Exclusion Of UV-B Research Articles

Impacts of ambient solar uv (280-400 nm) radiation on three tropical legumes

Tropical regions receive the highest level of global solar ultraviolet (UV) radiation especially UV-B (280-320 nm). The average daily dose of the UV-B radiation in Madurai, South India (10°N) is 10 kJ m-2. This is approximately 50% more than the average daily UV-B radiation in many European countries. A field study was conducted using selective filters to remove either the UV-B (< 320 nm) or UV-B/A (<400 nm) of the solar spectrum, and the effects were followed inCyamopsis tetragonoloba, Vigna mungo, andVigna radiata to determine their sensitivity to UV. When compared to ambient radiation, exclusion of solar UV-B increased the seedling height, leaf area, fresh weight and dry weight and the crop yield by 50% in the case ofCyamopsis, and the extent of such increase was slightly less under UV-B/A exclusion. InV. mungo a significant reduction was seen in solar UV excluded plants whileV. radiata was found to be unaffected.

Changes in Ultrastructure, Photosynthetic Activity and Pigments in the Antarctic Red Alga Palmaria decipiens during Acclimation to UV Radiation

The effect of ultraviolet (UV) radiation on ultrastructure, variable fluorescence of photosystem II and concentrations of photosynthetic pigments in the endemic Antarctic Rhodophyta Palmaria decipiens was studied. After 6 and 8 h of artificial UV-exposure a vesiculation of the chloroplast thylakoids and changes in the membrane structure of mitochondria were observed, which disappeared after 12 h of UV treatment. A 60% reduction of maximum quantum yield of photosynthesis (F v /F m ) was obtained after 4 h of UV-A+B exposure, which recovered up to 80% after 8 h in darkness and 10 h of white light. Exclusion of UV-B led to a minor reduction of F v /F m to 60% in the first 4 h of irradiation. The concentration of chlorophyll a increased after 4 h of UV exposure, whereas concentrations of phycoerythrin and phycocyanin decreased at the same time. After 12–16 h of UV exposure no significant changes compared to the control were detectable. These findings give an insight into the fine structural and physiological changes during and after UV exposure, and indicate an acclimation of the alga to UV radiation.

Exclusion of solar UV-B (280–315 nm) radiation on vegetative growth and photosynthetic activities in Vigna unguiculata L.

The impact of solar radiation with and without UV-B component was studied in a tropical legume Vigna unguiculata L. The average level of ambient UV-B was 10 kJ m −2 day −1. Exclusion of solar UV-B increased the seedling height, leaf area and fresh weight. On a unit fresh weight basis, a 50% increase in total chlorophyll and 47% decrease in flavonoids was noticed after 20 days of growth. Decrease in flavonoid content in UV-B filtered seedlings indicates the plant responsiveness to minimal UV-B radiation existing inside the filter cage. UV-B exclusion during the early phase of seedling growth also promoted photosynthetic activities, measured as O 2 evolution or fluorescence transients. Such an enhancement in activity was attributed to modification in thylakoid organization under UV-B exclusion.

Bagging `Fuji' Apples during Fruit Development Affects Color Development and Storage Quality

Enclosing `Fuji' apple (Malus ×domestica Borkh.) fruit in paper bags 2 months after full bloom delayed the increase in internal ethylene concentration at the onset of fruit ripening, and increased the respiration rate early in the bagging period. Bagging delayed and reduced red color development, especially on the blush side, but did not affect fruit resistance to gas diffusion. External surface color changed significantly within the first 4 days after bags were removed. Exclusion of UV-B from sunlight by Mylar film after paper bag removal impaired red color development. Bagging during fruit development increased superficial scald but eliminated stain during cold storage. Exposure to sunlight for 19 or 20 days before harvest reduced scald incidence in comparison with leaving bags on until harvest.

The effect of solar UVA and UVB on subarctic Daphnia pulicaria in its natural habitat

The effect of solar radiation, especially the ultraviolet regime (UVA and UVB), has been examined on Daphnia pulicaria (Forbes) in a subarctic lake. Daphnia were exposed to four radiation regimes: total radiation, exclusion of UVB, exclusion of UVA and UVB and dark controls. Exposure lasted 2–4 days in 2 depths (8 cm and 24 cm). In the subsurface (8 cm) exposure survival was significantly increased when UVB or UVB and UVA were excluded. In addition, the percentage of egg carrying Daphnia and the number of live offspring increased significantly when UVB was excluded. In 24 cm depth, an increase of survival was noticeable only in some of the experiments. Differences in reproduction due to different radiation regimes, too, were not significant. The results demonstrate that not only UVB, but UVA also may have a significant effect on Daphnia in their natural habitat.