Study Of Mechanism On Influence Of Phosphate Deficiency And 6-BA On Growth And Morphology Of Cucumber Hairy Roots

Effects of phosphorus deficiency alone or in combination with cytokinin 6-BA inthe medium on growth and morphology of Cucumber(Cucumis sativus L) hairy rootsas well as changes in contents of soluble proteins, activities of SOD and POD andutilization rate of nitrogen resource and calcium ion in the medium during the liquidculture of cucumber hairy roots were investigated in this paper. The main results wereas follows:The cucumber hairy roots can't grow in the MS medium without any phosphorus.The growth of cucumber hairy roots was inhibited by phosphorus deficiency in theMS medium. The hairy roots became thinner and its growth was significantlyinhibited with the decreasing Pi concentration of the medium. The multiplicationcoefficient of hairy roots cultured for 30 days in the modified MS medium withphosphorus concentration of 0μmol/L,250μmol/L,500μmol/L,750μmol/L,1000μmol/L,1250μmol/L was 0.7,9.96,18.8,15.14,35.53 and 31.36,respectively.Under Pi stress, content of soluble protein of cucumber hairy roots was decreased,while activities of SOD and POD were stimulated. At the same time, the absorptionand utilization of nitrogen (NO3-N and NH4+-N) of the medium by cucumber hairyroots was also inhibited.Compared to the control(MS medium without addition of 6-BA in themedium),the symptoms of growth inhibition of cucumber hairy roots by Pi deficiencycould be alleviated by addition of 1.0 mg/L or 5.0 mg/L 6-BA into the medium.Themorphology of cucumber hairy roots cultured under phosphorus deficiency plus 6-BAbecame thicker and shorter with the increasing concentration of 6-BA and almostlyformed no lateral roots.Addition of 6-BA into the medium supplemented withdifferent concentration of Phosphorus could delay the senescence of cucumber hairyroots. 1.0 mg/L 6-BA in combination with phosphorus deficiency could stimulate theabsorption and utilization rate of NO₃-N,NH₄⁺-N and Ca2+ of the medium andreduced the decline of soluble protein content and affect on the activities of SOD and POD in hairy roots.The micrographs of cross-sections of cucumber hairy roots showed that,compared to the control(without addition of 6-BA into the medium with phosphorusdeficiency), cytokinin 6-BA in combination with phosphorus deficiency in themedium could make cucumber hairy roots thicker, and the transection area of hairyroot tissue slice and the volume of root cells was increased than the control,, but thecell number of root transection was not increased. Our results showed that cytokinin6-BA could play a part in making cucumber hairy roots cultured under pi deficiencythicker and shorter by stimulating the increase of cell volume but not stimulating ofcell division.