Cytochemical Localization Of Ca²⁺ And Ca²⁺-ATPase In The Root Of Puccinellia Tenuiflora Under Saline-alkali Stress

Being a species of Puccinellia, Puccinellia tenuiflora is gramineous, perennial, and herbaceous. It can grow in the soil of pH10 owing to its salt-resistant ability.In order to reveal the function of ion balance and osmotic regulation in Rtenuiflora at sub-cellular, cellular, tissue and individual level, four stress (Na2CO3,NaHCO3,NaCl, PEG) with ten concentrations were carried out to seedlings of P.tenuiflora,respectively. The detailed treatment method were as follows:(1)the low-concentration iso osmotic solutions of 0.4%Na2CO3,0.277%NaCl, and 9.82%PEG; (2) the high-concentration iso osmotic solutions of 1.0% Na2CO3,0.781% NaCl, and 19.721%PEG with the equal osmotic pressure;(3)the low-concentration iso-natrium ionic solutions of 0.4%Na2CO3,0.184%NaCl, and 0.448%NaHCO3;(4) the high-concentration iso-natrium ionic solutions of 1.0% Na2CO3,0.395% NaCl, and 1.054%NaHCO3.Thus, the complexed saline-alkali stress was divided into various single factors, and it is better to analyze the ecophysiological mechisms in Puccinellia tenuiflora to cope with stress.At the physiological level, we determined the osmotic potential, electrolyte leakage rate, the content of Na, and K at the surface of root, and the concentration of Na+ and K+ within the root of P. tenuiflora under various stress conditions. The results showed that, compared with the control,under the low-concentration iso-natrium ionic and iso-osmotic stress,the content of Na, K on the surface of root, and the concent of Na+, K+ appeared the similar changes. Osmotic potential decreased not obviously, and electrolyte leakage rate increased not significantly. This showed that P. tenuiflora can use its own control mechanism regulating the intracellular ion balance of at the lower concentration saline-alkali stress.However, the changes of the content of Na, K on the surface of root and the concents of Na+, K+are inconsistent. The osmotic potential significantly reduced, and electrolyte leakage rate increased under the high concentration of saline-alkali stress.This noted that under the high concentration of alkali-salt stress, pH stress is more primary than osmotic and ion stress.Furthermore, to investigate the relationships between the localization of calcium and Ca2+-ATPase, and the capacity of P.tenuiflora resistance to saline-alkali stress, an experiment for ultracytochemical localization of calcium and Ca2+-ATPase in the root of P. tenuiflora under the stress of saline-alkali stress were carried out using a potassium pyroantimonate precipitation and a lead phosphate precipitation technique, respectively.Our results showed that, in normal condition, the deposits of calcium antimonite was less precipitation in the cytoplasm, and it is mainly concentrated within the plasma membrane and vacuoles in the zone of root hair. Ca2+-ATPase had a certain activity and mainly localized in the plasma membrane and tonoplast. Moreover, under the low concentrations stress of iso-natrium ionic and iso- osmotic, the distribution of Ca2+ precipitation particles increased in the cytoplasm, decrease in the vacuole, and mainly concentrated in the vicinity of tonoplast. Meanwhile, the activity of Ca2+ -ATPase was significantly increased in plasma membrane and tonoplast.Furthermore, under the high stress of iso-natrium ionic and iso-osmotic, the distribution of Ca2+ precipitation particles was continued to increase in the cytoplasm, but absent in the vacuole.The activity of Ca2+-ATPase also reduced. All these results highlight that the changes of Ca2+ localization and Ca2+-ATPase activity plays important roles in P. tenuiflora resistance to saline-alkali stress.