The experiment has been carried out in the Syrian National Commission of Biotechnology, during the growing season 2018/2019, to study the effect of abiotic stresses (salinity and osmotic stresses) on the activity of some antioxidant enzymes and biochemical traits in Catharanthus roseus. The experiment has been laid according to (CRD) with three replications. The seeds have been sterilized by NaOCl solution (0.5% v/v), then planted on MS medium. Plantlets have been moved to MS medium enriched with NAA (1 mg.L-1) and BA (2 mg.L-1). The callus has been initiated from leaves using MS medium containing NAA (1 mg L-1) and KIN (2 mg.L-1). After 60 days, callus has been transferred to MS medium supplemented with different concentrations of PEG 6000 (-0.2,-0.3,-0.4,-0.5 MPa), and NaCl (25, 50, 75, 100 mM) in succession as stimulating agents. The results show that the top value of solutes leakage has been in the salt and osmotic treatments (28.04 and 26.98% respectively) compared with the control (8.563%). MDA content has significantly been higher in salt stress (102.3 µmol.g-1 FW) followed by the osmotic stress treatment (79.41 µmol.g-1 FW), while it was significantly lower in the non-stressed treatment (37.76 µmol.g-1 FW). An increase in the proline content occurred in both the stress treatments (4.623, 4.243 mmol.g-1 FW, respectively) compared with the control (2.477 mmol.g-1 FW). The activity of antioxidant enzymes (CAT, APX, and SOD) have significantly been higher in salt stress treatment (506.9, 12270.02 mol.min-1 .mg-1 protein, 191.4 U.mg-1 protein respectively), followed by osmotic stress (259.4, 7106.22 mol.min-1 .mg-1 protein, 65.60 U.mg-1 protein, respectively), while it has been significantly lower in control (126.9, 1800.38 mol.min-1 .mg-1 protein, 36.03 U.mg-1 protein, respectively).

A study to observe and record the mode of gene action involved in some quantitative and physiological traits of three maize hybrids using generation mean analysis was conducted at Abu Garash Farm, Faculty of Agriculture, Damascus University, during two growing seasons (2018 and 2019). Genotypes were compared using Randomised Complete Block Design (RCBD) with three replicates. Significant differences in all studied traits for six populations within each cross were found. There was significant positive heterosis relative to intermediate and better parents for most studied traits of hybrids, except in nitrogen utilization efficiency. Most of the genetic parameters were significant for the three hybrids, indicating the importance of epistasis in the inheritance of studied traits. The dominance gene effect was more pronounced than the additive gene effect in the inheritance for all traits. The values of the phenotypic coefficient of variance were greater than the values of the genotypic coefficient of variance, indicating the effect of environmental factors on the expression of the studied traits. High narrow-sense heritability values were associated with high genetic advance for nitrogen use efficiency and biological yield per plant. It is recommended that selection in early segregating generations of the studied hybrids is useful.