Submitted to: Plant Physiology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/29/2005
Publication Date: 2/15/2006
Citation: Bai, C., Reilly, C.C., Wood, B.W. 2006. Nickel deficiency disrupts metabolism of ureides, amino acids, and organic acids of young pecan [carya illinoinensis (wangenh.) k. koch] foliage. Plant Physiology. 140:433-443. Interpretive Summary: Unexplained nutritional-like disorders have eluded correction in many plant species, thus directly or indirectly limiting yields. Nickel deficiency has now been identified as being the causal factor of nutrient associated disruptions. Research on the influence of nickel deficiency on primary plant metabolism has found that nitrogen metabolism is a key aspect of plant physiology that is being adversely affected by nickel deficiency; however, there are also effects on organic acid metabolism. This information expands knowledge of the role of nickel in plant physiology and notes the importance of nickel in agricultural systems.
Technical Abstract: The existence of nickel (Ni) deficiency is becoming increasingly apparent in crops, especially for ureide transporting woody perennials, yet its physiological role is poorly understood. We evaluated the concentrations of ureides, amino acids, and organic acids in photosynthetic foliar tissue from “Ni-sufficient” (Ni-S) vs. “Ni-deficient” (Ni-D) pecan [Carya illinoinensis (Wangenh.) K. Koch]. Foliage of Ni-D pecan seedlings exhibited metabolic disruption of nitrogen metabolism via ureide catabolism, amino acid metabolism, and ornithine cycle intermediates. Disruption of ureide catabolism in Ni-D foliage resulted in accumulation of xanthine, allantoic acid, ureidoglycolate, and citrulline; yet, total ureides, and urea concentration and urease activity were reduced. Disruption of amino acid metabolism in Ni-D foliage resulted in accumulation of Gly, Val, Ile, Tyr, Trp, Arg, and total free amino acids; and lower concentrations of His and Glu. Ni deficiency also disrupted the citric acid cycle, the second stage of respiration, where Ni-D foliage contained very low levels of associated organic acids compared to Ni-S foliage. This disruption indirectly affected spin-off products of glycolysis, the first stage of respiration. Disruption of carbon metabolism was also via accumulation of lactic and oxalic acids. The results indicate that “mouse-ear”, a key morphological symptom enabling field identification of Ni deficiency, is likely linked to the toxic accumulation of oxalic and lactic acids in the rapidly growing tips and margins of leaflets. Results also indicate that Ni deficiency disrupts chemical composition and several metabolic pathways, thus supporting the role of Ni as an essential plant nutrient element. The magnitude of metabolic disruption exhibited in Ni-D pecan is evidence of the existence of unidentified physiological roles for Ni in pecan and other ureide transporting woody perennials.