The aim of this study was to identify the cellular and physiological mechanism(s) for the action of the <i>Rht3</i> (dwarfing) allele in near-isogenic lines of wheat (<i>Triticum aestivum</i> L. <i>cv</i> Maris Huntsman). The <i>Rht3</i> allele did not affect the rate of initiation, or total number, of new leaf primordia and therefore stem internodes, formed by the shoot apex. The first observable effect of the <i>Rht3</i> allele was to reduce stem internode lengths, compared to those in the <i>rht3</i> wild-type, beginning <i>ca</i> 15 d after sowing. The second leaf (L2) was chosen as the model system in which to investigate the cellular basis for the effects of the <i>Rht3</i> allele. The <i>Rht3</i> allele did not reduce the maximum relative elemental growth rate (REGR) in L2 grown at 20<SUP>o</SUP>C compared to the <i>rht3</i> wild-type or the distance from the leaf base at which this was achieved. However, distal to the position of maximum REGR within the L2 extension zone the <i>Rht3</i> allele significantly reduced both the REGR and the rate of cell extension compared to the <i>rht3</i> wild-type. At 20<SUP>o</SUP>C, the <i>Rht3</i> allele reduced the length of the L2 extension zone from <i>ca</i> 20 mm to <i>ca</i> 13mm. The <i>Rht3</i> allele reduced both the rate of cell extension and final epidermal cell length, but did not cause any significant reduction in total cell number. In the <i>rht3</i> wild-type the length of the extension zone could be modified by the application of growth regulators, GA<SUB>3</SUB>, 2<i>S</i>, 3<i>S</i> paclobutrazol and/or growth at 10<SUP>o</SUP>C. However, the <i>Rht3</i> mutant allele could be mimicked in the <i>rht3</i> wild-typeby the application of 2<i>S</i>, 3<i>S</i> paclobutrazol and/or growth at 10<SUP>o</SUP>C.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:662994 |
| Date | January 1992 |
| Creators | Tonkinson, Claire L. |
| Publisher | University of Edinburgh |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Source | http://hdl.handle.net/1842/14552 |
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