Calcium-Regulated Metabolism in Seed Germination

Abstract

The past decade has seen a dramatic growth of interest in Ca²⁺ as a stimulus-response coupler in plant cells. Key discoveries that ignited this interest were that plant cells, like animal cells, maintain their cytosolic free Ca²⁺ concentration ([Ca²⁺]_cyt) near 10^-7 M (Gilroy et al., 1986; Bush and Jones, 1987; Brownlee et al., 1987); plant cells contain a variety of Ca²⁺ -binding proteins that can become metabolic regulators at [Ca²⁺]_cyt of 10^-6 or above (Biro et al., 1984; Harmon et al., 1987 Boustead et al., 1989), and stimulus-response coupling in many different plant cells can be blocked by Ca²⁺ chelation, Ca²⁺ channel blockers, and antagonists of Ca²⁺ -binding proteins (Daye et al., 1984; Serlin and Roux, 1984; Saunders and Hepler, 1983). There is now a major and rapidly expanding literature implicating Ca²⁺ in the control of many aspects of plant metabolism, growth and development, including gravitropism (Roux and Serlin, 1987), photomorphogenesis (Roux et al., 1986), photosynthesis (Homann, 1987), mitosis (Lambert and Vantard, 1986) and stress responses (Kauss, 1987), to name only a few of the best studied.