DORMANCY
Plants respond to their external environment largely by changes in growth rate. As you might imagine, the ability to stop growing altogether when conditions are not favorable is a critical factor in their survival.
In temperate regions, we generally associate dormancy with winter, when low temperatures and the unavailability of water because of freezing make it impossible for plants to grow. During this season the buds of deciduous trees and shrubs remain dormant, and the apical meristems remain well protected inside enfolding scales. Perennial herbs spend the winter underground as stout stems of roots packed with stored food. Many other kinds of plants, including most annuals, pass the winter as seeds.
In climates that are seasonally dry, dormancy will occur primarily during the dry season, whenever in the year it falls. In dry conditions, plants stay in a dormant condition by using strategies similar to those which the plants of temperate areas rely on in winter.
Annual plants occur frequently only in areas of seasonal drought. Seeds are ideal mechanisms for allowing annual plants to bypass the dry season, when there is insufficient water for growth. When it rains, they can germinate and the plants can grow rapidly to take advantage of the relatively short period when water is available.
แหล่งข้อมูล: Understanding Biology. Page 731.
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