growth and reproductive success, and of seed bank changes were made for one Sorghum intrans population and for three S. stipoideum populations over two growing seasons. On wetting, 90% of the non-dormant, viable seeds of nil species germinated within five days. The temperature range for optimal germination was 25 - 35°C, and germination declined with decreasing water potential. The seeds of all species had high innate dormancy at seedfall, and this was broken down over the ensuing dry season. For S. intrans and S. stipoideum height and tiller number increased steadily after emergence up to the time of floral initiation, which occurred simultaneously for primary tillers within each population. Most vegetative tillers died after this leaving a single reproductive culm which rapidly elongated to reach 1 – 4 mat maturity, depending on site and season. Seedfall occurred over a short, c. two-week period before the rainy season had finished. Seeds were dispersed within 2 m of the parent plant. Seeds were buried to less than 2 cm by the screwing action of their hygroscopically-active awns. All these annual Sorghum species appear to have transient seedbanks, formed at seedfall near the end of one rainy season and exhausted by germination following the first rains of the next annual rainy season. We suggest that S. intrans and S. stipoideum persist despite this feature because they mature at the earliest time that the rainy season has been known to end in their respective localities. Persistence is further aided by adaptations which enable individuals to survive the unpredictable short droughts which occur while they are emerging and growing

Item Type: Article
Author Affiliation: CSIRO Division of Tropical Crops and Pastures, PMB 44, Winnellie, Australia 5789
Subjects: Crop Improvement
Divisions: Sorghum
Depositing User: Ms K Syamalamba
Date Deposited: 04 Apr 2012 09:00
Last Modified: 04 Apr 2012 09:00
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