Temperature and Imbibition Influence Serianthes Seed Germination Behavior

Abstract

The direct role of physical dormancy in delaying germination of Serianthes grandiflora Bentham, Serianthes kanehirae Fosberg, and Serianthes nelsonii Merrill seeds has not been adequately studied, nor has the role of temperature on germination behaviors. Imbibition testing indicated seeds with scarified testa absorbed water for the duration of a 24 h imbibition period, but seeds with an intact testa stopped absorbing water after 1 h. The behavior of S. nelsonii seeds most closely matched those of S. kanehirae, with the pattern of water absorption for S. grandiflora seeds deviating from that for the other species. Scarified seeds germinated readily, with initial germination occurring by 50 h for S. nelsonii and 90 hr for the other species, and maximum germination of 80% to 90% occurring by 60 h for S. nelsonii and 100 h for the other species. Predicted optimum temperature based on a fitted quadratic model was 26 °C for S. nelsonii, 23 °C for S. grandiflora, and 22 °C for S. kanehirae. Seed respiration increased within 3 h of imbibition for scarified seeds and continued to increase in a linear pattern. The linear slope was greatest for S. nelsonii, intermediate for S. grandiflora, and least for S. kanehirae, but ultimate respiration was greatest for S. kanehirae seeds. Seed respiration was so limited for un-scarified seeds that the instrument was unable to quantify any carbon dioxide efflux. Physical dormancy in seeds of these Serianthes species is a powerful trait that spreads out the timing of seedling emergence in natural settings and controls imbibition and germination speed in managed nurseries.

Extreme Wind Events Influence Seed Rain and Seedling Dynamics of Guam’s Serianthes nelsonii Merr

“…The seed-to-seedling strategies of S. nelsonii do not appear to be sophisticated. The seeds utilize a physical dormancy approach to delay germination after being added to the seed bank, as rapid germination occurs on stored seeds but only if the testa is scarified prior to imbibition of water (Marler, 2019;Marler, Cascasan, & Lawrence, 2015). The results herein indicate that the chronic seed bank that supports a chronic stand of young seedling turnover may play an ecological role as an insurance policy such that the S. nelsonii seedlings that are standing on the day of a tropical cyclone and that emerge immediately after a defoliating tropical cyclone are prepared to capitalize on the ephemeral stochastic posttyphoon habitat traits.…”

Repetitive pruning ofSerianthesnursery plants improves transplant quality and post-transplant survival

“…32 Management of S. nelsonii, S. kanehirae, and S. grandiflora in homogeneous nursery conditions has revealed similar growth and development behaviors among the three species from seed germination up to 2 m in stem height. [9][10][11] Concerning germination behaviors, S. nelsonii seeds exhibited faster initial germination speed than the other two species, but the responses to a temperature gradient were similar. 11 Concerning root growth behavior, the diel patterns of root extension were similar among the three species.…”

“…[9][10][11] Concerning germination behaviors, S. nelsonii seeds exhibited faster initial germination speed than the other two species, but the responses to a temperature gradient were similar. 11 Concerning root growth behavior, the diel patterns of root extension were similar among the three species. 9 Concerning stem growth, S. nelsonii plants exhibited greater growth rates than those of S. grandiflora but less than those of S. kanehirae under a range of conditions.…”

“…The recent small-scale research that has been conducted has been restricted to short-term studies of less than 1 y. [9][10][11]15,[28][29][30] When limited data are available for an endangered species of interest, conservation decisions can be made from data gleaned from congeneric species. 31 Indeed, biologists often examine surrogate species in pursuit of answers to various conservation questions.…”

“…Third, destructive sampling techniques are not appropriate during case studies using ESA-listed plant species. Fourth, S. kanehirae and S. grandiflora behave similar to S. nelsonii in a conservation nursery, [9][10][11] providing ample evidence that they are appropriate surrogate species to experimentally manipulate in order to inform adaptive management decisions during recovery of S. nelsonii.…”