DIFFERENTIAL TRANSLOCATION OF 59IRON IN IRON SUFFICIENT AND DEFICIENT SORGHUM PLANTS

Radioactively labeled iron (Fe-59) was used to study differential uptake in sorghum plants in the recovery stage of chlorosis. Radio-labeled 59Fe was supplied through root feeding in nutrient solution experiment (48 hrs, pH 6.2) to non-chlorotic and chlorotic plants. Chlorotic plants were further treated with foliar spray [ferrous sulfate (FeSO4), FeSO4 + thiourea (TU), FeSO4 + citric acid (CA), FeSO4 + thioglycollic acid (TGA)] to study the uptake of radio-labeled Fe-59 through root feeding timing recovery process of chlorosis. Under iron deficiency, the differential uptake of Fe-59 was markedly increased in leaves and stem of chlorotic control (-Fe) sorghum plants as compared to non-chlorotic control (+Fe) and foliar sprayed (FeSO4, FeSO4 + TU, FeSO4 + CA, and FeSO4 + TGA) plants. The lowest uptake of Fe-59 was observed in younger leaves (24.33 nmol, g(-1) fresh weight) h(-1)) and stem (1.98 nmol, g(-1) fresh weight h(-1)) of non-chlorotic control followed by foliar sprayed plants in comparison to chlorotic control, respectively. Similarly less 59Fe uptake was observed in the older leaves of FeSO4 + CA sprayed (21.70 nmol, g(-1) fresh weight h(-1)) plants in comparison to chlorotic control (35.60 nmol, g(-1) fresh weight h(-1)). The highest differential Fe-59 uptake through nutrient medium was in the roots of plants, which were foliar sprayed with FeSO4 along with TU. The role of iron alone and along with citric acid and thiol compounds is discussed in recovery of chlorosis.