Effect of phosphorus on growth and iron nutrition of millet and sorghum

Abstract

At the end of twenty-four days, two plants from each treatment were supplied with 0.31 ~tci/ml of radioactive iron (5~Fe) (with the same P levels used to grow them) and then allowed to absorb the 55Fe for 3 hours after which they were harvested, separated into roots and shoots.The two components were wet-ashed separately, and assayed for 5SFe. The rest of the plants in Hoagland solution were also harvested, separately into roots and shoots. The components parts were also wet-ashed separately and assayed for iron (Fe), manganese (Mn), zinc (Zn), copper (Cu) and phosphorous (P).High P concentration in the growth medium inhibited ~ 5 Fe absorption and translocation in both millet and sorghum but millet was more tolerant of P-induced Fe deficiency than sorghum.Millet and sorghum grew best at 1.0 and 0.1 mM P, respectively. Fe concentrations in plant declined as P levels increased; while Mn increased in both millet and sorghum with increasing P levels. Millet, however, maintained higher concentrations of Fe and Mn.The distribution patter of 5SFe, regardless of P levels could be summarized as follows: Roots > Vascular tissue > leaf-sheaths > leaf blade. Less 55Fe was absorbed and translocated to shoots at 2.5 mM P, in millet and sorghum.

Variability in pearl millet (Pennisetum americanum) fields in semiarid West Africa

“…Phosphorus deficiencies are indicated at all soil sites when compared with P concentrations reported by Ajakaiye (1979). Phosphorus availability can be depressed in low pH soils by the formation of Al phosphate compounds (Birch 1951).…”

“…Gregory (1979) showed that N concentrations in millet fell rapidly from 60 g kg" 1 at emergence to less than 20 g kg" 1 at flowering. Ajakaiye (1979) found that maximum millet growth 24 days after planting in Hoagland's solution was achieved when millet P concentrations were between 4.9 and 5.7 g kg" 1 . Critical nutrient concentrations vary depending on the growth stage of the plant.…”

The maize shoot ionome: Its interaction partners, predictive power, and genetic determinants

“…This link between P and Fe is in accordance with earlier studies. DeKock, Hall, and Inkson (1979) and Zheng et al (2009) have shown that elevated P supplies decrease the availability and mobility of Fe in soils as well as in plants and therewith provoke Fe deficiency-induced chlorosis (Ajakaiye, 1979).…”

Variable sorghum growth in acid soils of subhumid West Africa

“…Ajakaiye (1979) reported that sorghum grew best when the P concentration in its shoot (about 24 days after planting) was within the range of 2.2-8.1 g kg-I. The Phosphorus concentration was less than 2 g kg I in the shoot of plants grown without P application.…”

“…Walker et al (1975) found sorghum more sensitive than millet to excesses of Al and Mn in plant tissues. In addition, millet seems to require less P than sorghum (Ajakaiye, 1979;Fox et aI., 1974). Millet also seems to be more tolerant than sorghum to low soil pH (Walker et aI., 1975).…”