Subcellular Localization Of Ca²⁺ In Calcicole Seedling Leaves And Effect Of Ca²⁺ On Nitrogen, Phosphorus Deficiency In Calcicole

In order to know the adaptive mechanisms of calcicole to calcareous environment------higher calcium concentration, drought, nutrient deficiency, we studied the one-year seedlings of calcicole (Carpinus pubescens), comparing the one-year seedlings of calcifuge (Camellia oleifera). Using the potassium pyroantimonate precipitation method with transmission electron microscope, Ca²⁺ distribution change in the cell were observed under higher calcium, drought treatment condition. And effect of higher calcium on nitrogen metabolic enzyme and phosphorus metabolism were determined by physiological and chemical method. The conclusions are:1. 1) Ca²⁺ deposits can not be observed in the leaves cell in two species, imposed with 0.5mmol/LCa²⁺ for 4h. Some Ca²⁺ precipitates were observed in the cell wall of Carpinus pubescens and can not be found in Camellia oleifera, but subcellular organelles were destroyed in Camellia oleifera stressed with 0.5mmol/L Ca²⁺ for 48h. 2) The two plants were treated with 5mmol/LCa²⁺. Ca²⁺ deposits were observed to be localized in the cytoplasm and internal of plasma membrane of Carpinus pubescens for 4h and can not be found in Camellia oleifera, but subcellular organelles were destroyed in Camellia oleifera. Ca²⁺ precipitates were seen in the cell wall and disappeared in the cytoplasm and plasma membrane of Carpinus pubescens for 48h. Ca²⁺ deposits were found in the plasma membrane, at the same time, subcellular organelles were destroyed in Camellia oleifera for 48h. 3) A large number of calcium deposits were localized in the cytoplasm and a few precipitates were found in plasma membrane of Carpinus pubescens treated with 30mmol/LCa²⁺ for 4h. And calcium deposits can not be found in the cell of Camellia oleifera and subcellular structures were destroyed. The plants were subjected to treat with 30mmol/LCa²⁺ for 48h. The number of calcium deposits in the cytoplasm significantly decreased and increased in the plasma membrane of Carpinus pubescens. Nevertheless, Ca²⁺ precipitates were seen in the plasma membrane of Camellia oleifera and subcellular structures were destroyed. We presumed that this change is the difference of the Ca²⁺-ATPase activity in plasma membrane, resulting form calcicole acclimation to higher calcium environment. 2. Ca²⁺ deposits can not be found in the cell in two plants under normal growth condition. A large number of calcium precipitates were seen in plasma membrane of Camellia oleifera and can not be found in the cell of Carpinus pubescens stressed with 5% polyethylene glycol-6000 solution for 4h. Ca²⁺ precipitates can not be found in the cell of Carpinus pubescens and the number of calcium deposits in the plasma membrane of Camellia oleifera significantly increased when stressed with 30% polyethylene glycol-6000 solution for 4h. Ca²⁺ precipitates can not be found in the cell of Carpinus pubescens and a large number of calcium deposits were observed in plasma membrane of Camellia oleifera treated with 5% polyethylene glycol-6000 solution for 48h. More granules of Ca²⁺ deposits were seen in the exterior cell wall of two species stressed with 30% polyethylene glycol-6000 solution for 48h. We presumed that this change is the difference of the Ca²⁺-ATPase activity in plasma membrane, resulting form calcicole acclimation to drought environment.3. 1) NADH-GOGAT activity of leaves in two plants decreased when supply of nitrogen in the medium declined. NADH-GOGAT activity increased in the Carpinus pubescens Seedlings and decreased in the Camellia oleifera Seedlings treated with 30mmol/LCa²⁺. 2) GS activity of leaves in two plants reduced with nitrogen concentration decreasing in the medium. GS activity of leaves in two plants risen with treatment 30mmol/LCa²⁺. 3) NADH-GDH activity of leaves in the Carpinus pubescens Seedlings had trends of first increase and following decrease. And NADH-GDH activity of leaves in the Camellia oleifera Seedlings decreased. The plants were subjected to treat with 30mmol/LCa²⁺, NADH-GDH activity in two plants declined when N were not added in the medium, and NADH-GDH activity in two plants increased when N were added in the medium. 4) Asparaginase activity of leaves in two plants had trends of first decrease and following increase. Asparaginase activity of leaves in two plants had no change with 30mmol/L Ca²⁺ treatment. Conclusions show: higher calcium concentration was able to improve the NADH-GOGAT activity in Carpinus pubescens and elevated nitrogen assimilation, so it adapted low nitrogen environment.4. 1) When given a reduced supply of phosphate, the activity of acid phosphatase of leaves in two plants increased. The plants were subjected to treat with 30mmol/LCa²⁺. The activity of acid phosphatase in two plants declined. 2) The activity of excreted acid phosphatase of roots in the plants increased when supply of phosphorus in the medium declined. The activity of excreted acid phosphatase of roots in the plants decreased with 30mmol/L Ca²⁺ treatment. 3) The phosphorus content in the roots in Carpinus pubescens had the treads of first decrease and following increase when supply of phosphorus in the medium declined, and declined in Camellia oleifera. The phosphorus content in the roots in Carpinus pubescens increased and decreased remarkably in Camellia oleifera with 30mmol/L Ca²⁺ treatment. Conclusions show: higher calcium was able to improve phosphorus absorption in Carpinus pubescens, so it adapted low phosphorus environment.Summarization, Ca²⁺ localization in the cell and the effect of higher Ca²⁺ on nutrient deficiency had mostly difference between calcicole and calcifuge. The reason is that calcicole is long-term adapted to karst environment.