Journal Article

Leaf development in <i>Ricinus communis</i> during drought stress: dynamics of growth processes, of cellular structure and of sink–source transition

U. Schurr, U. Heckenberger, K. Herdel, A. Walter and R. Feil

in Journal of Experimental Botany

Published on behalf of Society for Experimental Biology

Volume 51, issue 350, pages 1515-1529
Published in print September 2000 | ISSN: 0022-0957
Published online September 2000 | e-ISSN: 1460-2431 | DOI:
Leaf development in Ricinus communis during drought stress: dynamics of growth processes, of cellular structure and of sink–source transition

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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 density). Tip‐to‐base gradients in carbohydrate concentrations 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.

Keywords: Drought; leaf growth; sink–source transition; diurnal growth patterns; carbohydrate; amino acid; chlorophyll; protein; sucrose phosphate synthase; sucrose synthase.; LML, length of the middle lobe of the Ricinus leaf; MOPS, 3‐(N‐morpholino)propane sulphonic acid; EDTA, ethylene diamine tetraacetic acid; EGTA, ethyleneglycol‐bis‐(2‐aminoethyl‐)‐tetraacetic acid; DTT, dithiothreitol; PMSF, phenylmethylsulphonylfluoride.

Journal Article.  9874 words.  Illustrated.

Subjects: Plant Sciences and Forestry

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