Intra-annual spiral compression wood: A record of low-frequency gravitropic circumnutational movement in trees

Abstract

The majority of detailed studies on circumnutational growth movements have focused on herbaceous plants or on the primary growth of woody plant seedlings, ignoring completely secondary growth in woody plants. The relatively rapid movement in herbaceous tissues consists of two components: an autonomous growth rhythm and a gravitropic response. Since there is a gravitropic component to circumnutational movement and a gravitropic stimulus can induce compression wood formation, the formation of a compression wood spiral may be expected if there is a circumnutational movement of a woody stem. It is suggested here, that observed spirals of compression wood within annual growth rings in Pinus taeda L. and Abies concolor (Gord. & Glend.) Lindl. ex Hildebr. represents an annual record of a slower circumnutational growth movement. Data derived from observations of greenhouse-grown 3-year-old Pinus taeda seedlings indicate that there are two distinct circumnutational patterns of different rotational frequency present in woody plants associated with primary and secondary tissues.