Seed dormancy regulates germination response to smoke and temperature in a rhizomatous evergreen perennial

Seed dormancy status regulates the response of seeds to environmental cues that can trigger germination. Anigozanthos flavidus (Haemodoraceae) produces seeds with morphophysiological dormancy that are known to germinate in response to smoke, but embryo growth dynamics and germination traits in response to temperatures and after-ripening have not been well characterized.

Elongation of Anigozanthos flavidus seeds in response to after-ripening and treatment with smoke derived glyceronitrile
Embryo growth for seeds of A. flavidus in this study was demonstrated by continually measuring the increase in length (mm) of embryos during incubation at suitable temperatures. Examples of an intact seed (a), embryo before growth (b) and embryo before germination (c) are shown visually here. Scale bar = 1 mm. Image credit: H. Ma.

In a recent Editor’s Choice article published in AoBP, Ma et al. investigate germination traits of A. flavidus seeds to determine whether (1) incubation temperature influences seed germination potential by affecting embryo elongation; and (2) seed sensitivity to smoke derived glyceronitrile is dictated by dormancy status. Fresh seeds of A. flavidus were found to have differentiated but underdeveloped embryos and possess non-deep morphophysiological dormancy. This dormancy could be broken by treatment with smoke-derived glyceronitrile or after ripening (dry storage at 15 °C for 28 months). After-ripened seeds could germinate readily at 15 – 20°C, and glyceronitrile did not improve germination following the loss of physiological dormancy. Embryo growth occured at 5°C and 10°C, with faster growth occurring with increasing temperature, but seeds could not germinate until the temperature reached 15 °C. When un-germinated seeds were moved from 5/10°C to 15°C for a further 28 days, germination increased from 0 to >80 % in significantly less time than after-ripened seeds indicating that cold stratification may play a key role in the germination process during winter and early spring in A. flavidus. The lower germination rates (<50 %) of seeds moved from 25 to 15 °C resulted from the induction of secondary dormancy. Induction of secondary dormancy in seeds exposed to warm stratification, a first report for Anigozanthos species, suggests that cycling of physiological dormancy may be an important mechanism of controlling germination timing in the field.

Reference List

Ma, H., Erickson, T. E., & Merritt, D. J. (2018). Seed dormancy regulates germination response to smoke and temperature in a rhizomatous evergreen perennial. AoB PLANTS, 10(4). https://doi.org/10.1093/aobpla/ply042