Look back over the studies of lignin biochemistry

The role of the cinnamate pathway in monolignol biosynthesis based on feeding experiments with lignifying plant stems and characterization of the enzymes in the pathway, O-methyltransferase (OMT), cinnamyl alcohol dehydrogenase (CAD), etc. is discussed. Monolignol biosynthesis via metabolic grids according to newly characterized enzymes in the pathway is also reviewed and discussed. The cleavage mechanisms of side chains and aromatic rings by lignin peroxidase and laccase elucidated by using ¹⁸O, ²H, and ¹³C labeled lignin substructure dimers and DHP with ¹⁸O₂ and H₂ ¹⁸O are reviewed. Finally, the prospects of lignin biochemistry in the wood and paper industries are discussed according to the recent progress on gene technology on wood formation and microbial degradation of lignin.     

The biological effects of three insect growth regulators onCulex pipiens L

Tests were made to determine the possible juvenilizing effects of three insect growth regulators (IGRs) namely, IKI 7899, SIR 8514 and Dowco 439 on immature stages and adults ofCulex pipiens L. using the IC₅₀ values (concentration to inhibit the emergence of 50% of adults) as a criterion. The results indicated that IKI 7899 (0.00031 μg/ml) proved to be the most effective compound followed by SIR 8514 (0.0052 μ/ml) and Dowco 439 (0.029 μg/ml). Apart from lethal action, treatment of fourth larval instars with the IC₂₅ values (concentration to inhibit the emergence of 25% of adults) of the above-mentioned IGRs affected the reproductive capacity of surviving adults. Moreover, larval treatments with these compounds led to a marked prolongation in the duration of first gonotrophic cycle. There was also an increase in the proportion of survived females/males ofC. pipiens after these larval treatments.     

Einige entomologische Probleme der Libanesischen Landwirtschaft

Zusammenfassung In Folge seiner geographischen Lage und zweier paralleler Gebirgsketten erfreut sich das Land Libanon trotz seiner geringen Größe drei verschiedener Klimate: Einer mediterranen, einer alpinen und einer kontinentalen Zone. Sie ermöglichen ausgedehnte Monokulturen: Bananen, Ölbaum und Citrus an der Küste, Steinobst und Äpfel im Gebirge und Weingarten im Hochtal. Auf Grund dieser Bedingungen konnten sich einige polyphage Insekten zu epidemischem Ausmaß vermehren. 17 wichtige Schädlinge werden kurz erörtert und die ö kologischen Bedingungen, welche einige Schädlinge besonders begünstigen, werden besprochen. Beispiele für die Folgen des Insektizid-Mißbrauches werden aufgezeigt.

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Summary The geographical situation of Lebanon, and the fact that it comprises two parallel chains of high mountains, makes the country, inspite of its small area, enjoy three types of climates: a typical mediterranean climate, an alpine type, and a continental type of climate. It further allows the establishment of extensive monocultures in the different regions. This monoculture comprises bananas, olives and citrus on the coast, stone fruits and apples in the mountains, and vineyards in the high valley. As a result of this type of culture, a number of polyphagous pests were able to multiply to epidemic levels. Seventeen major pests of crops are briefly discussed. The ecological conditions that favour the creation of particular pest problems, and examples on the mis-use of insecticides are mentioned.

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Résumé La situation géographique du Liban, et le fait qu'il est formé de deux chaines de montagnes parallè les, confèrent à ce pays, malgré sa petite étendue, trois genres de climat: un climat méditerraneen, un climat du type alpin, et un climat du type continental. En outre, la topographie lui permet d'établir des monocultures extensives dans les différentes régions. Ces monocultures comprennent les agrumes, les olives et les bananes sur la côte, les fruits à noyaux et à pépins dans les montagnes, et la vigne sur le plateau. Il en résulte de ce type de culture qu'un grand nombre d'insectes polyphages se multiplient jusqu'à atteindre le niveau d'épidémie. Dix-sept importants ennemis des cultures sont brièvement exposés. L'attention du lecteur est attiré vers les conditions é cologiques qui favorisent la création de problèmes entomologiques spéciaux et sur l'abus d'emploi des insecticides.

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Authorized for publication on Dec. 21, 1962 as journal No. 97 by the Faculty of Agricultural Sciences of the American University of Beirut.