Fig 1.
Newly released and 1-week-old seeds of P. oceanica.
(A) Newly released seeds inside a fruit and (B) 1-week-old seeds of Posidonia oceanica. FP, fruit pericarp; NRS, newly released seeds; WS, 1-week-old seeds; H, adhesive hairs; S, seed; R1, primary root; Rh, rhizome; L, leaves.
Fig 2.
Details of the histology, ultrastructure and morphology of the fruit pericarp and 1-week-old seeds of Posidonia oceanica.
Images show (A) the histological fruit pericarp sections and (B and C) the ultrastructure of the adhesive basal hairs of a 1-week-old seed. Green arrows indicate chloroplasts, while blue arrows denote air lacunae. Ed, epidermis; Hd, hypodermis; M, mesophyll; H, adhesive hairs; S, seed.
Fig 3.
Influence of light on the sexual recruitment of P. oceanica.
The graphs show the results obtained in the experiments performed to test the influence of light on the sexual recruitment of Posidonia oceanica (mean±SE; n = 5): (A) light transmitted by the fruit pericarps in a gradient of light irradiance; (B) RLCs; (C) light-adapted yields of the fruit pericarp and seeds; (D) GPP; (E) NPP; and (F) respiration obtained in newly released (NRS) and 1-week-old seeds (WS) at a light intensity of 10 μE · m-2 · s-1. Lines indicate significant regressions (p< 0.01) in the fruit pericarps (black lines; R2 = 0.98), newly released seeds (dotted black lines; R2 = 0.96) and 1-week-old seeds (dotted grey lines; R2 = 0.97). Letters indicate significant pairwise differences between the treatments.
Table 1.
Summary of the results obtained by one-way ANOVA and Tukey's HSD test of the photophysiology parameters (α, β, rETRmax, EK and light-adapted yield) of the fruit pericarps (FP), newly released (NRS) and 1-week-old seeds (WS) of Posidonia oceanica (n = 5).
The numbers in bold indicate significant effects (p <0.01). An asterisk over the response variable indicates that the data did not meet the assumptions, and a significance level of α = 0.01 was applied.
Fig 4.
Root hair ultrastructure of P. oceanica.
Images obtained by scanning electron microscopy of the root hairs of the Posidonia oceanica seedlings grown in different types of sediment treatments: (A) root hairs adhered by their basal extreme in the pebble treatment, (B) root hairs surrounding grains of sand in the sand treatment, (C) root hairs that interwove a fibre in the fibreglass treatment, (D) the branched edges of root hairs, (E) the basal extreme of a root hair anchored to the pebble treatment and (F) the microvillus of the lateral surface of root hairs.
Table 2.
Summary of the statistical results obtained by the Kruskal-Wallis and Kramer (Nemenyi) tests on the effect of the substrata type on the root system morphology of Posidonia oceanica (n = 5).
The numbers in bold indicate significant effects (p < 0.01). S: sand treatment, S+P: sand+pebble treatment, P: pebble treatment and F: fibreglass treatment.
Fig 5.
Schematic representation of the three sexual recruitment stages of P. oceanica, including dispersion and settlement.