Study On The Release Of Ca²⁺ From Protoplasts Of Aloe Vera Under External Stress

Calcium ions play a variety of roles in the physiological activities of plant cells,which are particularly important in the involvement of cellular metabolism.Numerous studies have shown that different external stimuli affect the changes in calcium concentration in cells.In this paper,the distribution of intracellular Ca²⁺in low temperature,ZnO NPs,CuO NPs,heavy metal cadmium,rare earth strontium and ethanol were studied.And this helps to more fully understand the toxicity of external stress to cells.In this paper,ion-selective microelectrodes were used to measure the calcium ion concentration pulse signals formed during the rupture of plant cell protoplasts.Ion-selectivemicroelectrode is an electrochemical sensor.It can be used to determine the concentration of various ions in the cell and the ion flow in the extracellular space in single cell assays.This paper presents a new method for single cell detection using an ion-selective microelectrode,which uses an ion-selective microelectrode to measure the ion concentration pulse signal formed during the rupture of plant cell protoplasts.And then analyze the distribution of Intra-sytosol ion concentration.Analysis of ion concentration pulse signals we found that the Ca²⁺concentrations around the protoplast were stable at the beginning,both in the control group and in the experimental group.After the ruptures of the protoplast,the calcium ion concentrations raised to a peak quickly and finally slowly decreased to a stable value,thus forming a concentration pulse.Usually,the extracellular calcium concentration is greater than the intracellular calcium concentration.The calcium ion concentration increased after the protoplast rupture.This phenomenon might be due to the rupture of intracellular calcium stores leading to leakage of calcium ions.Compared with the control group,the Ca²⁺concentration in the experimental group took a longer time to reach the peak value,indicating that freezing treatment could reduce the intracellular calcium ion mobility.In addition,we found an interesting phenomenon that there were significant depressions at the front edge of the calcium ion concentration pulse in the experimental groups.Finally,the calcium ions diffused in the hypotonic fluid and the concentration reached a stable background value.Then,we measured the release of Ca²⁺from protoplasts at different times after the protoplasts of the experimental group were thawed.It was found that this concentration drop disappeared about 23 h after protoplast melting.The method was used to study the distribution of Ca²⁺concentration in the sytosol of aloe protoplasts under the stresses of zinc oxide nanoparticles,nano copper oxide,CdCl2,Tb?NO₃?₃ and ethanol.It was found that the sag phenomenon appeared at the front edge of the protoplast pulse signal after treatment with ZnO NPs,CuO NPs,cadmium chloride and lanthanum nitrate.However,the aloe protoplasts after ethanol treatment did not show a decrease in Ca²⁺concentration.The experimental results showed that the mobility of calcium ions in cells deteriorates under freezing stress.As a result,stratification occurs in the intracellular concentration distribution.And ZnO NPs,CuO NPs,CdCl2,Tb?NO₃?₃ could also redistribute intracellular calcium ions to form stratification.But the stress of ethanol could not affect the distribution of calcium ion concentration in the protoplasts.The results of this study indicated that the distribution of calcium ion concentrations in protoplasm was different under different stresses.The method proposed in this paper has the advantages of strong anti-interference ability and easy operation,which provides a new way to more fully reveal the response of cells to external stimuli.