Date of Award

1998

Document Type

Thesis

Publisher

Edith Cowan University

Degree Name

Bachelor of Science Honours

Faculty

Faculty of Communications, Health and Science

First Supervisor

Dr Ian Bennett

Abstract

Seagrass communities are of high ecological and economic significance. They provide a nursery area for commercial and recreational juvenile fish and crustacea. Seagrasses also play an important role in influencing the structure and function of many estuarine and nearshore marine environments. Unfortunately, the decline of seagrasses, as a result of human impact, has increased in recent years. This decline has become a major problem throughout the world. Current methods used to restore degraded seagrass beds are limited, the most promising being transplanting material from healthy donor beds. This approach is expensive because it is labor intensive and damages the donor bed. Consequently, large scale transplanting programmes are not considered to be feasible. An alternative to using donor material may be found in the propagation of seagrasses. This has been attempted through the production of seedlings in tissue culture. Tissue culture has shown to be successful in the rapid cloning of terrestrial plants and may be applied to develop a protocol which can be utilised to restore seagrass meadows. Five clones of Halophila ovalis Hook F., (initiated from seed) and one clone of Ruppia megacarpa Mason (initiated from rhizome) were obtained from stocks at Edith Cowan University, School of Natural Sciences. Posidonia coriacea Cambridge and Kuo was initiated in tissue culture during this study. These trials were undertaken in order to develop suitable tissue culture methods to be applied to the propagation of seagrasses for future revegetation programs. The addition of sucrose to the medium resulted in increased growth and chlorophyll content of H. ovalis. There was no difference between the concentrations applied (30mM, 60mM and 120mM) with regard to growth, but between clones there were observed differences in the chlorophyll content. A comparison of one, two, four and eight week periods between subculture on basal medium showed no effect on the growth of H. ovalis, though after two weeks, cultures appeared healthier. Cultures of H. ovalis grown in buffered (10mM MES) medium showed an increase in growth and chlorophyll content between initial pH 6 and 8 compared to those grown on unbuffered medium. These results suggest that medium buffering is important for tissue culture of seagrasses. When cytokinins (5µM concentration) were added to the medium, there was no effect on growth or chlorophyll content for three H. ovalis clones or one R. megacarpa clone.

Seeds with the pericarp intact were more successful in initiating P. coriacea in tissue culture than those with rhizomes and those without the pericarp. These have continued to grow over seven months, but have not produced rhizome extension as in H. ovalis or R. megacarpa. These studies have shown that the requirements for tissue culture of seagrasses may be substantially different from that of terrestrial plants, and have produced a good base line of information for the propagation of seagrasses in tissue culture.

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