Light Quality Influences on Early Developmental Stage of a Tropical Seagrass, Enhalus acoroides: Growth and Physiological Responses

Abstract

The impact of light quality on the early development of the seagrass Enhalus acoroides remains poorly understood. To bridge this gap in knowledge, we conducted aquarium-based experiments to assess the growth and physiological responses of E. acoroides seeds from germination to seedling development over 15 days. We subjected the seeds to different light conditions, including darkness, white light (λ = 460−630 nm), red light (peak λ = 630 nm), and blue light (peak λ = 460 nm), all at an intensity of 100 μmol photons·m^-2·s^-1. Our results revealed unique responses in darkness and red light. Darkness stimulated shoot and root elongation, while red light resulted in the lowest shoot/root ratio. Seedlings grown in darkness displayed suppressed photosynthetic activity, as evidenced by the lowest maximum quantum yield, electron transport rates, and initial slope of the light response curve. These seedlings also had the lowest photosynthetic pigments and xanthophyll cycle-related attributes. On the other hand, red light promoted high light responses, as indicated by the lowest chlorophyll b/a ratio (an indicator of the size of the light-harvesting antenna) and the highest de-epoxidation state of xanthophyll (an indicator of photoprotective effort). Our findings highlight the significant impact of changes in light quality on the growth and physiological performance of E. acoroides during early development. Interestingly, white light and blue light resulted in similar outcomes. More research is necessary to shed light on the underlying mechanisms driving these responses and the implications for seagrass adaptation to marine environments.