Al toxicity effects on radiation interception and radiation use efficiency of Al-tolerant and Al-sensitive wheat cultivars under field conditions

Soil acidity and Al toxicity are highly extended in agricultural lands of Chile, especially where wheat is widely sown. To evaluate quantitatively the response of wheat biomass and its physiological determinants (intercepted radiation and radiation use efficiency) to Al toxicity, two field experiments were conducted in an Andisol in Valdivia (39 degrees 47'S, 73 degrees 14'W), Chile, during the 2005-2006 and 20062007 growing seasons. Treatments consisted of a factorial arrangement of: (i) two spring wheat cultivars with different sensitivity to Al toxicity (the sensitive cultivar: Domo.INIA and the tolerant cultivar: Dalcahue.INIA) and (ii) five exchangeable Al levels (from 0 to 2.7 cmol((+)) kg(-1)) with three replicates. Crop phenology and intercepted radiation (IR) were registered during the entire crop cycle, while 10 samples of above-ground biomass were taken at different stages between double ridge and maturity. Both biomass and leaf area index (LAI) were recorded in these 10 stages. Radiation use efficiency (RUE) was Calculated as the slope of the relationship between accumulated above-ground biomass and accumulated photosynthetically active radiation intercepted by the canopy (IPARa). Crop phenology was little affected by soil A] treatments. showing only up to 17 days delay in the M-sensitive cultivar under extreme Al treatments. Above-ground biomass at harvest was closely associated (R-2 = 0.92) with the crop growth rate but no relationship (R-2 = 0.14) was found between the crop cycle length. IPARa explained almost completely (R-2 = 0.93) the above-ground biomass reached by the crop at harvest under the wide range of soil Al concentrations explored in both experiments. Oil the other hand, a weaker relationship was found between above-ground biomass and RUE. The effect of soil Al concentration on IPARa was mainly explained by LAI as a single relationship (R-2 = 0.93) between IR (%) and LAI at maximum radiation interception showing a common light attenuation coefficient (k = 0.33). (C) 2009 Published by Elsevier B.V.