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Advisor(s)
Abstract(s)
Posidonia oceanica (L.) Delile is a subtidal seagrass whose leaves are commonly colonized
by epiphytes. Epiphytes pose physical barriers to light penetration within the leaves, with
possible significant impacts on photosynthesis. Furthermore, epiphytes can indirectly
be responsible for leaf chlorosis, necrosis and senescence which are known to be related
with the increase of oxygen reactive species (ROS) levels, potentially leading to oxidative
stress. The aim of this work was to investigate in situ (i) the effect of epiphytes on the
composition and balance of light harvesting pigments in leaves of the naturally growing seagrass P. oceanica, and (ii) evaluate differences in antioxidant responses. Epiphytized and
non-epiphytized plants were analyzed to establish potential photosynthetic pigment roleshift
between light harvesting and photoprotection functions. The experiments were carried
out in Cabo de Gata Natural Park, southern Spain, where epiphytized and non-epiphytized
plants can be found at identical depths and light exposure. The results showed that both
O2 evolution rate along the day and chlorophyll a/b ratio were higher in non-epiphytized
plants, indicating a negative effect of epiphytes on photosynthesis and light harvesting.
Although under high irradiance (at solar noon) the xanthophyll cycle was activated in both
epiphytized and non-epiphytized leaves, the de-epoxidation-ratio (AZ/VAZ) was lower in
epiphytized leaves, due to light attenuation by epiphytes. The antioxidant capacity (TEAC
and ORAC essays) and the activity of the antioxidant enzymes ascorbate peroxidase and
dehydroascorbate were higher in epiphytized plants, showing that epiphytes can also be a
potential source of oxidative stress to P. oceanica. Our results show that despite the light
attenuation effect, leaf colonization by epiphytes can also be potentially stressful and reduces
plant productivity.
Description
Keywords
Epiphytes Light harvesting Antioxidants Seagrass Posidonia oceanica Oxygen reactive species Oxidative stress Photosynthetic pigments Xanthophyll cycle Antioxidant enzymes
Citation
Costa MM, Silva J, Olivé I, Barrote I, Alexandre A, Albano S, Santos R (2013) The effects of epiphytes on light harvesting and antioxidant responses in the seagrass Posidonia oceanica. Coastal and Estuarine Research Federation’s 21st Biennial Conference, San Diego, California, EUA, p47
Publisher
Coastal & Estuarine Research Federation