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DIVISION S-4-SOIL FERTILITY & PLANT NUTRITION

HEDTA–Nitrilotriacetic Acid Chelator-Buffered Nutrient Solution for Zinc Deficiency Evaluation in Rice

^a Texas A&M Univ. Research & Extension Center, Route 3, Box 213AA, Lubbock, TX 79403
^b Dep. of Soil, Water, & Climate, Univ. of Minnesota, 439 Borlaug Hall, 1991 Upper Buford Circle, St. Paul, MN 55108-6028

Corresponding author (c-trostle{at}tamu.edu)

Chelator-buffering methods with N-(2-hydroxyethyl)ethylenedinitrilotriacetic acid (HEDTA) are used to elucidate Poaceae growth response to micronutrient metal activities including (Zn²⁺), but reliable hydroponic methods that maintain stable (Zn²⁺) for evaluating Zn deficiency in rice (Oryza sativa L.) have not been reported. The objective was to develop a chelator-buffered method that gauges rice growth response to (Zn²⁺) in an otherwise chemically stable environment. Using GEOCHEM-PC to estimate solution activities, an aerobic HEDTA–nitrilotriacetic acid (NTA) dual-chelator method was developed that imposed five (Zn²⁺) levels on cv. IR-36 seedlings for 21 d after transplanting (DAT) in a growth chamber. Control of pH 5.50 ± 0.05 using 3.0 mM 2-(4-morpholino)-ethanesulfonic acid (MES) combined with periodic adjustment was critical to preserving target (Zn²⁺). Solution treatments ranged from Zn deficient, where (Zn²⁺) = 10^-10.0 M (0.25 µM total chelated Zn), to fully Zn sufficient where (Zn²⁺) = 10^-8.8 M (4.00 µM total chelated Zn). Using 200.0 µM total chelated Fe(III), adequate Fe was maintained at (Fe³⁺) = 10^-14.3 M. Phosphorous supply was controlled to prevent toxic P accumulation at low (Zn²⁺). With increasing (Zn²⁺), total biomass at 21 d ranged from 0.94 to 1.90 g plant^-1. Shoot Zn responded to (Zn²⁺), not total chelated Zn²⁺, and roots responded similarly. Critical (Zn²⁺) for normal growth was 10^-9.1 M, and leaf Zn-deficiency symptoms were observed at (Zn²⁺) 10^-9.4 M (28 mg Zn kg^-1 shoot). The HEDTA-NTA method provides a rapid and reliable means for evaluating Zn deficiency tolerance in IR-36 via diagnostic visual and physical symptoms in response to a range of (Zn²⁺) levels.

Abbreviations: DAT, days after transplanting • HEDTA, N-(2-hydroxyethyl)ethylenedinitrilotriacetic acid • ICP-AES, inductively coupled plasma atomic emission spectroscopy • MES, 2-(4-morpholino)-ethanesulfonic acid • NTA, nitrilotriacetic acid