Ecological aspects of cold-adapted plants with a special emphasis on environmental control of cold hardening and dehardening

Abstract

The distribution of plant species is limited mainly by two environmental factors, the availability of water and temperature. Based on these factors, vegetation on the earth can be divided into a number of major vegetation zones. Biochemical reactions and growth processes in plants are temperature-dependent and have their minimum, optimum and maximum conditions. Temperature conditions are often suboptimal for growth, development, propagation and survival, and low temperatures commonly limit the growth of plants. In large areas of the earth’s land surface, temperatures decrease either periodically in a seasonal pattern, or episodically below 0°C (Fig. 1). Approximately one-third of the land area is frost-free and areas with the minimum temperature below −20°C comprise about 42%.1, 2 In these areas, frost can be one of the most important factors limiting distribution of plants. Of the estimated 250,000 species of vascular plants existing today, approximately 40% grow in tropical forests and the number of species strongly decreases with increasing altitude and latitude. Over evolutionary time, plant species have developed various adaptive strategies and mechanisms for survival in freezing conditions, but still the number of species capable of surviving periodic freezing is very low. However, native plant species are well adapted to survive in their ambient climatic conditions, and are damaged only if temperature and/or precipitation strongly deviates from the long-term mean, either transiently or more permanently in the event of changes in the global climate.