Inhibition of the Gravitropic Response of Snapdragon Spikes by the Calcium-Channel Blocker Lanthanum Chloride

• Published in: Plant physiology (Bethesda) 1998-10, Vol.118 (2), p.483-492
• Main Authors: Friedman, Haya, Shimon Meir, Ida Rosenberger, Halevy, Abraham H., Kaufman, Peter B., Sonia Philosoph-Hadas
• Format: Article
• Language: English
• Subjects: Agronomy. Soil science and plant productions; Antirrhinum majus; Bending; Biological and medical sciences; Calcium; Calcium - metabolism; Calcium Channel Blockers - pharmacology; Calcium channels; Chloroplasts; Chloroplasts - drug effects; Chloroplasts - physiology; Chloroplasts - ultrastructure; Cross-sections; Curvature; Cytosol - metabolism; Economic plant physiology; Ethylenes - metabolism; Fundamental and applied biological sciences. Psychology; Gravitation; Gravitropism; Gravitropism - drug effects; Gravity perception; Growth and Development; Lanthanum; Lanthanum - pharmacology; Lanthanum chloride; Magnoliopsida - cytology; Magnoliopsida - drug effects; Magnoliopsida - growth & development; Magnoliopsida - metabolism; Movements; Plant cells; Plant Growth Regulators - metabolism; Plant Physiological Phenomena; Plant physiology and development; Plant Stems - cytology; Plant Stems - drug effects; Plant Stems - growth & development; Plant Stems - metabolism; Plants; Plastids - metabolism; Specific gravity; Stem cells; Stem elongation; Tropism and nastic movements
• ISSN: 0032-0889; 1532-2548
• DOI: 10.1104/pp.118.2.483

The putative Ca2+-channel blocker LaCl3 prevented the gravitropic bending of cut snapdragon (Antirrhinum majus L.) spikes (S. Philosoph-Hadas, S. Meir, I. Rosenberger, A. H. Halevy [1996] Plant Physiol 110: 301-310) and inhibited stem curvature to a greater extent than vertical and horizontal stem elongation at the bending zone. This might indicate that LaCl3, which modulates cytosolic Ca2+, does not influence general stem-growth processes but may specifically affect other gravity-associated processes occurring at the stem-bending zone. Two such specific gravity-dependent events were found to occur in the bending zone of snapdragon spikes: sedimentation of starch-containing chloroplasts at the bottom of stem cortex cells, as seen in cross-sections, and establishment of an ethylene gradient across the stem. Our results show that the lateral sedimentation of chloroplasts associated with gravity sensing was prevented in cross-sections taken from the bending zone of LaCl3-treated and subsequently gravistimulated spikes and that LaCl3 completely prevented the gravity-induced, asymmetric ethylene production established across the stem-bending zone. These data indicate that LaCl3 inhibits stem curvature of snapdragon spikes by preventing several gravity-dependent processes. Therefore, we propose that the gravitropic response of shoots could be mediated through a Ca2+-dependent pathway involving modulation of cytosolic Ca2+ at various stages.