Author
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Jaradat, Abdullah |
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Riedell, Walter |
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Submitted to: Journal of Plant Nutrition
Publication Type: Peer Reviewed Journal Publication Acceptance Date: 7/25/2009 Publication Date: 6/25/2010 Citation: Jaradat, A.A., Riedell, W.E. 2010. Nutrient Densities, Carbon:Nitrogen Ratios, and Midday Differential Canopy Temperature Impact Grain Yield of Stressed Oat. Journal of Plant Nutrition. 33(10):1531-1554. Interpretive Summary: We quantified the impact of biotic stresses caused by aphid feeding or by aphid-vectored disease (barley yellow dwarf virus) during two years of contrasting rainfall and temperature regimes on grain yield (Mg ha**-1) and its components (kernels m**-1 and kernel weight) of oat. Simple measurements at the boot stage of plant architecture (i.e., leaf area per plant, leaf area index, number of leaves and number of tillers per plant) and midday differential canopy temperature (dT) were indicative of how plants reacted to biotic stresses. Plant architecture changes caused by these stresses impacted dT, which in turn, negatively impacted grain yield and its components. Additionally, stressed plants capable of maintaining larger C:N ratios in groats produced larger grain yields and larger number of kernels m**-1. These indirect relationships among plant architecture components, dT, and C:N ratios illustrate the complex interactions of biotic and abiotic stresses and their impact on grain yield and its components in oat. This information is of value to crop physiologists in designing experiments to decipher the impact of biotic and abiotic components of climate change on potential crop yield. Technical Abstract: Plant architecture components (i.e., leaf area per plant, leaf area index, number of leaves and number of tillers per plant), midday differential canopy temperature, nutrient densities and C:N ratio were assessed in oat (Avena sativa L.) plants subjected to biotic stresses caused by aphid feeding or by aphid-vectored disease (barley yellow dwarf virus) during two years of contrasting rainfall and temperature regimes. Biotic stress caused by aphid-vectored disease resulted in more yield reduction than that caused by aphid feeding. Large portions of variation in nutrient densities (R**2 range 51-89%) and C:N ratio (R**2=96%) of leaves at the boot stage and of kernels and groats were impacted by the 2- and 3-way interactions of these plant tissues with the biotic stress treatments and years. Plant architecture components were negatively (p<0.05) correlated with and accounted for 62-98% of variation in midday differential canopy temperature (dT) in plants subjected to biotic stresses, the impact of which was negative (p<0.01) on kernel weight (R**2 range 19-96%), kernels m**-1 (R**2 range 29-85%) and grain yield (R**2 range 25-65%). On average, a reduction of 83.3 kernels m**-1, 1.73 mg kernel**-1 and 0.34 Mg ha**-1 grain yield can be attributed to an increase of 1 deg C dT. A positive (p<0.05) relationship between C:N ratio and total nutrients, with (r=0.75), or without (r=0.63) N was disrupted by biotic stresses. C:N ratios (14.5:1 vs. 19.1:1), but not nutrient densities (11.92 vs. 12.76 µg g**-1) were always smaller (p<0.05) in groats than in kernels, and during the stress (16.3:1 and 12.4 µg g**-1) than the no-stress (18.3:1, and 12.28 µg g**-1) year. C:N ratios in groats were better predictors of grain yield (R**2=53%) and kernels m**-1 (R**2=68%) than C:N ratios in kernels (R**2=32 and 51%, respectively), but not of kernel weight (R**2=22 and 19%, respectively). Plants that maintained larger C:N ratios in groats produced larger yield (223 kernels m**-1 and 1.11 Mg ha**-1 grain yield C:N**-1 ratio). These indirect relationships among plant architecture components, dT, nutrient densities and C:N ratios illustrate the complex interactions of biotic and abiotic stresses and their impact on grain yield and its components in oat. |
