Photosynthetic capacity in seagrass seeds and early‐stage seedlings of <i>Zostera marina</i>

Abstract

Summary In many terrestrial seeds, photosynthetic activity supplies O 2 to the developing plant embryo to sustain aerobic metabolism and enhance biosynthetic activity. However, whether seagrass seeds possess similar photosynthetic capacity to alleviate intra‐seed hypoxic stress conditions is unknown. We used a novel combination of microscale variable chlorophyll fluorescence imaging, a custom‐made O 2 optode microrespirometry system and planar optode O 2 imaging, to determine the O 2 microenvironment and photosynthetic activity in developing seeds and seedlings of seagrass ( Zostera marina ). Developing, sheath‐covered seeds exhibited high O 2 concentrations in the photosynthetic active seed sheath and low O 2 concentrations in the centre of the seed at the position of the embryo. In light, photosynthesis in the seed sheath increased O 2 availability in central parts of the seed enabling enhanced respiratory energy generation for biosynthetic activity. Early‐stage seedlings also displayed photosynthetic capacity in hypocotyl and cotyledonary tissues, which may be beneficial for seedling establishment. Sheath O 2 production is important for alleviating intra‐seed hypoxic stress, which might increase endosperm storage activity, improving the conditions for successful seed maturation and germination.

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