Experimental and ecological studies on the red alga Gigartina stellata (Stackh. in With.) Batt

Khfaji, Abdul Karim (1978) Experimental and ecological studies on the red alga Gigartina stellata (Stackh. in With.) Batt. PhD thesis, University of Glasgow.

Abstract

1. Plants of Gigartina stellata from three different localities in the Firth of Clyde were examined and showed some clear cut variation in their morphological characters. 2. The field transplant experiments in which plants of Gigartina from the three localities were transplanted in reciprocal fashion indicated that the morphology of Gigartina is principally controlled by environmental conditions with possible genetic variability. 3. Plants of Gigartina stellata required more than three years to establish themselves from spores on the denuded and sterilized areas of the shore. 4. Plants of Gigartina regenerate only when parts of the flattened fronds were left intact on the basal crusts. Regeneration is a slow process and some plants formed numerous small proliferations from the margin of the fronds. 5. The period of maximum spore discharge in Gigartina from all three localities was recorded in September through December, whilst the period of minimum spore discharge was recorded in April through July. 6. Culture of fronds of Gigartina from the different localities under the same conditions showed similar growth rates in all plants except plants from Loch Long, which showed slightly slower growth rates which may suggest a lack of ability to adapt to the experimental conditions. 7. Culture of fronds of Gigartina from one locality (Cumbrae Island) under a variety of laboratory induced environmental conditions emphasised the important role of environmental, conditions and confined the results of field transplant experiments. 8. Culture of carpospores of Gigartina under laboratory conditions showed that the disc-like sporelings grew healthily for 5 months in which time the average diameter of sporelings reached 0.5 mm, then they detached and lost into the surrounding medium with no sign of forming the erect branches. The carpospores of the related species Chondrus crispus grew much faster and reached 0.8 mm in 3.5 months in which time they formed their first erect branches. The sporelings of Chondrus crispus were found to produce an antibiotic substance but not those of Gigartina. 9. Carrageenan showed some obvious variation in its quantity and quality in plants from the three localities. Portencross plants contained higher quantities of carrageenan but with weaker gel strength, and plants from Loch Long contained lower carrageenan content with stronger gel, while plants from Cumbrae Island showed an intermediate value in both carrageenan contents and gel strengths. 10. Carrageenan showed seasonal variations in its quantity and quality. Maximum carrageenan content was recorded in March through May, whilst the minimum carrageenan content was recorded in September through December. Strongest gels were recorded in December through March whilst the weakest gel was recorded in April through August. 11. The transplants experiments indicated that both carrageenan contents and gel strengths are controlled by environmental conditions. 12. Plants of Gigartina collected from one locality (Cumbrae Island) and kept two weeks under varieties of laboratory induced environmental conditions showed the important role of all conditions studied in controlling both carrageenan contents and gel strengths. 13. The most fertile plants of Gigartina in all the three localities contained lower carrageenan contents with stronger gel, whilst the sterile plants (with no papillae) had higher carrageenan contents, but with weaker gel strength. 14. Plants from Portencross were better able to postpone the tissue dehydration than plants from Loch Long. 15. Plants from Portencross were also better able to control the rate of chloride ions loss than plants from Loch Long. 16. Plants of Gigartina from the different localities have similar rates of photosynthesis. Plants from Portencross were better able to recover after drying for 12 hours under laboratory conditions and have considerably high photosynthetic rates. The various salinities were found to affect the photosynthesis in similar ways as the effects observed on the growth rates of fronds of Gigartina.

• Item Type: Thesis (PhD)
• Qualification Level: Doctoral
• Additional Information: Adviser: A D Boney
• Keywords: Microbiology
• Date of Award: 1978
• Depositing User: Enlighten Team
• Unique ID: glathesis:1978-73696
• Copyright: Copyright of this thesis is held by the author.
• Date Deposited: 14 Jun 2019 08:56
• Last Modified: 14 Jun 2019 08:56
• URI: https://theses.gla.ac.uk/id/eprint/73696