Chapter 1 The Biosphere Chapter 2 The Anthroposphere Introduction Air Pollution Water Pollution Soil Plants Chapter 3 Soils and Soil Processes Introduction Weathering Processes Pedogenic Processes Chapter 4 Soil Constituents Introduction Trace Elements Minerals Organic Matter Organisms in Soils Chapter 5 Trace Elements in Plants Introduction Absorption Translocation Availability Essentiality and Deficiency Toxicity and Tolerance Speciation Interaction Chapter 6 Elements of Group 1 (Previously Group Ia) Introduction Lithium Rubidium Cesium Chapter 7 Elements of Group 2 (Previously Group IIa) Beryllium Strontium Barium Radium Chapter 8 Elements of Group 3 (Previously Group IIIb) Scandium Yttrium Lanthanides Actinides Chapter 9 Elements of Group 4 (Previously Group IVb) Titanium Zirconium Hafnium Chapter 10 Elements of Group 5 (Previously Group Vb) Vanadium Niobium Tantalum Chapter 11 Elements of Group 6 (Previously Group VIb) Chromium Molybdenum Tungsten Chapter 12 Elements of Group 7 (Previously Group VIIb) Manganese Technetium Rhenium Chapter 13 Elements of Group 8 (Previously Part of Group VIII) Iron Ruthenium Osmium Chapter 14 Elements of Group 9 (Previously Part of Group VIII) Cobalt Rhodium Iridium Chapter 15 Elements of Group 10 (Previously Part of Group VIII) Nickel Palladium Platinum Chapter 16 Elements of Group 11 (Previously Group Ib) Copper Silver Gold Chapter 17 Trace Elements of Group 12 (Previously of Group IIb) Zinc Cadmium Mercury Chapter 18 Elements of Group 13 (Previously Group IIIa) Boron Aluminum Gallium Indium Thallium Chapter 19 Elements of Group I4 (Previously Group IVa) Silicon Germanium Tin Lead Chapter 20 Elements of Group 15 (Previously Group Va) Arsenic Antimony Bismuth Chapter 21 Elements of Group 16 (Previously Group VIa) Selenium Tellurium Polonium Chapter 22 Elements of Group 17 (Previously Group VIIa) Fluorine Chlorine Bromine Iodine

Trace elements in soils and plants

Our understanding of plant mineral nutrition comes largely from studies of herbaceous crops that evolved from ruderal species characteristic of nutri­ ent-rich disturbed sites (52). With the development of agriculture, these ancestral species were bred for greater productivity and reproductive output at high nutrient levels where there was little selective advantage in efficient nutrient use. This paper briefly reviews the nature of crop responses to nutrient stress and compares these responses to those of species that have evolved under more natural conditions, particularly in low-nutrient envi­ ronments. I draw primarily upon nutritional studies of nitrogen and phos­ phorus because these elements most commonly limit plant growth and because their role in controlling plant growth and metabolism is most clearly understood (51). Other more specific aspects of nutritional plant ecology not discussed here include ammonium/nitrate nutrition (79), cal­ cicole/calcifuge nutrition (51,88), heavy metal tolerance (4), and serpentine ecology (133).

The Mineral Nutrition of Wild Plants

1. Plant Nutrients. 2. The Soil as a Plant Nutrient Medium. 3. Nutrient Uptake and Assimilation. 4. Plant Water Relationships. 5. Plant Growth and Crop Production. 6. Fertilizer Application. 7. Nitrogen. 8. Sulphur. 9. Phosphorus. 10. Potassium. 11. Calcium. 12. Magnesium. 13. Iron. 14. Manganese. 15. Zinc. 16. Copper. 17. Molybdenum. 18. Boron. 19. Further Elements of Importance. 20. Elements with More Toxic Effects. General Readings. References. Index.

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Principles of plant nutrition

I. CONTEXT * The Ecosystem Concept * Earth's Climate System * Geology and Soils * II. MECHANISMS * Terrestrial Water and Energy Balance * Carbon Input to Terrestrial Ecosystems * Terrestrial Production Processes * Terrestrial Decomposition * Terrestrial Plant Nutrient Use * Terrestrial Nutrient Cycling * Aquatic Carbon and Nutrient Cycling * Trophic Dynamics * Community Effects on Ecosystem Processes * III. PATTERNS * Temporal Dynamics * Landscape Heterogeneity and Ecosystem Dynamics * IV. INTEGRATION * Global Biogeochemical Cycles * Managing and Sustaining Ecosystem * Abbreviations * Glossary * References

Principles of Terrestrial Ecosystem Ecology

Na+ Tolerance and Na+ Transport in Higher Plants

Broadly, the approach which researchers have adopted in this review has been to ask the following questions about mineral nutrients: What properties make them essential. How are they obtained. How effectively are they used. We shall not be considering two most important, but frequently reviewed, aspects of the subject, namely biological fixation of N/sub 2/ and its assimilation and mechanisms of membrane transport.

The Mineral Nutrition of Higher Plants

Factors Affecting Mineral Nutrient Acquisition by Plants

The exodermis (hypodermis with Casparian bands) of plant roots represents a barrier of variable resistance to the radial flow of both water and solutes and may contribute substantially to the overall resistance. The variability is a result largely of changes in structure and anatomy of developing roots. The extent and rate at which apoplastic exodermal barriers (Casparian bands and suberin lamellae) are laid down in radial transverse and tangential walls depends on the response to conditions in a given habitat such as drought, anoxia, salinity, heavy metal or nutrient stresses. As Casparian bands and suberin lamellae form in the exodermis, the permeability to water and solutes is differentially reduced. Apoplastic barriers do not function in an all-or-none fashion. Rather, they exhibit a selectivity pattern which is useful for the plant and provides an adaptive mechanism under given circumstances. This is demonstrated for the apoplastic passage of water which appears to have an unusually high mobility, ions, the apoplastic tracer PTS, and the stress hormone ABA. Results of permeation properties of apoplastic barriers are related to their chemical composition. Depending on the growth regime (e.g. stresses applied) barriers contain aliphatic and aromatic suberin and lignin in different amounts and proportion. It is concluded that, by regulating the extent of apoplastic barriers and their chemical composition, plants can effectively regulate the uptake or loss of water and solutes. Compared with the uptake by root membranes (symplastic and transcellular pathways), which is under metabolic control, this appears to be an additional or compensatory strategy of plants to acquire water and solutes.

/pdf/the-exodermis-a-variable-apoplastic-barrier-4h5fr9tlf0.pdf

The exodermis: a variable apoplastic barrier

Three plant sulfate transporter cDNAs have been isolated by complementation of a yeast mutant with a cDNA library derived from the tropical forage legume Stylosanthes hamata. Two of these cDNAs, shst1 and shst2, encode high-affinity H+/sulfate cotransporters that mediate the uptake of sulfate by plant roots from low concentrations of sulfate in the soil solution. The third, shst3, represents a different subtype encoding a lower affinity H+/sulfate cotransporter, which may be involved in the internal transport of sulfate between cellular or subcellular compartments within the plant. The steady-state level of mRNA corresponding to both subtypes is subject to regulation by signals that ultimately respond to the external sulfate supply. These cDNAs represent the identification of plant members of a family of related sulfate transporter proteins whose sequences exhibit significant amino acid conservation in filamentous fungi, yeast, plants, and mammals.

https://www.pnas.org/content/pnas/92/20/9373.full.pdf

Plant members of a family of sulfate transporters reveal functional subtypes

It has been shown that N-, P- and S-deficiencies result in major reductions of root hydraulic conductivity (Lp r ) which may lead to lowered stomatal conductance, but the relationship between the two conductance changes is not understood. In a variety of species, Lp r decreases in the early stages of NO 3 - , H 2 PO 2- 4 and SO 2- 4 deprivation. These effects can be reversed in 4-24h after the deficient nutrient is re-supplied. Diurnal fluctuations of root Lp r have also been found in some species, and an example of this is given for Lotus japonicus. In nutrient-sufficient wheat plants, root Lp r is extremely sensitive to brief treatments with HgCl 2 ; these effects are completely reversible when Hg is removed. The low values of Lp r in N- or P-deprived roots of wheat are not affected by Hg treatments. The properties of plasma membrane (PM) vesicles from wheat roots are also affected by NO 3 - deprivation of the intact plants. The osmotic permeability of vesicles from N-deprived roots is much lower than that of roots adequately supplied with NO 3 - , and is insensitive to Hg treatment. In roots of L. japonicus, gene transcripts are found which have a strong homology to those encoding the PIP1 and PIP2 aquaporins of Arabidopsis. There is a very marked diurnal cycle in the abundance of mRNAs of aquaporin gene homologues in roots of L. japonicus. The maxima and minima appear to anticipate the diurnal fluctuations in Lp r by 2-4 h. The temporal similarity between the cycles of the abundance of the mRNAs and root Lp r is most striking. The aquaporin encoded by AtPIP1 is known to have its water permeation blocked by Hg binding. The lack of Hg-sensitivity in roots and PMs from N-deprived roots provides circumstantial evidence that lowered root Lp r may be due to a decrease in either the activity of water channels or their density in the PM. It is concluded that roots are capable, by means completely unknown, of monitoring the nutrient content of the solution in the root apoplasm and of initiating responses that anticipate by hours or days any metabolic disturbances caused by nutrient deficiencies. It is the incoming nutrient supply that is registered as deficient, not the plant's nutrient status. At some point, close to the initiation of these responses, changes in water channel activity may be involved, but the manner in which monitoring of nutrient stress is transduced into an hydraulic response is also unknown.

David T. Clarkson

Papers

The Mineral Nutrition of Higher Plants

Factors Affecting Mineral Nutrient Acquisition by Plants

The exodermis: a variable apoplastic barrier

Plant members of a family of sulfate transporters reveal functional subtypes

Root hydraulic conductance: diurnal aquaporin expression and the effects of nutrient stress