UV-A Irradiation Guards the Photosynthetic Apparatus Against UV-B-Induced Damage

In clusterbean leaves UV-B radiation caused a reduction in contents of chlorophylls and carotenoids and in the efficiency of photosystem 2 photochemistry. The degree of damage was reduced when UV-A accompanied the UV-B radiation. This indicates the counteracting effect of UV-A radiation against UV-B-induced impairment.     

Effect of high irradiance and high temperature on chloroplast composition and structure of Dioscorea zingiberensis

High irradiance (HI) and high temperature (HT) increased in chloroplasts the content of monogalactosyldiacylglycerol (MGDG) and decreased the contents of digalactosyldiacylglycerol (DGDG), sulfoquinovosyldiacylglycerol (SQDG), and phosphatidylinositol (PI). HI and HT accelerated the transformation of DGDG to MGDG. The contents of unsaturated fatty acids in chloroplasts increased, while those of saturated fatty acids decreased. The contents of total carotenoids, neoxanthin, violaxanthin, lutein, and -carotene increased first, then decreased. The content of chlorophyll decreased. HI caused the unfolding of thylakoids that was not resumed after a 72-h recovery.This revised version was published online in March 2005 with corrections to the page numbers.     

Effects of CO<Subscript>2</Subscript> concentration on acclimatization and physiological responses of two cultivars of carob tree

This study reports survival and physiological responses of micropropagated Ceratonia siliqua L. cvs. Galhosa and Mulata plants during ex vitro acclimatization under ambient (AC; 330 mol mol^–1) or elevated (EC; 810 mol mol^–1) CO₂ concentration and a photosynthetic photon flux density of 125 mol m^–2 s^–1. CO₂ enrichment during acclimatization did not improve survival rate that was around 80 % for both treatments. Eight weeks after ex vitro transplantation, photosynthetic capacity and apparent quantum yield in acclimatized leaves were higher in comparison with those in in vitro-grown leaves, without any significant difference between CO₂ treatments. Chlorophyll content increased after acclimatization. However, EC led to a decrease in the total amount of chlorophyll in new leaves of both cultivars, compared to those grown at AC. Soluble sugars and starch contents were not markedly affected by growth EC, although starch had significantly increased after transfer to ex vitro conditions. EC induced an increase in the stem elongation and in the effective life of leaves, and a decrease in the number of new leaves.     

Influence des traitements phytosanitaires sur les biocoenoses du phytoplancton limnique

We used specific diversity of phytoplankton and chlorophyll concentrations as a measure of algal biomass in ponds located in agricultural areas where pesticides and fertilizers are currently used and in natural meadows where pesticides spraying has never occurred.A comparison of the biocoenotic structure of the primary producers in the two types of ponds shows conspicuous differences. Species richness is higher in meadow ponds (25 species) than in agricultural area ponds (10 species). The chlorophyll levels are reduced in agricultural area ponds. These effects could be ascribed to contamination by pesticides.

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Influence des traitements phytosanitaires sur les biocoenoses du phytoplancton limnique

     

Effect of Morpholine Systemic Fungicides on the Chloroplast Pigments of Wheat and Maize

Abstract

The growth, chlorophyll and carotenoid contents of wheat and maize seedlings as influenced by a soil drench of 250 μM of tridemorph or fenpropimorph, were studied. It was found that the length of the shoot, primary leaf, and root, as well as the leaf area were significantly reduced in the fungicide treated seedlings. Although the dry matter percentage was higher in the treated seedlings as compared to the control, the fresh or dry weight per shoot remained lower in the fungicide treated seedlings. The chloroplast pigments in the treated seedlings of both crops were unaffected, suggesting that the fungicides had no significant effect on the chlorophyll or carotenoid biosynthesis.     

Synthesis of (–)-Muricatacin

The synthesis of (–)-muricatacin starting from 1-bromododecane and 2-pentyn-l-ol is described. 2-Pentadecyn-1-ol (4), which was prepared from 1-bromododecane (2) and 2-pentyn-1-ol (3), was converted to epoxy alcohol 6 through a two-step reaction sequence, 6 being successively submitted to tosylation, iodination, chain extension with tert-butyl lithioacetate, and acid-catalyzed cyclization to give (–)-muricatacin (1a). Recrystallization afforded optically pure 1a.     

Identification of Olfactory Volatiles using Gas Chromatography-Multi-unit Recordings (GCMR) in the Insect Antennal Lobe

All organisms inhabit a world full of sensory stimuli that determine their behavioral and physiological response to their environment. Olfaction is especially important in insects, which use their olfactory systems to respond to, and discriminate amongst, complex odor stimuli. These odors elicit behaviors that mediate processes such as reproduction and habitat selection^1-3. Additionally, chemical sensing by insects mediates behaviors that are highly significant for agriculture and human health, including pollination^4-6, herbivory of food crops⁷, and transmission of disease^8,9. Identification of olfactory signals and their role in insect behavior is thus important for understanding both ecological processes and human food resources and well-being.To date, the identification of volatiles that drive insect behavior has been difficult and often tedious. Current techniques include gas chromatography-coupled electroantennogram recording (GC-EAG), and gas chromatography-coupled single sensillum recordings (GC-SSR)^10-12. These techniques proved to be vital in the identification of bioactive compounds. We have developed a method that uses gas chromatography coupled to multi-channel electrophysiological recordings (termed ''GCMR'') from neurons in the antennal lobe (AL; the insect''s primary olfactory center)^13,14. This state-of-the-art technique allows us to probe how odor information is represented in the insect brain. Moreover, because neural responses to odors at this level of olfactory processing are highly sensitive owing to the degree of convergence of the antenna''s receptor neurons into AL neurons, AL recordings will allow the detection of active constituents of natural odors efficiently and with high sensitivity. Here we describe GCMR and give an example of its use.Several general steps are involved in the detection of bioactive volatiles and insect response. Volatiles first need to be collected from sources of interest (in this example we use flowers from the genus Mimulus (Phyrmaceae)) and characterized as needed using standard GC-MS techniques^14-16. Insects are prepared for study using minimal dissection, after which a recording electrode is inserted into the antennal lobe and multi-channel neural recording begins. Post-processing of the neural data then reveals which particular odorants cause significant neural responses by the insect nervous system.Although the example we present here is specific to pollination studies, GCMR can be expanded to a wide range of study organisms and volatile sources. For instance, this method can be used in the identification of odorants attracting or repelling vector insects and crop pests. Moreover, GCMR can also be used to identify attractants for beneficial insects, such as pollinators. The technique may be expanded to non-insect subjects as well.     

Host selection by ovipositing cowpea weevils: patterning of input from separate sense organs

Ablations were performed to identify the sense organs used in host selection by ovipositing cowpea weevils, Callosobruchus maculatus. Antennae, foretarsi and palpi (maxillary + labial) were removed singly or in combination, and females were offered pairwise choices of four host species. Removal of the palpi consistently had the greatest effect on host choice, whereas the relative importance of other organs depended on the pair of hosts tested. Different organs may provide conflicting input as to the preferred host; certain ablations led to a complete reversal in preference (as opposed to a simple loss of discrimination). Input from separate organs appeared to be received in a dominance hierarchy.

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Sélection de l'hôte lors de la ponte de Callosobruchus maculatus: modélisation des influx provenant séparément des divers organes sensoriels

Résumé Les ablations ont servi d'étape initiale lors de la détermination des organes sensoriels impliqués dans la sélection du lieu de ponte par C. maculatus. Les antennes, les tarses antérieurs, les palpes (maxillaires et labiaux) ont été retirés seuls ou en combinaison. Les femelles ont eu des choix binaires entre les graines de 4 légumineuses: Cicer arietinum, Glycine max, Phaseolus vulgaris, Vigna unguiculata. Chaque combinaison d'ablations était accompagnée d'un témoin chez lequel les mêmes ablations étaient unilatérales. C'est l'ablation des palpes qui a le plus modifié le choix de l'hôte; l'influence relative des autres organes dépendait des paires d'hôtes offerts. Différents organes peuvent fournir des influx opposés quant à l'hôte préféré certaines ablations ont conduit à une inversion complète des préférences. Il semble que les influx sensoriels formaient une gamma avec hiérarchie dominante. Dans les choix binaires, les préférences initiales des femelles intactes ont été supprimées avec l'ablation des palpes seuls, cependant elles n'avaient pas été modifiées par l'ablation conjointe des palpes et des tarses. Dans ces expériences, l'influx antennaire ne devenait dominant qu'après ablation des deux autres organes sensoriels. Les préférences des femelles avec ablations unilatérales ne différaient pas de celles des femelles intactes.