Effect of mechanical scarification, chilling, and gibberellic acid on germination of Leucaena leucocephala seeds

Abstract

Leucaena leucocephala is a tree species used for several agricultural purposes in Mediterranean region. The seeds of these species exhibit dormancy causing delayed germination. A series of experiments evaluated the effects of various treatments on the germination of leucaena leucocephela L. seeds. Germination of fresh seeds was 46% but it was improved (to about 70%) by mechanical scarification using sand paper. A germination of about 60% was obtained when dry seeds were pre-chilled at 4 ̊C for 2,3 and 4 weeks prior to germination that various storage periods of pre-chilling had no influence upon germination enhancement of seeds. Exposure of seeds to -18 ̊C inhibited germination in comparison to the control. There was no significant increase in germination percentage after cold treatment. Maximum improvement being achieved when seeds were kept dry under alternating cold/ warm temperatures for 8days at two day intervals prior to germination, since germination percentage increased to 73%. A significant promotion was recorded when seeds treated with 100 mg/l GA3 prior to germination and that pre-chilled treatment improved germination percentage compared with those un-chilled the maximum (70%) at 100 mg/l of GA3.The effect of nutrient media on seed germination was studied on MS and B5 media after being stored for one week in refrigerator (at 4°C) or in the freezer (-18°C). The germination percentage of Leucaena seeds cultured on MS medium showed a significant increase over the control for those stored one week at 4°C, when the effect of B5 medium on seed germination was found to be similar to the control (50%) for seeds stored one week at 4°C. These results demonstrate that alternating temperatures (cold/warm) provide faster and highest germination percentage and could be secured at low cost which would be adequate to large scale treatment of Leucaena leucocephala seeds.