Adaptations of Plants to Metal/Salt Contained Environments: Glandlar Structure and Salt Excretion

1 A quantitative assessment was made of metal contamination levels and salinization of Kyzylkum Deserts territories and an analysis of plant/soil samples were investigated in relation to the natural cellular mechanism of plant adaptations to environmental agro-industrial pollutants. Preliminary results provide strong evidence that tailing sands and wet-marsh lands polluted with cadmium, copper, iron, nickel, manganese, chromium, strontium, lead, zinc, various toxic salts and organic pollutants are first colonized by plant species that develop strategies for avoidance and/or tolerance to toxic metals. Our analyses show that the native desert plants, grown on the metalliferous and/or salinized soils tend to accumulate the highest ions concentrations in epidermal and subepidermal tissues, as well as in water bearing parenchyma, including various glandular structures of bracts/bracteoles and perianth segments. A specific adaptive defending strategy by reproductive organs occurred between the vegetative and reproductive functional systems of the resistant plants that ensure them successful sexual reproduction and seed germination. In Chenopods like in some species of Poaceae, glandular structures are usually bicellular, comprising a basal and cap cell, and are referred to as salt glands, trichomes or microhairs. Salt secretion is considered as an adaptive strategy to regulate plant tissue ion concentration. We suggest that the different appearance of the glandular structures in some chenopods and graminous species of Kyzylkum flora is due to differences in their function connected both with accumulation of various ions and /or secretory process. The prismatic crystals secreted by epidermal salt glands and analyzed by X-ray absorption spectrometry contain primarily cations Na, K, Ca, and anions Cl, SO4, carbonate, although other ions such as Mg, Si, and Sr also were detected. Structurally, SEM methods also revealed a high diversity in the micromorphology of epicuticular wax (epicuticular secretion) and silicon deposits that was mostly peculiar for perennial Salsola and gramineous species. The natural plant-cellular mechanism of salt/metal tolerance observed in this study should permit the development and testing of more informed hypotheses regarding adaptations required for colonization and survival of plants, growing under extremely harsh arid and, simultaneously metaliferous/salinized environments. Phytoremediation technology is considered a potentially valuable technique for dealing with heavy metals, which are the most difficult pollutants to remove from soils. 1

[1]  N. Hallam.  Growth and regeneration of waxes on the leaves of Eucalyptus , 1970, Planta.

[2]  H. Ziegler,et al.  Photosynthesis in Salsola Species (Chenopodiaceae) from Southern Africa Relative to their C4 Syndrome Origin and their African-Asian Arid Zone Migration Pathways , 2002 .

[3]  P. Soltis,et al.  Phylogenetic analysis of tribe Salsoleae (Chenopodiaceae) based on ribosomal ITS sequences: implications for the evolution of photosynthesis types. , 2001, American journal of botany.

[4]  T. Tsukatani,et al.  Conservation and Regeneration of Arid/Saline Lands of Ecological System Development in Kyzylkum Desert , 2001 .

[5]  K. Idzikowska,et al.  Environmental State and an Analysis of Phytogenetic Resources of Halophytic Plants for Rehabilitation and Livestock Feeding in Arid and Sandy Deserts of Uzbekistan , 2001 .

[6]  U. Japakova,et al.  Halophytes: Structure and Adaptation , 2001 .

[7]  M. Leblanc,et al.  Zinc and cadmium hyperaccumulation by Thlaspi caerulescens from metalliferous and nonmetalliferous sites in the Mediterranean area: implications for phytoremediation. , 2000, The New phytologist.

[8]  Y. Naidoo,et al.  Cytochemical localisation of adenosine triphosphatase activity in salt glands of Sporobolus virginicus (L.) Kunth , 1999 .

[9]  M. Leblanc,et al.  The phytomining and environmental significance of hyperaccumulation of thallium by Iberis intermedia from southern France , 1999 .

[10]  R. Meagher,et al.  Phytoremediation of Mercury- and Methylmercury-Polluted Soils Using Genetically Engineered Plants , 1998 .

[11]  Y. Naidoo,et al.  Sporobolus virginicus leaf salt glands: morphology and ultrastructure , 1998 .

[12]  Wilhelm Barthlott,et al.  Classification and terminology of plant epicuticular waxes , 1998 .

[13]  A. Jordaan,et al.  Notes on the cuticular ultrastructure of six xerophytes from southern Africa , 1998 .

[14]  I. Solodov.  The retardation and attenuation of liquid radioactive wastes due to the geochemical properties of the zone of injection , 1998, Geological Society, London, Special Publications.

[15]  A O Summers,et al.  Mercuric ion reduction and resistance in transgenic Arabidopsis thaliana plants expressing a modified bacterial merA gene. , 1996, Proceedings of the National Academy of Sciences of the United States of America.

[16]  R. Paul,et al.  Bicellular Trichomes of Johnsongrass (Sorghum halepense) Leaves: Morphology, Histochemistry, and Function , 1995, Weed Science.

[17]  J. Lester,et al.  The occurrence and distribution of trace metals in halophytes , 1994 .

[18]  W. Barthlott.  Epicuticular Wax Ultrastructure and Systematics , 1994 .

[19]  John J. Bozzola,et al.  Electron microscopy : principles and techniques for biologists , 1992 .

[20]  R. Molyneux,et al.  Plant toxins and palatability to herbivores. , 1992 .

[21]  Eun-soo Kim,et al.  CUTICLE DEVELOPMENT ON GLANDULAR TRICHOMES OF CANNABIS SATIVA (CANNABACEAE) , 1991 .

[22]  R. Cummings.  Poisonous Plants of California by Thomas C. Fuller, Elizabeth McClintock , 1987 .

[23]  M. Hodson,et al.  A Developmental Study of Silicification in the Trichomes and Associated Epidermal Structures of the Inflorescence Bracts of the Grass, Phalaris canariensis L , 1983 .

[24]  M. Hodson,et al.  SILICON DEPOSITION AND ANATOMICAL STUDIES IN THE INFLORESCENCE BRACTS OF FOUR PHALARIS SPECIES WITH THEIR POSSIBLE RELEVANCE TO CARCINOGENESIS , 1983 .

[25]  D. Parry,et al.  Ultrastructure of Silica Deposits in Higher Plants , 1981 .

[26]  B. Verdcourt,et al.  Poisonous Plants of Australia , 1976 .

[27]  W. Thomson.  The Structure and Function of Salt Glands , 1975 .

[28]  Y. Waisel,et al.  EXISTENCE OF SALT GLANDS IN VARIOUS GENERA OF THE GRAMINEAE , 1974 .

[29]  U. Luttge.  Structure and Function of Plant Glands , 1971 .

[30]  D. Hall,et al.  Infra-Specific Variation in Wax on Leaf Surfaces , 1965 .

[31]  John Merriam Kingsbury,et al.  Poisonous plants of the United States and Canada , 1964 .

[32]  K. Schmidt-Nielsen,et al.  Salt glands. , 1959, Scientific American.