پديد آورندگان :
پورممبنی، صفدر نويسنده دانشآموخته كارشناسی ارشد گروه علوم باغبانی Pour Mombeini, S. , معلمی، نوراله نويسنده استاد گروه علوم باغبانی moalemi, noorolah
چكيده لاتين :
Introduction: Dodonaeaviscosa is an evergreen and perennial shrub which distributed widely in warm regions throughout the world. Untreated seeds germinatewell, but to shorten germination, seeds werefloated in hot water for 30 seconds, then cooled down rapidly. In addition, scarification as pre-treatment and dipping the seed in boiling water improve seed germination. Under salinity,the level of abscisic acid increases more than gibberellic acid which prevents seeds germination. Accumulation of Na+ and Cl- ions can lead to changes in water status in plant tissues and creating a series of second stress, such as oxidative stress. In priming, seeds are authorized to absorb some water, sothat, the early stages of germination are donewithout root emerging. The country of Iran and especiallyKhozestan province is located in arid and semi-arid region of the world, sounder such conditionand dueto high temperature and low rainfall, and salinity of water sources and media, D.viscosasexual reproduction is suffered by serious challenges. Consequently,the objective of this study was to investigate the effectsof hydro and osmo-priming in combining withgibberellic acid and potassium nitrate on seed germination of D.viscosaunder salinity stress.
Materials and Methods: Two experiments in 2010 wereconducted separately and consecutively in completely randomized design with five treatments and four replications in the plant propagation laboratory of faculty of Agriculture, ShahidChamran University of Ahvaz (latitude 31.33° N, longitude 48.69° E, altitude 23 m). In the first experiment, 500 seeds were selected from seed lot, and were disinfectedwith sodium hypochlorite 2.5%, afterwards, divided into five categories (each category consisted of 100 seeds in four replicates) and were treated as : 1) Osmo-priming with gibberellic acid 50 and 100 mg.l-1 and potassium nitrate 0.5 and 1 % for 12 h. 2) hydro-primed with distilled water (as control) for 12 h. A week later second experiment wascarried out (with 500 seeds from some initial seedlot) base of the best result obtained in the first experiment to study theeffects of salinityonseed germination. Seeds weretreated withgibberellic acid(50 mg.l-1)for 12 h. During germination, seeds were irrigated with different levels of salinity, including 0.0 (distilled water as control), 3, 6, 9 and 12 ds.m-1using NaCl salt (as halopriming). Analysis of data (ANOVA) wasperformed by procedure within thestatistical software MSTAT-C and means were separated by multiple-rangetest of Duncan’s at (p <0.05).
Results and Discussion: The results of the first experiment indicated that osmo-priming treatment had significant effect on germination percentage, plumuleand radicle lengthand radicle fresh weight. Gibberellic acidat 50 mg.l-1 had the highest performance compared to the other treatments. Maximum germination percentage (68%), plumule(71.50 mm) andradicle length (41.25 mm) and radicle fresh weight (0.12 g) were found under influence of gibberellic acid 50 mg.l-1. Potassium nitrate in 1%had the least effect on germination percentage (50%), radicle length (21.75 mm) and fresh weight of radicle (0.06 g). It seems thatprimingwithgibberellic acid(50 mg.l-1)somehowinducedsalinity tolerance inseed,andseed coat become morepermeable towaterabsorption. Priming can increase the activity of antioxidant enzymes such as ascorbate and glutathione, and these enzymes can reduce lipid peroxidation during seed germination, which is enhanced consequently the germination percentage.Osmoprimingwith increasing inaquaporinhelpstoenhance thegermination rate. Increasing in plumuleand radicle length affected by gibberellic acid 50 mg.l-1 can be attributed to the activity or synthesis of several enzymes, enhancing the metabolic and production of active substances. The other positive effects of gibberllic acid on germination are breaking of seed dormancy, growth of embryonic axis and development of later buds.In the second experiment, the results showed that gibberellic acid 50 mg.l-1under salinity stress had a significant positive effect on all other germination atttributes at p < 0.01, so the highest and the lowest germination rate features were achieved in salinity of 3 and 12 dsm-1. Duringgermination period, salinitythroughits effect onmetabolic processes (increased levels of soluble proteins) as aphysiologicaleffectwouldreducegermination percentage.Increase in D.viscosaseed germinationin3and6dS m-1 salinity levels than control probably isrelatedtophysiologicalcomplexity, specialstructuralseedandcell metabolism,especiallyactivity of cell membranes that hasa moderatetolerancetosalinitytogermination.Undersalinity stress,gibberellicacid lead to synthesis of ethylene. Hence, ethyleneasagermination stimulant helps toovercome salinityandfacilitate thegermination.By the way, with increasing thesalinity level it can result in abscisic acid biosynthesis and so prevention of gibberellic acidsynthesis and this hormonal imbalance can prevent or reduce seed germination.In general, salinityduetoionic effects (damage to the metabolic processes) or by reducing thewater potential(osmotic effect) ortheir combinations prevents germination.
Conclusion:Briefly, gibberellic acid50 mg.l-1 in salinity of 3 ds.m-1 showed better results than other treatments for D.viscosaseed germination in this investigation.
