Efficacy of Rare Earth Elements on the Physiological and Biochemical Characteristics of Zea Mays L (Report‪)‬

Introduction Rare earth elements are applied to improve crop production, and the distribution patterns of individual rare earth elements in native plants have widely been reported. But the knowledge is still limited about the dose-dependent accumulation of individual rare earth elements in agricultural crops after application of rare earth elements (Xu, 2003). Application of mixtures of rare earth elements at 10 mg [kg.sup.-1] soil, resulted in significant increase in contents of light rare earth elements in the roots, and at a dose of 50 mg [kg.sup.-1] soil, a similar phenomenon was found at the plant tops. Rare earth elements (REEs) frequently occur together as rare earth minerals and have similarities in ionic radii and chemical activities (Henderson, 1984). Although they are called rare earth elements because of their similarity to the earth (i.e., magnesia, lime, etc.), REEs are not all rare but represent a group of 15th most abundant component of the earth's crust. The activity or certain plant enzymes have been found to be enhanced by the application of REE (Brown et al., 1990). Application of REEs in agriculture has been carried out intensively since 1972, aiming at increasing crop yields. Chinese researchers have reported both physiological and yield responses with no adverse environmental effects (Xiong, 1995). With this regard, many research works have been done to show the beneficial effects of REEs on plant growth and soil properties which stimulate the synthesis of chlorophyll (Guo, 1988), to promote seedling development (Chang, 1991; Wu et al., 1983), to stimulate root and shoot growth in crops such as (Triticum aestivum L.), cucumber (Cucumis sativus L.), soybean [Glycine max (L.) Merr.], and corn using both pot and plot experiments. REEs in plants showed dose-dependent accumulation (Wu et al., 1983). Effects of REEs on POD activity of tea plant were also analyzed by Wang et al. (2003). Much less work has been done on the adverse effects of REEs. Many studies have reported the accumulation of RE in different types of cereal crops or in different parts of plants (Liu et al., 1997; Lao et al., 1996). There is an increasing interest in the bioaccumulation processes of REEs due to the wide application of REEs in a variety of non-nuclear industries and agriculture, resulting in possible environmental contamination (Choppin et al., 1986; Wang et al., 2001). Meanwhile, due to their unique chemical structures, they may be used to trace the sources of inorganic elements in plants (Fu et al., 2001; Fu and Tasuku, 2000). Investigations into the bioaccumulation characteristics of REEs have been carried out in recent years as sensitive techniques such as inductively coupled plasmamass spectrometry has become available (Fu et al., 2001; Wei et al., 2001). Concentrations of REEs in plants are extremely variable, with about 700 ng [g.sup.-1] of La has been reported in a new species of fern (Matteuccia) (Fu et al., 1998), but it can be less than 10 ng [g.sup.-1] La in the needles of Norway spruce (Wyttenbach et al., 1994). In India, much less work has been concentrated upon the bioaccumulation and effects of REEs on corn plants. Hence in the present study, fractionation of REEs in various parts of corn plant was analyzed and the effect of REEs on biochemical and physiological characteristics of corn plant have been carried out.