Calcium in gravitropism. A re-examination

• Published in: Planta Vol. 203; no. Suppl 1; pp. S85 - S90
• Main Authors: Sinclair, W, Trewavas, A.J
• Format: Journal Article Conference Proceeding
• Language: English
• Published: Berlin Springer-Verlag 01-01-1997; Springer
• Subjects: Bending; Biological and medical sciences; Calcimycin - pharmacology; Calcium; Calcium - metabolism; Calcium - pharmacology; Calcium - physiology; Calmodulin - metabolism; Calmodulin - physiology; cell growth; Cell Wall - drug effects; Cell Wall - physiology; cell walls; Chara; Chelating Agents - pharmacology; Chlorophyta - cytology; Chlorophyta - metabolism; Chlorophyta - physiology; Corn; cytosol; Edetic Acid - pharmacology; Egtazic Acid - analogs & derivatives; Egtazic Acid - pharmacology; Fundamental and applied biological sciences. Psychology; genetically modified organisms; Gravitropism; Gravitropism - drug effects; Gravitropism - physiology; Gravity Sensing - drug effects; Gravity Sensing - physiology; inorganic ions; ion transport; literature reviews; Movements; Multicellular plants: Graviperception; Plant cells; Plant physiology and development; Plant Root Cap - drug effects; Plant roots; Plants; Pollen tubes; position; Root cap; Roux; Second Messenger Systems - physiology; signal transduction; Signal Transduction - physiology; Space life sciences; Signal transduction; Vegetals; Calcium; Second messenger; Gravitropism; Curvature; Calmodulin; Cell wall; Gravity
• ISSN: 0032-0935; 1432-2048
• DOI: 10.1007/PL00008120

For more than a decade it has been assumed that there is a strong relationship between Ca2+ and gravitropism. There is evidence to suggest that the movement of Ca2+ in the wall might regulate extension growth and that free intracellular Ca2+ might mediate signalling in statocytes. However, it is unlikely that changes in either wall Ca2+ or the concentration of free intracellular calcium, [Ca2+]i, act independently of each other. This results in ambiguity in both experimentation and interpretation of experimental information. It is also uncertain that the observed redistributions of wall Ca2+ are sufficient to induce bending and there is at present no direct evidence from measurement or imaging that changes in [Ca2+]i initiate or transduce gravitropic signals. The evidence relating Ca2+ to gravitropism is therefore substantial but still circumstantial. The involvement of free intracellular Ca2+ might best be tested using the new technologies of transgenic aequorin targeted to columella cells and thus resolve this important question. New information which relates control or orientation of tip-growing cells, such as pollen tubes, to cytosolic Ca2+ manipulation is presented. This information may be directly applicable to a gravitropic model system studied for many years, the Chara rhizoid.