Influence of temperature and light on growth and photosynthetic physiology of Fucus evanescens (Phaeophyta) embryos

• Published in: European journal of phycology Vol. 33; no. 2; pp. 129 - 138
• Main Authors: MAJOR, KELLY M. (MACHALEK), DAVISON, IAN R.
• Format: Journal Article
• Language: English
• Published: Cambridge University Press 01-05-1998
• Subjects: Fucus evanescens; Marine; Phaeophyta; photoacclimation; Fucus evanescens; physiological ecology; photosynthesis; Phaeophyta; thermal acclimation
• ISSN: 0967-0262; 1469-4433
• DOI: 10.1017/S0967026298001620

The influence of temperature and light on growth and photosynthetic
physiology were investigated in embryos of Fucus evanescens grown
at 5 or 20°C under irradiances of 15 or 150 μmol photons
m−2 s−1 for 7–10 days. Growth was
light-independent, but high-temperature
embryos were always significantly larger than those grown at low
temperature. Photosynthesis-irradiance responses were measured at
growth temperature and a standard temperature (20°C) to isolate
instantaneous effects of temperature from acclimation responses. Our
data indicate that growth and photosynthesis are uncoupled during the
early development of Fucus, and that acclimation of the
photosynthetic light-harvesting apparatus occurred. Light-limited net
photosynthesis (Psub-sat) responded similarly to high
temperature and
low light. Rates of Psub-sat were similar in embryos
grown at 20°C
(regardless of light) and at 5°C in low (c. 1.2 nmol
O2 mm−3 min−1),
whereas those of 5°C high-light embryos were lower (c. −0.04
nmol
O2 mm−3 min−1). Changes in
Psub-sat were associated with changes
in initial slope of the photosynthesis-irradiance curve (α)
and dark respiration. Differences in α were attributed to increased
absorption
due to increased chlorophyll a content and PSII reaction centre
densities. Changes in α were also correlated with changes in fluorescence
induction kinetics, with high-temperature and/or low-light embryos
exhibiting higher ratios of variable: maximum fluorescence
(Fv/Fm)
than 5°C high-light embryos (c. 0.5 vs. 0.19). In contrast
to Psub-sat, changes in light-saturated photosynthesis
(Pmax) in response to growth
under different temperature/light regimes did not confer metabolic
compensation. Rates of Pmax were highest in 20°C
high-light embryos
(7.3 nmol O2 mm−3 min−1),
lower in
20°C low-light and 5°C low-light embryos (c. 2.6 nmol
O2 mm−3 min−1) and lowest
in 5°C
high-light embryos (2.3 nmol O2 mm−3 min−1).
We suggest that the ability to achieve temperature-independent rates of
Psub-sat may be
important for fucoid embryos that recruit in intertidal microhabitats
where photosynthesis is often light-limited.