Abstract
Juniper (Juniperus procera) is a common forest tree species in Saudi Arabia. The Juniper forests face frequent episodes of wildfires; therefore, reforestation is necessary to maintain optimum forest cover in the country. However, Juniper seeds are extremely dormant and germinating them is a tough task. This study assessed the potential of different seed dormancy release treatments in improving the seed germination of Juniper.
Eight different seed dormancy-release treatments, i.e., boiling seeds for 2, 4 and 6 min, chemical scarification with concentrated sulfuric acid for 2, 4 and 6 min, stratification at 4 °C for 8 weeks and mechanical scarification with sandpaper were tested. A control treatment without any seed dormancy-release treatment was included in the experiment for comparison. The experiments were conducted under three different light:dark regimes, i.e., continuous dark, continuous light and alternating light and dark period of 12 h. Furthermore, the impact of four different potassium nitrate (KNO3) levels, i.e., 0, 2.5, 5 and 10 Mm was tested on seedling traits. Data related to seed germination was recorded at 4, 6, 8 and 10 weeks after initiation of the experiment.
The seeds were highly dormant and those in control treatment failed to germinate after 4 weeks. The highest seed germination was recorded for mechanical scarification under all light dark periods (37, 33 and 41 % for continuous dark, continuous light and alternating light and dark, respectively). Overall, the improvement in seed germination by mechanical scarification was 47, 25 and 34 % under continuous dark, continuous light and alternating light and dark, respectively compared to control treatment after 10 weeks. Seedling traits were significantly improved by the application of 5 Mm KNO3 compared to control treatment and higher concentration proved toxic.
It is concluded that mechanical scarification can be used to releases seed dormancy of Juniper seeds. Furthermore, 5 Mm KNO3 could be utilized to improve the early seedling growth.