Plant growth substances. Second edition: By L. J. Audus, Bedford College, London, England. Interscience Publishers, New York, 1959. xxii + 554 pp. $10.00

Abstract

This chapter provides an overview of the features of the nature and periodicity of shoot growth, cambial growth, and root growth of trees of the temperate zone and tropics. Woody plants of the temperate zone alternate from active growth during the warm season to cessation of growth during the cold season. Control of and release from dormancy of buds has been variously correlated with plant hormone levels, but no convincing model of hormone control of dormancy has emerged. Plants grow through the activity of meristematic tissues, which constitute only a small fraction of the plant body. Shoot elongation generally arises from expansion of buds and shoot thickening through activity of the cambium. Shoots may be formed by fixed growth, free growth, or a combination of both. The pattern and periodicity of shoot growth vary greatly with species and genotype and with environmental influences. Particularly strong differences in shoot growth patterns often are observed between temperate and tropical species. Gibberellins and auxins have been implicated in control of shoot growth. Increase in tree diameter arises from activity of the vascular cambium, a tissue that produces xylem inwardly and phloem externally. Cambial growth is not continuous in space or time. Temperate-zone trees exhibit seasonal activity of the vascular cambium, with reactivation in the spring and significant growing season influences, particularly those associated with drought.