An investigation into some aspects related to the phytoremediation potential of Pinus radiata (D. Don) & Chamaecytisus proliferus (L.f.) Link ssp. proliferus var. palmensis (H. Christ.).
Thesis DisciplinePlant Biotechnology
Degree GrantorUniversity of Canterbury
Degree NameDoctor of Philosophy
Both Pinus radiata and Chamaecytisus palmensis were inducted into tissue culture. In vitro clonal shoots were generated from cotyledon-derived meristematic cultures of P. radiata. Attempts were made to induce shoot organogenesis in C. palmensis explants, on solid media supplemented with a range of plant growth regulators. In vitro clonal shoots of C. palmensis were generated from seedling explants. The potential for Pb phytoextraction was investigated in seedlings and clones of P. radiata and C. palmensis. Aspects of tolerance, uptake, and translocation of Pb were studied within each species and in comparison to each other. Effects of Pb on different aspects of plant growth were examined including inhibition of seed germination, root growth inhibition, fresh weight changes of in vitro tissue, and responses of seedlings and excised shoots in solution culture. Both P. radiata and C. palmensis were insensitive to Pb during seed germination. Pb inhibited formation of lateral roots and inhibited root and shoot elongation in P. radiata seedlings. C. palmensis displayed greater tolerance to Pb than P. radiata during early seedling growth. Plants growing in hydroponic culture were exposed to Pb(N0₃)2, with and without the addition of the chelating agents H-EDTA and EDTA. Subsequently treated materials were examined for Pb uptake by flame atomic absorption spectrometry. Both P. radiata and C. palmensis accumulated unchelated Pb predominantly in root tissue, while Pb, in the presence of H-EDTA or EDTA, was taken up principally by the shoots in both species. With transmission electron microscopy, ultrastructural observations were carried out on ultra-thin sections, derived from tissues treated with Pb in the presence and absence of chelators, from both P. radiata and C. palmensis. In P. radiata, Pb was deposited in cell walls in root tissues; and in intercellular spaces in shoot tissues. In C. palmensis, Pb was found in cell walls, bacteroids and mitochondria in root nodule tissue; in middle lamellae and intercellular spaces in root tissues; and in chloroplasts, pit membranes, and plasmodesmata in shoot tissues. When acid phosphatase activity, in response to Pb exposure, was examined in both species, no substantial differences were found with regard to treatment but some evidence was found of differences in response among P. radiata clones. No new isozymes of acid phosphatase were found in C. palmensis in response to Pb but evidence was found that root isozyme activity increased in response to unchelated Pb.