The role of gibberellic acid, temperature and scarification on in/ex vitro germination of Rosa persica Michx ex Juss.

Persian rose or Varak (Rosa persica) is a thorny shrub belongs to Rosaceae family. This small scented plant due to the having a yellow-flower with a distinct reddish-brown spot in petals base and tremendous resistance to heat and drought has a great potential for modern rose breeding. Since there are not any available reports on germination habit of this aforementioned species, therefore the goal of this experiment is to evaluate the seed viability and type of dormancy in this anomalous species.

To increase the germination percentage of R. persica, collected seeds were exposed to 96% of sulfuric acid for 0, 10 and 30 min. whereupon sulfuric acid-exposed seeds were sown on MS (Murashige and Skoog) media supplemented with 0, 0.1, 1 and 10 mg/l gibberellic acid. This combination was evaluated under ex vitro (Petri dish) and in vitro (in MS media) condition at 4 and 24°C in incubator. Data collected from many traits related to the root and stem after 6 weeks of the experiments.

Despite confirmation of seed viability via Tetrazolium test, standard germination test was failed under ex vitro condition and a few weeks after the beginning of the experiment all specimens became infected with fungus. However, under in vitro condition, treatment of seeds with sulfuric acid for 10 min and then 1 mg/l gibberellic acid, were significantly effective on germination percentage and more than 60% germination frequency was observed in 10-minute sulfuric acid treatment in a hormone-free medium while no seeds have germinated in the control. The maximum root and stem length, hypocotyl length, epicotyl length, seedling length and the number of leaves has achieved when seeds exposed to sulfuric acid for 30 min. However, 10 min treatment of seeds with sulfuric acid was more effective in increasing the length and number of lateral roots and stem diameter. Root and stem length, hypocotyl length and seedling length has increased when gibberellic acid augmented. Stem diameter, length and number of lateral roots were higher in hormone free medium while the number of leaves and epicotyl was higher in medium supplemented with 0.1 mg/l gibberellic acid.

The effect of sulfuric acid on improving germination indicates physical dormancy of Iranian rose seeds. Application of whole treatments did not result to germination at 4°C. Seeds respond to germination treatments only at 24°C. The result of our study on temperature unlike other rose species reveals no need for stratification treatment.