Regulation of Fe‐stress response in some crop varieties: Anomaly op a mechanism for recovery through non‐redumptive pH reduction

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Abstract
The cultivars of some crop varieties were examined for Fe‐stress tolerance by growing them in complete nutrient solutions and then transferring to one without Fe. The response to stress was rated from the onset of and recovery from chlorosis. The pH change was recorded. Several cultivars of four crop plants, viz., Cajanus indicus Spreng., Cicer arletlnum L., Corchorus capsularis L., C. olitorius L., and Oryza sativa L. In the case of pigeon‐pea, the varieties TT‐9 and TT‐11 were found to be Fe‐stress tolerant. Experiments with another set of four pigeon‐pea varieties showed that the chlorosis was severe and did not recover at all. These varieties did not show any difference whether grown in Hoagland's or Steinberg's solutions. In the case of chickpea, two varieties, BD‐9–3 and Chaffa showed remarkable Fe‐stress tolerance by reducing the pH of the medium to as low as 3.5. When the varieties of jute were subjected to Pe‐stress, JRC‐212 exhibited a very unique capacity to reduce the pH very rapidly from the next day, and remained green throughout. There was no Fe‐stress response in the case of rice even though the variety Basmati showed tolerance under upland nursery conditions. The studies with diverse crop species revealed that there are more than one mechanisms by which the plants could regulate Fe uptake. Pigeon‐pea tolerant varieties withstand stress probably by redistributing the internal Fe. The jute variety JRC‐212 regulated by reducing the pH immediately, even without developing chlorosis. On the other hand, the varieties JRO‐832 and JRO‐7835 developed chlorosis, followed by pH reduction and chlorosis recovery. This mechanism was similar to that in sorghum, although less efficient. The chick‐pea varieties showed mild chlorosis but recovered by lowering the pH. One contrast between the tolerant jute and chick‐pea, as against sorghum is that the pH was kept low throughout, even after recovery from chlorosis, if occurred.