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This article in AJ

  1. Vol. 83 No. 2, p. 270-274
    Received: Mar 5, 1990

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Apical Development of Spring Barley in Relation to Chlormequat and Ethephon

  1. B. L. Ma and
  2. D. L. Smith 
  1. Dep. of Plant Science, Macdonald College of McGill University, 21 111 Lakeshore Road, Ste. Anne de Bellevue, PQ., Canada, H9X 1CO



There is considerable interest in the use of plant growth regulators (PGR) to control lodging in spring barley (Hordeum vulgare L.), and to increase the number of spike-bearing tillers through early application. Application of PGR is likely to have effects on the development of reproductive structures in both main-stem and tiller apices. The objective of this study was to investigate the timing and dynamics of barley main-stem apical development as influenced by chlormequat chloride (2-chloroethyl trimethylammonium chloride; CCC) or ethephon (2-chloroethyl phosphonic acid) treatment. A 3-yr field study using widely grown cultivars, ‘Leger’ and ‘Cadette’, was conducted on Bearbrook clay soil (fine, mixed nonacid, mesic Humaquept) at Emile A. Lods Agronomy Research Centre, McGill University, Canada, from 1987 to 1989. Treatments consisted of application with CCC and ethephon at Zadoks growth stages (ZGS) 13, 30, and 39. Data were collected on growth regulator induced plant changes in (i) external morphological characters, (ii) apical development, and (iii) spikelet primordium abortions. Application of CCC at ZGS 13 retarded development of the main-stem apex from shortly after application to awn elongation and reduced the number of aborted spikelet primordia. Unlike CCC, the retarding effect of ethephon on main-stem apical development was not shown until a few days after its application (when the maximum number of main-stem primorida was reached), which may have promoted tiller survival. In general, the application of PGR reduced the apical dominance of dominant sinks (main-stem apex and/or central spikelets of the rachis) allowing the survival and greater development of more subordinate sinks (tillers and/or distal rachis spikelets).

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