title: Zinc stress induces physiological, ultra-structural and biochemical changes in mandarin orange (Citrus reticulata Blanco) seedlings.
abstract: Zinc (Zn) is an essential micronutrient for higher plants; yet, at higher concentrations it is toxic. In order to explore the effect of Zn stress on growth, biochemical, physiological and ultra-structural changes, 1 year old mandarin plants were grown under various Zn concentrations (1, 2, 3, 4, 5, 10 15 and 20 mM) for 14 weeks. The biomass of the plants increased with increasing Zn concentrations and finally declined under excess Zn concentration but the prime increase was observed at 4 and 5 mM Zn. Zn stress reduced the photosynthetic rate, stomatal conductance, and transpiration along with reduction of chlorophyll a, chlorophyll b, and carotenoids content in leaf. Superoxide anion, malondialdehyde, hydrogen peroxide and electrolyte leakage were elevated in Zn stressed plants. The activities of ascorbate peroxidase (EC 1.11.1.11), catalase (EC 1.11.1.6), superoxide dismutase (EC 1.15.1.1) and peroxidase (EC 1.11.1.7) enzymes were increased in both Zn-deficient and Zn-excess plants. Therefore it is suggested that antioxidant defense system did not sufficiently protect the plants under rigorous Zn stress which was also corroborated by the alteration in cell ultrastructure as revealed by transmission electron microscopy.
authors.affiliation: Biotechnology Laboratory, Faculty of Horticulture, Uttar Banga Krishi Viswavidyalaya, Cooch Behar,, 785165 West Bengal India.
authors.forename: Pratap
authors.initials: P
authors.lastname: Subba
authors.affiliation: Biotechnology Laboratory, Faculty of Horticulture, Uttar Banga Krishi Viswavidyalaya, Cooch Behar,, 785165 West Bengal India ; Department of Botany, University of Kalyani, Kalyani, Nadia,, 741235 India.
authors.forename: Mainaak
authors.initials: M
authors.lastname: Mukhopadhyay
authors.affiliation: Biotechnology Laboratory, Faculty of Horticulture, Uttar Banga Krishi Viswavidyalaya, Cooch Behar,, 785165 West Bengal India.
authors.forename: Suresh Kumar
authors.initials: SK
authors.lastname: Mahato
authors.affiliation: Biotechnology Laboratory, Faculty of Horticulture, Uttar Banga Krishi Viswavidyalaya, Cooch Behar,, 785165 West Bengal India.
authors.forename: Karma Diki
authors.initials: KD
authors.lastname: Bhutia
authors.affiliation: Biotechnology Laboratory, Faculty of Horticulture, Uttar Banga Krishi Viswavidyalaya, Cooch Behar,, 785165 West Bengal India ; Division of Genomic Resources, National Bureau of Plant Genetic Resources, Pusa, New Delhi, 110012 India.
authors.forename: Tapan Kumar
authors.initials: TK
authors.lastname: Mondal
authors.affiliation: Biotechnology Laboratory, Faculty of Horticulture, Uttar Banga Krishi Viswavidyalaya, Cooch Behar,, 785165 West Bengal India.
authors.forename: Swapan Kumar
authors.initials: SK
authors.lastname: Ghosh
keywords: Antioxidative enzymes; Citrus reticulate; Pigments; Reactive oxygen species; Transmission electron microscopy; Zinc stress