Journal Article

Calcium Requirement for the Induction of Hydrotropism and Enhancement of Calcium-Induced Curvature by Water Stress in Primary Roots of Pea, <i>Pisum sativum</i> L.

Mamoru Takano, Hideyuki Takahashi and Hiroshi Suge

in Plant and Cell Physiology

Published on behalf of Japanese Society of Plant Physiologists

Volume 38, issue 4, pages 385-391
Published in print January 1997 | ISSN: 0032-0781
Published online January 1997 | e-ISSN: 1471-9053 | DOI: http://dx.doi.org/10.1093/oxfordjournals.pcp.a029180
Calcium Requirement for the Induction of Hydrotropism and Enhancement of Calcium-Induced Curvature by Water Stress in Primary Roots of Pea, Pisum sativum L.

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Positive hydrotropic curvature in the roots of the agravitropic pea (Pisum sativum L.) mutant, ageotropum, occurred when the root cap was exposed to a gradient of water potential by an asymmetric application of agar containing sorbitol [Takano et al. (1995) Planta 197: 410]. As previously reported [Takahashi and Suge (1991) Physiol. Plant. 82: 24], in this study the hydrotropic response due to unilateral application of sorbitol to the root cap was totally inhibited by pretreatment with ethyleneglycol-bis-(β-amino-ethylether) N,N,N′,N′-tetraacetic acid (EGTA). However, hydrotropic response of the EGTA-treated roots was recovered only when EGTA was replaced by a 10 mM calcium (CaCl2) solution prior to hydrostimulation. A calcium channel blocker, lanthanum (LaCl3), also inhibited hydrotropic curvature of ageotropum roots, whereas the hydrotropic response was affected by neither nifedipine nor vera-pamil. Application of calcium ionophore, A23187, resulted in a significant promotion of hydrotropic curvature. Furthermore, ageotropum roots curved away from a calcium source when an agar block containing 10 mM calcium was asymmetrically applied to the root cap. This calcium-induced curvature was found to be accelerated by water stress and significantly inhibited by LaCl3. While the calcium-induced curvature commenced within 1 h after application, hydrotropic curvature became visible 3 to 4 h after an exposure to a gradient of water potential. These results indicate that apoplastic calcium and its influx through the plasmamembrane are involved in the induction of hydrotropism in roots. A gradient of water potential in the root cap may cause a physiological change that is mediated by calcium, which ultimately leads to the curvature in the elongation region associated with the hydrotropic response.

Keywords: Ageotropum; Calcium; Calcium channel; Pea (Pisum sativum L.); Root hydrotropism; Water stress

Journal Article.  0 words. 

Subjects: Biochemistry ; Molecular and Cell Biology ; Plant Sciences and Forestry

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