Copper‐deficiency‐induced phytosiderophore release in in the calcicole grass Hordelymus europaeus

Abstract

Phytosiderophore (PS) release occurs under both iron and zinc deficiencies in representative Poaceae and has been speculated to be a general adaptive response to enhance the acquisition of micronutrient metals. We tested this hypothesis within an on-going study of the role of micronutrient metal nutrition for patterns of spontaneous vegetation in relation to soil pH and carbonate content. Hordelymus europaeus (L.) Harz, a negative grass species commonly found on soils rich in CaCO $ in Western Central Europe, was subjected to deficiencies of Fe, Zn, Mn and Cu using chelator-buffered nutrient solutions. PS release rates were determined at 3-5 d intervals during onset and development of deficiency symptoms. Plant dry matter yields and nutrient concentrations, measured at three time points were used to construct growth curves for calculation of PS release per unit root mass. In comparison with trace metal-sufficient control plants, dry matter production was markedly reduced in the Fe, Zn, Mn and Cudeficiency treatments, with final relative yields of 6, 11, 15 and 31 %, respectively. The phytosiderophore produced under Fe-and Cu-deficiency treatments was identified, using HPLC, as desoxymugineic acid. The highest rate of PS release (18 µmol g −" root d. wt in 2 h) was measured in the Fe-deficiency treatment, and there was substantial release in the Cu-deficiency treatment (7n25 µmol g −" root d. wt in 2 h). No PS release above control levels (2n6 µmol g −" root d. wt in 2 h) was observed in the Zn-or Mn-deficiency treatments (1n5 and 2n6 µmol g −" root d. wt in 2 h, respectively). It remains to be clarified whether PS release in response to Cu deficiency is a primary reaction to the deficiency, or is caused by a chain of events similar to that observed in Zndeficient wheat, which involves internal Fe deficiency. Our results suggest that PS release in the native plant species H. europaeus is a specific response to Fe and Cu deficiency and is not significantly induced in response to deficiencies of Zn and Mn. Induction of the PS mechanism in different plant species might be more diverse than previously thought.

Zinc deficiency-induced phytosiderophore release by the Triticaceae is not consistently expressed in solution culture

“…Uptake of the PS-Zn complex by maize (Zea mays L.) has been observed (von Wire n et al 1996). Gries et al (1998) observed Cu-de®ciency-induced PS release from the grass Hordelymus europaeus (L.) Harz. Increased exudation of PS by Zn-de®cient wheat (Triticum aestivum L. cv.…”

Metal micronutrients in xylem sap of iron-deficient barley as affected by plant-borne, microbial, and synthetic metal chelators

“…In contrast, the Strategy II mechanism involves the 1) synthesis of phytosiderophore (PS) in apical root zones (Romheld and Marschner 1986); 2) release of PS from the root apex (Marschner et al 1987); 3) solubilization of sparingly soluble Fe3+ by chelation with PS (Takagi et al 1984;Romheld and Marschner 1986); and 4) uptake of the PS-Fe3+ complex by roots (Takagi et al 1984;Marschner et al 1987). Furthermore, the release of PS has also been shown to be induced by Cu deficiency in calcicole grass (Gries et al 1998), Zn deficiency in wheat (Zhang et al 1991a), and Mn toxicity in barley (Alam et al 2000).…”

Iron and phosphate uptake explains the calcifuge–calcicole behavior of the terricolous lichens Cladonia furcata subsp. furcata and C. rangiformis

“…Whether the limited availability of essential transition metals other than Fe, including Cu, Mn and Zn (Gries et al 1998), plays an Fig. 1 Total P concentrations of Cladonia furcata or C. rangiformis exposed for 1 h min to a deionized water or b KH 2 PO 4 (a=2 mM) at pH 3 or 8.…”

“…Calcifuge vascular plants are excluded from calcareous soils by their lacking ability to fulfill either their Fe or P requirements at high pH (Gries and Runge 1995;Tyler 1996;Zohlen and Tyler 2000). The availability of other transition metals, which are essential micronutrients (including Cu, Mn, Zn), can also be limiting (Gries et al 1998). Calcicole plants can, in turn, suffer from high concentrations of transition metals or Al at acidic sites (Tyler 1993).…”