In vitro sterile hydroponic culture system to study iron chlorosis¹

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Abstract

A sterile hydroponic culture system (SHCS) suitable for studying iron (Fe) chlorosis in vitro was developed. This system, consisting of a 38 × 200 mm culture tube, a Kap‐ut closure, a foam platform, and an aluminum sleeve, resembled a greenhouse hydroponic system. In this SHCS, the plants were positioned upright within the culture tube using the foam plug platform; the roots are submerged in liquid Murashige and Skoog basal medium (basal medium) containing 3 % sucrose. Onion plants (Allium sativum L. cv. ‘Sweet Spanish, Yellow Utah Jumbo'), grown in the SHCS on basal medium without FeEDTA exhibited gradual chlorosis, i.e. leaf yellowing, with leaf SPAD values of 34.9 ± 1.9 at the end of 8 wks. Non‐chlorotic plants grown in the SHCS on basal medium with 80 μM. FeEDTA had leaf SPAD values of 51.3 ± 2.3. Gradual regreening of leaves was achieved when chlorotic plants were recultured into basal medium with FeEDTA. The occurrence of Fe‐deficiency responses in the roots of the chlorotic plants grown in the SHCS was tested. The staining patterns that resulted from the reduction of MTT (3‐[4,5‐dimethylthiazol‐2‐yl]‐2,5‐diphenyltetrazolium bromide) by the roots of plants grown on sterile basal medium resembled the staining patterns found in seedlings grown in the greenhouse under non‐sterile hydroponic conditions. A procedure to quantify the reduction of MTT by roots is presented. The stimulation of root surface electron transfer, a typical Strategy I response to Fe‐deficiency, is further shown by the rapid FeHEDTA reduction by the roots of the chlorotic, sterile‐grown onion plants.

Notes

Mention of a trademark or proprietary product is for identification only and does not imply a guarantee or warranty of the product by the U.S. Department of Agriculture. All programs and services of the U.S. Department of Agriculture are offered on a nondiscriminatory basis without regard to race, color, national origin, religion, sex, age, marital status, or handicap.