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Ultraviolet B-light (UV-B) can exert indirect effects on plant-herbivore interactions by inducing changes in constitutive and induced chemical defenses, since it modulates physiological aspects of plants. This study evaluated the action of UV-B radiation on photosynthesis and production of secondary metabolites in Nymphoides humboldtiana and the cascade effects on the relationship of this macrophyte with a generalist herbivore, the gastropod mollusk Biomphalaria glabrata. After 13 days of UV-B exposition under laboratory conditions, the floating macrophyte N. humboldtiana responded increasing its photosynthetic potential and the production of flavonoids with a correlated enhance in antioxidant activity. However, these changes observed in its metabolism were not enough to alter their palatability to consumption by B. glabrata verified through laboratory feeding choice experiments. Despite the known deleterious effects of exposure to UV-B on terrestrial plants, we found that N. humboldtiana does have physiological/biochemical mechanisms as a strategy or restorative response to this potencially adverse or impacting agent without changing its relationships with herbivores., (Copyright © 2020 Elsevier B.V. All rights reserved.)

A field experiment was conducted under tropical climate for assessing the effect of ambient UV-B and UV-A by exclusion of UV components on the growth, photosynthetic performance and yield of C3 (cotton, wheat) and C4 (amaranthus, sorghum) plants. The plants were grown in specially designed UV exclusion chambers, wrapped with filters that excluded UV-B (<315nm), UV-A+B (<400nm), transmitted all the UV (280-400nm) or without filters. All the four plant species responded to UV exclusion by a significant increase in plant height, leaf area, leaf biomass, total biomass accumulation and yield. Measurements of the chlorophyll, chlorophyll fluorescence parameters, gas exchange parameters and the activity of Ribulose-1,5-bisphosphate carboxylase (Rubisco) by fixation of (14)CO2 indicated a direct relationship between enhanced rate of photosynthesis and yield of the plants. Quantum yield of electron transport was enhanced by the exclusion of UV indicating better utilization of PAR assimilation and enhancement in reducing power in all the four plant species. Exclusion of UV-B in particular significantly enhanced the net photosynthetic rate, stomatal conductance and activity of Rubisco. Additional fixation of carbon due to exclusion of ambient UV-B was channeled towards yield as there was a decrease in the level of UV-B absorbing substances and an increase in soluble proteins in all the four plant species. The magnitude of the promotion in all the parameters studied was higher in dicots (cotton, amaranthus) compared to monocots (wheat, sorghum) after UV exclusion. The results indicated a suppressive action of ambient UV-B on growth and photosynthesis; dicots were more sensitive than monocots in this suppression while no great difference in sensitivity was found between C3 and C4 plants. Experiments indicated the suppressive action of ambient UV on carbon fixation and yield of C3 and C4 plants. Exclusion of solar UV-B will have agricultural benefits in both C3 and C4 plants under tropical climate., (Copyright © 2013 Elsevier B.V. All rights reserved.)

The responses of two amphibious species, Batrachium trichophyllum and Potamogeton alpinus to different UV-B environments were studied. Plant material from natural environments, as well as from outdoor treatments was examined. In long-term outdoor experiments plants were grown under three different levels of UV-B radiation: reduced and ambient UV-B levels, and a UV-B level simulating 17% ozone depletion. The following parameters were monitored: contents of total methanol soluble UV-absorbing compounds and chlorophyll a, terminal electron transport system (ETS) activity and optimal and effective quantum yield of photosystem II. No effect of the different UV-B levels on the measured parameters was observed. The amount of UV-B absorbing compounds seems to be saturated, since no differences were observed between treatments and no increase was found in peak season, when natural UV-B levels were the highest. Physiological measurements revealed no harmful effects; neither on potential and actual photochemical efficiency, nor on terminal ETS activity. The contents of UV-B absorbing compounds were examined also in plant material sampled in low and high altitude environments during the growth season. Both species exhibited no seasonal dynamics of production of UV-absorbing compounds. The contents were variable and showed no significant differences between high and low altitude populations.

Some responses of various meadow species to enhanced UV-radiation of the natural daylight spectrum are described together with the experimental protocol employed. Growth responses to supplementary UV-B+A are mostly inhibitory when compared to the ambient daylight treatment for Bellis perennis, Cardamine pratensis, Cynosurus critatus and Ranunculus ficaria. However, the response of UV-A treatment compared to that of the UV-B+A varies in significance according to the species and parameter investigated. The pertinence of the ambient and UV-A treatment to data interpretation is discussed. Stomatal conductance of B. perennis was measured throughout the 24 h cycle. Although no significant difference could be found between the stomatal conductance of UV and ambient treated plants during the hours of daylight, at night it was found that the UV-B+A treated plants were unable to achieve the same degree of closure as the ambient treated plants. UV-damage and growth responses could alter the diversity of the meadow ecosystem and these effects could be exacerbated by water loss.