4.5 Article

Impact of defoliation severity on photosynthesis, carbon metabolism and transport gene expression in perennial ryegrass

Journal

FUNCTIONAL PLANT BIOLOGY
Volume 38, Issue 10, Pages 808-817

Publisher

CSIRO PUBLISHING
DOI: 10.1071/FP11048

Keywords

defoliation intensity; nitrogen; pasture; regrowth; water-soluble carbohydrates

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Funding

  1. DairyNZ Inc.
  2. Foundation for Research, Science and Technology
  3. T.R. Ellett Agricultural Research Trust
  4. University of Tasmania

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Defoliation severity affects grass regrowth. The changes to biological processes affecting regrowth induced by severe defoliation are not fully understood, nor have they been investigated at a molecular level in field-grown plants. Field-grown perennial ryegrass (Lolium perenne L.) plants were defoliated to 20, 40 or 60 mm during winter. Throughout regrowth, transcript profiles of 17 genes involved in photosynthesis and carbon metabolism or transport were characterised in stubble and lamina tissue. Although defoliation to 20 mm reduced residual lamina area and stubble water-soluble carbohydrate reserves compared with plants defoliated to 40 or 60 mm, net herbage regrowth was not reduced. Transcript profiles indicated a potential compensatory mechanism that may have facilitated regrowth. At the one-leaf regrowth stage, plants defoliated to 20 mm had greater abundance of photosynthesis-related gene transcripts (rca, rbcS1, rbcS2, fba, fbp and fnr) and 20% greater stubble total nitrogen than plants defoliated to 60 mm. A greater capacity for photosynthesis in outer leaf sheaths may be one potential mechanism used by severely defoliated plants to compensate for the reduced residual lamina area; however, this premise requires further investigation.

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