EARLY DIAGNOSIS OF BORON DEFICIENCY IN CHESTNUT

This study aims to identify an alternative plant tissue to be used in the early diagnosis of boron (B) deficiency in chestnut (Castanea sativa Mill.). A B-deficient orchard was selected, and 16 trees were submitted to two levels of B fertilization. When flowers were in bloom, the following tissues were sampled: leaves, androgynous catkins and flowers. There was a significant increase in B content in plant tissues due to B application. In July, the highest B content was observed in flowers in B0, but leaves had the greatest content in B1. Boron content in the tissues collected in July was positively correlated with B contents in leaves sampled in September. Foliar B concentrations, irrespective of the sampling period, were correlated with chestnut productivity, while the other tissues did not. These results suggest that the leaves, sampled in bloom, were the most efficient tissue for the early diagnosis of B deficiency.     

Effect of root temperature on carob growth: Nitrate versus ammonium nutrition

The response of carob (Ceratonia siliqua L.) seedlings grown at different root zone temperatures affected by nitrate and ammonium nutrition was studied. When root temperatures ranged from 10 to 35°C, ammonium‐fed plants were significantly larger than nitrate‐fed plants. Ammonium‐fed plants displayed toxicity symptoms and were much smaller at 40°C root temperature in comparison with the nitrate‐fed plants grown at the same root temperature. Root/shoot ratio slightly increase with root temperature in ammonium‐ and nitrate‐fed plants in a similar way, and shoot demand per root unit decreased with root temperature between 15 and 25°C. There was a general increase in net photosynthesis with root temperature, though nitrate‐fed plants were more sensitive to low and ammonium‐fed plants to high temperatures. Increasing the root temperature of ammonium fed plants from 10 to 40°C leads to a 30% increase in the amount of photosynthates sent to the roots. The presence of ammonium resulted in the distribution of newly fixed carbon away from carbohydrates and into nitrogen compounds. Potassium, calcium, and nitrogen content of the plants also increased with increasing root temperature.     

Changes in amino acid and organic acid composition in tomato and cucumber plants in relation to salinity and nitrogen nutrition

Under conditions of salt stress, plants show qualitative and quantitative alterations in various organic compounds, such as nitrogen (N) compounds and organic acids. In this work, the effect of different saline levels as well as various N levels, supplied as nitrate (NO₃) or as ammonium (NH₄)+NO₃ on the concentration of amino acids and organic acids in the leaves of tomato and cucumber plants has been studied. The effect of the source of N on individual amino acid contents varied with plant species. Most of the amino acids increased when the concentration of N in the nutrient solution was increased, except when N was added as NH₄+NO₃ for tomato. The effect of salt stress depended on which amino acid was considered. The data also indicate that the effect of salinity on each particular amino acid was greatly dependent on the plant species and N source. Organic acids were differently affected by salinity and by the N source, depending on the plant species. In tomato, the concentrations of short‐chain organic acids were 2–3 times higher in NO₃‐supplied plants than in those grown with NH₄+NO₃. Finally, in cucumber, malic acid concentration increased as a function of the saline level in the medium.     

Die Wirkung von Düngungsänderungen auf die mikrobielle Aktivität von Löss‐Schwarzerde nach 96 Jahren differenzierter organischer und mineralischer düngung im “Statischen Düngungsversuch”; Bad Lauchstädt

Über den Zeitraum, in dem langjährige Düngungsänderungen die mikrobielle Aktivität eines Bodens in Abhängigkeit vom C_org‐Gehalt beeinflussen, liegen bisher wenige Kenntnisse vor. Auf ausgewählten Prüfgliedern des Statischen Dauerdüngungs versuches Bad Lauchstädt wurde die Langzeitwirkung differenzierter Düngung in Abhängigkeit vom C_org‐Gehalt des Bodens auf die mikrobielle Aktivität von Löß‐Schwarzerde untersucht. Geprüft wurden die Parameter mikrobielle Biomasse, die Enzyme Protease, β‐Glucosidase, alkalische Phosphatase und Dimethylsulfoxidreduktion, sowie das Mineralisierungsvermögen des Bodens und der Anteil des heißwasserlöslichen Kohlenstoffs (C_hwl). Die Ergebnisse zeigen, dass nach 20 Jahren organischer bzw. fehlender Düngung das Ausgangsniveau der mikrobiellen Aktivität der Vergleichsprüfglieder noch nicht erreicht worden ist. Die Unterlassung einer organischen Düngung auf LößSchwarzerde führte in Abhängigkeit vom C_org‐Ausgangsniveau zu einer Abnahme der mikrobiellen Biomasse zwischen 22 und 31%. Bei Unterlassung einer mineralischen Düngung sank die mikrobielle Biomasse um 13–15%. Die Zufuhr von 15t/ha.a Stalldung zu den Prüfgliedern mit organisch schlecht versorgtem Boden führte mit der Erhöhung des C_org‐Gehaltes zu einem Anstieg der mikrobiellen Biomasse um 31–39%. Zwischen C _org, C_hwl, CO₂‐Freisetzung und mikrobieller Biomasse bestehen enge Beziehungen. Die Enzymaktivitäten zeigten ein differenziertes Verhalten.

Langjährige organische und mineralische bzw. unterlassene Düngung hatte eine nachhaltige Wirkung auf die mikrobielle Aktivität von Löß‐Schwarzerde. Ein Fließgleichgewicht stellt sich demnach auch bei mikrobiellen Parametern erst nach längeren Zeiträumen ein.     

Mikrobielle prozesse im asche‐klärschlamm‐kompost bei der rekultivierung von hochhalden in abhängigkeit von der dauer seiner aufbringung

Zur Abdeckung einer Hochhalde im Industriegebiet der Leuna‐Werke zum Schutz der Umwelt vor Staub‐und Schadstoffemmission wurde ein Asche‐Klärschlamm‐Kompost eingesetzt. Er wurde in Abhängigkeit von der Dauer der Aufbringung und der Lage auf den Halden hinsichtlich seiner mikrobiellen Aktivität untersucht (Mikrobielle Biomasse, Enzymaktivitäten, Mineralisierbarkeit in der Langzeitinkubation, N‐Nachlieferungsver‐mögen, Keimgehalt an Bakterien, Actinomyceten und Pilzen, Bakterien‐ Pilz‐Verhältnis, ökophysiologische Parameter wie metabolischer Quotient und C_mik/C_org‐Verhältnis).

Die Ergebnisse haben gezeigt, daß die eingesetzten Substrate über einen längeren Zeitraum mikrobiell sehr aktiv sind und einer starken Mineralisierung unterliegen. Sie ist im Jahr der Aufbringung am stärksten. Die Besiedlung der Substrate trotz eines hohen C_org‐Gehaltes ist gering (C_mik in C_org‐Verhältnis von rd. 0,3%). Das Pilz‐Bakterien‐Verhältnis hat sich während des Versuchszeitraumes von 4 Jahren nur unwesentlich verändert. Die mikrobielle Aktivität nimmt in der Bodentiefe im Vergleich zu Ackerböden langsam ab.

Bis in eine Tiefe von 100 cm lagen mehr als 50% des mineralischen Stickstoffs als Ammonium vor, ab 150 cm war nur noch Nitrat nachzuweisen. Eine Belastung des Grundwassers mit Stickstoff konnte bisher ausgeschlossen werden.

Die eingesetzten Substrate bieten günstige Voraussetzungen für das Pflanzenwachstum. Durch die Begrünung der Halden wird die Staubbelastung in Wohnsiedlungen stark vermindert.     

The Impact of Fertilization Methods on the Nutrient Balance and Changes of Soil Chemical Features in Crop Rotation

The effect of various fertilization methods on the simplified nutrients balance and changes of soil chemical features in crop rotation was estimated on the basis of 7-year (1994-2000) studies carried out on loess-based, sedimentary-gley, light-clay soil. Different fertilization methods were used: A - mineral fertilization; B - mineral and manure fertilization; C - straw, green manure and mineral fertilization; D - ecological compost and biodynamic preparation fertilization. Particular fertilization methods caused a significant differentiation of the nutrients balance. A positive phosphorus balance was found out in all the fertilization systems. It has been observed that the nitrogen and potassium carry-in with fertilizers was higher than the carry-out with crops in system B and C. A favorable calcium balance was achieved in systems C and D while a favorable magnesium balance - only in the ecologically fertilized systems (D). The changes of soil chemical features were only insignificantly dependent on the nutrient balance. After seven years of research, the contents of humus, phosphorus, potassium, magnesium and calcium increased while the soil reaction decreased in the soil of all the fertilized systems except the ecologically fertilized system.     

Kaolin influences tomato response to salinity: physiological aspects

Environmental stress as salinity can negatively affect the physiology of tomato plants. Conditions leading to a reduction of transpiration can contribute to greater tolerance to salinity. Use of kaolin-based particle film technology (PFT) may be an effective tool to control stomatal conductance and transpiration rate, thus mitigating the detrimental effect of salinity. The present three-year study has investigated the effects of kaolin application on leaf gas exchange, leaf water potential, leaf and canopy temperature of field-grown tomato, irrigated with brackish water by drip method, in southern Italy. Treatments were: (1) three salinity levels of irrigation water (electrical conductivity of water = 0.5, 5 and 10 dS m^?1); (2) tomato plants treated or not with kaolin; and (3) two cultivars in each year. The increase in salinity caused the reduction of leaf water potential, stomatal conductance, net photosynthesis and transpiration rate, and the increase of leaf and canopy temperature. Kaolin has resulted in an improvement of leaf water potential, and the reduction in gas exchange variables in low-salinity conditions. Under high salinity, kaolin was effective in limiting the reductions in net photosynthesis and reducing leaf and canopy temperature. These latter variables were slightly affected by kaolin, in different ways in respect to the saline treatments; while in non-saline conditions were 0.2–0.5°C higher in the kaolin-treated plants, the situation was reversed in more saline treatment. The variation of leaf and canopy temperature shows that kaolin influences the thermal balance mainly for the dual effect of reflection of the incident radiation and partial occlusion of the stomata. Kaolin mitigated detrimental effects of salinity also on yield, contributing to the improvement of income for the farmers. The use of kaolin-based PFT may be an effective tool to alleviate salinity stress in tomato production under arid and semi-arid conditions.     

Fungal pathogens in Norwegian lettuce fields

Abstract

Norwegian field production of lettuce has increased considerably since the early 1990s. Disease problems rarely required fungicide applications before 1996, when lettuce downy mildew (Bremia lactucae) caused severe losses. From 2002 to 2004, surveys were conducted to identify fungal diseases in Buskerud, Vestfold and Østfold counties in the south-east and Rogaland County in the south-west, representing the main lettuce production regions of Norway. The distribution and incidence of B. lactucae was highly variable, but this pathogen was the most important due to the destructive nature of uncontrolled epidemics. Septoria lactucae caused severe damage, but was found in only one field. Sclerotinia sclerotiorum was the most widespread pathogen, found in 32% of the fields, but usually affecting less than 10% of the plants. Pythium tracheiphilum was reported from 33% of the fields in south-east Norway, but was not found in the south-west. Disease incidence was usually less than 5%, and a disease incidence of more than 10% was reported in one field only. Other pathogens of potential economic importance in Norwegian lettuce fields are Alternaria spp., Botrytis cinerea and Rhizoctonia solani, although they were sporadically distributed in relatively few fields in this survey.     

Genetic diversity and population structure of a common bean (Phaseolus vulgaris L.) collection from Calabria (Italy)

Eighty-seven Phaseolus vulgaris landraces, still cultivated in Calabria (Italy), were investigated in order to study the patterns of common bean genetic diversity in this region, to better understand the evolutionary development of beans in Europe and to properly manage these genetic resources. Four American accessions and five Italian varieties were also included. Different markers, such as 12 microsatellites, seed traits, phaseolins and 100-seed weight were combined with different statistical approaches. For each microsatellite, expected (H _e ) and observed (H _o ) heterozygosities, polymorphism information content (PIC), probability of identity (PI) and homozygosity were calculated. Furthermore, in Calabrian group of bean landraces, total (N _a ) and private (N _pa ) number of alleles, observed (H _o ), expected heterozygosities (H _e ) and allelic richness (AR) were calculated. Genetic distances among landraces were estimated using Nei’s coefficient and a cluster analysis using the UPGMA algorithm was performed. The results clearly indicated that: (1) Calabrian germplasm showed a high level of diversity (H _e  = 0.595); (2) Mesoamerican and Andean gene pools were clearly distinguished in Calabrian germplasm, with the Andean gene pool predominating (83 %); (3) Calabrian landraces were largely hybridized within and between the gene pools. A model-based approach, using the STRUCTURE software, was adopted. Six groups, including 4 of Andean origin and one of Mesoamerican origin were identified. Even more interesting, a small group (8 %) showed a distinct genetic structure, in which interspecific hybridizations with runner bean (Phaseolus coccineus L.) could have occurred. Nevertheless, a relatively high proportion of Calabrian bean landraces (12.6 %) was derived from intra and interspecific hybridizations.     

Distribution and secondary effects of EDDHA in some vegetable species

Tomato (Lycopersicum esculentum), cucumber (Cucumis sativus), pepper (Capsicum annuum), and lettuce (Lactuca sativa) were grown on rockwool or perlite substrate with nutrient solution. Fe was administered as the Fe complex of the chelator ethylenediamine di-(o-hydroxyphenylacetic acid) (EDDHA) or Fe(NH₄)₂(SO₄)₂ in the nutrient solution or as inorganic iron in the substrate. Roots and leaves of plants grown on Fe-EDDHA contained EDDHA in quantities up to 0.27 × the amount of Fe, which is interpreted as an indication of the contribution of passive chelate absorption to Fe uptake. Fruits of tomato and pepper, and leaves of lettuce contained only traces of EDDHA. Breakdown of the chelator in leaves of pepper and tomato is estimated to have been between 0.5 and 2% per day. In tomato fruits, lycopene content was lowered in plants growing on Fe-EDDHA. Cucumber growing on Fe-EDDHA suffered from serious infection by the mildew Sphaerotheca fusca; the plants growing on an inorganic source of iron were resistant. These results exemplify physiological effects of EDDHA other than those directly associated with iron nutrition.