Effect of Dormancy Breaking Treatments on Seed Quality during Storage of Four Acacia species

Abstract

Seeds in Acacia species show seed coat imposed dormancy which results in delayed and irregular germination and is a constraint for efficient nursery management and large scale plantation programmes. Seeds of A. leucophloea, A. holosericea, A. tortilis, and A. victoreae were subjected to various physico-chemical dormancy breaking treatments. The seeds after giving appropriate dormancy breaking treatment were further stored at room temperature, 4oC and -20oC to understand the effect of storage conditions on seed quality. In A. victoreae and A. holosericea hot water treatment at 70oC for 30 minutes, and 80oC for 10 minutes respectively; and in A. leucophloea and A. tortilis sulphuric acid treatment for 20 minutes and 40 minutes were found to be best treatment for breaking dormancy. Storage of seeds after giving dormancy breaking treatments shows varied response in all four species as indicated by changes in germination percentage, rate of germination, root and shoot vigour and vigour index as measured periodically over 30 months. Seeds of all the four species show a decline in seed quality attributes at ambient storage temperature. In A. leucophloea, A. holosericea and A. tortilis the decline was observed after 6 months (with complete loss of viability in 30 months in A. leucophloea, while in A. victoreae decline had set in after 18 months of storage. Storage under lower temperatures, however, proved to be better. The study indicates that seeds given dormancy breaking treatments can be stored under 4oC and -20oC temperature conditions for 30 months without any significant quality loss. This would allow flexibility in seed handling as the seeds can be given bulk dormancy breaking treatments and stocked as ready to sow seeds for distribution later.