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

Abstract

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. Ca 2+ -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 Ca 2+ - ATPase activity again appeared on the interior face of the PM. The results seemed suggesting that two kinds of Ca 2+ -ATPases may be present on the PM during the SD-induced dormancy in poplar. One is the Ca 2+ -pumping ATPase, which is located on the interior face of the PM, for maintaining and restoring the Ca 2+ homeostasis. The other might be an ecto-Ca 2+ -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.

Quantitative X‐ray microanalysis of hydrogen peroxide within plant cells

“…-ATPase, could be measured by the formation of cerium phosphate precipitates when the tissues were stained with CeCl 3 (Jian et al, 2000). However, these precipitates can not be distinguished from cerium perhydroxides by transmission electron microscopy (TEM A woody plant species, Populus euphratica Oliv., was used in this study.…”