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Reduced Poaceae pollen under conditions of severe summer drought in the Middle East: Implications for rainfall seasonality in pollen diagrams
- El-Moslimany, Ann
- Review of palaeobotany and palynology 2019
- Amaranthaceae, Artemisia, Pleistocene epoch, Poaceae, annuals, asexual reproduction, autumn, cleistogamy, drought, drought tolerance, flowering, grasses, perennials, pollen, rain, seeds, selfing, summer, Iraq, Middle East
- Based on the facts that the Poaceae, in general, require summer precipitation, and that Artemisia and many Chenopods thrive in conditions of 4 summer drought, I have previously attributed the rise in grass pollen at the expense of Artemisia and Chenopodiaceae in Middle Eastern pollen diagrams at the end of the Pleistocene to a period of summer precipitation.Here, using present-day Iraq as an example, I assemble ecological and physiological information providing additional support for minimal Poaceae pollen release under conditions of summer drought, including: (1) dominance of the annual life-form over the usual perennials due to their ability to survive the summer as drought-resistant seeds and their ability to grow rapidly in the autumn, (2) abbreviated flowering of the annuals, (3) increased self-fertilization, including cleistogamy, in both annuals and perennials, and (4) the prevalence of vegetative reproduction, including apomixes, in the perennials.