Allelopathic and Water Conserving Functions of Leaf Epicuticular Exudates in the Mediterranean Shrub Dittrichia viscosa

1995 ◽  
Vol 22 (5) ◽  
pp. 755 ◽  
Author(s):  
M Stephanou ◽  
Y Manetas
Keyword(s):  
Water Conservation ◽  
Laboratory Experiments ◽  
Photochemical Efficiency ◽  
Ultraviolet B ◽  
Water Soluble ◽  
Considerable Decrease ◽  
Ultraviolet B Radiation ◽  
Lettuce Seeds ◽  
Dittrichia Viscosa ◽  
Mediterranean Shrub

The possible ecophysiological roles of the water soluble, epicuticular material accumulated on the leaves of Dittrichia viscosa (L.) W.Greuter (syn. Inula viscosa (L.) Aiton) (Asteraceae), were investigated in laboratory experiments. It was found that: (a) the material reduced cuticular transpiration; (b) it had a strong absorbance in the ultraviolet, apparently offering the leaves an ultraviolet-B radiation screen; (c) removal of this material, however, and exposure of the leaves to visible light supplemented with ultraviolet-B radiation had no effects on photosystem II photochemical efficiency or stomatal functions and caused no epidermal browning; and (d) the material was strongly inhibitory against germination of lettuce seeds and caused considerable decrease in the radicle length of Phlomis fruticosa L., a species often occupying the same habitat as D. viscosa. We infer from the above that D. viscosa leaves may be resistant to ultraviolet-B radiation damage and, accordingly, the water conservation and allelopathic functions of the epicuticular material may predominate over its potential to protect against ultraviolet-B radiation.

scholarly journals Non-synergistic effects of water-soluble crude oil and enhanced ultraviolet-B radiation on a natural plankton assemblage

2005 ◽  
Vol 294 ◽  
pp. 63-77 ◽  
Author(s):  
P Sargian ◽  
B Mostajir ◽  
K Chatila ◽  
GA Ferreyra ◽  
E Pelletier ◽  
...  
Keyword(s):  
Crude Oil ◽  
Synergistic Effects ◽  
Ultraviolet B ◽  
Water Soluble ◽  
Ultraviolet B Radiation

scholarly journals Physiological Assessment of Cool-season Turfgrasses Under Ultraviolet-B Stress

HortScience ◽  
2009 ◽  
Vol 44 (6) ◽  
pp. 1785-1789 ◽  
Author(s):  
Xunzhong Zhang ◽  
Erik H. Ervin
Keyword(s):  
Festuca Arundinacea ◽  
Poa Pratensis ◽  
Photochemical Efficiency ◽  
Kentucky Bluegrass ◽  
Physiological Parameters ◽  
Ultraviolet B ◽  
Cool Season ◽  
Sod Activity ◽  
Ultraviolet B Radiation ◽  
Tolerant Species

Ultraviolet-B (280–320 nm) radiation is one of the major factors causing quality decline of transplanted turfgrass sod. Information on physiological parameters for assessing turfgrass tolerance to ultraviolet-B stress is lacking. The objective of this study was to evaluate ultraviolet-B tolerance of four cool-season turfgrass species and varieties using selected physiological parameters under artificial ultraviolet-B radiation stress. The physiological performance of 18 varieties of tall fescue (TF; Festuca arundinacea Schreb.), chewings fescue (CF; Festuca rubra L. ssp. commutata Gaud.), perennial ryegrass (PRG; Lolium perenne L.), and kentucky bluegrass (KBG; Poa pratensis L.) were subjected to continuous, artificial ultraviolet-B radiation (70 μmol·m−2·s−1) for 10 days. Visual quality ratings of TF, CF, PRG, and KBG measured at Day 10 were reduced by 49%, 18%, 51%, and 74%, respectively, relative to that at trial initiation. Ultraviolet-B tolerance in CF was the greatest, KBG was the least, and TF and PRG were intermediate. ‘Ebony’ was the most ultraviolet-B-tolerant TF variety, whereas ‘BlueTastic’, ‘BlueRiffic’, and ‘747’ had greater ultraviolet-B tolerance than the other four KBG varieties. No differences were observed in ultraviolet-B tolerance between varieties in either CF or PRG. The ultraviolet-B-tolerant species had less electrolyte leakage (EL), greater canopy photochemical efficiency (PEc), and relatively smaller and slower upregulation in antioxidant superoxide dismutase (SOD) activity relative to ultraviolet-B-sensitive ones. The results suggest that EL, PEc, and SOD may be used as physiological parameters in selecting ultraviolet-B-tolerant species and varieties for sod production and lawn establishment.

Leaf Hairs of Olive (Olea europaea) Prevent Stomatal Closure by Ultraviolet-B Radiation

1994 ◽  
Vol 21 (3) ◽  
pp. 293 ◽  
Author(s):  
G Grammatikopoulos ◽  
G Karabourniotis ◽  
A Kyparissis ◽  
Y Petropoulou ◽  
Y Manetas
Keyword(s):  
Photosystem Ii ◽  
Water Vapour ◽  
Photosynthetic Rate ◽  
White Light ◽  
Photochemical Efficiency ◽  
Ultraviolet B ◽  
Hair Removal ◽  
Leaf Hairs ◽  
Ultraviolet B Radiation ◽  
Leaf Resistance

In olive (Olea europaea L.), hair removal had no effect on the photosynthetic rate and the apparent leaf resistance to water vapour diffusion in leaves illuminated with white light (900 μmol m-2 s-1 photosynthetically active radiation) devoid of ultraviolet-B radiation. In addition, intact and dehaired leaves showed no significant differences in absorptance in the visible spectral region, while leaf temper- ature was independent of hair removal. These results indicate that leaf hairs of O. europaea may play only a marginal role in leaf energy balance and transpiration. When the white light was supplemented with ultraviolet-B radiation (5.89 W m-2), however, there was a considerable decrease in the photo- synthetic rate, and a simultaneous increase in leaf resistance to water vapour in dehaired leaves. Photochemical efficiency of photosystem II, evaluated from chlorophyll fluorescence emitted from the illuminated side, was reduced in all cases, but the reduction in dehaired, ultraviolet-B treated leaves was more pronounced and irreversible, indicating that the reduction of the photosynthetic rate may result from both stomatal limitation and electron flow inhibition. Photosynthetic capacity of dehaired leaves, measured at 5% CO2, however, was not influenced by ultraviolet-B radiation. We suggest, therefore, that ultraviolet-B radiation reduces photosynthetic rates by closing the stomata, while the observed reduction in photosystem II photochemical efficiency may concern only a superficial chloroplast population, contributing negligibly to whole leaf photosynthesis. Under the conditions of our experi- ments, the protective function of the indumentum against ultraviolet-B radiation predominates over the water conservation function.

Activation of HIV in Human Skin by Ultraviolet B Radiation and its Inhibition by NFκB Blocking Agents¶

2001 ◽  
Vol 74 (6) ◽  
pp. 805 ◽  
Author(s):  
Joan Breuer-McHam ◽  
Eric Simpson ◽  
Irene Dougherty ◽  
Makoto Bonkobara ◽  
Kiyoshi Ariizumi ◽  
...  
Keyword(s):  
Human Skin ◽  
Ultraviolet B ◽  
Ultraviolet B Radiation ◽  
Blocking Agents

Ancestral U.S. Soybean Cultivars Characterized for Tolerance to Ultraviolet‐B Radiation

Crop Science ◽  
1992 ◽  
Vol 32 (5) ◽  
pp. 1214-1219 ◽  
Author(s):  
Herbert E. Reed ◽  
Alan H. Teramura ◽  
William J. Kenworthy
Keyword(s):  
Ultraviolet B ◽  
Ultraviolet B Radiation ◽  
Soybean Cultivars
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