Relationships between physiological mechanisms of tolerances to drought and salinity in melons

In this study, designating the resistant and sensitive melon genotypes initially, determination of the defense the antioxidative enzyme activity, ion regulation with citrulline mechanisms of tolerant or sensitive genotypes cultivated under saline and drought conditions and revealing the possibility of existence of relationships between defense mechanism in tolerances against to such two stress conditions were aimed to investigate.For this aim, 31 melon genotypes were evaluated with respect to some growth parameters and physiological changes via an overall screening. According to the obtained results, the investigated parameters were repeated in specific screening stage by using 20 genotypes which were selected and divided into three groups as tolerant, medium-tolerant, and sensitive. With respect to overall findings, in order to perform detailed physiological investigations by determining salt and drought resistant CU 159 and CU 196 genotypes, salt and drought sensitive CU 40 and CU 252; they were evaluated in terms of ion regulation, antioxidative enzyme activities (GR, CAT, APX, SOD), antioxidant amounts (Vitamin C, SH compounds) and citrulline changes.At the end of the study, it was observed that salinity and drought inhibited the plant growth in melon genotypes and these genotypes differed in terms of reactions to stress factors. Especially, it was also investigated that examining the activities of CAT and GR enzymes with citrulline were remarkably effective by means of investigation of tolerance aptitude to salt and drought. According to the results, similar mechanisms of salt and drought stresses were observed while ion regulation and enzymatic changes of melon genotypes were further affected by salt stress.