Harald Bolhàr-Nordenkampf

Development and germination of Abies alba somatic embryos

Mature zygotic embryos of Abies alba mull were placed on a modified MCM medium (basal medium-BM) with 2.2 μM benzyladenine and 2.3 μM kinetin to induce embryogenic suspensor masses (ESM). These ESM proliferated on induction medium supplemented with 0.2 μM 2,4-dichlorophenoxyacetic acid. From 61 ESM lines induced, 36 are still in culture after 2 years, of which 18 show embryogenic potential indicated by spontaneous formation of globular somatic embryos on the proliferation medium supplemented with 500–1000 mg l-1 casein hydrolysate and 500 mg l-1l-glutamine. ESMs from cell line 2/56 were conditioned 1 week on BM with 58 mM sucrose and 10 g l-1 activated charcoal for maturation of somatic embryos. Maturation was achieved on BM containing 20 μM (±)cis-trans-abscisic acid in combination with 111 mM maltose. Organic nitrogen supplements improved the proliferation rate of cell line 2/56 as well as the maturation and vitality of the somatic embryos. Partial drying was necessary for subsequent root development. Plantlets with a root, primary needles and a terminal bud developed on BM when a combination of 30 mM sucrose and 50 mM maltose was provided as carbon source.

Analysis of light-induced reduction of the photochemical capacity in field-grown plants. Evidence for photoinhibition?

It was tested whether field-grown plants (Phaseolus vulgaris, Zea mays and Helianthus annuus) reflect photoinhibitory effects under natural conditions. Attached leaves were used for determination of the photochemical capacity of Photosystem II (Fv/Fm) by means of a portable fluorimeter (PSM, BioMonitor, S.). For a more qualitative description of Fv/Fm, the modifications of the absolute values F0, Fm as well as of the half-rise time of Fm (T/2) were also considered. By comparing artificially shaded and ‘sun exposed’ plants, the direct influence of light on the photochemical capacity was investigated. Under low natural light conditions the differences of the photochemical capacity between shaded and ‘sun exposed’ leaves were negligible in all three species. On a day with full sunlight a decline of Fv/Fm was observable at noon-time in the ‘sun exposed’ leaves of all three species, although the absolute values differed between the species compared. Additionally, the extent of the recovery of Fv/Fm was varying. Both phenomena could be due to differences in the photosynthetic apparatus (e.g., C3−C4, ontogenetic stage, sun-shade type), to self-shading phenomena (comparing leaf layers of Zea and Helianthus) or to differences in the activity of repair mechanisms possibly caused by other environmental factors (vapour pressure deficit = VPD, drought and temperature phenomena).Nevertheless, the results of the shading experiments and the comparison of species lead to the conclusion that primarily light-induced reduction of the photochemical capacity appears at noon in leaves exposed to full sunlight, a partial restoration of Fv/Fm takes place till the evening. Artifically shaded plants show only a slight alteration of the photochemical capacity.

Temperature and light dependent modifications of chlorophyll fluorescence kinetics in spruce needles during winter

Prompt chlorophyll a fluorescence kinetics at room temperature were measured from intact spruce needles. The fluorescence signal was recorded after varying light pretreatments. During the winter, induction curves showed characteristic changes in both the initial peak of fluorescence FV/FP (FP-FO/FP) and the steady state level Fdr (FP-FT/FP). Winter stress induced decreases in both values which showed close correlation to the light and temperature pre-history of the plants. In February changes in fluorescence induction indicative of a restoration of photosynthesis were detected and these corresponded to a rise of temperature above zero in combination with low light levels. In March increasing light intensity combined with chilling temperatures induced again decreases of both values of chlorophyll fluorescence induction suggesting the occurrence of photoinhibition.

Zur Physiologie der Fluorescein-Speicherung in Pflanzenzellen

Inhaltsverzeichnis soite E,inleitung . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 133 Material und Methode . . . . . . . . . . . . . . . . . . . . . . . . . . . . 135 Der Farbstoff . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 135 a) Chemismus . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 135 b) Dissoziation und Fluoreszenzintensit/it, Farbe . . . . . . . . . . . . . . 136 c) Der F~irbebereich . . . . . . . . . . . . . . . . . . . . . . . . . . . . 137 d) Das F/irbebild . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 139 Modellversuche . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 141 Zum Umlagerungsph~inomen . . . . . . . . . . . . . . . . . . . . . . . . 142 Die Farbstoffspeicherung . . . . . . . . . . . . . . . . . . . . . . . . . . 150 Zusammenfassung . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 153 Literatur . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 154

Mechanisms of Impairment of the Photosynthetic Apparatus in Intact Leaves by Ozone

Tropospheric ozone has been recognised as a limiting factor for plant growth since late fifties of our century. The decrease in the rate of light saturated net photosynthesis (Asat) was shown to be the major effect of ozone in leaves with negative consequences for plant growth and the development of plant communities. The reasons for the ozone-induced decrease in Asat are still under investigation. Possible mechanisms are an increasing stomatal limitation, an increase in mesophyll limitation including a reduction of the CO2 fixation in the Calvin cycle and an impairment of the photochemical reactions in the grana membranes of chloroplasts. We conclude from the reviewed literature and from our own experiments that a decrease in carboxylation efficiency (CE) seems to be an early event caused by ozone leading to a decrease in Asat. The loss in current photochemical capacity (Fv/Fm) appears with a lag phase of many days and therefore the loss is thought to be a secondary effect due to a decreased demand of ‘assimilatory power’

Modelling critical levels of ozone for the forested area of austria modifications of the aot40 concept

Goal, Scope and BackgroundOzone is the most important air pollutant in Europe for forest ecosystems and the increase in the last decades is significant. The ozone impact on forests can be calculated and mapped based on the provisional European Critical Level (AOT40 = accumulated exposure over a threshold of 40 ppb, 10,000 ppb.h for 6 months of one growing season calculated for 24h day-1).For Norway spruce, the Austrian main tree species, the ozone risk was assessed in a basis approach and because the calculations do not reflect the health status of forests in Austria, the AOT40 concept was developed.MethodsThree approaches were outlined and maps were generated for Norway spruce forests covering the entire area of Austria.•The 1st approach modifies the AOT40 due to the assumption that forests have adapted to the pre-industrial levels of ozone, which increase with altitude (AOTalt).•The 2nd approach modifies the AOT40 according to the ozone concentration in the sub-stomata cavity. This approach is based on such factors as light intensity and water vapour saturation deficit, which affect stomatal uptake (AOTsto).•The 3rd approach combines both approaches and includes the hemeroby. The pre-industrial ozone level approach was applied for autochthonous (‘natural’) forest areas, the ozone-uptake approach for non-autochthonous (‘altered’) forest areas.Results and DiscussionThe provisional Critical Level (AOT40) was established to allow a uniform assessment of the ozone risk for forested areas in Europe. In Austria, where ozone risk is assessed with utmost accuracy due to the dense grid of monitoring plots of the Forest Inventory and because the continuously collected data from more than 100 air quality measuring stations, an exceedance up to the five fold of the Critical Level was found. The result could lead to a yield loss of up to 30–40% and to a severe deterioration in the forest health status. However, the data of the Austrian Forest Inventory and the Austrian Forest Damage Monitoring System do not reflect such an ozone impact. Therefore, various approaches were outlined including the tolerance and avoidance mechanisms of Norway spruce against ozone impact.Taking into consideration the adaptation of forests to the pre-industrial background level of ozone, the AOT40 exceedances are markedly reduced (1st approach). Taking into account the stomatal uptake of ozone, unrealistic high amounts of exceedances up to 10,000 ppb.h were found. The modelled risk does not correspond with the health status and the wood increment of the Austrian forests (2nd approach). Consolidating the forgoing two approaches, a final map including the hemeroby was generated. It became clear that the less natural (‘altered’) forested regions are highly polluted. This means, that more than half of the spruce forests are endangered by ozone impact and AOT40 values of up to 30,000 ppb.h occur (3rd approach).ConclusionsThe approaches revealed that a plausible result concerning the ozone impact on spruce forests in Austria could only be reached by combining pre-industrial ozone levels, ozone flux into the spruce needles and the hemeroby of forests.

Beiträge zur Frage der lichtmikroskopischen Sichtbarkeit des endoplasmatischen Retikulums in Pflanzenzellen

Die an Innenepidermiszellen der Zwiebelschuppe vonAllium cepa zu beobachtenden schlauchförmigen „intraplasmatischen Vakuolen“, in der vorliegenden Arbeit kurz als „Schläuche“ bezeichnet, werden näher untersucht. Sie heben sich im Protoplasma im Phasenkontrast als nichtkontrastierte, massearme Zonen ab. Diese Gebilde werden als Elemente des endoplasmatischen Retikulums (ER) angesprochen. Vergleichende Literaturstudien bekräftigen diese Ansicht. An tierischen Zellen wurden mehrfach im positiven Phasenkontrast dunkle, längliche oder netzförmige Gebilde als Elemente des ER erkannt. Die bei Pflanzenzellen auftretenden, äußerlich sehr ähnlichen Gebilde sind dagegen Plasmaleisten. Sie entstehen zwischen vergrößerten vakuolenartigen Elementen des ER. In jedem Fall ist es notwendig, streng zwischen dem ER sensu strictu, welches aus den Membranen und der von diesen umschlossenen intrazisternalen Phase (IZP) besteht, und dem „Grundplasma“, der extrazisternalen Phase (EZP), in der die Organellen liegen, zu unterscheiden. Im Lichtmikroskop (Phasenkontrast) werden an erwachsenen Pflanzenzellen die Membranen des ER nicht aufgelöst. Wenn die Membranen aber auseinanderweichen und die IZP durch Wasseraufnahme ein größeres Volumen einnimmt, kann man den Kontrastunterschied zwischen IZP und EZP sehen.

Does Ozone Exposure Protect from Photoinhibition

Tropospheric ozone and high light intensities are two stress factors that often occur simultaneously under natural conditions. Ozone is well known to form oxygen radicals in the apoplastic water and long lasting photoinhibition can cause photooxidative damage also by formation of several species of oxygen radicals. We were interested whether moderate levels of ozone would be able to modulate the response of leaves to photoinhibitory conditions naturally occurring around noon on a bright day. Cuttings of Populus sp. were cultivated in two separate greenhouse-compartments adapted as fumigation chambers. In the two compartments plants were grown in ambient air containing about 20 nmol mol(-1) ozone and in elevated ozone concentrations supplied for 8 h per day. During the midday of bright days Fv/Fm decreased by the same amount in all leaves, indicating photoinhibition. At the same time Fo increased in control leaves more than in ozone-exposed leaves indicating a higher amount of heat-deactivating PSII centres in the latter. This was confirmed by a higher epoxidation state in ozone-exposed leaves during midday of a bright day. The contents of chlorophyll a and chlorophyll b were significantly decreased in ozone-exposed leaves. In older leaves the ratios chlorophyll a : b, and xanthophylls: chlorophyll b were increased indicating an adaptation to higher light stress. From this we conclude that by increasing the amount of heat-deactivating centres ozone seems to protect PSII from photoinhibition.

Evaluation of the ozone-related risk for Austrian forests

Forest ecosystems are particularly affected by the impact of stress factors. Apart from natural stressors, there are also anthropogenic ones such as air pollutants. Ozone is considered to be the most phytotoxic air pollutant in Austria on a regional scale. In the past decade, concentrations in forested areas have increased significantly by up to 1.6 ppb per year. In order to assess the ozone impact on forests, a nationwide mapping of the AOT 40 for the forested area of Austria was done with the objective to take the ozone Critical Level as defined by the UN-ECE as the basic concept and to develop a threshold value with the help of three approaches. The adaptation of trees to the pre-industrial ozone levels, the parameters affecting stomatal uptake such as light intensity and water vapour saturation deficit, and the hemeroby (altered and natural) of the forest stands were taken into consideration. 61 % of the forest area showed a level of more than 10,000 ppb.h. Lower altitude areas with predominantely altered stands were affected more heavily.

Determination of the total chlorophyll distribution pattern in living leaves.

Tradescantia albiflora-leaves were used in developing a determination method for chlorophyll in living leaves using a microscopic spectro photometer (MPV, Leitz).The wavelength of the maximal absorption for chlorophyll a was found to be at 670 nm and for chlorophyll b at 652 nm. To calculate the reference values the intensity of the transmitted light at 750 nm was measured. The absorption at 750 nm results only from the chlorophyll free structure in the leaves. To correct optical errors the two-wavelength method was used. The values gained in arbitrary units were calibrated against data measured in the conventional way. The resulting calibration line shows a very high correlation coefficient where r2=0.997. It was proved that the calibration line was also correct for determinations with leaves from other plant species.Using this determination method the chlorophyll content of small areas on the living leaf blade of Phaseolus vulgaris was determined.As consequence of the thicker mesophyll accompanying the veins the chlorophyll concentration is 30% higher in this tissue. A lower chlorophyll concentration was observed in the thinner leaf tip and in the oldest regions at the leaf ground.At the leaf tip, the leaf ground and in the tissue along the veins an iron deficit causes less bleaching than in the areoles. In the same leaf regions the bleaching herbicide atrazine induces rapid bleaching if supplied through transpiration stream. The application of Atrazine on the leaf surface gives rise to the contrary effect.All these phenomena seem to be a result of a differing water supply by the xylem vessels.