AOBPreview originally published online on February 7, 2006
Annals of Botany 2006 97(4):649-658; doi:10.1093/aob/mcl020
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Cessation of Tillering in Spring Wheat in Relation to Light Interception and Red : Far-red Ratio
1 Crop and Weed Ecology, Plant Sciences Group, Wageningen University, Haarweg 333, 6709 RZ Wageningen, The Netherlands and 2 UMR Environnement et Grandes Cultures, Institut National de la Recherche Agronomique, 78850 Thiverval-Grignon, France
* For correspondence. E-mail: jochem.evers{at}wur.nl
Received: 17 October 2005 Returned for revision: 10 November 2005 Accepted: 22 December 2005 Published electronically: 7 February 2006
• Background and Aims The production of axillary shoots (tillering) in spring wheat (Triticum aestivum) depends on intraspecific competition. The mechanisms that underlie this competition are complex, but light within the wheat canopy plays a key role. The main objectives of this paper are to analyse the effects of plant population density and shade on tillering dynamics of spring wheat, to assess the canopy conditions quantitatively at the time of tillering cessation, and to analyse the relationship between the tiller bud and the leaf on the same phytomer.
• Methods Spring wheat plants were grown at three plant population densities and under two light regimes (25 % and 100 % light). Tiller appearance, fraction of the light intercepted, and red : far-red ratio at soil level were recorded. On six sampling dates the growth status of axillary buds was analysed.
• Key Results Tillering ceased earlier at high population densities and ceased earlier in the shade than in full sunlight. At cessation of tillering, both the fraction of light intercepted and the red : far-red ratio at soil level were similar in all treatments. Leaves on the same phytomer of buds that grew out showed more leaf mass per unit area than those on the same phytomer of buds that remained dormant.
• Conclusions Tillering ceases at specific light conditions within the wheat canopy, independent of population density, and to a lesser extent independent of light intensity. It is suggested that cessation of tillering is induced when the fraction of PAR intercepted by the canopy exceeds a specific threshold (0·40–0·45) and red : far-red ratio drops below 0·35–0·40.
Key words: Triticum aestivum, wheat, tiller, bud, plant population density, shade, PAR, red : far-red ratio, functional–structural model
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