Effect of Seed Priming on Germination and Seedling Characteristics of Aged Squash Seeds under Drought Stress

In order to investigate the effect of priming on different aspects of germination of aged pumpkin seeds under drought stress, a factorial experiment was conducted based on a completely randomized design with four replications in the laboratory. Treatments included different levels of aging (control, 85% and 75% of control germination), drought stress (0, -0.75 and -1.5 MPa), and priming with 100 μM of (control, hydro, gibberellin, GR24, benzyl aminopurine and spermidine). The seeds reached the desired vigor level by accelerated ageing test. Results of mean comparison showed that the lowest germination rate (2.11), fresh weight of radical (0.075 g), fresh weight of plumule (0.123 g), dry weight of radical (0.0082 g), dry weight of plumule (0.0079 g), chlorophyll a (0.403 mg.g-1FW), chlorophyll b (0.43 mg.g-1FW), chlorophyll a/b (0.99), photosynthesis 0.723 µmolCO2.mm-1.s-1) and α-amylase activity (12.37 μgSturch.g-1.minFW) were related to drought treatment with an intensity of -1.5 MPa and with 75% aging in the absence of priming. The lowest of germination uniformity (0.97) was obtained in the absence of drought and aging in priming with gibberllin. The lowest amount of carbohydrates (354.33 µmol.g-1FW) and total oil percentage (11.16) were obtained in the absence of drought and priming with 75% aging. The highest germination rate (15.56) in hormone-priming with gibberllin, fresh weight of radical (0.255 g) in priming with hydropriming, fresh weight of plumule (0.305 g) in priming with hydropriming, dry weight of radical (0.014 g) in hormone-priming with gibberllin, dry weight of plumule (0.0188 g) in priming with gibberllin, chlorophyll a (1.876 mg.g-1FW) in priming with spermimin, chlorophyll b (0.76 mg.g-1FW) in priming with spermimin, chlorophyll a/b (0.99) in priming with hydropriming, photosynthesis (5.833 µmolCO2.mm-1.s-1) in priming with spermimin and α-amylase activity (66.4 μgSturch.g-1.minFW) in hormone-priming with gibberlin were obtained in the absence of drought and aging stress. The highest germination uniformity (4.87) was related to drought treatment with an intensity of -1.5 MPa and with 75% aging in the absence of priming. The highest amount of carbohydrate (1561.33 µmol.g-1FW) was related to drought treatment with an intensity of -0.75 MPa and in the absence of aging and with of priming hydropriming. The highest amount of total oil percentage (21.2) was related to drought treatment with an intensity of -1.5 MPa, absence of ageing and priming with spermidin.