Studies on the structure and function of codium fragile chloroplasts

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Benson, E.E., 1983. Studies on the structure and function of codium fragile chloroplasts. PhD, Nottingham Trent University.

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Abstract

Studies on C. fragile chloroplasts show that this alga is well adapted to its intertidal zone habitat. Photosynthesis in isolated chloroplasts saturates at low light intensities and their pigment composition confers an environmental adaptation to submarine light fields. Chlorophyll a:b ratios are low in this alga and an average of 75% of the total pigment content of the chloroplast pigment/proteins are located in the light-harvesting complexes. These complexes are enriched in chlorophyll b and siphonein and siphonoxanthin which absorb in the "green gap" region of the visible spectrum. The pigment composition of C. fragile is particularly unique as β-carotene is absent in this alga, and α- and ϵ-carotene are the only carotene isomers detected.

Although photosynthesis in C. fragile is adapted to low light intensities, photostability studies show this alga to be particularly stable when exposed to high non-fluorescent light regimes typical of those encountered at low tide. Photooxidative symptoms in C. fragile were only induced on exposure to environmentally atypical fluorescent light. These studies indicate that photooxidation in C. fragile is atypical of that in other plants as chlorophyll is preferentially degraded compared to the carotenoid pigments and ethylene is the major photooxidation product. The absence of β-carotene may suggest that photoprotective mechanisms in this alga are also different.

A study of the growth of C. fragile in the intertidal zone at Bembridge, shows that the life cycle of this alga also confers an adaptive advantage. The alga maximises nutrient and carbon assimilation during the winter and this is evidenced by increased pigment content, vegetative growth and photosynthetic rates. In the summer when competition from faster growing algae and epiphytic attack occurs C. fragile enters the reproductive phase of the life cycle which is presumably supported by the mobilization of winter-stored nutrients. Thus, the alga employs a strategic survival mechanism in which the timing and not extent of vegetative growth is the important factor.

Item Type:

Thesis

Creators:

Benson, E.E.

Date:

1983

ISBN:

9781369315974

Identifiers: