© 2000 Heron Publishing—Victoria, Canada
Seasonal alteration in amount of Ca2+ in apical bud cells of mulberry (Morus bombciz Koidz): an electron microscopy–cytochemical study
Ling-Cheng Jian (1), Ji-Hong Li (1, 2) and Paul H. Li (1, 3)
1. Laboratory of Plant Hardiness, Department of Horticultural Science, University of Minnesota, St. Paul, MN 55108, USA / 2. Department of Agricultural, Food, and Nutritional Science, University of Alberta, Edmonton, Alberta, T6G 2P5, Canada / 3. Author to whom correspondence should be addressed (lixxx008@tc.umn.edu) / Received June 15, 1999
Summary
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 Ca2+ 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 Ca2+. As the day length became shorter (e.g., August 8), Ca2+ 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 Ca2+ 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 Ca2+ deposits in the cytoplasm and the nucleus compared with the sample collected on November 1. The number of Ca2+ deposits remained low even when day length increased in the spring (e.g., May 5). We conclude that the seasonal dynamics
of intracellular Ca2+ concentration bear a close relationship with growth cessation and the development of dormancy and cold hardiness in temperate
woody perennials.
Keywords:
calcium localization, cold hardiness, dormancy.
