Dormancy-breaking and germination requirements of seeds of the Hawaiian endemic Dianella sandwicensis (Xanthorrhoeaceae)
Dustin Wolkis A D , Carol C. Baskin B C and Jerry M. Baskin BA Department of Science and Conservation, National Tropical Botanical Garden, 3530 Papalina Rd, Kalāheo, HI 96741, USA.
B Department of Biology, University of Kentucky, 101 T.H. Morgan Building, Lexington, KY 40506, USA.
C Department of Plant and Soil Sciences, University of Kentucky, 105 Plant Science Building, Lexington, KY 40546, USA.
D Corresponding author. Email: dwolkis@ntbg.org
Australian Journal of Botany 66(3) 213-217 https://doi.org/10.1071/BT17214
Submitted: 31 October 2017 Accepted: 3 April 2018 Published: 14 May 2018
Abstract
One problem with including some wild plant species in restoration projects is that seeds are dormant and fail to germinate. Thus, information on the dormancy-breaking and germination requirements facilitates propagation of species, such as the Hawaiian endemic Dianella sandwicensis Hook. & Arn., for conservation. In seeds of this species the embryo is shorter than the endosperm, and seeds sown in early summer in Hawai‘i did not germinate until autumn. Thus, we hypothesised that seeds have morphophysiological dormancy (MPD) and that germination is promoted by low (autumn) temperatures. Studies on embryo growth and the temperature requirements for dormancy-break and germination were conducted on seeds of D. sandwicensis collected on three Hawaiian Islands. Prior to germination the embryo length : seed length ratio increased 16.3 to 17.6%; thus, seeds have MPD. Since both embryo growth and germination occurred at 25/15°C, seeds have a simple level of MPD. Seeds germinated to 90–100% at both 20/10 and 25/15°C, but germination was faster at 20/10°C. However, seeds incubated for 12 weeks at 25/15°C then moved to 20/10°C reached 100% germination as rapidly as seeds kept at 20/10°C. Our results show that exposure of seeds to relatively cool autumn (20/10°C) conditions facilitates propagation of this species from seeds.
Additional keywords: Dianella, embryo growth, morphophysiological seed dormancy, tropical montane (Hawaii).
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