Ultraviolet-B Radiation-induced Inhibition of Leaf Expansion and Promotion of Anthocyanin Production

Abstract

Leaf discs from expanding leaves of Rumex patientia L. were exposed to 7 hours of visible plus different levels of ultraviolet radiation in the 290 to 315 nm waveband (UV-B) and then placed in darkness. Leaf disc expansion was reduced and anthocyanin production was increased in discs exposed to moderate or high levels of UV-B radiation when compared to control discs. The possibility that the inhibition of leaf expansion by UV-B radiation might be at least partially phytochrome-mediated was examined by giving discs brief red or far red irradiation folowing exposure to UV-B radiation. Brief red radiation (R) following treatment with moderate or high UV-B radiation did not alter the pattern of growth or anthocyanin production compared to discs placed in darkness following UV-B treatment. However, a posttreatment with far red radiation (FR) reduced the growth of discs subjected previously to either moderate UV-B or no UV-B irradiation to the level of growth of discs given high UV-B. FR posttreatment also decreased anthocyanin production in discs in moderate and high UV-B treatments. Effects of FR and UV-B radiation apparently do not involve the same mechanism. This was demonstrated by experiments in which FR following the UV-B treatments was in turn followed by R, which reversed the effects of the FR but did not alter the growth inhibition or increased anthocyanin production induced by moderate or high levels of UV-B radiation.Recent work has shown that enhanced UV-B (280-320 nm) radiation corresponding to global solar UV irradiance which would occur with a substantial atmospheric ozone reduction resulted in inhibition of photosynthesis and leaf growth (23). The effect on photosynthesis was cumulative, but the inhibition of leaf expansion was most pronounced during the first days of leaf expansion. Fully expanded leaf dimensions were also less than those of control plants. Even UV-B irradiation corresponding to present-day levels of solar radiation was sufficient to effect some inhibition of leaf growth (24).The mechanism by which UV-B radiation inhibits leaf expansion is not known. It appears that inhibition of expansion is not entirely due to reduction of photosynthetic rates (23). It is important to elucidate the physiological mechanisms involved in UV-B radiation inhibition of leaf expansion and how these may interact with mechanisms known to control leaf expansion. One mechanism operating in the control of leaf expansion is the low irradiance phytochrome system. Brief R2 promotes expansion (18), and 'Research supported by the National Aeronautics and Space Administration.2 Abbreviations: R: red radiation; FR: far red radiation; UV-BBE: biologically effective UV-B radiation; HIR: high irradiance reaction. this can be reversed by brief FR (14), which can be given 8 to 48 hr after the R, showing persistent photoreversibility in control of leafgrowth (4, 13). Growth, as measured by fresh weight increases, of bean seedlings grown in light can be depressed by exposure to brief FR (13).Butler et al. (2) show...

The effects of various drip fertigated water quantities on flavonoid and anthocyanin content on hydroponically cultivated Cucumis sativa L.

“…2 and absorbance of the clear supernatant measured spectrometrically at 300, 530, and 657 nm using acidified methanol as standard. Concentrations of flavonoids were measured at 300 nm and expressed as Abs gDM −1 (Mirecki and Teramura, 1984), while anthocyanin concentration was measured as Abs530 −1/3Abs657 (Lindoo and Caldwell, 1978) and expressed as Abs gDM −1 .…”

Inhibition of Seagrass Photosynthesis by Ultraviolet-B Radiation

“…Recently, UV-B irradiation has been shown effective in inhibiting leaf expansion (22,29,30), seedling growth (1, 21), dark respiration (29), and ion transport (1), as well as altering membrane permeability (9-11). Ultraviolet-B radiation has also been shown to be a potent inhibitor of photosynthesis (4,5,16,26,29,30, 35) 4 To whom all correspondence should be addressed.…”

Enhanced UV‐B radiation under field conditions increases anthocyanin and reduces the risk of photoinhibition but does not affect growth in the carnivorous plant Pinguicula vulgaris

“…1), indicating a differential acceleration in some terminal reaction(s) of anthocyanin formation. In laboratory experiments, simple phenolics, flavonoids and anthocyanins could be induced by UV-B radiation, although the corresponding photoreceptors might be different (Lindoo & Caldwell, 1978 ;Hashimoto et al, 1991 ;Brandt et al, 1995). Under field conditions however, with balanced visible\UV-A\UV-B radiation and mild UV-B supplementation, the anthocyanin content remained unaffected (Dillenburg et al, 1995).…”

“…UV-B absorbing capacity was assessed spectrophotometrically after appropriate dilution of the cleared extracts. The relative amounts of anthocyanins were estimated from the absorbance of the same extracts in the visible part of the spectrum (peak absorbance at 531.6 nm) after applying a correction factor for the contribution of chlorophyllous pigments at this wavelength (Lindoo & Caldwell, 1978). In all cases a Shimadzu UV-160A recording spectrophotometer was used.…”