title: Seasonal alteration in amount of Ca(2+) in apical bud cells of mulberry (Morus bombciz Koidz): an electron microscopy-cytochemical study.
abstract: Subcellular localization of calcium in apical bud cells of mulberry (Morus bombciz Koidz) was investigated by a combination of calcium antimonate precipitation and electron microscopy (EM), over a 10-month period extending from July to May. Calcium antimonate deposits, an indication of Ca(2+) localization, were found mainly in the intercellular spaces and vacuoles of tissues collected in summer (e.g., July 10). Few deposits were seen in the cytosol and the nucleus, indicating that when plants were actively growing, the cytoplasm had a low concentration of Ca(2+). As the day length became shorter (e.g., August 8), Ca(2+) deposits increased in the cytosol and the nucleus. When plant dormancy and cold hardiness were rapidly developing in September and October, a large number of Ca(2+) deposits were seen in the cytoplasm and the nucleus, where they remained for about 60 days. Tissue samples collected during midwinter (e.g., January 20) displayed few Ca(2+) deposits in the cytoplasm and the nucleus compared with the sample collected on November 1. The number of Ca(2+) deposits remained low even when day length increased in the spring (e.g., May 5). We conclude that the seasonal dynamics of intracellular Ca(2+) concentration bear a close relationship with growth cessation and the development of dormancy and cold hardiness in temperate woody perennials.
authors.affiliation: Laboratory of Plant Hardiness, Department of Horticultural Science, University of Minnesota, St. Paul, MN 55108, USA.
authors.forename: Ling-Cheng
authors.initials: LC
authors.lastname: Jian
authors.forename: Ji-Hong
authors.initials: JH
authors.lastname: Li
authors.forename: Paul H.
authors.initials: PH
authors.lastname: Li