The natural isotope composition (δ 3 4 S and δ 1 8 O values) of sulfate (SO 4 2-) was determined in humus layers and needles from adult Scots pine stands at three sites between 1993 and 2001, which differed markedly regarding both mean SO 2 concentrations and annual mean throughfall rates of SO 4 2--S (Neuglobsow < Taura < Rosa). The isotope measurements were complemented by δ 3 4 S and δ 1 8 O analyses of atmospheric SO 2 and SO 4 2- in throughfall as well as in samples of external bark layer in order to identify S sources. In all three areas δ 3 4 S values of H 2 O-soluble SO 4 2- in the humus layer were similar to the mean δ 3 4 S values of throughfall and bark surface SO 4 2- (range of +3.6 to +6.0‰). A depletion of δ 3 4 S in sulfate was not observed. This indicates that atmospheric deposition and not the mineralization of organic S is the main source of this inorganic SO 4 2- pool. However, comparison of the δ 1 8 O values in SO 4 2- from atmospheric deposition showed that H 2 O-soluble SO 4 2- in the humus layer had been depleted by several per mil (+4.5 to +8.6‰). These results show clearly that a considerable proportion of H 2 O-soluble sulfate is derived from mineralization of organic S compounds. On the other hand, temporal variations in the natural isotope ratios of SO 4 2- were only found for 1 8 O. The δ 1 8 O values of H 2 O-soluble SO 4 2- in humus layers and in pine needles have significantly increased since 1993, indicating that Scots pines took up deposited sulfate, which was probably reversibly bound onto the surface of Fe-humus complexes. This part of H 2 O-soluble SO 4 2- pool with higher δ 1 8 O values is released and is more and more plant-available, because the S depositions were decreased between 1993 and 2001.
Asparagus is classified to these vegetable products which are characterized by an extremely high metabolic activity after harvest leading to a high deterioration rate and thus to a loss in quality. Therefore, the effect of selected temperatures (2degreesC for simulating cool storage, 20degreesC for simulating temperature conditions in distribution and marketing) on the internal and external quality of packed and unpacked asparagus spears was investigated. The results revealed that asparagus stored at 2degreesC showed minor changes in external quality characteristics (fresh matter, colouring and colour saturation), physical quality characteristics (tissue toughness) and internal quality characteristics (dietary fibres) than at 20degreesC stored asparagus within two or four days of storage. The negative temperature effect on fresh matter, tissue toughness and dietary fibre content can be compensated by oriented polypropylene film (OPP) wrapping, but changes in soluble sugars (sucrose, glucose, fructose) could not prevented. The use of film packaging offers the opportunity to extend the marketability of asparagus and to avoid oversupply.
The effect of anaerobic storage conditions (0,2 % O-2) led to striking production of ethanol in fruit flesh of apple, peach, sweet cherries, plums which reached 600 - 1200 mg.l(-1) within 16 to 25 days, respectively. Subsequent exposition of the fruits to air but still under cold-storage temperature resulted in a linear or exponential decrease of ethanol to half or even one third of its previous value. The speed of the oxidative degradation was much slower than in the cumulative phase. The apple and plum cultivars reflect differential course of degradation in contrast to the sweet cherries. Cold-storage of plum fruit led to a sharp increase of ethanol during senescence phase.
The millet tef is being grown mainly in Ethiopia and Eritrea, East Africa, recently also in some other countries. With a production of 1.67 million tons and an acreage of 2.11 million hectares tef is the prevailing crop plant in Ethiopia. Among the numerous products from tef, the most important for the nutrition of the people is injera, a very soft flat bread. A broad genetic variability of qualitative and quantitative traits of the crop is available which is the basis for future progress in the improvement of drought tolerance, lodging resistance, quality and disease resistance. However, breeding efforts in the improvement of yield is urgently needed. Thus tef may contribute also in the future to the feeding of a rapidly growing population.
UV-B irradiation (280-310 nm) is known to induce oxidative stress in plants and can result in crop loss and minor fruit quality. In this study the reflecting and absorbing properties of white particle film-based ZnO and an UV-absorbing cinnamic acid derivative were used to reduce solar injuries on Phaseolus vulgaris leaves and Malus domestica fruits. The results were compared with the biological efficiency of a sun-protecting agent (alpha-toc./MOC). The solutions were applied until run-off on Phaseolus vulgaris leaves and on yellow-green Malus domestica fruits cv. Golden Delicious. After drying of the application solutions, leaves and fruits were exposed to UV-B-radiation (1.8 kJ/m(2)/d). Application of alpha-toc./MOC prevented a major decrease of the relative chlorophyll fluorescence parameter Fv/Fm in comparison to the level of the UV-B irradiated and non pre-treated plants in both plant species. Treatment of Phaseolus vulgaris leaves with ZnO and cinnamic acid resulted in a minor decrease of Fv/Fm compared to the unprotected plants, but both treatments were not as effective as alpha-toc./MOC. Application of cinnamic acid on Malus domestica fruits did not show any significant differences compared to the untreated fruits. On apple fruits, a reduction of the color formation in apple skin after application of the UV-absorbing substances was noted.
A dependable estimation of nitrogen status of field crops is important for an efficient usage of fertilisers. Remote sensing already uses spectral traits of plants to determine biomass and vitality of crops. The parameters of pulse amplitude modulated (PAM) and laser-induced chlorophyll fluorescence (LIF) techniques have been compared for the detection of nitrogen deficiency in leaves of sugar beet (Beta vulgaris L.) and winter wheat (Triticum aestivum L). Both methods were suitable to detect nitrogen deficiency in the tested species two Weeks following induced N-deficiency. At this time nitrogen and chlorophyll content of sugar beet leaves reached only 49 % and 40 % of N+ control plants and in wheat leaves nitrogen and chlorophyll content declined to 39 % and 48 % of the control treatment. Sugar beet and wheat leaves showed different degrees of correlation between their nitrogen and chlorophyll contents and parameters of PAM and LIF fluorescence from the adaxial leaf side. The nitrogen content of sugar beet leaves correlated to the same extent with maximum photochemical efficiency Fv/Fm (R=0.67) and the F685/F740 ratio (R=-0.68). The chlorophyll content Of Sugar beet correlated somewhat less with the photochemical efficiency (R=0.73), than with the F685/F740 ratio (R=-0.77). In winter wheat leaves nitrogen content correlated stronger with photochemical efficiency (R=0.78) than With F685/F740 fluorescence ratio (R=-0.62). Also chlorophyll content showed a higher correlation with photochemical efficiency (R=0.68) than with he F685/F740 ratio in wheat leaves (R=-0.58). Independent from nitrogen treatments, wheat leaves had almost the same laser induced fluorescence values on upper and lower leaf side. Sugar beet leaves, in contrast, showed higher F685/F740 fluorescence ratios for the lower leaf side. Under optimal N-supply these effects were significant and persisted tendentiously under N-deficiency.
Changes in length, diameter, fresh mass, dry mass, epidermal cell dimensions, osmotic concentration of tissue sap, potassium content and enzymes/sugars of sucrose metabolism were determined in hypocotyls of sunflower (Helianthus annuus L.) seedlings raised in the absence or presence of a (1)/(2) strength Hoagland nutrient solution. Enhancement in hypocotyl growth due to the supply of nutrients is attributable to a promotion of cell elongation, presumably via uptake of potassium salts. The specific catalytic activity of the enzyme soluble acid invertase was enhanced in nutrient solution-grown seedlings, whereas that of the alternative enzyme of sucrose catabolism (sucrose synthase) was unaffected. The levels of sucrose and hexoses were higher in water-grown hypocotyls compared to those raised in nutrient solution. The results are discussed with reference to sources of osmotica for cell elongation and to the phenomenon of phenotypic plasticity in higher plants.
A total of 43 Allium species or types were investigated via SPME-HS-GC-analysis (Solid Phase Micro Extraction-Head Space-Gas Chromatography). The resulting aroma profiles, including 24 volatile sulphur compounds, were statistically evaluated by cluster analysis using the WARD-method. The three known main groups (methiin-, garlic- and onion-type) can be discriminated in the presentation of the euklidic distances. Moreover, these three main groups can clearly be divided into seven chemotypes. This fine-structure leads to a better selection of wild species for breeding experiments, aiming a purposeful improvement in aroma, taste and also pharmacological properties of interspecific Allium hydrids.
This paper presents an overview of the dramatic changes in the understanding of the quality of fruits and vegetables during the past years. The national and international agricultural reformation, the aggravation of competition and surplus production of many horticultural crops as well as the rising awareness of environmental, nutritional and health concerns of the society have led to an alteration process in the view of quality being indicated by alterations of the purchasing behaviour of consumers increasingly demanding only highest quality standard products. Several definitions of quality were already developed considering mainly product attributes or product characteristics (market quality, technological quality, biological quality). Recently, various attempts are ongoing to define quality more comprehensively in developing either quality indices, quality models or quality management systems in which the step from a view of product-oriented quality over process-oriented quality to consumer-oriented quality has been conducted. However, new laws and orders (e.g. residue law, HACCP-concept) as well as new trends (e.g. functional food, gene-food) have to be implemented into these new approaches. Thus, quality is not a fixed value, but a time, product, and consumer dependent dimension. With this new and comprehensive understanding of the quality dynamics it will be possible to face increasing and alterations in consumer requirements as well as to improve the competitiveness on the European and international trade markets.
Phenolic compounds are plant secondary metabolites that are naturally present in essentially all plant material, including food products of plant origin. They are particularly prominent in fruit and vegetables where they are important in determining colour, appearance, flavour and taste. These compounds form one of the main classes of secondary metabolites, with a large range of structures: monomeric, dimeric and polymeric phenolics have been identified. Given a free choice the consumer selects foods with a low content of lignin (toughness) and/or tannin (astringency), but sometimes with a relatively high anthocyanin content (appearance and/or ripeness indicator). During the postharvest life of fruit and vegetables and the different technological treatments to which these plant tissues are submitted in order to extend their shelf life, some changes in secondary metabolism occur. These metabolic changes of phenolic compounds, often coupled with the activity of polyphenol oxidase, are responsible for some phenomena affecting the quality of stored plant commodities. In this connection two important aspects, related to the presence of phenolics, receiving increasing attention from biochemists, plant physiologists and food technologists, are the role of phenolics in browning reactions and the resistance mechanism against storage fungi. This paper emphasizes some aspects related to low temperature metabolism of endogenous phenolics in plant tissue under chill stress with reference to shelf life of cold stored fresh fruit and vegetables.
The University of Giessen long-term Free Air Carbon dioxide Enrichment experiment (GiFACE) started in 1998 to study responses of a semi-natural grassland to elevated CO2. Permanent grasslands managed as hay meadows, represent about 13% of the agricultural and approximately 6% of the total land area in Germany. GiFACE grassland site has not been ploughed for at least 100 years. During the last decades, it has been mown twice a year and fertilized with 50-80 kg N ha(-1) a(-1). Since 1995, the fertilizer has been reduced to 40 kg N ha(-1). The vegetation is an Arrhenatheretum elatioris (Br.-B1.) Filipendula ulmaria sub-community with approximately 60 species. The Giessen Free Air Carbon dioxide Enrichment technique (PlumeX) was developed based on the classical FACE technique in order to adapt it to local site requirements. The main features of the PlumeX are: (1) A circular active plenum (CAP) which consists of a modular structure with individually controlled exhausting and sucking vent pipes; (2) the symmetric layout without any external blower providing wind-direction independent CO2 enrichment control; (3) the regulation of the CO2 target concentration with an electronic controller (PID), which leads to CO2 concentrations of 22% above ambient in a height of 40 cm above ground; (4) low maintenance requirements and (5) a reduction of the CO2 usage by approximately 5%. The CO2 enrichment is applied throughout the year during daylight hours. Since the start of fumigation the system worked continuously with the exception of 5 days. The homogeneity of the CO2 enrichment in 40 cm above ground in the central 16m(2) large ring area was for instance in the vegetation period 1999 (April to September) 122.1+/-2%. The GiFACE is currently the oldest and only running long-term FACE experiment on a semi-natural grassland ecosystem in Europe.
For the study of cytotoxic effects of the arsenic species arsenite, arsenate, monomethylarsonate and dimethylarsinate the pollen tube growth test (PTG test) with pollen of Nicotiana sylvestris Spegazz & Comes was used. The inhibition concentration of the pollen tube growth to 50% (IC50) was determined and compared with LD50 values of the compounds from the literature. With respect to the inorganic species a higher cytotoxicity was found for arsenate in the PTG test. The cytotoxic effects of the methylated arsenic species were lower in comparison to the inorganic compounds. Possible explanations of the mode of action of the arsenic species were discussed.
Pepino (Solarium muricatum) is a little studied Andean crop grown for its edible fruit. It is propagated clonally. Selection of new clones with improved fruit quality has contributed to the market development of this crop. In this paper, we study the possibilities of using wild relatives from section Basarthrum for the genetic improvement of the pepino. Among all the species of this section, we consider S. caripense and S. tabanoense as the most promising. These wild species are sexually compatible with pepino; bear relatively large fruits, especially S. tabanoense; and have high soluble solids content (SSC), titratable acidity (TA) and ascorbic acid content (AAC). Results from three experiments show that interspecific hybrids are intermediate for most traits, but are very vigorous and their yield can be as high as those of cultivated clones. Backcrosses followed by selection show that it is possible to rapidly recover the productive traits characteristic of the pepino, while increasing the SSC and AAC, thus contributing to the overall improvement of fruit quality. Results indicate that wild species can make a significant contribution to pepino breeding and can be easily integrated in local breeding programmes.
Infection of leaf tissue by Plasmopara viticola is mainly initiated by contact between the motile free-swimming zoospores and the leaf surface. The mass accumulation of P. viticola zoospores on vine stomata is certainly suggestive of an attractive mechanism. The following encystment and penetration involves also a sensorial process. Nevertheless the biological basis involved in taxis and tropism is still unknown. Following the question if zoospores can use surface structures to locate stomata the present investigation compares the response to a putative topographical stimulus of leaves and artificial leaf replicas to zoospores of P. viticola. In order to obtain a picture of zoospore response, a relation of a general zoospore encystment versus zoospore encystment in stomata was drawn. The experiments demonstrated that zoospores of Plasmopara viticola encyst just as instantly on leaves as they do on replicas, indicating that no inhibiting compounds were leached out of the replicas during treatment. Nevertheless 12 h after inoculation more than 80% of the zoospores on real leaves but less than 17% on the replicas were encysted in stomata. On replicas there was no evidence of a tactic or tropic response by a zoospore or germ tube to a stoma reproduction. Zoospores of P. halstedii showed a different behaviour on the non-host grapevine: Only 44% of the germinated zoospores were able to locate stomata, suggesting that the stimulus is not identical, at best similar. It is concluded therefore that zoospore attraction is physiological in nature and adapted to a distinct host-parasite relationship.
The effect of salinity on growth, photosynthesis, leaf chlorophyll concentration and mineral uptake of baobab seedlings (Adansonia digitata L.) was investigated. Four weeks old seedlings were grown in sand Culture and were treated with different salt Solutions. Treatments were Prepared by adding 0, 20, 40, 60, and 80 mM NaCl to the nutrient Solution. Plant growth was strongly affected by the salt treatments. In the 20 mM NaCl variant, a reduction of 66% dry weight Occurred in comparison to the control plants. Foliar injuries (necrosis) and defoliation appeared within all salt treatments. However, with increasing salinity levels, leaf moisture content increased, indicating a salt-induced leaf succulence. Increased NaCl salinity decreased the net photosynthesis rate. Chlorophyll content of leaves at higher salinity levels was lower than at lower salinity levels. Raising NaCl in the irrigation solution increased Na+ and Cl- concentration in the plant tissue. Ca2+/Na+ and K+/Na+ ratios in the leaves were strongly reduced in salt treated plants. The results indicate that salinity significantly influences growth and metabolism of A. digitata seedlings. Therefore, in the seedling stage, baobab can be characterised as a very salt-sensitive species.
Somatic hybridization of sexual incompatible species results in highly heterogeneous hybrids. In breeding for resistance to Sclerotinia Sclerotiorum, all economically important disease affecting sunflower, the search for new sources of durable resistance includes many wild Helianthus species aiming at the introgression of the resistance into breeding lines. The strategy using asexual symmetric and asymmetric somatic hybridization produced fertile plants that are being back-crossed to sunflower. This strategy is ideal to overcome sexual barriers and even for gene transfer of an unknown background. To date, more than two hundred viable symmetric and asymmetric sunflower hybrids have been produced with a wide range of variability. The disease resistance and agronomic performance of these plants is varied, and the current results are inconclusive; some partial hybrids showed a very promising performance.
The use of chemicals to reduce microbial contaminations on raw materials for the production of organic food such as sprout seeds is not allowed in Germany. To develop an alternative decontamination procedure, we studied the effect of hot water at various time/temperature regimes. Mung bean seeds were inoculated with >10(8) cfu/g Salmonella Senftenberg W775 by immersion. This strain is known for its unusual high heat resistance. The seeds were dried and stored at 2 degreesC. The salmonella counts on the dried seeds remained unchanged during storage for 8 weeks. The contaminated seeds were treated at 55, 58 and 60 degreesC for 0.5-16 min. D-values of 3.9, 1.9 and 0.6 min, respectively, were determined and a z-value of 6.2 (r(2)=0.99) was calculated for the inactivation of S. Senftenberg W775 on the mung bean seeds. The thermal treatment at time/temperature regimes of 55 degreesC/20 min, 60 degreesC/10 min, 70 degreesC/5 min and 80 degreesC/2 min reduced the pathogens on the mung bean seeds by >5 log units without affecting the germination rate of the seeds.
The genus Angelonia is native to tropical America and has played a role in European horticulture since the early nineteenth century (ENCKE, 1958). Recently the plant has become important as a "New Ornamental", especially as a flowering potted plant. New, vegetative propagated cultivars are currently being introduced to the market. Angelonia belongs to the family Scrophulariaceae. Peloric flower shape occurs in this plant family. Such radially symmetric flowers are prominently visible in what is a normally dorsiventral flowering plant. Changes of the flower morphology, including spontaneously occurring Peloria, in Angelonia are discussed.
Eight species of the important medicinal and ornamental genus Eleutherococcus (Araliaccae) were tested upon their ability to regenerate roots and shoots from detached mature leaves in a minimal nutrition Solution. Additional,, leaflets, leaflets with their petiolules detached, and leaves with abscised leaf bases, of E. gracilistylus were also tested, accordingly.The capability for adventitious root development at leaves differed between species. Leaf cuttings of E. divaricatus, E. gracilistylus, E. seoulensis, E. koreanus and E. sieboldianus regenerated abundant adventitious roots at their petioles and survived up to 8 months (E. gracilistylus). From E. lasiogyne only one sample grew minute roots , but died off little later than the other samples of that species. E. henryi did develop callus tissue, but failed to grow adventitious roots and wilted soon. E. losiogyne x E. sessiliflorus failed to regenerate roots as well as callus tissue at all. Leaflets with or without petiolules as well as leaves with detached bases of E. gracilistylus developed adventitious roots, just like the regular leaf cuttings of this species. Under white light none of all samples grew an adventious shoot, although the leaf cuttings which develop adventitious roots may stay alive for many months. However, leaves of E. gracilislylus, treated the same as all other samples but kept under red light, did develop adventitious shoots: first time in Araliaceae. Since according to the literature most other woody plants also failed to propagate from leaf cuttings so far. our results should be of interest for growers and breeders looking for a cheap and preserving proliferation method.
Glomus brohultii forms ellipsoid to sub-globose or irregular or globose, yellow-brown to brown spores, 95 - 130 x 70 - 105 mum in diam., with a smooth, 3.5 - 16 mum thick laminated wall. The wall consists of two layers being the outer thin, < 1 mum, and the inner laminated. The outer layer is seldom seen. The hyphal connection is often recurved, has frequently a bulbous or bi-furcate shape, or is straight. The pore of the hyphal connection is often closed by a septum. The shape of the hyphal connection differentiates this species from other Glomerales species. Spores of Glomus brohultii are described from specimens found in Cuba, Costa Rica as well as in the Kivu region of the Democratic Republic of the Congo (Zaire). The new species was named in honour of the founding president of the International Foundation of Science, Sven Brohult.
