“…Naturally, it may be expected that during this period of SD exposure the PM Ca 2+ pumping should be very low or inactive, and thus would result in no cerium phosphate grains on the interior face of the PM. When the plant has completed its dormancy process, we believe the plant should be back to the status of a resting low Ca 2+ concentration, as evidenced by the observation in poplar after a 70-d SD exposure in which the PM Ca 2+ pumping was restored (Fig 4) and a low concentration of intracellular Ca 2+ was observed [16]. As shown in Fig 2 and 3, many reaction products were present on the exterior face of the PM during the dormancy development.…”
Section: Discussionmentioning
confidence: 94%
“…Between the 28 and 42 d of SD exposure, when the dormancy was developing, no reaction products of the enzymatic activity were seen on the interior face of the PM. The dynamic of Ca 2+ -ATPase activity appears to be an adaptive nature corresponding to the alterations of the intracellular Ca 2+ concentration [16].…”
Section: Discussionmentioning
confidence: 99%
“…Active calcium pumping is necessary in order to maintain a Ca 2+ -homeostasis, as plants such as poplar are actively growing. When poplar plants were exposed to SD, e.g., between the 28-42 d period, the dormancy was developing, and intracellular Ca 2+ concentration was increased [16]. Naturally, it may be expected that during this period of SD exposure the PM Ca 2+ pumping should be very low or inactive, and thus would result in no cerium phosphate grains on the interior face of the PM.…”
Section: Discussionmentioning
confidence: 99%
“…ex March) plants were established as previously described [16]. They were grown in a greenhouse with 16 h light (long day, LD) at 25/21 o C day/night (D/N).…”
Section: Plant Materialsmentioning
confidence: 99%
“…Because of its high affinity for calcium, this enzyme can either reduce the cytoplasmic concentration of free calcium ions to extremely low levels (thus maintaining a Ca 2+ homeostasis), or restore it after a specific stimulus causes an increase in cytosolic Ca 2+ concentration [11], [15]. We previously found a dynamic change in calcium distribution in poplar apical bud meristematic cells when dormancy was induced by short days (SD) [16]. For example, during SD exposures of up to 20 d (prior to a measurable level of dormancy), Ca 2+ increased in cytosol and nuclei.…”
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.
“…Naturally, it may be expected that during this period of SD exposure the PM Ca 2+ pumping should be very low or inactive, and thus would result in no cerium phosphate grains on the interior face of the PM. When the plant has completed its dormancy process, we believe the plant should be back to the status of a resting low Ca 2+ concentration, as evidenced by the observation in poplar after a 70-d SD exposure in which the PM Ca 2+ pumping was restored (Fig 4) and a low concentration of intracellular Ca 2+ was observed [16]. As shown in Fig 2 and 3, many reaction products were present on the exterior face of the PM during the dormancy development.…”
Section: Discussionmentioning
confidence: 94%
“…Between the 28 and 42 d of SD exposure, when the dormancy was developing, no reaction products of the enzymatic activity were seen on the interior face of the PM. The dynamic of Ca 2+ -ATPase activity appears to be an adaptive nature corresponding to the alterations of the intracellular Ca 2+ concentration [16].…”
Section: Discussionmentioning
confidence: 99%
“…Active calcium pumping is necessary in order to maintain a Ca 2+ -homeostasis, as plants such as poplar are actively growing. When poplar plants were exposed to SD, e.g., between the 28-42 d period, the dormancy was developing, and intracellular Ca 2+ concentration was increased [16]. Naturally, it may be expected that during this period of SD exposure the PM Ca 2+ pumping should be very low or inactive, and thus would result in no cerium phosphate grains on the interior face of the PM.…”
Section: Discussionmentioning
confidence: 99%
“…ex March) plants were established as previously described [16]. They were grown in a greenhouse with 16 h light (long day, LD) at 25/21 o C day/night (D/N).…”
Section: Plant Materialsmentioning
confidence: 99%
“…Because of its high affinity for calcium, this enzyme can either reduce the cytoplasmic concentration of free calcium ions to extremely low levels (thus maintaining a Ca 2+ homeostasis), or restore it after a specific stimulus causes an increase in cytosolic Ca 2+ concentration [11], [15]. We previously found a dynamic change in calcium distribution in poplar apical bud meristematic cells when dormancy was induced by short days (SD) [16]. For example, during SD exposures of up to 20 d (prior to a measurable level of dormancy), Ca 2+ increased in cytosol and nuclei.…”
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.
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