Effects of Natural Radiation, Photosynthetically Active Radiation and Artificial Ultraviolet Radiation-B on the Chloroplast Organization and Metabolism ofPorphyra acanthophoravar.brasiliensis(Rhodophyta, Bangiales)

Abstract

We undertook a study of Porphyra acanthophora var. brasiliensis to determine its responses under ambient conditions, photosynthetically active radiation (PAR), and PAR+UVBR (ultraviolet radiation-B) treatment, focusing on changes in ultrastructure, and cytochemistry. Accordingly, control ambient samples were collected in the field, and two different treatments were performed in the laboratory. Plants were exposed to PAR at 60 μmol photons m-2 s-1 and PAR + UVBR at 0.35 W m-2 for 3 h per day during 21 days of in vitro cultivation. Confocal laser scanning microscopy analysis of the vegetative cells showed single stellate chloroplast in ambient and PAR samples, but in PAR+UVBR-exposed plants, the chloroplast showed alterations in the number and form of arms. Under PAR+UVBR treatment, the thylakoids of the chloroplasts were disrupted, and an increase in the number of plastoglobuli was observed, in addition to mitochondria, which appeared with irregular, disrupted morphology compared to ambient and PAR samples. After UVBR exposure, the formation of carpospores was also observed. Plants under ambient conditions, as well as those treated with PAR and PAR+UVBR, all showed different concentrations of enzymatic response, including glutathione peroxidase and reductase activity. In summary, the present study demonstrates that P. acanthophora var. brasiliensis shows the activation of distinct mechanisms against natural radiation, PAR and PAR+UVBR.

Physiological performance by growth rate, pigment and protein content of the brown seaweed <em>Sargassum filipendula</em> (Ochrophyta: Fucales) induced by moderate UV radiation exposure in the laboratory

“…In a previous study using Sargassum cymosum C. Agardh as a biological model to evaluate the combined effects of UV radiation and salinity, Polo et al (2014a) found that UVA and UVB together in low doses such as the ones used herein stimulated the growth rate, leading to an increase in the amount of mitochondria, which could support the metabolic energy demand required for this process. Indeed, studies with different algal species at low doses of UV radiation show that the UV level modulates diverse physiological responses besides growth through up-or downregulation, such as induction of Chl a, phenolic compounds and antioxidant activity (Polo et al 2014a), alteration in putrescine/spermidine ratio (Polo et al 2014b), variation of photosynthetic performance and accessory pigments (Simioni et al 2014, Schmidt et al 2015, and ultrastructural organization (Bouzon et al 2012, Pereira et al 2017.…”

Growth and photosynthetic pigments of Gracilariopsis tenuifrons (Rhodophyta, Gracilariaceae) under high light in vitro culture

“…Phycobiliproteins, the characteristic reddish pigment of red macroalgae, are the most sensitive antenna pigment, localized externally to the reaction center and the first photosynthetic pigment to decrease in concentration under light stress (Bouzon et al 2012, Gouveia et al 2013. Under the most extreme condition of this experiment (day 7, 1000 μmol photons m −2 s −1 ), the apical portions of G. tenuifrons were completely yellowish (Fig.…”

Effects of UV-B radiation on germlings of the red macroalga Nemalion helminthoides (Rhodophyta)

“…Control and treated samples were attached on slides and sealed using colorless nail polish. A Leica HCX PLAPO lambda 63x/1.4-0.6 oil immersion objective was fitted on the inverted fluorescent microscope [ 32 ]. Chloroplast auto-fluorescence was observed at 488 nm laser wavelength excitation with emission spectrum from 639 nm to 701 nm [ 33 ].…”