Effect of Zinc on Translocation of Iron in Soybean Plants

Abstract

shading to favor stem elongation. Seven-day-old plants, with stems 10 to 15 cm long, were grouped in two 15-plant bundles per 10-liter Pyrex jar. The nutrient solution volume, unless specified otherwise, was 8 liters. Mild iron deficiency symptoms appeared in the new growth of the plants on the 17th day. Plants were used ("harvested") on the 18th day of growth.For stem exudate collection, roots were washed briefly with deionized water, and the bundled plant groups were placed individually in 1-liter beakers of aerated nutrient solution. Plant tops were decapitated 10 cm above the roots, and the ends of the cut stems were placed in half-inch Tygon tubing which extended into a calibrated tube in an ice bath. Exudate was collected over a 20-hr period in the dark at 24 C.Cation Isotopes and Assays. In certain experiments, 59Fe (7.3 c/g Fe) or 65Zn (3.94 c/g Zn) was used in nutrient solutions at 10 juc/l as 59FeEDDHA and 65Zn(NO3)2, respectively. Radioassay of 65Zn, in nutrient solution, was made in a gamma scintillation spectrometer. In stem exudate, total iron and zinc were determined spectrophotometrically by the o-phenanthroline method (11), and by atomic absorption analysis, respectively.Expressed root sap was obtained from 10 g of previously frozen roots. A Carver press was used at 844 kg/cm2 pressure to express the sap.Experiments. Preliminary experiments were done with various concentrations of zinc to determine its effect upon the translocation of iron. From these studies, 5 ,UM Zn was selected to be used in these studies.1. Uptake of Zinc with Time. Five micromoles of 65Zn (10 ,uc/l) were added to the nutrient solution 96 hr before plants were 18 days old. At selected times, 1-ml volumes of the 1-liter nutrient solution were analyzed for 65Zn and returned to the solution. Effect of Pretreatment with

Impacts of silicon nutrition on growth and nutrient status of rice plants grown under varying zinc regimes

“…The iron uptake in rice competes with Zn uptake as it is carried out by similar metal transporters (ZIP transporters) (Masuda et al 2012). Declined iron concentration in stem exudates by increasing zinc in the nutrient solution have also been reported previously (Ambler et al 1970). Wang et al (2009) have reported that excess Zn leads to reduction of iron content in both root and shoot.…”

Toxicity and Tolerance in the Responses of Plants to Metals

“…In leaves, zinc toxicity characteristically gives rise to chlorosis (AGARWALA et al 1977;CHAPMAN et al 1939), which in species such as soybean may arise from Zn inhibition of translocation of Fe from root to shoot (AMBLER et al 1970). Zn toxicity in Zea mays also causes chlorosis of the leaves which can be alleviated by increased supply of Fe; in this case, however, the Zn-induced chlorosis is not correlated with a decreased transport of Fe to the leaves (ROSEN et al 1977).…”

Zinc, Iron, and Chlorophyll Metabolism in Zinc-toxic Corn

“…Hydroponic studies using several species, including soybeans (1, 13) and navy beans (17), suggested that high nutrient Zn did interfere with Fe uptake and/ or translocation, resulting in manifestations of Fe deficiency. The addition of Fe to the growth medium of soybeans could overcome the effects of high nutrient Zn, suggesting a competition between Zn and Fe at some site (1).…”