D. A. Wilkins

Bio: D. A. Wilkins is an academic researcher. The author has contributed to research in topics: Agrostis & Festuca ovina. The author has an hindex of 1, co-authored 1 publications receiving 296 citations.

A Technique for the Measurement of Lead Tolerance in Plants

Abstract: BRADSHAW reported1 that root growth was inhibited when plants of Agrostis tenuis were grown in soil from the tip of an old Welsh lead mine, while plants originally growing on the tip produced normal roots. This suggested that some plants of A. tenuis were inherently more tolerant of the lead and zinc in the soil than others. On similar waste tips in Scotland, A. tenuis is replaced by Festuca ovina and Deschampsia flexuosa, and a method has been worked out for the measurement of lead tolerance in F. ovina from soils of different lead contents.

Heavy metal tolerance in plants

Abstract: Publisher Summary This chapter illustrates the literature on those plants and micro-organisms which can combat excessive quantities of heavy metal ions. Heavy metals include those metals which have density greater than five. Their common feature in regard to biological life is that in excessive quantities they are poisonous and can cause death of most living organisms. However, certain organisms possess an ability to survive under conditions of metal contamination which can prove toxic to other living things. Toxic levels of heavy metals can occur under several circumstances. The chapter focuses on the type of contamination in which the soil itself contains large quantities of these metals. The contamination results from the presence of undisturbed metal ore near the soil surface causing anomalies or from the actual mining of ore bodies. The vegetation in such areas is influenced by one overriding factor, namely, metal concentration. The habitats are usually spatially distinct and clear cut. It is observed that the sequence and pattern of genetic change responsible for colonization of metal-contaminated areas serves as a unique record of natural selection in action.

Breeding for Salinity Tolerance in Plants

Abstract: Accumulation of high levels of salts in the soil is characteristic of arid and semi-arid regions. Although different curative and management measures are being used to render salt-affected soils fit for agriculture, they are extremely expensive and do not provide permanent solutions to overcome the salinity problem. In contrast, a biotic approach for overcoming salinity stress has gained considerable recognition within the past few decades in view of the vast experimental evidence from what has happened in nature concerning the evolution of highly salt-tolerant ecotypes of different plant species, and also from the remarkable achievements that have been made in improveing different agronomic traits through artificial selection. Considerable improvements in salt tolerance of important crop species have been achieved in the past 2 decades using barley, rice, pearl millet, maize, sorghum, alfalfa, and many grass species. Such achievements relied solely on assessment of the phenotypic expression of t...

Metal tolerance in plants

Abstract: Nearly 60 years ago, Prat (1934) initiated the research of heavy metal resistance in plants when he was analysing the growth performance of two populations of Silene dioica (Melandrium sylvestre), one from a copper mine and one from a non-mine soil. He was able to demonstrate a heritable copper resistance in the mine population, relative to the non-mine population, which he explained as a result of evolution by natural selection. Nearly 20 years later Bradshaw (1952) and Baumeister (1954) started further research on ecological and physiological differentiation between plants from metal-enriched and noncontaminated habitats. The species chosen for study were predominantly Agrostis capillaris in the Bradshaw group (Jowett 1959; Gregory 1965; McNeilly 1965; Antonovics 1966) and Silene vulgaris in the Baumeister group (Broker 1962; Ernst 1964; Gries 1965; Riither 1966). In the late 1950s Duvigneaud (1958), while studying the vegetation on metalliferous soils in Central Africa, added to the above approaches a phytogeographic one and introduced the study of speciation processes in metallophytes. In the 1950s, the study of evolutionary and physiological aspects of metal resistance was hampered by the absence of convenient techniques for measuring metal concentrations in small plant samples. The techniques available for metal analysis were either timeconsuming, such as phase separation (Ernst 1964), or costly and only applicable for laboratory-raised plant material, i.e. radiolabelling (Turner & Gregory 1967; Peterson 1969). Only after applying atomic absorption spectrophotometry on wet-ashed plant material (Reilly 1967) did time and cost-effective metal analyses become possible.

The measurement of tolerance to edaphic factors by means of root growth

Abstract: SUMMARY The tolerance of plants to toxic metals is frequently measured by comparing rates of root growth in culture solutions with and without the addition of the metal, but many variants of the technique are available. Toxicity is often reduced by the presence of other ions, particularly calcium. Control growth rates may be measured beforehand on the same roots or in parallel on a duplicate set. With a single toxic concentration tolerance is defined as the ratio of the two growth rates; with a range of concentrations the slope of the regression of growth on concentration may be used, but there are some complications with stimulation at low concentrations. Probit analysis may be valuable. There is good evidence that tolerance differences are largely of genetical origin.