Thermal Contraction in Twigs

Abstract

CHANGES in linear dimensions or volume of plant parts often are assumed to represent changes in growth. However, plants routinely undergo reversible changes in size resulting from hydration and thermal effects. Sometimes such reversible changes are not very large and do not complicate growth studies. At other times, however, they may actually exceed changes resulting from accretion through meristematic activity. For this reason more attention should be given to distinguish between total dimensional changes of plants and those caused by tissue growth alone. Hydration effects on plants are considered elsewhere^1,2. The I present discussion deals primarily with thermal influences on dimensional changes in woody plants.