Seasonal Cambial Activity in Larix laricina Saplings in Relation to Endogenous Indol-3-ylacetic Acid, Sucrose, and Coniferin

Abstract

Although some quantitative research on the role of endogenous auxin (indol-3-ylacetic acid, IAA) in regulating anatomical aspects of diameter growth in trees has been reported, there have been no attempts to correlate cambial IAA content with biochemical aspects of wood formation. In this study, the cambial region (phloem, cambial zone, and differentiating cambial derivatives when present) at four positions (1, 3, 8, and 17 years) in the main stems of 20-year-old Larix laricina (Du Roi) K. Koch were sampled to determine the endogenous contents of IAA, sucrose and coniferin in relation to seasonal cambial growth. IAA and sucrose were both present throughout the dormant period, and their concentrations increased in late spring and summer in association with leaf and shoot development. Coniferin, the principal molecule supporting lignification in conifers, was not detected throughout the winter period of cambial dormancy, but was detected in spring immediately preceding resumption of cambial cell division, was present throughout the period of cambial growth, but then disappeared after the last-produced latewood tracheids had completed their differentiation. The coniferin content varied independently of IAA and sucrose, suggesting that the cambium's seasonal competence for coniferin biosynthesis is controlled by factors other than IAA or sucrose availability. For. Sci. 37(3):953-958.