The effect of lead and copper on apical segments of Gracilaria domingensis was examined. Over a period of 7 days, the segments were cultivated with concentrations of 5 and 10 ppm under laboratory conditions. The samples were processed for light, confocal, and electron microscopy, as well as histochemistry, to evaluate growth rates, mitochondrial activity, protein levels, chlorophyll a, phycobiliproteins, and carotenoids. After 7 days of exposure to lead and copper, growth rates were slower than control, and biomass loss was observed on copper-treated plants. Ultrastructural damage was primarily observed in the internal organization of chloroplasts and cell wall thickness. X-ray microanalysis detected lead in the cell wall, while copper was detected in both the cytoplasm and cell wall. Moreover, lead and copper exposure led to photodamage of photosynthetic pigments and, consequently, changes in photosynthesis. However, protein content and glutathione reductase activity decreased only in the copper treatments. In both treatments, decreased mitochondrial NADH dehydrogenase activity was observed. Taken together, the present study demonstrates that (1) heavy metals such as lead and copper negatively affect various morphological, physiological, and biochemical processes in G. domingensis and (2) copper is more toxic than lead in G. domingensis.

Ultraviolet-B radiation (UVBR) affects plants in many important ways, including reduction of growth rate and primary productivity, and changes in ultrastructures. Rice (Oryza sativa) is one of the most cultivated cereals in the world, along with corn and wheat, representing over 50% of agricultural production. In this study, we examined O. sativa plants exposed to ambient outdoor radiation and laboratory-controlled photosynthetically active radiation (PAR) and PAR + UVBR conditions for 2 h/day during 30 days of cultivation. The samples were studied for morphological and ultrastructural characteristics, and physiological parameters. PAR + UVBR caused changes in the ultrastructure of leaf of O. sativa and leaf morphology (leaf index, leaf area and specific leaf area, trichomes, and papillae), plant biomass (dry and fresh weight), photosynthetic pigments, phenolic compounds, and protein content. As a photoprotective acclimation strategy against PAR + UVBR damage, an increase of 66.24% in phenolic compounds was observed. Furthermore, PAR + UVBR treatment altering the levels of chlorophylls a and b, and total chlorophyll. In addition, total carotenoid contents decreased after PAR + UVBR treatment. The results strongly suggested that PAR + UVBR negatively affects the ultrastructure, morphology, photosynthetic pigments, and growth rates of leaf of O. sativa and, in the long term, it could affect the viability of this economically important plant.

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.

The in vitro effect of cadmium (Cd) on apical segments of Pterocladiella capillacea was examined. Over a period of 7 days, the segments were cultivated with the combination of different salinities (25, 35, and 45 practical salinity units) and Cd concentrations, ranging from 0.17 to 0.70 ppm. The effects of Cd on growth rates and content of photosynthetic pigments were analyzed. In addition, metabolic profiling was performed, and samples were processed for microscopy. Serious damage to physiological performance and ultrastructure was observed under different combinations of Cd concentrations and salinity values. Elementary infrared spectroscopy revealed toxic effects registered on growth rate, photosynthetic pigments, chloroplast, and mitochondria organization, as well as changes in lipids and carbohydrates. These alterations in physiology and ultrastructure were, however, coupled to activation of such defense mechanisms as cell wall thickness, reduction of photosynthetic harvesting complex, and flavonoid. In conclusion, P. capillacea is especially sensitive to Cd stress when intermediate concentrations of this pollutant are associated with low salinity values. Such conditions resulted in metabolic compromise, reduction of primary productivity, i.e., photosynthesis, and carbohydrate accumulation in the form of starch granules. Taken together, these findings improve our understanding of the potential impact of this metal in the natural environment.

The incidence of light in terms of quality and quantity into the aquatic ecosystem is an important factor determining the distribution and abundance of macroalgae. Ultraviolet radiation which is one of the most debated factors that can affect these responses can cause significant cellular damage through photooxidation and oxidative stress, resulting in several vital metabolic changes such as DNA replication, transcription and translation, growth rate and development, photosynthesis and respiration, and promotion of apoptosis. Based on the aforementioned information, the present study aimed to contribute to the knowledge of the effect of UV radiation on macroalgae by using Sargassum spp. as biological model by integrating diverse physiological, cellular defenses, biological activities, and proteomic approaches for understanding the impact and sensitivity of this stressor under laboratory conditions. The different responses of the seaweed were evaluated under PAR, PAR+UVA and PAR+UVB treatments. Physiological parameters showed little variation between the treatments suggesting that moderate UV radiation doses could regulate resistance responses through the activation of antioxidant defense system by production of UV-absorbing compounds with photoprotective function, such as phlorotannins, flavonoids, and carotenoids that could provide adaptive advantages for organisms exposed to UV radiation. Moreover, extracts from the treated algal material presented high antiviral potential, which may be related to the presence of phenolic compounds and sulfated polysaccharides in the tested extracts. Then, the species can be considered as a potential biotechnology source of natural bioactive compounds. In relation to the proteomic profile of S. filipendula, were identified 40 proteins differentially abundant with respect to the UV treatments, which were mainly related to photosynthesis (32%), energy metabolism (12%), carbohydrate metabolism (7%), ROS scavenging defense and stress related metabolism (7%). Proteomic results showed target proteins that could improve the ability of the species to adapt to UV exposure, contribuiting significantly in our understanding of the molecular mechanisms underlying stress tolerance. Additionally, composition and abundance of fatty acids, chlorophylls, and carotenoids of S. vulgare after exposure to different light qualities: SOX (low pressure sodium lamps as control), SOX+Blue, SOX+Green, SOX+Red, and SOX+UV, showed that SOX supplemented with UV radiation provoked the decrease of certain carotenoids. On the other hand, the content of certain fatty acids under these SOX treatments showed slighty variation under the different light qualities, presenting a high percentage of PUFAs; however, there is need to perform future researches that allow the establishment of light condition for the stimulation of these compounds from S. vulgare. RESUMO GERALA incidência de luz em termos de qualidade e quantidade no ecossistema aquático é um fator importante que determina a distribuição e a abundância de ma...