Some relationships between enviornmental relaibility and seed dormancy in desert annual plants

TitleSome relationships between enviornmental relaibility and seed dormancy in desert annual plants
Publication TypeJournal Article
Year of Publication1983
AuthorsFreas K.E., Kemp P.R.
JournalJournal of Ecology
Date Published1983
Call Number00685
Keywordsannual plant, germination, annual plant, rainfall, article, articles, journal, journals, Lappula, germination, Lepidium, germination, Pectis, germination, seed, germination
Abstract(1) There are two groups of annual species that grow in the northern Chihuahuan Desert of North America. Plants in one group germinate and complete their life cycle in late summer. Those in the other germinate in winter or early spring and complete their life cycle in the spring. The late summer season in characterized by abundant and reliable rain, while the winter-spring season has less abundant and less reliable rain. (2) Several theoretical models have been suggested which predict that annual plants from uncertain environments may or may not have evolved innate dormancy to offset the possibility of population extinction due to complete germination followed by complete mortality under severely unfavourable conditions. (3) We have tested these models with a comparative experiment examining the germination responses of seeds collected from an annual species which grows during the more reliable summer season and two annual species which grow during the less reliable winter-spring season. (4) The summer annual species does not have a genetically fixed innate dormancy, but the two winter annual species apparently have evolved a genetically controlled innate dormancy. (5) All three annual species exhibited environmentally-controlled seed dormancy with respect to amount of rainfall. Seeds germinated only when the equivalent of more than 10 mm of rain fell. Above 15 mm of simulated rain, germination was positively correlated with increasing amount of rain in all three species. (6) The importance of innate dormancy, water-controlled dormancy, and seed dispersal to the long-term survival of these species is discussed.