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Physiological and morphological responses of the seagrass Zostera capricorni Aschers, to light intensity

Abal, E.G., Loneragan, N., Bowen, P., Perry, C.J., Udy, J.W. and Dennison, W.C. (1994) Physiological and morphological responses of the seagrass Zostera capricorni Aschers, to light intensity. Journal of Experimental Marine Biology and Ecology, 178 (1). pp. 113-129.

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The responses of the seagrass Zostera capricorni Aschers, to changes in light intensity were examined in flowing seawater aquaria experiments. Plants were grown in six light regimes: full sunlight (100%), 50, 30, 20, 15, and 5% of full light over a 2-month period. Measurements of growth, biomass, pigments, stable isotopes and leaf anatomy were made at the end of the experiment. Plants survived under all light treatments, even below minimum light requirements of related seagrasses. However, the experimental light levels possibly do not correspond to light reaching seagrass leaves under natural conditions. Plants grown under high light conditions (50–100% light) had smaller shoots, higher biomass and productivity, less negative δ13C values, lower leaf nitrogen content, less chlorophyll and more ultraviolet light absorbing pigment than plants grown under low light conditions (<20% light). Photoadaptation by ultraviolet light absorbing pigment(s) was noted, with more variability in ultraviolet light pigments than in chlorophyll levels. Increased CO2 demand and/or increased CO2 recycling in internal gas spaces may account for the less negative δ13C values in high light treatments, indicating less isotopic discrimination in seagrass leaves in high light. A saturation response of growth rates to light intensity was observed, with less substantial growth reductions at lower light intensities than observed in other seagrass shading experiments. Nutrient limitation in high light was inferred by a growth maximum at 50% light level, increased root biomass and lower leaf nitrogen content in high light treatments. Overall, a wide range of morphological and physiological photoadaptive responses not previously reported in Zostera capricorni was observed.

Item Type: Journal Article
Publisher: Elsevier BV
Copyright: © 1994 Published by Elsevier B.V.
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