Leaf development in ricinus communis during drought stress:Dynamics of growth processes, of cellular structure and of sink-source transtion
Loading...
Files
Date
2000-09
Journal Title
Journal ISSN
Volume Title
Publisher
Abstract
Dicot leaf growth is characterized by partly transient tip-to-base gradients of growth processes, structure and function. These gradients develop dynamically and interact with dynamically developing stress conditions like drought. In Ricinus communis plants growing under well-watered and drought conditions growth rates peaked during the late night and minimal values occurred in the late afternoon. During this diurnal course the leaf base always showed much higher rates than the leaf tip. The amplitude of this diurnal course decreased when leaves approached maturity and during drought stress without any significant alteration of the diurnal pattern and it increased during the first
days after rewatering. Unique relationships between leaf size and cytological structure were observed. This provided the framework for the analysis of changes in assimilation, transpiration and dark respiration, chlorophyll, protein, carbohydrate, and amino acid
concentrations, and of activities of sink–source related enzymes at the leaf tip and base during leaf development in well-watered and drought-stressed plants. Gas exchange was dominated by physiological rather than by anatomical properties (stomatal den
sity). Tip-to-base gradients in carbohydrate concentra tions per dry weight and sink–source-related enzymes were absent, whereas significant gradients were found in amino acid concentrations per dry weight. During drought stress, growing leaves developed source function at smaller leaf size, before specific physiological adaptations to drought occurred. The relevance of the developmental status of individual leaves for the drought-stress response and of the structural changes for the biochemical composition changes is discussed.
Description
Keywords
Drought, leaf growth, sink–source transition, diurnal growth patterns, carbohydrate, amino acid, chlorophyll, protein, sucrose phosphate synthase, sucrose synthase
Citation
Journal of Exp. Bot. 51(350)1515-1529 September 2000