Sowing Media and Gibberellic Acid Influences Germination and Seedling Growth of Chilgoza Pine (Pinus gerardiana. Wall)

Pinus gerardiana Wall. recognized for its significant contribution to nut production, holds ecological and economic importance as a forestry species with limited range primarily found in Afghanistan. The species displays either extremely low or non-existent levels of natural regeneration. Due to irregular and uncommon seed years, problems with dormancy, and other factors, this species' natural habitat renewal is slowed down. Hence, we conducted a study to examine how different substrates and gibberellic acid (GA3) affect the germination and growth of Chilgoza pine seedlings. The substrates were grouped into three types, each containing varying proportions of soil, sand, and farmyard manure (FYM): M1 (1:1:1), M2 (1:1/2:1/2), M3 (1:1/3:2/3). Additionally, three concentrations of GA3 (0, 50, and 100 ppm) were used to assess their impact on germination and seedling growth. The results revealed that, with the exception of mean germination time (MGT) at 42.36 days, the highest values for final germination percentage (FGP) at 58.66%, germination index (GI) at 274, germination rate index (GRI) at 75.01, shoot fresh weight (SFW) at 8.74 g, shoot dry weight (SDW) at 4.78 g, shoot length (SL) at 219.80 mm, and seedling vigor index (SVI) at 1291926.02 were achieved when seeds were initially soaked in a 100 ppm GA3 solution for 6 hours and then planted in a medium with equal proportions of soil, sand, and FYM. The effects of GA3 concentrations were significant in influencing seedling growth, while substrate effects strongly impacted seed germination. This indicates that Chilgoza seeds possess ample gibberellin for germination but this is reduced during the seedling growth phase. The response of seedling vegetative growth to GA3 concentrations exhibited a notable linear trend, whereas the relationship between FGP and MGT with GA3 concentrations showed a significant quadratic pattern. This suggests that GA3 concentrations can effectively promote seedling growth. The substrate choice notably influenced FGP and MGT due to its role in nutrient provision and aeration. The highest GA3 concentration led to the greatest enhancement in seedling vegetative growth, implying that prolonged usage might yield further benefits over time. In conclusion, the findings suggest that both GA3 and substrate have the potential to enhance Chilgoza seed germination and subsequent seedling growth, and their combined application could be a beneficial approach.