The effect of artificial warming during winter on white clover (Trifolium repensLinn): overwintering and adaptation to coldness in late spring

Abstract

Perennial plants that normally experience dormancy during winter may be subjected to more cycles of freeze鄄thaw caused by warming winter. We explored the physiological mechanisms of adaptation of white clover, Trifolium repens Linn, to freeze鄄thaw stress. In late fall of 2009, uniform plots of white clover grown in a natural environment (NE) were covered with a plastic house (pH) to simulate the effect of a warmer winter or left uncovered (control). During the winter and following spring, growth capacity and physiological indices related to resistance to adverse environment were measured in leaves of white clover grown in both conditions. In the winter of 2009, the average temperature ranged from below zero (-10益) to 7益 in the NE during which leaves experienced thawing鄄freezing鄄thawing鄄freezing, and above zero (from 1 益 to 7 益) in the pH where leaves were never frozen. In late fall of 2009, all white clover was of uniform height. But in spring 2010, plants grown in the PH (26 cm) were 3 times taller than those in the NE (8 cm). This difference in height disappeared by June 2010. In winter, the relative membrane permeability, MDA(malondialdehyde) , proline, and soluble