The role of calcium ions in phytochrome-mediated germination of spores of Onoclea sensibilis L. |
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Authors: | Randy Wayne Peter K Hepler |
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Institution: | (1) Department of Botany, University of Massachusetts, 01003 Amherst, MA, USA |
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Abstract: | Phytochrome is confirmed to be the photoreceptor pigment in the germination response of Onoclea sensibilis L. by demonstrating red-far-red (R-FR) photoreversibility. External Ca2+ is required for this response with a threshold at a submicromolar concentration. Ethylene glycol-bis( -amino-ethyl ether)-N,N,N ,N -tetraacetic acid, La3+ and Co2+ reversibly inhibit germination. Lanthanum only inhibits germination when applied before or during irradiation, indicating that the external Ca2+ requirement is transient, although in the absence of Ca2+ the R-stimulated system remains maximally poised to accept the ion for over 4 h after irradiation. The ability to respond to Ca2+ 4.1 h after R-irradiation is not reversed by FR-irradiation, indicating that Ca2+ transport has been uncoupled from phytochrome. Barium and Sr2+, but not Mg2+ can substitute for Ca2+. Artificially increasing the concentration of intracellular free Ca2+ with the ionophore A 23187 stimulates germination in the dark. The Ca2+-calmodulin antagonists, trifluoperizine and chlorpromazine, reversibly inhibit germination. Calcium is required in phytochrome-mediated fern spore germination; it may be acting as a second messenger.Abbreviations EGTA
ethylene glycol-bis( -aminoethyl ether)-N,N,N ,N -tetraacetic acid
- FR
far-red light
- R
fed light |
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Keywords: | Calcium Calmodulin Germination (spore) Onoclea Phytochrome and Ca2+ Pteridophyta |
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