Abstract
The marine Magnoliophyte Posidonia oceanica and Cymodocea nodosa are widely used as
indicators of the quality of the marine environment in the Mediterranean. These plants
produce tannin cells, specialized in the production of phenolic compounds, essential for their
adaptation and defense against environmental and biological aggressions. However, the
precise role of these compounds in the defense mechanisms of these plants remains little
studied. Indeed, only a few studies have investigated the variability of tannin cell abundance
in Posidonia oceanica in the face of environmental stress. Therefore, this study has set as
objectives the evaluation of the abundance of tannin cells in these 2 magnoliophytes, at the
level of 5 stations subjected to different types of anthropogenic pressures. The biometric
parameters accounting for the vitality of marine magnoliophytes were also measured with
the aim of establishing a relationship between the abundance of tannin cells and the vitality
of these cells. The determination of the abundance of tannin cells was carried out using 2
methods, the first is based on the calculation of the density of tannin cells (number of tannin
cells per unit area) and the second is based on the calculation of an index (proportion of cells
to parenchymal cells). The results obtained indicate a highly significant correlation between
the density and index of tannin cells (R=0.8, p<0.05). The density and index of tannin cells
increase when Posidonia oceanica and Cymodocea nodosa undergo the disturbances of the
medium, as well as the interspecific competition with the introduced alga Caulerpa
cylindracea. This sensitivity to environmental conditions opens up interesting prospects for
the use of tannin cell density as a descriptor (environmental biomarker) in coastal monitoring
programmes. Furthermore, the correlation between the density and index of tannin cells in
the 2 plants studied is not significant. It confirms the adaptive capacity of Cymodocea nodasa
in anthropized environments compared to Posidonia oceanica.
Keywords: Posidonia oceanica, Cymodocea nodosa, Tannin cells, Foliar biometrics,
Anatomy
The marine Magnoliophyte Posidonia oceanica and Cymodocea nodosa are widely used as
indicators of the quality of the marine environment in the Mediterranean. These plants
produce tannin cells, specialized in the production of phenolic compounds, essential for their
adaptation and defense against environmental and biological aggressions. However, the
precise role of these compounds in the defense mechanisms of these plants remains little
studied. Indeed, only a few studies have investigated the variability of tannin cell abundance
in Posidonia oceanica in the face of environmental stress. Therefore, this study has set as
objectives the evaluation of the abundance of tannin cells in these 2 magnoliophytes, at the
level of 5 stations subjected to different types of anthropogenic pressures. The biometric
parameters accounting for the vitality of marine magnoliophytes were also measured with
the aim of establishing a relationship between the abundance of tannin cells and the vitality
of these cells. The determination of the abundance of tannin cells was carried out using 2
methods, the first is based on the calculation of the density of tannin cells (number of tannin
cells per unit area) and the second is based on the calculation of an index (proportion of cells
to parenchymal cells). The results obtained indicate a highly significant correlation between
the density and index of tannin cells (R=0.8, p<0.05). The density and index of tannin cells
increase when Posidonia oceanica and Cymodocea nodosa undergo the disturbances of the
medium, as well as the interspecific competition with the introduced alga Caulerpa
cylindracea. This sensitivity to environmental conditions opens up interesting prospects for
the use of tannin cell density as a descriptor (environmental biomarker) in coastal monitoring
programmes. Furthermore, the correlation between the density and index of tannin cells in
the 2 plants studied is not significant. It confirms the adaptive capacity of Cymodocea nodasa
in anthropized environments compared to Posidonia oceanica.
Keywords: Posidonia oceanica, Cymodocea nodosa, Tannin cells, Foliar biometrics,
Anatomy