Study On The Direct Adventitious Bud Induction From Cotyledonary Node Of Luffa Cylindrical (L.) Roem

To establish a stable and efficient micro-propagation system for Luffa cylindrical(L.) Roem.,which was the prerequisite for the research of genetic transformation,the cotyledonary nodes,used as explants,were cultured in vitro for the direct organogenesis system in this study.The affecting factors were analyzed and discussed,including the age of seeding,genotypes,the manner of cutting,plant growth regulators,concentrations of AgNO₃ and sucrose.The results were as follows.(1) The age of the seedling had extremely significant effect on the induction of direct adventitious buds from cotyledonary nodes and 5-7d-old seedlings were optimal for explant isolation for in vitro culture.(2)The manner of cutting of cotyledonary nodes had significant effect on the induction rate and had extremely significant effect on the average number of buds per explant.Rejecting the apical or axillary buds,longitudinally cutting the hypocotyl of approximately 2mm long and cutting off half the cotyledon was the best manner of cutting for explant preparation.(3) The induction rate and average number of buds per explant were extremely significantly affected by the kinds and concentrations of plant growth regulators.BA was more effective than auxin,and of the four kinds of auxins tested in the study,2,4-D had no inducing effect,but the other three kinds of auxins could stimulate the induction of buds, especially IBA.The optimal induction medium was MS +BA 1.0mg/L + IBA 0.5 mg/L,on which bud induction rate was 80—87.5%,and average number of buds per explant was 5.87-7.3.(4) The induction rate and average number of buds per explant were extremely significantly affected by the genotypes;of the four cultivars used in the experiments,V1 showed low induction response,while V2 and V3 were the readily responsive.(5) Concentration of sucrose had no significant effect on the induction rate,but had extremely significant effect on the average number of buds per explant;30 g/L or 40 g/L was the optimal concentration,high(60 g/L) or low(10 g/L) concentration resulted in lower average number.Furthermore,it played an important role in the induction reaction of explants:with the increase of sucrose concentration,the resultant buds became stronger and healthier,and elongated longer.(6) The induction rate in the medium,added lower concentration(1.0 and 2.0 mg/L) of AgNO₃,was not significantly affected,but the differentiation of callouses was obviously suppressed,and at the concentration of 4.0 mg/L,the induction rate was significantly decreased,the activity of explants was obviously repressed,and the number of abnormal buds increased.(7) The multiplication rate of buds did not vary with the tow kinds of CTK,BA and KT,but extremely significantly differed among the four concentrations of CTK,and was significantly increased in the medium added CTK,but on the contrary,too high concentration of CTK(2.0 mg/L) would decrease the multiplication rate.The optimal concentration of BA or KT was 0.5 mg/L and 1.0 mg/L.(8) Roots could be easily induced,reaching a rooting rate of 100%on all of the rooting media tested,but the quality of the resultant roots on different media was different obviously;the best quality of roots,with several healthy branches and no callus,could be induced on the optimal rooting medium 1/2MS + NAA 0.2mg/L or MS + NAA 0.2mg/L.