The effect of seed priming on germination and growth of madagascar periwinkle (Catharanthus roseus( seedling under environmental stresses

In order to study the effect of seed priming on germination and seedling growth of periwinkle seeds, the preliminary experiment was conducted with the aim of determination of the best duration and concentration of the different primings in a completely randomized design with three replications. The treatments include as the hydropriming, ascorbic acid (50, 100 and 200 ppm), sodium chloride (10, 30, 50 mM) and potassium nitrate (5, 10, 20 and 30 mM) and zinc (4 and 5 mg/l) for 6, 12, 24, 48, 60 and 72 hours and control seeds. According to the results of the preliminary experiment, the optimum levels of each priming were selected. In the mainweinvestigate the effect of above mentioned optimum primings levels on the germination, growth and biochemical characteristics of periwinkle seedlings under drought, salinity and temperature stress in a factorial experiment basted on a completely randomized design with three replications. The experimental factors include the drought (0, -2, -6, -10 and -12 bar), salinity (0, -2, -6, -8 and -10ds/m) and temperature (10, 15 , 20, 25, 30 and 35°C) stresses; seed pre-treatments (hydropriming for 60 hours, 200 ppm ascorbic acid, 20 mM potassium nitrate, 50 mM sodium chloride, 5 mg/l Zinc for 72 hours) and control seeds.The results showed that the rate and percentage of germination, seedling length and dry weight were decreased, with increasing the levels of drought, salinity and temperature (from 20 to 35°C) stresses. In these conditions, the catalase and peroxidase enzymes activity and proline contents of seedlings were also increased. Although, these stresses reduced seed germination and seedling growth.,all seed priming methods weere significantgy improved the growth and physiological characteristics of the seedlings, as compared to the those of control seeds. Generally, hydropriming for 60 hours had the most positive effects on the seed germination, growth and biochemical characteristics of periwnkle seedlings under the both of the stress and optimal conditions.