Effects Of Lanthanides On Potassium Channels In Guard Cells And Mesophyll Cells And On Stomatal And Transpiration Regulation

Rare earth elements have been widely applied in agriculture, industry, medicine and stockbreeding and so on. Rare earth elements have special biology effects on organisms, including of improving the production of crops, promoting seeds sprout and young plants growth. So rare earth fertilizer has been widely applied in crops in our country. Plant water shortage is one of the main suffers from its environmental surroundings, losses from aridity of the global food productivity are the sums of losses from the other disasters. Stomata are the gas gateway of plants with the surrounding, and photosynthesis (absorbing CO2) and transpiration (losing water) are controlled by stomatal movements. Activities of plasma membrane ion channels in guard cells and mesophyll cells have close relationships with stomata movements, and K+ was the dominant osmoticum, so it was important to illustrate the relationships between stomatal movement, transpiration and activities of K+ channels in guard cells and in mesophyll cells. Effects of some lanthanide ions on K+ channels in guard cells and in mesophyll cells were investigated using whole-cell patch clamp technique, and influences of lanthanide ions on stomatal movements and transpiration were studied using epidermis biology analyse and other methods. We aim at posting some evidence to reveal rare earth elements might have potential practical values in regulating plant water status. The results show as below:Whole cell inward and outward K+ channels currents in vicia guard cells were recorded seperately by patch clamp technique and effects of lanthnide ions on the K+ channels currents were investigated. Both of inward and outward K+ channels currents in vicia guard cells were depressed by extracellular La3+; inward K+ channels currents in guard cells were depressed by intracellular La3+ and outward K+ channels currents in guard cells were activated at smaller concentration and depressed at higherconcentration by intracellular La3+. Effects of extracellular Eu3+ on inward and outward K+ channels currents in guard cells were similar to that activated at smaller concentration and depressed at higher concentration. Inward K+ currents in guard cells were activated by Eu + at concentration of <2mmol/L and depressed by Eu3+ at concentration of >5mmol/L; outward K+ currents in guard cells were activated by Eu3+ at concentration of <200 u mol/L and depressed by Eu3+ at concentration of >lmmol/L. So, it is diverse of different type K+ channels reaction to the same metal ions. While extracellular Nd3+ at concentration of <5mmol/L had minor effects on both inward and outward K+ currents in guard cells.Whole cell outward K+ channels currents in vicia mesophyll cells were recorded by patch clamp, and effects of lanthanide ions on outward K+ channels currents were studied. Outward K+ channels currents were both depressed by extracellular and intracellular La +. Outward K+ currents in mesophyll cells were slightly depressed by extracellular Eu3+; and extracellular Nd3+ had no significant effects on outward K+ currents in mesophyll cells. Inward K+ currents had not been recorded in our patch clamp experiments.Effects of lanthanide ions on stomatal movements, transpiration, relative water retention in vicia leaves were investigated in our experiments also. Some concentration of La3+ and Eu3+ had effects on depressing stomatal opening, alleviating transpiration, promoting relative water content in vicia leaves. And Nd3+ had no significant differences compare with the control experiments.K+ remains the dominant osmoticum. Therefore, effects of La3+ and Eu + on regulating stomatal aperture and transpiration in vicia leaves may have relations to their reactions to K+ channels in guard cells and mesophyll cells. La3+ and Eu3+ inhibited stomata opening by regulating K+ channels currents in guard cells, and promoted mesophyll cells water retention potential and prevented water flowing into guard cells from mesophyll cells by regulating mesophyll cells K+ channels currents. Nd3+ at concentration of...