The Role And Relationship Of CO₂ And ABA In Dark-induced Stomatal Closure

Stomatal movement is regulated by various internal and external factors,including ABA,light/darkness and CO2.A lot of research has indicated that ABA and high CO2 concentration can close stomata.Linked with the fact that intercellular CO2 concentration increases under darkness,and high CO2 concentration appear to induce ABA synthesis,we propose that high CO2 concentration and ABA mediate darkness-induced stomatal closour.Here,Arabidopsis(Arabidopsis thaliana)wild type(Col-0)and relevant mutants,pharmacological method and fluorescent microscope technology were used,and the roles of high CO2 concentration and ABA and the relation between them during darkness-induced stomatal closure were studied.The main results were as follows:1.Dark induced stomatal closure in wild type(Col-0),this effect was prevented in carbonic anhydrase(CA)mutant cal,ca4 and ca1ca4,and HIGH LEAF TEMPERATURE1(HT1)mutant ht1-1 ht1-2 and ht1-8d.The data show that high CO2 concentration is involved in dark-induced stomatal closure.2.Dark closed the stomata of wild type(Col-0),but did not close the stomatal of wild type treated with ABA synthesis inhibitor fluridon(FLU),ABA synthesis mutant nced3,nced5,nced3nced5,aba2-3,aba3-1 and aba2-4,and ABA receptor mutant pyrlpyllpyl2pyl4.The results show that ABA mediates dark-induced stomatal closure.3.Dark induced hydrogen peroxide(H2O2)and nitric oxide(NO)production in guard cells and stomatal closure in wild type(Col-0),these effects were impaired in mutant ca1,ca4,ca1ca4 and ht1-8d.H2O2 and sodium nitrate(SNP),a NO donor,closed the stomata of ca1,ca4,calca4 and htl-8d.The results support that high CO2 concentration is involved in dark-induced stomatal closure via inducing H2O2 and NO production.4.Dark induced H2O2 and NO production in guard cells and stomatal closure in wild type(Col-0),these effects were inhibited in wild type treated with FLU and mutant nced3,nced5,nced3nced5,aba2-3,aba3-1,aba2-4 and pyrlpyllpyl2pyl4.H2O2 and SNP closed the stomata of wild type and mutant nced3,nced5,nced3nced5,aba2-3.aba2-4,aba3-1 and pyrlpyllpyl2pyl4.The data indicate that ABA mediates dark-induced stomatal closure via triggering H2O2 and NO production.5.ABA closed the stomata of cal,ca4,ca1ca4,ht1-1,ht1-2 and ht1-8d,but NaHCO3 did not close the stomata of wild type(Col-0)treated with FLU and mutant nced3,nced5,nced3nced5,aba2-3,aba2-4,aba3-1 and pyr1pyl1pyl2pyl4.The results show that high CO2 concentration mediates dark-induced stomatal closure via inducing ABA synthesis.In conclusion,our results suggest that dark-induced the increase of intercellular CO2 concentration stimulates ABA synthesis,and then promoting H2O2 and NO production in guard cells,and finally closes stomata.