Experimental analysis of rhodophyte photoacclimation to PAR and UV-radiation using in vivo absorbance spectroscopy

Ks. Beach et al., Experimental analysis of rhodophyte photoacclimation to PAR and UV-radiation using in vivo absorbance spectroscopy, BOTAN MARIN, 43(6), 2000, pp. 525-536
Citations number
Categorie Soggetti
Aquatic Sciences
Journal title
ISSN journal
0006-8055 → ACNP
Year of publication
525 - 536
SICI code
Analysis of absorbance spectra of the red alga, Ahnfeltiopsis concinna, rev ealed the capacity of tissues from the canopy and understory to respond to changes in the intensity of photosynthetically active radiation. No differe nces in photoacclimation responses were observed in the experiments perform ed with A. concinna under PAR-only, PAR+UV-A, and PAR+UV-A+UV-B treatments. In situ, photoacclimation capacities were manifested as marked alterations in pigmentation for tissues from canopy to understory microsites in indivi dual thalli of this dense tropical turf. This phenotypic adjustment is dyna mic and recovery from irradiance stress induced by canopy removal simulatin g herbivory or bleaching events is complete within 29 days. In vivo absorba nce spectra allowed simultaneous observation of multiple pigment pools and monitoring photoacclimation changes over the course of days in this alga. I nsight into the cascade of photoacclimation events was revealed by concurre nt measurement of pigments and photosynthetic performance. Overall, acclima tion from a sun to shade or shade to sun states proceeded faster for degrad ative than for synthetic processes. Specifically, phycobilin degradation in tissues from understory microsites exposed to high photon flux density (PF D) was faster than phycobilin synthesis in tissues from canopy microsites e xposed to low PFD. Additionally, levels of phycoerythrin changed to a great er relative extent than did shifts of compensation or saturation irradiance thresholds for photosynthesis in acclimation from shade to sun conditions. Compensation and saturation irradiances changed to a greater relative exte nt than did levels of phycoerythrin in acclimation from sun to shade condit ions. Lastly, carotenoid and putative mycosporine amino acid absorbances ad justed in response to changes in quantity of incident photon flux regardles s of light quality (PAR, UV-B, UV-A). This suggests a similar signal transd uction mechanism or other metabolic linkages in this photoacclimation mecha nism.