HEDTA–Nitrilotriacetic Acid Chelator-Buffered Nutrient Solution for Zinc Deficiency Evaluation in Rice
- Calvin L. Trostle *a,
- P.R. Bloomb and
- D.L. Allanb
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.Please view the pdf by using the Full Text (PDF) link under 'View' to the left.
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