Evaluating rootzone stresses and the role of the root system on rose crop productivity and fertilizer-water use efficiency: Tissue nutrient contents, whole plant biomass and quality
In the last report we commented on the highest EC readings (avg. EC of 8.1 dS/m) observed in the leachates collected from one-half root sections receiving the supplemental urea applications, values even higher than those exposed to the NaCl stress (avg. leachate EC of 7.0 dS/m). We proceeded to analyze the collected leachates for total carbon (C) and nitrogen (N) concentrations (Fig. 1). Regarding leachate C, the root halves exposed to the high pH solutions had significantly higher concentrations (Fig. 1A) compared to the rest of the treatments, albeit those root halves receiving the NaCl stress were second in carbon concentrations. The supplemental bicarbonate (HCO3-) salts used in the high pH (alkalinity) treatment was likely the main contributor to the high leachate C in this treatment, but a high root carbon exudation activity was also probable in the root sections subjected to high pH and salt stress. The literature indicates that under high pH conditions, dicotyledonous plants like roses release C-containing compounds (like carboxylates and phenolics) to acidify the areas next to the roots as a strategy to enhance the solubility and uptake of micronutrients like iron (Marschner, 1995). The osmotic and nutrient imbalance effects of NaCl stress could have also led to the production of carbon compounds that were exuded or leaked into the soil solution (Henry et al. 2002).
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Keywords: ICFG Hill Final Report 2010-2011