Nickel in Plants

Abstract

The gross tissue distribution, intraceRular fate, and chemical behavior of Ni2+ in soybean plants (Glycine max cv. Williams) were investigated.Following root absorption, Ni was highly mobile in the plant, with leaves being the major sink in the shoots for Ni during vegetative growth. A senescence >70% of the Ni present in the shoot was remobilized to seeds. Fractionation of root and leaf tissues showed >90% of the Ni to be associated with the soluble fraction of tissues; ultrafiltration of the solubles showed >77% of the Ni to be associated with the 10,000 to 500 molecular weight components of both roots and leaves. Chemical characterization of the soluble components (10,000 to 500 and >500 molecular weight) by thin layer chromatography and electrophoresis resolved a number of Ni-containing organic complexes. Major Ni-containilng components formed in the root are transported in the xylem stream, and undergo partial modification on deposition in leaves. Nickel accumulated in seeds is primarily associated with the cotyledons. Chemical fractionation of cotyledon components showed 80% of the Ni to be associated with the soluble whey fraction, while 70% of this fraction was composed of Ni-containing components with molecular weight <10,000.Plants are known to accumulate Ni readily (9), and unlike most nonessential elements, Ni is mobile in plants and accumulated in seeds (9). The unusual behavior of Ni in plants may be a result of its behavior as an analog of Cu and Zn as shown in root transport studies (3). If Ni behaves as an analog (functional or nonfunctional) of essential nutrients in plants, the metabolic potential may exist to alter its chemical form and thereby alter its potential for uptake and toxicity to successive trophic levels. Studies on the toxicological aspects of Ni in animal systems (5, 6) suggest that organonickel compounds and complexes are more toxic than inorganic forms of Ni.Relatively few studies have been concemed with the form of metals in plant tissues. Investigations of the form of cations such as Fe, Cu, Zn, and Mn in leaf tissues of agronomic species (2,8) (14) has shown that Ni transported in the xylem fluid of crop plants was present as an anionic complex that had similar electrophoretic behavior in five species. In addition, Tiffm demonstrated that the form of Ni in exudate was dependent on metal concentration in xylem fluid. In tomato, a cationic Ni complex was found in the xylem in addition to the anionic form when physiological levels (<3 ,M) in the xylem were exceeded. This latter observation indicates a need for care in defining the fate and chemical form of metals in plants, since the plant-available concentration oftrace elements in the environment will generally be low.Although studies have dealt with specific aspects ofthe behavior of Ni in plants, none have fully described the fate of Ni following root absorption, vegetative growth, and senescence. The present study describes the over-all behavior of Ni2" in soybean plants by evaluating its gross distribution and fa...

Methods to Quantify Nickel in Soils and Plant Tissues

“…The less significant correlation for leaf in relation to grains levels can be related to the mobility of Ni in plant tissue. Findings of Cataldo et al (1978) confirm this assumption. They observed that 70 % of the Ni present in soybean leaves in the senescent state was remobilized from the leaf tissue to the grains.…”

Rhizobium leguminosarum hupE Encodes a Nickel Transporter Required for Hydrogenase Activity

“…In symbiosis, bacteroid nickel ions are obtained from the plant cytosol surrounding the bacteroids. In this environment, nickel is likely to be present not as a free ion but rather as complexes with organic compounds (13). Although the possibility that different nickel transporters are induced in pea bacteroids but are absent in cultured cells and lentil bacteroids cannot be excluded, we favor the hypothesis that the observed differences are due to the presence of different nickel complexes in both symbioses (11).…”

Biogeochemistry of Nickel and Its Release into the Environment

“…In some plant species, e.g., oat (Avena sativa L.) and legume species (Fabaceae) associated with Rhizobium bacteria such as peas and beans, Ni is primarily enriched in the seeds [71,143]. Cataldo et al [168] concluded that the leaves of soybean plants were a major sink during vegetative growth, while more than 70% of the Ni in shoot was remobilized to the seeds at senescence. During autumnal senescence, 5-20% of the Ni incorporated in the senescent needle mass was translocated to the remaining tissues of adult Scots pine trees growing in conditions of excess Ni [169].…”