| Abstrakt: |
A comparative study of shoot cultures of two Grevilleaspecies exposed to various levels of NaCl (for 6 weeks) indicated that Grevillea ilicifoliawas significantly more tolerant to salt than Grevillea arenaria. Growth (explant height and numbers of shoots and leaves) in G. ilicifoliasignificantly declined at salt concentrations greater than 100 mmol · L-1, whilst growth of G. arenariawas significantly impaired at 40 mmol. L-1NaCl. Protochlorophyll, chlorophylls and carotenoids were significantly reduced as the salt concentration was increased, with both of the Grevilleaspecies being equally sensitive to NaCl. The rate of decline of protochlorophyll and chlorophyll bwith NaCl exposure was greater than that of chlorophyll a and carotenoids for both species. Anthocyanin pigments on the other hand significantly increased with salt stress in both of the Grevilleaspecies. Levels of Na and Cl were significantly elevated during salt exposure, while K, Ca and Mg levels were markedly reduced. The levels of malondialdehyde significantly declined in both species as a result of salt exposure, and this was accompanied by significant increases in both acid protease and neutral protease activities. Four other key enzymes involved in oxidative stress and tissue degradation (catalase, polyphenol oxidase, superoxide dismutase and lypoxygenase) were also significantly increased in both Grevilleaspecies as a result of NaCl treatment. The main difference between the two Grevilleaspecies appeared to be that the more salt tolerant G. ilicifoliahad significantly lower levels of the oxidative/degrading enzymes, compared with the more salt sensitive G. arenaria. |
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