Effects of seed pretreatment and seed source on germination of five Acacia spp.
The effects of seed pre-sowing treatment and geographic source of seeds on three germination parameters of five Acacia species (GP = germination percent; GMT = germination mean time (days) and GI = germination index) were studied. Pre-sowing treatment included immersion in concentrated sulphuric acid for 5, 10 and 15 min; immersion in hot water for 2, 4 and 6 min; abrasion of the seed coat and control. Seeds were collected from three geographical regions in the Kingdom of Saudi Arabia (Aseer and Al Baha regions in South-Western and Al Madinah region in the West). Experiments were carried out on Petri dishes containing moistened filter papers and incubated in a growth chamber. Seed pretreatment significantly (P < 0.0001) affected GP, GMT and GI in all tree seed species studied. Generally, scarification (acid and mechanical abrasion) resulted in the best GP, GMT and GI. Hot water also gave good germination for most tree seed species. Germination behavior of A. ehrenbergiana seeds was different compared to other species. More also, increasing the time of immersion in acid decreased the GP in seeds collected from both Aseer and Al Baha regions, while in contrast, A. origena germinated better with increasing time of immersion in acid and hot water. Geographic source of seeds significantly affected most germination parameters, although it was comparatively inconsistent compared to seed treatment. Highly significant interactions (P < 0.0001) were recorded between seed pretreatment and seed source.
Key words: Acacia species, pretreatment, seed source, germination, scarification, hot water.