Environmental effects of ozone depletion and its interactions with climate change: progress report, 2009.

The parties to the Montreal Protocol are informed by three panels of experts. One of these is the Environmental Effects Assessment Panel (EEAP), which deals with UV radiation and its effects on human health, animals, plants, biogeochemistry, air quality and materials. Since 2000, the analyses and interpretation of these effects have included interactions between UV radiation and global climate change. When considering the effects of climate change, it has become clear that processes resulting in changes in stratospheric ozone are more complex than believed previously. As a result of this, human health and environmental problems will likely be longer-lasting and more regionally variable. Like the other panels, the EEAP produces a detailed report every four years; the most recent was that for 2006 (Photochem. Photobiol. Sci., 2007, 6, 201-332). In the years in between, the EEAP produces a less detailed and shorter progress report, as is the case for this present one for 2009. A full quadrennial report will follow for 2010.

Environmental effects of ozone depletion and its interactions with climate change: progress report, 2008.

After the enthusiastic celebration of the 20th Anniversary of the Montreal Protocol on Substances that Deplete the Ozone Layer in 2007, the work for the protection of the ozone layer continues. The Environmental Effects Assessment Panel is one of the three expert panels within the Montreal Protocol. This EEAP deals with the increase of the UV irradiance on the Earth's surface and its effects on human health, animals, plants, biogeochemistry, air quality and materials. For the past few years, interactions of ozone depletion with climate change have also been considered. It has become clear that the environmental problems will be long-lasting. In spite of the fact that the worldwide production of ozone depleting chemicals has already been reduced by 95%, the environmental disturbances are expected to persist for about the next half a century, even if the protective work is actively continued, and completed. The latest full report was published in Photochem. Photobiol. Sci., 2007, 6, 201-332, and the last progress report in Photochem. Photobiol. Sci., 2008, 7, 15-27. The next full report on environmental effects is scheduled for the year 2010. The present progress report 2008 is one of the short interim reports, appearing annually.

Terrestrial ecosystems, increased solar ultraviolet radiation, and interactions with other climate change factors.

There have been significant advances in our understanding of the effects of UV-B radiation on terrestrial ecosystems, especially in the description of mechanisms of plant response. A further area of highly interesting research emphasizes the importance of indirect UV radiation effects on plants, pathogens, herbivores, soil microbes and ecosystem processes below the surface. Although photosynthesis of higher plants and mosses is seldom affected by enhanced or reduced UV-B radiation in most field studies, effects on growth and morphology (form) of higher plants and mosses are often manifested. This can lead to small reductions in shoot production and changes in the competitive balance of different species. Fungi and bacteria are generally more sensitive to damage by UV-B radiation than are higher plants. However, the species differ in their UV-B radiation sensitivity to damage, some being affected while others may be very tolerant. This can lead to changes in species composition of microbial communities with subsequent influences on processes such as litter decomposition. Changes in plant chemical composition are commonly reported due to UV-B manipulations (either enhancement or attenuation of UV-B in sunlight) and may lead to substantial reductions in consumption of plant tissues by insects. Although sunlight does not penetrate significantly into soils, the biomass and morphology of plant root systems of plants can be modified to a much greater degree than plant shoots. Root mass can exhibit sizeable declines with more UV-B. Also, UV-B-induced changes in soil microbial communities and biomass, as well as altered populations of small invertebrates have been reported and these changes have important implications for mineral nutrient cycling in the soil. Many new developments in understanding the underlying mechanisms mediating plant response to UV-B radiation have emerged. This new information is helpful in understanding common responses of plants to UV-B radiation, such as diminished growth, acclimation responses of plants to UV-B radiation and interactions of plants with consumer organisms such as insects and plant pathogens. The response to UV-B radiation involves both the initial stimulus by solar radiation and transmission of signals within the plants. Resulting changes in gene expression induced by these signals may have elements in common with those elicited by other environmental factors, and generate overlapping functional (including acclimation) responses. Concurrent responses of terrestrial systems to the combination of enhanced UV-B radiation and other global change factors (increased temperature, CO2, available nitrogen and altered precipitation) are less well understood. Studies of individual plant responses to combinations of factors indicate that plant growth can be augmented by higher CO2 levels, yet many of the effects of UV-B radiation are usually not ameliorated by the elevated CO2. UV-B radiation often increases both plant frost tolerance and survival under extreme high temperature conditions. Conversely, extreme temperatures sometimes influence the UV-B radiation sensitivity of plants directly. Plants that endure water deficit stress effectively are also likely to be tolerant of high UV-B flux. Biologically available nitrogen is exceeding historical levels in many regions due to human activities. Studies show that plants well supplied with nitrogen are generally more sensitive to UV-B radiation. Technical issues concerning the use of biological spectral weighting functions (BSWFs) have been further elucidated. The BSWFs, which are multiplication factors assigned to different wavelengths giving an indication of their relative biological effectiveness, are critical to the proper conduct and interpretation of experiments in which organisms are exposed to UV radiation, both in the field and in controlled environment facilities. The characteristics of BSWFs vary considerably among different plant processes, such as growth, DNA damage, oxidative damage and induction of changes in secondary chemicals. Thus, use of a single BSWF for plant or ecosystem response is not appropriate. This brief review emphasizes progress since the previous report toward the understanding of solar ultraviolet radiation effects on terrestrial systems as it relates to ozone column reduction and the interaction of climate change factors.

Harmonic scalpel tonsillectomy: a prospective study.

The harmonic scalpel has been in use for tonsillectomy for the last 5-6 years in western Europe and North America. Although some studies have found this technique to be superior to other conventional methods, its use is still not very popular. In this single-blinded prospective study, the intraoperative events and postoperative morbidity after the use of harmonic scalpel in tonsillectomy (HST) was evaluated in 180 cases in two hospitals and compared with conventional steel tonsillectomy (CST) and hemostasis secured by bipolar diathermy or ligatures in 100 cases. Both bipolar diathermy and ligatures were used to control the intraoperative bleeding in all cases of CST and some cases (n =9) of HST. The study was done in two hospitals. Patients were randomized irrespectively of their age, sex, past history or indication for surgery. The total number of patients operated on was 180 for HST and 100 for CST. The surgical duration, intraoperative blood loss and postoperative pain were compared between the patients who only had tonsillectomy done in either group (n =120 in HST and n = 70 in CST). The mean operative time in the HST group was not longer than the CST group, but the intraoperative blood loss was significantly less in the HST group. Postoperative pain was present in all patients in the HST group, but to a lesser extent than in the CST group. There was no major postoperative hemorrhage in the HST group that required surgical attention. HST has the advantage over CST when secondary hemorrhage after tonsillectomy is considered. Thus, following the results of the National Prospective Tonsillectomy Audit (NPTA), it may be safe to say that HST is superior to most other conventional methods in reducing secondary hemorrhage. The use of disposable blades in CST certainly reduces the risk of the transmission of Cruetzfield-Jacob disease (CJD).

Environmental effects of ozone depletion and its interactions with climate change: progress report, 2004.

The complexity of the linkages between ozone depletion, UV-B radiation and climate change has become more apparent.

Terrestrial ecosystems, increased solar ultraviolet radiation and interactions with other climatic change factors.

Based on research to date, we can state some expectations about terrestrial ecosystem response as several elements of global climate change develop in coming decades. Higher plant species will vary considerably in their response to elevated UV-B radiation, but the most common general effects are reductions in height of plants, decreased shoot mass if ozone reduction is severe, increased quantities of some phenolics in plant tissues and, perhaps, reductions in foliage area. In some cases, the common growth responses may be lessened by increasing CO2 concentrations. However, changes in chemistry of plant tissues will generally not be reversed by elevated CO2. Among other things, changes in plant tissue chemistry induced by enhanced UV-B may reduce consumption of plant tissues by insects and other herbivores, although occasionally consumption may be increased. Pathogen attack on plants may be increased or decreased as a consequence of elevated UV-B, in combination with other climatic changes. This may be affected both by alterations in plant chemistry and direct damage to some pathogens. Water limitation may decrease the sensitivity of some agricultural plants to UV-B, but for vegetation in other habitats, this may not apply. With global warming, the repair of some types of UV damage may be improved, but several other interactions between warming and enhanced UV-B may occur. For example, even though warming may lead to fewer killing frosts, with enhanced UV-B and elevated CO2 levels, some plant species may have increased sensitivity to frost damage.

Response of senescing wheat leaves to ultraviolet A light: changes in energy transfer efficiency and PS II photochemistry.

Response of senescing leaves of wheat seedlings to ultraviolet A (UVA) radiation (365 nm) has been examined. The results indicate that senescence-induced disorganization of thylakoid membrane, decline in carotenoid-to-chlorophyll energy transfer, and enhancement of lipid peroxidation are furthered by radiation. The senescence-induced decline in photochemical activity of photosystem II further declines on irradiation. UVA does not specifically alter any site other than those damaged by senescence.

Species specific chlorophyll a fluorescence-temperature profile at high temperatures in the leaves.

Chlorophyll a (Chl a) fluorescence-temperature profile in the region of 20-80°C was recorded for fourteen different plant species. In all the species studied, there was a rise in the fluorescence intensity in the region of 45-50°C and around 55°C the fluorescence intensity started to decline. In four of the species (Acacia melanoxylon, Ervatamia montana, Eucalyptus tertecornius and Azardicta indica) tested, there was a secondary rise in the fluorescence intensity around 65-70°C whereas in all other species a sharp decline in the fluorescence intensity was observed at this point. These changes in the fluorescence intensity at high temperatures (65-70°C) appear to be species specific and cannot be explained either in terms of changes in the stoichiometry between the two photosystems or in terms of Chl a fluorescence emission from photosystem I (PS I) at higher temperatures. This conclusion is supported by following observations: (1) there was no definite correlation between the Chl a/Chl b ratio and the pattern of fluorescence-temperature profile at high temperatures; (2) the sun and shade plants of the same species had a similar pattern of fluorescence-temperature profile; and (3) preferential excitation of PS I did not alter the fluorescence-temperature profile.

Oxygenic photoreduction of methyl viologen and nicotinamide adenine dinucleotide phosphate without the involvement of photosystem I during plastid development.

Studies on the appearance of various electron transport functions were followed during greening of etiolated cucumber cotyledons. Appearance of dichlorodimethoxy-p-benzoquinone, dimethyl quinone, tetramethyl-p-phenylenediamine, dichlorophenol indophenol and ferricyanide Hill reactions were observed after 8h of greening. However, photoreduction of methyl viologen (MV) and nicotinamide adenine dinucleotide phosphate (NADP) was observed from 2h of greening. Variable fluorescence, which is a direct indication of water-splitting function, was observed from 2h of greening in cotyledons, thylakoid membranes and photosystem II (PSII) particles. The decrease in variable fluorescence in the presence of MV (due to rapid reoxidation of Q-) observed from early stages of greening confirmed the photoreduction of MV by PSII. The early development of water-splitting function was further confirmed by the abolition of variable fluorescence in thylakoid membranes and PSII particles by heat treatment and concomittant loss of light dependent oxygen uptake in the presence of MV in heat treated chloroplasts. However, the photoreduction of MV and NADP was insensitive to intersystem electron transport inhibitors, dichlorophenyl dimethylurea or dibromomethyl isopropyl-p-benzoquinone till 8h of greening. Though the oxidation of intersystem electron carrier cytochrome f was observed from early stages of greening, the reduction of cytochrome f was not observed till 8h of greening. All these observations confirm that during early stages of greening MV and NADP are photoreduced by PSII without the involvement of intersystem electron carriers or the collaboration of PSI. Since these observations are at variance with the currently prevalent concept (Z-Scheme) of the photosynthetic generation of reducing power, which requires definite collaboration of the two photosystems, an alternate electron flow pathway is proposed.

Photochemical activities and organization of photosynthetic apparatus of C3 and C 4 plants grown under different light intensities.

Changes in the photochemical activities, influenced by variation in the growth light intensity, were followed in typical C3 (Phaseolus, Ipomoea) and C4 (Amaranthus, Sorghum) plants. Progressive decrease in the growth light intensity accelerated the O-P fluorescence induction in whole leaves. Such acceleration of the fluorescence kinetics was found to be not due to enhanced photosystem II activity but possibly a result of reduced rate of electron flow between the two photosystems. This is supported by 4 lines of evidence: (1) by the Hill activity determined in the presence of electron acceptors functioning before and after plastoquinone; (2) the photosynthetic unit size determined after flash excitation showing variations that were apparently too small to account for the changes observed fluorescence induction; (3) modification of the kinetics of secondrange light-induced absorbance changes at 520 nm; and (4) absence of significant changes in the ratio of P700/total chlorophyll ratio.The P700/cytochrome f ratio, however, increased from the usual 1-1.5 to 3-4 in plants grown under 9% sunlight. Increase in the P700/cytochrome f ratio was found to be due to a decrease in the cytochrome f/chlorophyll ratio, and this was due to perhaps to a simultaneous increase in chlorophyll and decrease in cytochrome content.

Photochemical activities and organization of photosynthetic apparatus of C3 and C 4 plants grown under different light intensities.

Changes in the photochemical activities, influenced by variation in the growth light intensity, were followed in typical C3 (Phaseolus, Ipomoea) and C4 (Amaranthus, Sorghum) plants. Progressive decrease in the growth light intensity accelerated the O-P fluorescence induction in whole leaves. Such acceleration of the fluorescence kinetics was found to be not due to enhanced photosystem II activity but possibly a result of reduced rate of electron flow between the two photosystems. This is supported by 4 lines of evidence: (1) by the Hill activity determined in the presence of electron acceptors functioning before and after plastoquinone; (2) the photosynthetic unit size determined after flash excitation showing variations that were apparently too small to account for the changes observed fluorescence induction; (3) modification of the kinetics of second-range light-induced absorbance changes at 520 nm; and (4) absence of significant changes in the ratio of P700/total chlorophyll ratio.The P700/cytochrome f ratio, however, increased from the usual 1-1.5 to 3-4 in plants grown under 9% sunlight. Increase in the P700/cytochrome f ratio was found to be due to a decrease in the cytochrome f/chlorophyll ratio, and this was due to perhaps to a simultaneous increase in chlorophyll and decrease in cytochrome content.

Characterization of synchronized cultures of Bumilleriopsis filiformis. Changes in cytochrome-f photooxidation and fluorescence induction kinetics.

Activity of the photosynthetic apparatus of synchronized cultures was studied with the xanthophycean alga Bumilleriopsis filiformis, following the kinetics of fluorescence induction and photooxidation of cytochrome f (= cytochrome c-553) of intact cells. During the beginning of the cell-division phase, minimum cellular photosynthetic activity is observed and a maximum after its completion, which is accompanied by corresponding changes in Hill reaction activity and re-reduction of cytochrome f by photosystem II light. At minimum activity, the level of steady state fluorescence was higher than at the maximum. This is due, at least in part, to the diminished electron flow between the two photosystems seemingly caused by decreased photosystem I activity. This explanation was suported by the kinetics of cytochrome-f photooxidation. Thus, electron transport activity of both photosystems appears to vary during the cell cycle.

The 520 nm absorbance changes in Scenedesmus obliquus and its relation to photosystem I.

The kinetics (region of seconds) of the light-induced 520 nm absorbance changes and its dark reversal have been studied in detail in the wild type and in some pigment and photosynthetic mutants of Scenedesmus obliquus. The following 5 lines of evidence led us to conclude that the signal is entirely due to the photosystem I reaction modified by electron flow from Photosystem II. Gradual blocking of the electron transport with 3(3,4-dichlorophenyl)-1,1-dimethylurea resulted in diminution and ultimate elimination of the biphasic nature of the signal without reducing the extent of the absorbance change or of the dark kinetics. On the contrary, blocking electron flow at the oxidizing side of plastoquinone with 2,5-dibromo-3-methyl-6-isoprophyl-p-benzoquinone or inactivating the plastocyanin with KCN, prolonged the dark reversal of the absorbance change apart from abolishing the biphasic nature of the signal. Action spectra clearly indicate that the main signal (I) is due to electron flow in Photosystem I and that its modification (Signal II) is due to the action of Photosystem II. Signal I is pH independent, whereas Signal II demonstrates a strong pH dependence, parallel to the O2-evolving capacity of the cells. Chloroplast particles isolated from the wild type Scenedesmus cells demonstrated in the absence of any added artificial electron donor or acceptor and also under non-phosphorylation conditions the 520 nm absorbance change with approximately the same magnitude as whole cells. The dark kinetics of the particles were comparatively slower. Removal of plastocyanin and other electron carriers by washing with Triton X-100 slowed down the kinetics of the dark reversal reaction to a greater extent. A similar positive absorbance change at 520 nm and slow dark reversal was also observed in the Photosystem I particles prepared by the Triton method. Mutant C-6E, which contains neither carotenoids nor chlorophyll b and lacks Photosystem II activity, demonstrates a normal signal I of the 520 nm absorbance change. This latter result contradicts the postulate that carotenoids are the possible cause of the 520 nm absorbance change.

Site specific inhibition by alpha-benzyl-alpha-bromomalodinitrile (BBMD) of electron transport in spinach chloroplasts.

The addition of alpha-benzyl-alpha-bromomalodinitrile to different controlled states (non-phosphorylating [2]. phosphorylating [3], ATP-inhibited [4] and uncoupled) of photosynthetic electron transport to ferricyanide or benzoquinone demonstrate a significant inhibition in isolated spinach chloroplasts. alpha-Benzyl-alpha-bromomalodinitrile pretreatement of isolated chloroplasts or addition of alpha-benzyl-alpha-bromomalodinitrile at the onset of illumination completely abolished the O2 evolving reaction. The level of the steady state fluorescence in intact chloroplasts showed a alpha-benzyl-alpha-bromomalodinitrile concentration-dependent increase. The gradual decrease in the reoxidation capacity of the reduced quencher, Q with increasing alpha-benzyl-alpha-bromomalodinitrile concentrations provides evidence for an additional inhibitory site for alpha-benzyl-alpha-bromomalodinitrile between the two photosystems.

Ultrastructural changes in in vitro ageing spinach chloroplasts.

Ultrastructural changes in in vitro ageing spinach chloroplasts have been studied in detail. Prolonged storage caused swelling of the chloroplasts due to the increase in the thickness and spacing of the thylakoid membranes. The increase in the thickness of the membrane is partly accompanied by the release of lipids. Addition of crystalline bovine serum albumin was found to stabilize the membrane structures. Storage of the chloroplasts at 77 degrees K even though it resulted in complete breakage of the whole chloroplasts, maintained the thylakoid structures in a highly intact form.

Physiological studies with isolated leaf cells: early products of photosynthesis and their metabolic interconversions.

A number of plants have been surveyed with respect to isolation by mild grinding in large quantities of leaf cells. The extent of recovery of mesophyll cells per unit leaf area was found to vary with plant species and the method of grinding. Greater than 70% recovery was obtained from the leaves of Canna indica L., Crotalaria Laburnifolia L., and Thunbergia grandiflora Roxb.By pulse-chase time course experiments, the photosynthetically fixed primary carbon compounds of bean leaf cells were not converted into the ethanol-insoluble fraction. About 25% of total (14)C-photoassimilates were found to leak out into the incubation medium. In contrast, Euglena and Chlorella cells incorporated their primary photosynthetic products into cellular macromolecules and the amount of "leak" was very little. (14)C-Leucine supplied to the bean cells was absorbed readily and incorporated into the trichloroacetic acid insoluble fraction.

Photosynthetic studies with leaf cell suspensions from higher plants.

A technique for obtaining intact mesophyll cell suspensions derived from higher plant leaves is described. A large number of taxonomically unrelated plants were found suitable for cell ;extraction' including several plant species from monocotyledonous group.The absorption spectra of leaf cells in suspension differed only slightly from that of Chlorella cells. The higher plant cells respired and photosynthesized in aqueous solutions very much like algal cell suspensions. Only osmotically intact cells photosynthesized maximally and their activity was stimulated by 2 to several fold by the addition of bicarbonate to the medium. The isolated cells when stored at low temperature with proper aeration maintained their initial activity for a minimum of 9 hr. Cells stored at the room temperature (27 +/- 2 degrees ) lost their activity rather rapidly. The isolated cells were physiologically intact as tested by their metabolic response to diverse inhibiting chemicals and growth regulating substances.