Volume 10, No 2, Jun 2000

ISSN: 1001-0602 
EISSN: 1748-7838 2018 
impact factor 17.848* 
(Clarivate Analytics, 2019)

Volume 10 Issue 2, June 2000: 103-114

ORIGINAL ARTICLES

An electron microscopic-cytochemical localization of plasma membrane Ca²⁺-ATPase activity in poplar apical bud cells during the induction of dormancy by short-day photoperiods

JIAN Ling Cheng^{1, 2}, Ji Hong LI^{1, 3}, Paul H LI^{1, *}, Tony HH CHEN⁴

¹ Laboratory of Plant Hardiness, Department of Horticultural Science and Plant Biological Sciences Program, University of Minnesota, St. Paul, MN 55108, USA
² Visiting professor from Institute of Botany, Chinese Academy of Sciences, Beijing, China.
³ Visiting scientist from Beijing Agricultural University, Beijing, China.
⁴ Department of Horticulture and Center for Gene Research and Biotechnology, Oregon State University, Corvallis, OR 97331, USA Correspondence:

Plasma membrane (PM) Ca²⁺-ATPase activity in poplar apical bud meristematic cells during short-day (SD)-induced dormancy development was examined by a cerium precipitation EM-cytochemical method. Ca²⁺-ATPase activity, indicated by the status of cerium phosphate precipitated grains, was localized mainly on the interior face (cytoplasmic side) of the PM when plants were grown under long days and reached a deep dormancy. A few reaction products were also observed on the nuclear envelope.

When plant buds were developing dormancy after 28 to 42 d of SD exposure, almost no reaction products were present on the interior face of the PM. In contrast, a large number of cerium phosphate precipitated grains were distributed on the exterior face of the PM. After 70 d of SD exposure, when buds had developed a deep dormancy, the reaction products of Ca²⁺-ATPase activity again appeared on the interior face of the PM. The results seemed suggesting that two kinds of Ca²⁺-ATPases may be present on the PM during the SD-induced dormancy in poplar. One is the Ca²⁺-pumping ATPase, which is located on the interior face of the PM, for maintaining and restoring the Ca²⁺ homeostasis. The other might be an ecto-Ca²⁺-ATPase, which is located on the exterior face of the PM, for the exocytosis of cell wall materials as suggested by the fact of the cell wall thickening during the dormancy development in poplar.

Key words: Ca²⁺-homeostasis, Ca²⁺-ATPase, ecto-Ca²⁺-ATPase, poplar dormancy, populus deltoides.

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