Germination of Maiapilo (Capparis sandwichiana) Seeds: Determining Dormancy Classification

The Hawaiian archipelago’s sole native member of the Capparaceae plant family, the endemic maiapilo (Capparis sandwichiana), is a species of conservation importance with poor natural regeneration. This study identifies important seed characteristics, such as its seedcoat water permeability, embryo development, and time to germination, to determine dormancy classification. To test for water-permeable coats, seeds were mechanically scarified and imbibed in tap water over a 48-hour time period. During imbibition, scarified and nonscarified seed masses increased at similar rates. The same seeds were then tested for germination with daily alternating regimens of 12 hours of light/dark and temperatures of 25/15 °C. The nonscarified seeds germinated at a significantly higher rate than scarified treatments, indicating the presence of water-permeable seedcoats to rule out physical dormancy (PY). To test for physiological dormancy, gibberellic acid was used in germination tests. Caper seeds were sown without (control) and with (500, 1000 ppm) gibberellic acid (GA3) treatments to help determine dormancy classification. Mean germination for each replicate ranged between 10% (500 ppm GA3) and 60% (1000 ppm GA3). There was no significant difference with final germination or overall time (days) to reach 25% total germination (T25) among treatments and controls. Because 1) seedcoats were permeable to water, 2) embryos were fully developed, and 3) germination took longer than 30 days, Capparis sandwichiana seeds most likely have nondeep physiological dormancy. These results will benefit managers and growers with a better understanding of seed characteristics for dormancy alleviation and successful germination of this threatened endemic species.