Breaking seed coat dormancy in Macrotyloma daltonii

Abstract

Methods for breaking hard seed to allow germination of 2 seedlots of Macrotyloma daltonii (Webb) Verdc., were investigated. Treatments included soaking, application of dry heat, hot water, acid scarification, sand paper scarification, pre-chilling, alone and in combination with acid and dry heat. The treated seeds were tested for germination over 21 days in an incubator with 12 h of light and 12 h of darkness and temperatures of 25 and 18°C during the light and dark phases, respectively. A 20-min exposure to 98% concentrated sulphuric acid was most effective in increasing germination from 10 to 80% in seedlot 1. The 10-min acid treatment increased germination from 21 to 38% in seedlot 2, but 20 min reduced germination and increased the number of dead seeds. Seedlot 1 had greater levels of hard seed (88%) than seedlot 2 (61%). Soaking, hot water, dry heating, pre-chilling, or sandpaper scarification were not effective in breaking hard seed in either seedlot 1 or 2. Combining pre-chilling with 10 min of acid treatment damaged seed and impaired germination across the 2 seedlots. The range of pre-sowing seed treatments that indicated positive effects on germination, particularly acid treatments need to be further investigated in the field under different pedo-climatic conditions to allow appropriate rangeland management options to be developed.