Changes in stolon carbohydrates during the winter in four varieties of white clover (Trifolium repens L.) with contrasting hardiness

Abstract

Miniswards of white clover (Trifolium repens L.) varieties Menna, Huia, AberCrest and AberHerald, with contrasting winter hardiness, were established from cloned material in flat boxes. The miniswards were placed in an unheated glasshouse with natural lighting for the winter of 1995/96. During this time there were several periods of cold weather. The plants experienced temperatures at least as severe as those experienced by unprotected plants during preceding mild winters. Growth measurements carried out monthly suggested the cloned genotypes were representative of the varieties from which they were derived. Growth continued throughout the experiment, particularly when expressed as appearance of new internodes. During the coldest weather these internodes were short, and the amount of tissue produced was small. Starch concentration showed a complex pattern of changes during the winter. Older internodes were the major site of starch storage in the autumn; starch was lost from these internodes during the winter and early spring. Starch synthesis also occurred, even during the coldest periods. Starch accumulated in all new stolon tissue. There were significant differences between varieties. AberCrest and AberHerald retained higher concentrations of starch in older stolon tissue, synthesized higher concentrations of starch in young tissue and retained these for longer. There were few differences in soluble sugar concentrations between varieties, but there were significant changes during the winter. In mid-winter, sucrose and pinitol were at their highest concentrations, whereas reducing sugars were at their lowest concentrations. This study further supports the important role of starch reserves in supporting winter survival.