Germination response and seedling growth performance of Adansonia digitata L. tree seeds under innocuous pre-treatment techniques

Adansonia digitata is a multipurpose and highly valued tree species, which produces wild edible fruits. Its seeds are characterized by hard seed coat that impedes water and oxygen penetration into the seed, and thus inhibits seed germination. This investigation was aimed to evaluate the effects of various seed pre-treatment methods on seed germination response and seedling development of the species. The experiment was conducted in greenhouse and used a completely randomized design. Seven treatments ( Trt1 : Scarification, Trt2 : Soaking in cold water for 24 hours, Trt3 : Soaking in cold water for 24 hours and scarification, Trt4 : Soaking in hot water for 1 hour, Trt5 : Soaking in hot water for 1 hour and soaking in cold water for 24 hours, Trt6 : scarification and soaking in hot water for 1 hour, Trt7 : Soaking in cold water, scarification then soaking in hot water) and control (without any pre-treatment). Data on seed germination and seedling growth parameters were recorded. Germination percentage, germination velocity, and mean germination rate of seeds were calculated. The study showed that seed germination and seedling growth parameters significantly varied among the treatments. The highest seed germination (complete germination within a week) and highest seed germination velocity (3 days) were recorded in Trt7 (Soaking in cold water, scarification then soaking in hot water) followed by Trt 6 (96.67% germination in three weeks), Trt5 (93.33%), and Trt4 (86.67%). The lowest germination percentage (70% in 11 weeks) and lowest germination value (40 days) were recorded in seeds without any treatment. It was observed that seedlings with rapid seed germination resulted in robust and vigorous seedlings that attained approximately 15 cm in height after 11 weeks. We recommend soaking in cold water, scarification then soaking in hot water to break seed dormancy, promote seed germination, and produce vigorous seedlings of A. digitata.