Enhancing the germination of three fodder shrubs (Atriplex amnicola, A. nummularia, A. undulata; Chenopodiaceae): implications for the optimisation of field establishment
J. C. Stevens A E , E. G. Barrett-Lennard B C and K. W. Dixon A DA Kings Park and Botanic Garden, West Perth, WA 6005, Australia.
B Department of Agriculture and Food, Western Australia, South Perth, WA 6151, Australia.
C Cooperative Research Centre for Plant-based Management of Dryland Salinity.
D School of Plant Biology, University of Western Australia, Crawley, WA 6009, Australia.
E Corresponding author. Email: jstevens@bgpa.wa.gov.au
Australian Journal of Agricultural Research 57(12) 1279-1289 https://doi.org/10.1071/AR06031
Submitted: 1 February 2006 Accepted: 24 August 2006 Published: 21 November 2006
Abstract
Saltbush (Atriplex) species are widely grown in Australia as saltland pastures. Direct seeding practices for saltbush currently result in asynchronous and unreliable seedling establishment (5% successful establishment is not uncommon from field-sown seed). In part this may stem from a limited understanding of Atriplex seed germination requirements. This paper presents findings with 3 Atriplex species, A. amnicola (Paul G. Wilson.), A. nummularia (Lindl.), and A. undulata (D. Dietr), each of which differs in germination characteristics. For A. amnicola, the presence of light (and artificial substitution of light by 1000 ppm gibberellic acid) improved germination under controlled conditions and resulted in a 4-fold increase (70% total emergence) in field emergence of seedlings. For A. undulata, removing bracteoles increased germination under controlled conditions (~15%), with a 1.5-fold improvement in field seedling emergence (55% final emergence); however, seed priming or gibberellic acid application had no significant effect. In contrast, for A. nummularia, bracteole removal and light had minor positive effects on germination under controlled conditions, but this did not translate into improved emergence in soil or in the field. Under –0.5 MPa NaCl stress, application of gibberellic acid, salicylic acid, or kinetin to the germination medium significantly increased the final germination percentage of A. amnicola seeds (58, 16, and 14%, respectively) and improved the rate at which seeds germinated. All plant signalling compounds significantly increased final germination percentage and germination rate of A. undulata, albeit with a <10% increase at –0.5 MPa NaCl. Priming seeds with plant signalling compounds had similar effects on seed germination under low water potentials compared to direct treatment of the germination media. The effects of seed priming on Atriplex seedling emergence from saline soils varied among species. Priming with water significantly increased emergence percentage of A. amnicola but had no effect on A. nummularia and A. undulata. Gibberellic acid improved A. amnicola germination parameters only, whereas salicylic acid and kinetin improved the rate of emergence in all 3 species at various levels of salinity. This study suggests that a basic understanding of seed dormancy and germination requirements has the potential to substantially improve field emergence of saltbush species.
Additional keywords: gibberellic acid, kinetin, salicylic acid, salinity, saltbush, seed dormancy.
Acknowledgments
This research was supported by the Sustainable Grazing of Saline Lands (SGSL) initiative, a subprogram of Land Water and Wool. Land Water and Wool is a R&D funding arrangement between the Australian Wool Innovation Limited and Land and Water Australia. Additional investors include Meat and Livestock Australia, and the CRC for Plant-based Management of Dryland Salinity. The authors also thank Dr David Merritt and Dr Shane Turner for assistance and discussions pertaining to seed dormancy release.
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