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Acclimation of Potamogeton perfoliatus L. to periphyton accumulation-induced spectral changes in irradiance

Tóth, Viktor R., Palmer, Stephanie C. J.
Hydrobiologia 2016 v.766 no.1 pp. 293-304
Potamogeton perfoliatus, acclimation, biomass, buds, epiphytes, field experimentation, leaf area, leaves, light intensity, light quality, littoral zone, macrophytes, morphogenesis, periphyton, plantlets, red light, shade tolerance
The biomass and composition of autotrophic communities in the littoral zone are mainly affected by light availability. In a field study, the spectral attenuation of periphyton was assessed. Periphyton absorbed more light in the red than in the infrared spectral range, resulting in a lower red to infrared ratio (~0.3 during the most active period of periphyton accumulation, compared with 0.9–1 otherwise). The lowest red to infrared ratio was detected in the upper 20–40 cm of the water column. Epiphytic algae are therefore found to affect not only the quantity but also the quality of light passing through periphyton. Acclimation of Potamogeton perfoliatus L. plantlets to such infrared-enriched light was also studied in the laboratory. During leaf morphogenesis, lower red to infrared ratio light was associated with increased leaf area via the growth of existing (+85%) and the production of new leaves. Intensified internode length growth (+130%) was also observed. Post morphogenesis, no leaf or internode growth was observed and new shoot production was also intensive. Leaf photochemical activity did not significantly differ between groups or treatments. Results suggest that periphyton could trigger shade-tolerance (leaf growth), shade-avoidance (internode growth), and morphogenetic (branch production from axillary buds) adaptations in macrophytes.