Use of Synchrotron Phase-Sensitive Imaging for the Investigation of Magnetopriming and Solar UV-Exclusion Impact on Soybean (Glycine max) Leaves

The combined response of exclusion of solar ultraviolet radiation (UV-A+B and UV-B) and static magnetic field (SMF) pre-treatment of 200 mT for 1 h were studied on soybean (Glycine max) leaves using synchrotron imaging. The seeds of soybean with and without SMF pre-treatment were sown in nursery bags kept in iron meshes where UV-A+B (280–400 nm) and UV-B (280–315 nm) from solar radiation were filtered through a polyester filters. Two controls were planned, one with polythene filter controls (FC)- which allows all the UV (280–400 nm); the other control had no filter used (open control-OC). Midrib regions of the intact third trifoliate leaves were imaged using the phase-contrast imaging technique at BL-4, Indus-2 synchrotron radiation source. The solar UV exclusion results suggest that ambient UV caused a reduction in leaf growth which ultimately reduced the photosynthesis in soybean seedlings, while SMF treatment caused enhancement of leaf growth along with photosynthesis even under the presence of ambient UV-B stress. The width of midrib and second-order veins, length of the second-order veins, leaf vein density, and the density of third-order veins obtained from the quantitative image analysis showed an enhancement in the leaves of plants that emerged from SMF pre-treated seeds as compared to untreated ones grown in open control and filter control conditions (in the presence of ambient UV stress). SMF pre-treated seeds along with UV-A+B and UV-B exclusion also showed significant enhancements in leaf parameters as compared to the UV excluded untreated leaves. Our results suggested that SMF-pretreatment of seeds diminishes the ambient UV-induced adverse effects on soybean.

The Influence of UV on the Production of Free Terpenes in Vitis vinifera cv. Shiraz

Terpenes contribute to the desirable flavour and aroma of grapes and wine. The biosynthesis of these plant secondary metabolites is influenced by both physiological and environmental factors, such as grapevine phenological stage and sunlight exposure. In this study, we investigated the influence of ultraviolet (UV) at different grapevine phenological stages on free terpenes in grape at harvest. Two types of transparent polymer films were applied to grape bunches to eliminate both UV-A and UV-B or only eliminate UV-B, followed by the identification and quantification of terpenes using headspace solid-phase microextraction with gas chromatography–mass spectrometry (HS–SPME–GC–MS) analysis. In all, 27 free terpenes were identified, including eight monoterpenes/monoterpenoids, four norisoprenoids and fifteen sesquiterpenes. Higher concentrations of γ-terpinene, linalool and β-damascenone were observed in grapes with UV-B attenuation compared to the naturally exposed grape bunches. Elevated α-muurolene was observed in UV-attenuated grapes from pre-veraison to harvest, while higher concentrations of γ-cadinene were observed in naturally exposed grapes. The impacts of UV exclusion on grape terpenes at harvest were specific to phenological stages, where applying UV films from veraison to intermediate ripeness reduced the concentrations of key terpenes in grape harvest and UV attenuation from intermediate ripeness to harvest promoted the accumulation of α-muurolene and γ-cadinene. This study provides information for viticulturists to better manage grape terpene composition through UV shading.

UV radiation increases flavonoid protection but decreased reproduction in Silene littorea

Plants respond to changes in ultraviolet (UV) radiation via morphological and physiological changes. Among the variety of plant UV-responses, the synthesis of UV-absorbing flavonoids constitutes an effective non-enzymatic mechanism to mitigate photoinhibitory and photooxidative damage caused by UV stress, either reducing the penetration of incident UV radiation or acting as quenchers of reactive oxygen species (ROS). In this study, we designed a UV-exclusion experiment to investigate the effects of UV radiation in Silene littorea. We spectrophotometrically quantified concentrations of both anthocyanins and non-anthocyanin flavonoids (flavones) in petals, calyces, leaves and stems. Furthermore, we analyzed the UV effect on the photosynthetic activity in hours of maximum solar radiation and we tested the impact of UV radiation on male and female reproductive performance. We found that anthocyanin concentrations showed a significant decrease of about 20% with UV-exclusion in petals and stems, and 30% in calyces. Flavone concentrations showed a significant reduction of approximately 25% in calyces and stems, and 12% in leaves. Photochemical efficiency of plants grown under UV stress decreased sharply at maximum light stress, but their ability for recovery after light-stress was not affected. In addition, exposure to UV radiation does not seem to affect ovule production or seed set, but decreases the total seed production per plant and pollen production by 69% and 31%, respectively. Our results demonstrate that UV radiation produced opposite effects on flavonoid accumulation and reproduction in S. littorea. UV stress increased flavonoid concentrations, suggesting a photoprotective role of flavonoids against UV radiation, but had negative consequences for reproduction. We propose that this trade-off helps this species to occupy exposed habitats with high UV radiation.