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After a disturbance such as fire (very frequent in the Mediterranean basin), Cistus spp. and Pinus spp.,are obligatory seeder species. For a long time they have been considered as « social pyrophytes » (see Kuhnholtz-Lordat’s definition, 1938), i.e. obligatorily associated with fires. By comparing (from personal data and/or from bibliographic sources) experimental studies dealing more particularly with the effects of high temperatures on germination processes and field researches, it becomes evident that these species are not exclusively dependent on fire but are plants occupying open disturbed sites, generally with a scarce vegetative cover, and particularly without the presence of aggressive competitors., Après un incendie (perturbation fréquente dans la région méditerranéenne), les cistes et les pins sont des espèces à reproduction sexuée obligatoire. Ils ont été considérés pendant longtemps comme des « pyrophytes sociaux » (voir la définition de Kuhnholtz-Lordat, 1938), c’est-à-dire des espèces obligatoirement liées au feu. En confrontant (à partir de recherches personnelles et/ou issues de sources bibliographiques) des études expérimentales ayant trait plus particulièrement aux effets des températures élevées sur le processus de germination, et des travaux de terrain, il ressort que ces espèces ne sont pas exclusivement dépendantes du feu mais sont des végétaux occupant des sites ouverts à la suite d’une perturbation, généralement vides de couvert végétal, et surtout ne présentant pas de compétiteurs agressifs., Trabaud Louis. Modalités de germination des cistes et des pins méditerranéens et colonisation des sites perturbés. In: Revue d'Écologie (La Terre et La Vie), tome 50, n°1, 1995. pp. 3-14.

This forum brings together fire ecologists from outside the current wildfire controversy in the US to give their views on three central topics related to ecosystems in which wildfires are an important process. First, how do fire behavior and ecological effects vary between ecosystems? Second, why does this variation require an understanding that goes beyond simple correlations between various fire and ecosystem variables to more careful causal models? Third, how can human values and goals be reconciled with fire disturbance processes in an ecologically sound manner?

The effects of burning on plant nutrient budgets and rates of carbonic gas and particulate matter emission during fires were evaluated in aQuercus coccifera (garrigue) shrubland. Nutrient levels were determined in field-collected pre-fire vegetation and combustion residues. The losses (increased elemental transfer) were calculated as the difference between the quantity of an element in the fuel (combustible standing vegetation plus litter) before burning and that present in the postfire residues (ash). Weight losses of elements are correlated with weight losses of burnt plant biomass. The relative order of nutrient losses was: N>C>Na>Ca>P>K>Mg. Estimated losses of N, C and P from combustible plant matter exceeded 98, 97 and 79% respectively. Copious N, C and P volatilization during burning was promoted by high concentrations of these elements in foliage and fine woody biomass of the aboveground vegetation and leaf litter of the garrigue. Elements were principally removed in the smoke. The quantities of gaseous emissions of CO2, CO and particulate matter produced were estimated.

Light-induced chlorophyll fluorescence has become a tool which has ever-increasing potential application to experimental plant physiology. The effects of frost, heat, and drought have been analyzed using the kinetics of individual leaves of two representative types of life form: an evergreen tree (holm oak) dominant in the Mediterranean Basin and an annual cultivated legume (soybean). Various indices were used to quantify their response to environmental stress. Canopy fluorescence for the two types of plants was simulated. For two levels of measurement, leaf or canopy, light-induced fluorescence appears to be helpful for forest or crop management in the Mediterranean area.

Thermal stress tolerance of leaves and growing area of Quercus ilex. Thermal resistance of leaves of Quercus ilex L. (holm oak), a tree abundant in the western part of the Mediterranean Basin, has been studied in relation to the age of leaves by means of the method of chlorophyll fluorescence induction kinetics. The photosynthetic system is not destroyed when the duration of the exposure time is less than 2 hours for a temperature of -20 °C. The apparatus still works when exposed during 30 minutes at +50 °C. After sclérification at 1 -month old, the thermal resistance of young leaves is similar to that observed for older ones. Knowing the range of extreme temperatures allows to characterize the area in which Q. ilex can grow., La résistance thermique des feuilles de Quercus ilex L. (Chêne vert), arbre abondant dans la moitié occidentale du Bassin méditerranéen, a été étudiée, en relation avec leur âge, par la méthode de l’induction de la fluorescence de la chlorophylle. A -20 °C, le système photosynthétique n’est pas détruit pour une durée d’exposition inférieure à 2 heures. Une exposition à +50 °C durant 30 minutes n’altère pas ses capacités. Passé le premier mois, les jeunes feuilles ont acquis une sclérification qui leur permet de présenter une résistance au stress thermique comparable à celle des vieilles feuilles. Cette étude, tenant compte des extrêmes de températures dans lesquelles Q. ilex peut vivre, permet de comprendre et de préciser son aire de répartition., Trabaud Louis, Methy Maurice. Tolérance aux stress thermiques des feuilles et aire de répartition de Quercus ilex. In: Ecologia mediterranea, tome 20 n°1-2, 1994. pp. 77-85.

Polyclonal anti-idiotypic antibodies to human monoclonal anti-HBs antibodies (MoAb1) were raised in rabbits and designated Ab2-H1 and Ab2-H2. These Ab2 were characterized using three assays. A direct binding ELISA evaluated specificity towards a panel of human monoclonal antibodies and gamma globulins. Competition radioimmunoassay (CRIA) revealed Ab2 specificities towards Ab1 antigen binding sites by inhibition of HBsAg/Ab1 binding. Ab2-H1 and Ab2-H2 had comparable reactivities in ELISA and CRIA, whereas, using affinity purified Ab2, a fast (10 min) agglutination test (Spherotest) revealed different Ab1/Ab2 binding properties. Ab2-H1 reacted in this Spherotest with the Ab1 against which it was known to be specific (Ab1-H1), whereas in the same assay Ab2-H2 showed no activity towards the variable regions of the Ab1 used for its production (Ab1-H2). When injected into rabbits Ab2-H1 induced anti-HBs Ab3 antibodies but Ab2-H2 did not, thereby confirming the assay results.

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La resistance a la chaleur du systeme photosynthetique des feuilles d'un arbre sclerophylle de la region mediterraneenne (Quercus ilex) a ete analysee par la methode d'induction de la fluorescence. Le rapport de decroissance a ete mesure, chaque mois durant une annee, sur les cinetiques obtenues. Selon les dates de recoltes, les feuilles ont ete classees en 2 categories: âgees de plus de 3 mois et de moins de 3 mois. Elles ont ete exposees a des temperatures de 50, 55 et 60°C pendant des durees allant de 0 a 30 min. Apres l'etablissement de la sclerification, aux alentours d'un mois d'âge, les feuilles resistent, avec des dommages limites, a une temperature de 50°C (.)

Trichosanthin was purified from fresh Chinese root tubers of Trichosanthes kirilowii and evaluated for anti-HIV activity. Trichosanthin inhibited syncytium formation between infected H9 cells and uninfected Sup-T1 cells from 0.5 to 4 micrograms/ml. Trichosanthin also inhibited HIV replication in H9 and CEM-SS cells at 1 microgram/ml, but was toxic for MT-4 cells (HTLV-I-positive), at doses greater than 0.25 microgram/ml. This new purification procedure confirms the anti-HIV activity of trichosanthin on some cell lines in different biological assays.

Incubation of the human T cell lymphotropic virus (HTLV)-IIIB and HTLV-RF strains of human immunodeficiency virus type 1 (HIV-1) with normal seronegative human serum under conditions that allow complement activation resulted in enhancement of infection of the MT2 human T cell line cultured in the presence of low amounts of virus. Infection of MT2 cells was assessed by measuring reverse transcriptase activity in supernatants at day 9 of culture. Complement activation by viral suspensions occurred through the alternative pathway. Opsonization of HTLV-RF viral particles with complement was sufficient to allow a productive infection to occur in cells exposed to suboptimal amounts of virus. Infection of MT2 cells with suboptimal amounts of serum-opsonized HIV-1 was suppressed by blocking the C3dg receptor (CR2, CD21) on MT2 cells with monoclonal anti-CR2 antibody and rabbit F(ab')2 anti-mouse immunoglobulin antibodies. Blocking of the gp120-binding site on CD4 under similar experimental conditions had no inhibitory effect on infection of MT2 cells with opsonized virus. Opsonization of HIV-1 with seronegative serum also resulted in a CR2-mediated enhancement of the infection of normal peripheral blood mononuclear cells and T lymphocytes. These results indicate that complement in the absence of antibody may enhance infection of C3 receptor-bearing T cells with HIV-1, and that the interaction of opsonized virus with the CR2 receptor may result by itself in the infection of target T cells in a CD4- and antibody-independent fashion.

An autumn burn was conducted in an open coppice-woodland of Quercus ilex. Two control plots were located at proximity. The girth growth of trees was recorded during three and half years by means of permanent dendrometers. No significant statistical differences occurred between trees either they were burned or not; the annual means reached: 0.76, 0.89 and 0.72 cm respectively for the burned plot and the two other unburned ones. Growth periods took place at the same times: mid-spring to end of summer. Apparently burning did not induce any beneficial or detrimental effect on the tree growth. This clearing technique can be used cautiously in coppice-woodlands only when the stand structure allows it. S'ha realitzat un incendi controlat en una parcel·la d'alzinar de rebrot. Dues parcel·les contigües han servit de testimoni. S'ha seguit I'augment de la circumferència dels individus durant tres anys i mig gràcies a dendròmetres permanents. Aquest increment la parcel·la cremada (0.76 cm) no presenta cap diferencia significativa amb els que es donen a les testimoni (0.89 i 0.72 cm). Els períodes de creixement s'ha donat a la mateixa època: primavera fins a finals d'estiu. Aparentment el foc no ha augmentat ni disminuït el creixement dels arbres. Aquesta tècnica de neteja del sotabosc ha de ser utilitzada amb precaució i quan l'estructura de la població ho permeti. Un brúlage contrólé d'automne a été réalisé sur une parcelle de taillis clair de chêne vert. Deux parcelles situées a côté ont servi de témoins. L'accroissement de la circonférence des individus a été suivi pendant trois ans et demi grâce a des dendromètres permanents. Les accroissements des arbres ne présentent aucune différence significative que les parcelles aient subi Ie feu ou pas; ils sont respectivement de: 0.76, 0.89 et 0.72 cm en moyenne par an pourceux de la parcelle brûlée et des deux autres non brûlées. Les périodes d'accroissement ont lieu aux mêmes époques: mi-printemps jusqu'a fin été. Apparemment le feu n'a ni augmenté ni diminué l'accroissement des arbres. Cette technique de débroussaillement des taillis peut être utilisée, mais avec précaution et lorsque la structure des peuplements s'y prête.

(...)Pour les deux especes et pour les deux stades de developpement consideres, la reduction de la reponse observee est tres rapide. Bien qu'apparaissant comme le plus resistant, le systeme photosynthetique de Quercus ilex est detruit, sans possibilite de recuperation, apres 30 min d'exposition a -20°C. L'impact des temperatures hivernales sur les aires de repartition de Q. ilex et Q. coccifera est evoque

Fire often creates openings in vegetation where alien plants may try to establish. Some of the invading species were introduced in Europe a long time ago (e.g. Erigeron sp. pl.), others arrived from distant localities more recently. In Mediterranean ecosystems of southern France, annuals and biannuals are typically rapidly eliminated due to the strong competition by local species. If fire occurs frequently, however, some perennials can persist, but seldom become dominant species.