Effects of zinc toxicity on sugar beet (Beta vulgaris L.) plants grown in hydroponics

Abstract

The effects of high Zn concentration were investigated in sugar beet (Beta vulgaris L.) plants grown in a controlled environment in hydroponics. High concentrations of Zn sulphate in the nutrient solution (50, 100 and 300 microm) decreased root and shoot fresh and dry mass, and increased root/shoot ratios, when compared to control conditions (1.2 microm Zn). Plants grown with excess Zn had inward-rolled leaf edges and a damaged and brownish root system, with short lateral roots. High Zn decreased N, Mg, K and Mn concentrations in all plant parts, whereas P and Ca concentrations increased, but only in shoots. Leaves of plants treated with 50 and 100 microm Zn developed symptoms of Fe deficiency, including decreases in Fe, chlorophyll and carotenoid concentrations, increases in carotenoid/chlorophyll and chlorophyll a/b ratios and de-epoxidation of violaxanthin cycle pigments. Plants grown with 300 microm Zn had decreased photosystem II efficiency and further growth decreases but did not have leaf Fe deficiency symptoms. Leaf Zn concentrations of plants grown with excess Zn were high but fairly constant (230-260 microg.g(-1) dry weight), whereas total Zn uptake per plant decreased markedly with high Zn supply. These data indicate that sugar beet could be a good model to investigate Zn homeostasis mechanisms in plants, but is not an efficient species for Zn phytoremediation.

Zinc stress induces physiological, ultra-structural and biochemical changes in mandarin orange (Citrus reticulata Blanco) seedlings

“…In Beta vulgaris, stomatal size, density were smaller and stomatal slits were sealed in plants grown under high Zn (Sagardoy et al 2010) and citrus plants when grown under 15 mM Zn manifested stress imposition by keeping pores slightly opened. In high Zn plants stomata were smaller and had a more rounded shape than those present in control plants (Sagardoy et al 2009). In this study, when plants exposed to Zn-excess, stomata turned rounded and became comparatively smaller than the plants received Zn-optimum supply (Fig.…”

The impact of increased soil risk elements on carotenoid contents

“…In leaves of Cd-treated tomato, no changes were observed after high light illumination while significant decrease of violaxanthin and significant increase of both antheraxanthin and zeaxanthin occurred after the following 24 h of darkness [23]. Zn induced a large increase of all xanthophyll cycle pigments in duckweed plants [22] and increased de-epoxidation of violaxanthin cycle pigments in sugar beet plants [7].…”

“…Finally, although not widespread in the world's soils, zinc (Zn) toxicity is also an important problem, occurring particularly on mine spoils and mine-contaminated and sludge-treated soils [4][5][6]. When present at high concentrations, Zn can be toxic, and plants affected may show symptoms similar to those found in other risk element toxicities, such as those of Cd or Pb [7]. All these three toxic elements i.e.…”

Copper and zinc interactions: morphophysiological responses in sweet potato plants (Ipomoea batatas L.)

“…2D), especially in treatments with high Zn concentrations (T2 and T4). According to Sagardoy et al (2009), excessive Zn can induce Mg and Fe deficiencies, because the three metals possess similar ionic radii. Contrary to observations made by other researchers, Fe was compartmentalized, and the magnitude of Fe accumulation in the roots was greater under T2 and T4 conditions (Fig.…”

“…Plants aff ected by high Zn concentrations can present symptoms similar to toxicity symptoms associated with other heavy metals such as cadmium or lead (Sagardoy et al 2009). In most cases, excess Zn causes growth inhibition and root morphology alterations, biomass reduction, ROS generation and chlorosis induction in young leaves, decreased water content in tissues, and alterations in the uptake, translocation, and utilization of other essential elements (e.g., phosphorus, iron (Fe), or magnesium (Mg); Shi & Cai 2009, Yang et al 2011.…”