Plants vary considerably in their physiological response to selenium (Se). Some plant species growing on seleniferous soils are Se tolerant and accumulate very high concentrations of Se (Se accumulators), but most plants are Se nonaccumulators and are Se-sensitive. This review summarizes knowledge of the physiology and biochemistry of both types of plants, particularly with regard to Se uptake and transport, biochemical pathways of assimilation, volatilization and incorporation into proteins, and mechanisms of toxicity and tolerance. Molecular approaches are providing new insights into the role of sulfate transporters and sulfur assimilation enzymes in selenate uptake and metabolism, as well as the question of Se essentiality in plants. Recent advances in our understanding of the plant's ability to metabolize Se into volatile Se forms (phytovolatilization) are discussed, along with the application of phytoremediation for the cleanup of Se contaminated environments.

Selenium in higher plants.

Large herbivores must select food from a wide variety of plant parts, species, and strains. These differ in nutritional value (protein, carbohydrate, etc.), toughness, spinosity, etc. Even greater differences are found in types and concentrations of secondary compounds. Every plant produces its own set of secondary chemical compounds, which to a great extent are unique to it or its species. Ingestion of natural concentrations of these compounds can lead to either death or severe physiological impairment. The ubiquitous nature of these compounds would make herbivory impossible unless animals had mechanisms for degrading and excreting them. An animal displaying no obvious symptoms of poisoning is not free of the problem of ridding itself of toxic compounds; if it is eating plants, it almost certainly has this problem. Herbivores are capable of detoxifying and eliminating secondary compounds. Limitations of these mechanisms force mammalian herbivores to consume a variety of plant foods at any one time, to treat new foods with caution, to ingest small amounts on the first encounter, and to sample food continuously. Selection of foods is based on learning in response to adverse internal physiological effects, and herbivores probably cannot predict these from the smell or taste of new foods. Herbivores prefer to eat familiar foods and can seek out and consume foods that rectify specific nutritional deficiencies induced by detoxification. They should prefer to feed on foods that contain small amounts of secondary compounds, and their body size and searching strategies should be adapted to optimize the number of types of foods available with respect to the total amount of food that can be eaten and will be present in the future. Natural selection can increase the efficiency of degrading particular secondary compounds. Specialist herbivores, like koala and mountain viscacha, are expected where a large amount of several related toxic foods is present in a year-round supply. However, few large herbivores are specialized on such a restricted range of foods.

Strategies in herbivory by mammals: the role of

Large herbivores must select food from a wide variety of plant parts, species, and strains. These differ in nutritional value (protein, carbohydrate, etc.), toughness, spinosity, etc. Even greater differences are found in types and concentrations of secondary compounds. Every plant produces its own set of secondary chemical compounds, which to a great extent are unique to it or its species. Ingestion of natural concentrations of these compounds can lead to either death or severe physiological impairment. The ubiquitous nature of these compounds would make herbivory impossible unless animals had mechanisms for degrading and excreting them. An animal displaying no obvious symptoms of poisoning is not free of the problem of ridding itself of toxic compounds; if it is eating plants, it almost certainly has this problem. Herbivores are capable of detoxifying and eliminating secondary compounds. Limitations of these mechanisms force mammalian herbivores to consume a variety of plant foods at any one time, to tr...

Strategies in Herbivory by Mammals: The Role of Plant Secondary Compounds

https://scielo.conicyt.cl/pdf/ejb/v6n3/a12.pdf

Metal hyperaccumulation in plants: Biodiversity prospecting for phytoremediation technology

\"Many legumes contain poisonous principles, particularly alkaloids and glucosides, and we should expect Bruchids to be affected by some of these.\" With this statement, Bridwell (l918) anticipated the subject of this discussion: what traits of seeds may be the result of selective pressure by insects and other seed-eaters? In this discussion of the escape of the offspring of a large sessile organism from predators and parasites, Leguminosae (the bean family) and the bruchid beetles that attack their seeds are used as an empirical example. In a subsequent paper (Janzen, 1968b), a model of seed dispersal is developed as background for discussion of the relevance of seed dispersal and mortality to the density and presence of a species of plant in a community. I intend the data presented here to support the arguments advanced by Stebbins (1967) and Harper ( 1967) against the

Seed-eaters versus seed size, number, toxicity and dispersal

Changes in hydrogen‐ion concentration of culture solutions containing nitrate and ammonium nitrogen

Ion-exchange and filter-paper columns were used in a separation of amino acids from an extract of Astragalus bisulcatus Two amino acids were identified, S-methylcysteine and Se-methylselenocysteine

Seleno-Amino Acid Found in Astragalus bisulcatus

Selenium as a stimulating and possibly essential element for indicator plants

SOME SPECIES of Astragalus appear to be definite selenium indicators, occurring only on seleniferous soils and always containing selenium when collected in the field (Beath, Eppson, and Gilbert, 1935, 1939a, 1939b). Other species of Astragalus, however, are not limited to seleniferous soils. Even when growing on such soils in proximity to selenium-accumulating species, these are free from selenium or contain very low concentrations. Since two of the selenium indicators-A stragalus racemosus and Astragalus pattersonii-were found to be greatly

Sam F. Trelease

Papers

Changes in hydrogen‐ion concentration of culture solutions containing nitrate and ammonium nitrogen

Seleno-Amino Acid Found in Astragalus bisulcatus

Selenium as a stimulating and possibly essential element for indicator plants

Physiological differentiation in astragalus with reference to selenium

Photosynthesis of chlorella in heavy water