Changes Of The Existing Forms Of Vitamin B₆in Tobacco Plants In Response To The Major Abiotic Stress

Vitamin B₆（VB₆） is the general term for a kind of pyridine compounds.Pyridoxine（PN）, pyridoxal（PL） and pyridoxamine（PM） are the basic chemical forms ofVB₆,the phosphorylated forms are pyridoxine-5’-phosphate（PNP）, pyridoxal-5’-phosphate（PLP） and pyridoxamine-5’-phosphate（PMP）, PMP and PLP are active asenzyme cofactors.There are two independent routes of de novo VB₆biosynthesis.The oneroute named “DXP-dependent”,the sequential action of the enzymes PDXA and PDXJresults in the conversion of4-phosphohydroxy-L-threonine（4PHT） and deoxyxylulose5-phosphate into PNP.The other one route is PDX1and PDX2produce the cofactor PLPin the presence of either ribose5-phosphate or ribulose5-phosphate in combination withglyceraldehyde3-phosphate or dihydroxyacetone phosphate.It is called“DXP-independent”pathway, and now it has been shown to be in operation in plants.In recent years it has been found that VB₆is an important component of cellularantioxidant defenses,it is efficient quencher of both singlet oxygen and superoxide,and itserves as a defense against abiotic stress.In tobacco plants. Previous research focused onthe regulation of the de novo biosynthetic genes in response to abiotic stress, this paperanalysis the changes of the existing forms of VB₆intobacco plants in response to abioticstress.In this paper,the tobacco plants were cultivated in culture medium,liquid medium andsoil.The abiotic stress are5℃,15℃, UV-B, salt, sucrose, continuous irradiating withlight for24hours, continuous24hours without light, weak light, drought and sulfurdioxide stress.The time of treatment is1day,4day,6day,7day,and14day,different stresswith different treat time.The tobacco treated by abiotic stress was conserved in-20℃fridge. the determination of the content of the existing forms of VB₆was described byusing HPLC with fluorescence detector.The SPSS（PASW Statistics18） was adopted to doanalysis of varance of the date,testing the difference between the treat and thecontrol,P=0.05.The results indicate that:5℃,15℃, UV-B, salt, sucrose, drought and sulfur dioxidestress all can cause the changes of content of the existing forms of VB₆,in relativeterms,the influence of light stress（weak light, continuous irradiating with light for24hours and continuous24hours without light）is more small. PLP and PN are moresensitive to abiotic stress. The changes of the existing forms of VB₆are determined bytreat time and abiotic stress. The results reveal that the existing forms of VB₆havedefferent susceptibility to abiotic stress,Following the treatment of abiotic stress,the treattime is more important,and the environment of the tobacco plants cultivated also influencethe response of the existing forms of VB₆to abiotic stress.