Morphological Analysis of Leaf and Tiller Number Dynamics of Wheat (Triticum aestivumL.): Responses to Temperature and Light Intensity

In recent literature on Gramineae species, leaf and tiller numberdynamics have been studied by analysing site filling and thephyllochron of the mainstem. However, site filling is influencedby three components: (1) the phyllochron of the mainstem anddaughter tillers; (2) specific site usage (i.e. fraction ofbuds that ultimately develop into a visible tiller at a specificsite); and (3) HS-delay (i.e. difference in Haun Stage (HS)between the parent tiller and daughter tiller above the pointwhere the daughter tiller appears). These three morphologicalcomponents affecting site filling were studied under differentenvironmental conditions in a growth chamber experiment withspring and winter wheat (Triticum aestivumL.). Treatments weretemperature (daily average 10.5, 15.5 or 20.5 °C) and lightintensity (111, 191 or 286 µmol m^-2s^-1). Effects of temperatureand light intensity on phyllochron were well described by equationsalready reported in the literature. Specific site usage washigher at cooler temperatures and greater light intensitiesand was related to tiller position. It is proposed that theseeffects on specific site usage reflect differences in availabilityof local assimilate for tiller appearance. HS-delay of a tillerwas shorter if the expected tiller appearance was later andwas only slightly affected by light intensity or temperature.This new concept, combining HS-delay and specific site usage,can be useful in constructing more general models of the effectsof environmental factors on the dynamics of leaf number andleaf area ofGramineaespecies.Copyright 1998 Annals of BotanyCompany Triticum aestivum; wheat; phyllochron; temperature; light intensity; leaf number; tillering; site filling; site usage.