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The effects of salinity and/or low oxygen on the growth, development and metabolite production of the roots of Eucalyptus camaldulensis Denhn. clones resistant and sensitive to salinity

Kim, Siti (1998) The effects of salinity and/or low oxygen on the growth, development and metabolite production of the roots of Eucalyptus camaldulensis Denhn. clones resistant and sensitive to salinity. Honours thesis, Murdoch University.

Abstract

This project examined the effects of salinity and/or low oxygen on the roots of four Eucalyptus camaldulensis Denhn (River Red Gum) clones resistant (502 and 507) and sensitive (903 and 907) to salinity. The roots were grown aeroponically, with salt water was discharged from solution pumps, and nitrogen gas was utilised to reduce the oxygen concentration inside the aeroponic boxes.

There were two main experiments. First, plants were exposed to: 0, 100, 150 and 200mM NaCL Second, plants were exposed to: i) air with no salt (controls), ii) air with 150mM NaCl, iii) low oxygen with no salt, iv) low oxygen with 150m.M NaCl. After two weeks of treatment, root growth and the lignin deposition from the root apex were recorded. Roots were also sectioned and stained with toluidine blue 0 and aniline blue, quench root autofluorescence and to highlight the Casparian bands in the exodermis and endodermis. The distances from the root apex to the beginning of exodermis and endodermis differentiation were recorded. Metabolite production were also investigated in the roots exposed to salinity and/or low oxygen. In particular, soluble and cell wall• bound (ionic, static and covalent) peroxidase and phenolic biosynthesis were assayed in root tip and lignin samples.

The findings in this project showed that the exodermis, endodermis and lignin differentiated significantly (p< 0.05) closer to the root apex with 100, 150 and 200mM compared to the controls, but no significant (p< 0.05) differences were observed during the salt and/or low oxygen treatments. Few significant differences between salt resistant and sensitive clones in root growth and the maturation of exodermis, endodermis and lignin closer to the root apex were recorded. However, the salt resistant clones generally had greater static, ionic and covalent peroxidase activity and phenolic concentrations for the control, salt and/ or low oxygen treatments, which could suggest that peroxidase and phenolic biosynthesis are involved in salt and/or low oxygen tolerance. Interestingly, more soluble than cell wall- bound phenolic compounds were recorded, whilst more cell wall- bound than soluble peroxidase activity was recorded.

Salinity significantly (p< 0.05) reduced root growth, induced lignin biosynthesis and depressed metabolite production compared to the control roots, whilst low oxygen had the opposite effect. Thus, plants subjected to both salinity and low oxygen were more affected by salt stress than low oxygen stress.

Publication Type: Thesis (Honours)
Murdoch Affiliation: School of Biological and Environmental Sciences
Notes: A digital copy of this thesis is not available. Your library can request a copy from Murdoch University Library via Document Delivery. A fee applies to this service.
Supervisor: McComb, Jen and Hardy, Giles
URI: http://researchrepository.murdoch.edu.au/id/eprint/32809
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