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Environ Exp Bot. 2001 Apr;45(2):143-154.

Size and longevity of seed banks in Antarctica and the influence of ultraviolet-B radiation on survivorship, growth and pigment concentrations of Colobanthus quitensis seedlings.

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  • 1Department of Plant Biology, Box 871601, Arizona State University, 85287-1601, Tempe, AZ, USA

Abstract

Populations of Colobanthus quitensis and Deschampsia antarctica, the only two vascular plant species native to Antarctica, are increasing. We performed a seed bank assay to determine the persistence of seeds from intact vegetation/soil cores collected near Palmer Station on the west coast of the Antarctic Peninsula. Vegetation/soil cores were cold stratified at 3 degrees C for >4 years. Subsequent seed bank densities, estimated from seedlings germinated, averaged 847 and 5645 seedlings m(-2) for C. quitensis and D. antarctica, respectively. We also conducted germination trials on C. quitensis seeds collected at our field site and stored for either 120 days or >4 years at 3 degrees C. Germination rates ranged from 6% after 120 days of cold storage to 38% after >4 years of cold storage. These findings show that previous estimates of seed bank densities and germination rates in these species, based on short-term laboratory stratification experiments, may underestimate those found in the field. Stratospheric ozone depletion has lead to increases in ultraviolet-B radiation (UV-B; 280-320 nm) along the Antarctic Peninsula during the austral spring. In a separate experiment we manipulated levels of biologically effective UV-B (UV-B(BE)), over current-year C. quitensis seedlings near Palmer Station on the west coast of the Antarctic Peninsula by placing frames over them that either held filters that absorbed most UV-B(BE) ('reduced UV-B(BE)'), transmitted most UV-B(BE) ('near-ambient UV-B(BE)') or had no filters ('ambient UV-B(BE)'). We monitored seedling survivorship over the course of the growing season (January-March) and growth and pigment concentrations at the end of the season. There were no UV-B(BE) treatment effects on seedling survivorship over the course of the season and overwinter survivorship averaged 12%. However, seedlings growing under near-ambient and ambient UV-B(BE) had 25 and 48% smaller total leaf areas, 7 and 16% fewer leaves and 65 and 82% fewer branches, respectively, than those growing under reduced UV-B(BE). In addition, concentrations of methanol-soluble UV-B-absorbing compounds were 26% higher and concentrations of chlorophyll b were 26% lower in leaves of seedlings growing under ambient UV-B(BE) compared with those under reduced UV-B(BE).

PMID:
11275222
[PubMed - as supplied by publisher]
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