| || || Chandra, Romika Romelesh|
| || || Effects of nickel on some physiological aspects of development of Grevillea exul var. rubiginosa, a New Caledonian endemic species|
Author:Chandra, Romika Romelesh
Institution: University of the South Pacific.
Call No.: Pac QK 495 .P957 C53 2005
Copyright:20-40% of this thesis may be copied without the authors written permission
Abstract: Endemic plant species have been considered as one of the best means of ecological restoration of exploited mine sites in New Caledonia. These plants have the adaptability characteristics that allow them to thrive on serpentine soils. This study has investigated the physiological effects of nickel concentrations at different developmental stages on Grevillea exul var. rubiginosa an endemic New Caledonian species. The first two stages of a plant life cycle were studied: germination and post germination under controlled and semi-controlled conditions respectively. The initial stage of development involved Petri dish germination and growth of seeds and seedlings respectively with different salts of nickel (nickel acetate, nickel chloride and nickel sulphate) with 0 – 500 ppm concentrations. Results obtained show nickel chloride as the most toxic compared to nickel acetate and sulphate. Decrease in all studied parameters: germination rates, root lengths, total nitrate, total soluble protein and total soluble glucid contents were observed with increasing concentrations of nickel chloride as the salt solution supplied to seeds. No significant differences were observed for nickel sulphate and nickel acetate except for increase in all studied parameters for 50 and 100 ppm nickel acetate. These results suggest that the form of nickel used in laboratory experiments are essential for experimental work, in order to take into account the form in which it is present in the natural environment. Seedlings germinated with nickel chloride were analyzed for glutamine synthetase activity (GSA) and nitrate reductase activity (NRA). Results obtained show that 5 ppm of nickel caused a slight increase in GSA compared to 0 ppm (control), 10 ppm, and 50 ppm, whereas 100 ppm of nickel had the highest GSA. Nitrate reductase activity increased with increasing concentrations of nickel chloride in the medium, with 100 ppm having the highest NRA. Seedlings germinated and treated with nickel chloride solution (0 – 500 ppm) under greenhouse conditions were also analyzed morphologically and biochemically. Morphological analysis included growth parameters such as root length, shoot length x and number of leaves whereas biochemical analysis included total nitrate, total soluble protein and total soluble glucid contents as well as GSAand NRA. Plantlets treated with 0 – 500 ppm nickel chloride over a period of 3 months indicated the importance of a minimum concentration of nickel in the substrate for the species. Nickel salt effect was quite obvious with fresh root : shoot ratio, enzyme activities as well as in biochemical parameters analyzed. Minirhizotrons provided a clear demonstration of root colonization in the two major soil types used during revegetation. Saprolite soil amended with organic matter proved to improve plant growth and development as compared to red laterite soil. Proteoid roots were observed on principal roots in both soil types with branching of roots prominent only in the upper zones of the compartments. This project has hence provided important and useful information for the revegetation of mine sites in New Caledonia using Grevillea exul var. rubiginosa as a major part of the mine vegetation. Results obtained in the present investigation would be useful to revegetate mining sites not only in New Caledonia but also anywhere in the world where nickel mining is a major mining activity.