Growth Suppression of Canola through Wheat Stubble II. Investigating Impacts of Hypocotyl Elongation using Simulated Stubble |
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Authors: | S E Bruce M H Ryan S Hely J A Kirkegaard J Pratley |
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Institution: | (1) CSIRO Plant Industry, PO Box 1600, 2601 Canberra, ACT, Australia;(2) CSIRO Sustainable Ecosystems, PO Box 284, 2601 Canberra, ACT, Australia;(3) School of Plant Biology MO8, The University of Western Australia, 6009 Crawley, WA, Australia;(4) Charles Sturt University, 2678 Wagga Wagga, NSW, Australia |
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Abstract: | In south-eastern Australia, surface-retained wheat stubble can reduce the growth and yield of canola as a result of reductions
to the quality and quantity of light under the stubble and the associated elongation of the hypocotyl. This paper reports
a series of pot experiments that examined the effect of hypocotyl elongation on the leaf area development of canola, the allocation
of dry mass, and the absolute and relative growth rates compared to non-etiolated seedlings. The primary aim was to determine
the magnitude of the growth reductions caused by hypocotyl elongation in canola seedlings under controlled conditions. Seedling
hypocotyl elongation was induced by growing canola seedlings in narrow poly-pipe tubing of different lengths placed over the
seedlings as they began to emerge through the soil, and removing the shade cloth covering the top of the tube when the cotyledons
had reached it, to mimic the plant reaching and overtopping a stubble layer. Plants with longer hypocotyls had smaller root
systems, less leaf area and less leaf and root biomass. These plants had lower relative growth rates than plants that allocated
fewer resources to hypocotyls and more to roots and leaves. The magnitude of the growth responses observed in these experiments
was similar to those of plants with long hypocotyls growing through stubble layers in previously reported field studies. This
suggests that a significant portion of the effect of stubble observed in the field under stubble retention is due to the re-allocation
of resources to the production and growth of the hypocotyls, rather than other biochemical effects of the stubble. |
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Keywords: | allelopathy establishment etiolation hypocotyl phytotoxicity stubble retention |
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