Studies on Fe deficiency stress response in three cultivars of sunflower (helianthus annuus L.)

Iron deficiency stress was induced in cultivars, PKV‐7237, Morden and EC‐68414 of sunflower (Helianthus annuus L) by first growing them in full nutrient medium and transferring to minus Fe medium after a month. The minus Fe nutrient medium was changed again at 13 and 26 days. The change in pH and the degree of chlorosis were recorded. It was found that the pH decreased rapidly in all cultivers from 6.4 to 3.8 in 5 days. The cv. Morden was found more tolerant to the stress than others. Furthermore, the flavinlike pigments as shown by the yellow coloration of the medium were more intense in PKV than in Korden, and were very much less in EC. It was also noted that the pH reduction was non‐redumptive, a feature observed even after transferring twice to fresh minus Fe medium adjusted to pH 6.4. The results of the experiments showed that as long as Fe absorbed from the pre‐stress medium was available in the root, the chlorosis was not severe; but once it was nearly depleted, chlorosis appeared and persisted for a long time.