Iron Utilization by Efficient and Inefficient Sorghum Lines¹

Abstract

Iron‐efficient and Fe‐inefficient sorghum [Sorghum bicolor (L.) Moench.] inbred lines and their F1 hybrid differed in response to Fe deficiency. These lines were used in growth chamber studies with a soil and with several liquid‐nutrient media to determine Fe‐use efficiency. An Fe‐deficient Colby silt loam soil (5.2 ppm DTPA extractable Fe) with 22.4 kg Fe/ha and without added Fe was used for a potted‐soil, growth study. In the remaining studies seedlings were grown in Hoagland nutrient solution to induce Fe deficiency, to determine effects of P levels and Fe sources, and to measure root reduction potential. The respective solutions used were: (i) 0.2‐strength solution with no Fe; 2.0 μM Fe and 3.0 mg CaCO3/ liter; 2.0 μM Fe and 5.0 mM P; 2.0 M Fe and 2.5, 25.0, and 10.0 μM Cu, Mn, and Zn, respectively; (ii) 0.5‐strength solution with 10.0 μM Fe at O, 0.5, 1.0, 2.5, and 5.0 mM levels of P; (iii) 0.5‐strength solution with 10.0 μM ferric and ferrous Fe; (iv) 0.2‐strength solution containing 2.0 μM Fe with the last 24 hours' growth in a ferrichloride‐ferricyanide solution. Plants from all studies were separated to roots and shoots, wet‐ash digested, and assayed for Fe, Cu, Mn, Zn, Ca, and Mg by atomic absorption spectrophotometry. Phosphorus was determined by the vanadomolybdophosphoric method. The Fe‐efficient inbred usually maintained lower P concentrations in shoots and commonly in roots under Fedeficient conditions. Antagonism from other nutrients except P was not involved consistently in differential response of Fe‐efficient and Fe‐inefficient lines. Root reduction potential for ferrichloride‐ferricyanide was lower for sorghum than for other crops, but did not differ between inbred lines. Shoot and root growth was always greater with ferrous than with ferric Fe. Efficiency of Fe use by sorghum apparently was not inherited by the hybrid. Iron efficiency in sorghum probably can be improved by accumulating genes that increase uptake of Fe, or by decreasing interference of P in utilization of Fe.

Chlorosis of soybean [Glycine max(L.) Merr.] and its relation with the content of chlorophyll, phosphorus, phosphorus/iron and pH vegetative tissues

“…Recently, Uvalle (1983), reported that chlorotic plants had higher contents of nitrates, phosphorus and total iron and that indicated this was the cause of the precipitation of insoluble iron phosphate in soybean. Up to now, has been reported (Miller et al, 1960;Odurukme and Maynard, 1969;Mikesell et al, 1973;Brown and Jones, 1975) that the iron chlorosis is associated with the inbalance in the P/Fe relation.…”

Iron nutrition of sunflower(Helianthus annuusL.) as affected by various levels of p and ZN

“…Mikesell e_t al. (16) reported that when FeEDTA was added to the nutrient solution increasing the concentration of P from 0 to 5 mM significantly, increased the dry weight of Feefficient sorghum plants. Increased P and Fe levels in the nutrient solution, in most instances, had little or no effect on P content of sunflower shoots for both sources of iron.…”

Foliar Iron Spray Potentiates Growth of Seedlings on Iron-free Media

“…Fe deficiencies in seedlings can endanger survival by restricting root and shoot growth and by reducing the plant's ability to recover from water deficits (1,7,10, 15 for a further 4 days in the light on vermiculite irrigated with 0.1 strength Hoagland solution without micronutrients. The cotyledons were removed from 6-day-old plants, and batches of 10 plants were transferred on day 7 to trays containing 8 liters of aerated, full strength Hoagland solution.…”

“…Fe deficiencies in seedlings can endanger survival by restricting root and shoot growth and by reducing the plant's ability to recover from water deficits (1,7,10,15). It is clearly important that the roots of seedlings develop rapidly into a system capable of supplying additional Fe from the soil; paradoxically, Fe deficiencies of seedlings could restrict the development of the roots.…”