Notes: : Total polyphenols, total anthocyanins, and reduced ascorbic acid were evaluated in berries belonging to the genera Rubus, Ribes, and Aronia by means of spectrophotometric and high-performance liquid chromatography (HPLC) techniques. The 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging activity of the fruit extracts was tested. Total polyphenols ranged from 140.6 to 888.5 mg/100 g fresh weight (FW), total anthocyanins ranged from 22.0 to 460.5 mg/100 g FW, and reduced ascorbic acid ranged from 12.4 to 153.8 mg/ 100 g FW. The average EC50 values for Aronia melanocarpa, Ribes nigrum, Ribes rubrum, Rubus fruticosus, and Rubus idaeus were 1.8, 2.8, 5.3, 6.4, and 8.2 mg FW, respectively. The results indicate that the fruits tested are good sources of natural antioxidants.

Notes: Trials were carried out to study the germination and dormancy of Cuscuta campestris Y. (dodder) seeds and factors influencing the success of early parasitisation of sugarbeet. Primary dormancy can be removed by seed scarification. Germination was negligible at 10°C and optimal at 30°C, while it was not influenced by light. Seed burial induced a cycle of induction and breaking of secondary dormancy. Seedling emergence was inversely proportional to the depth of seed burial and only seed buried within 5 cm of the soil surface emerged. Storage of C. campestris seeds in a laboratory for 12 years resulted in the loss of primary dormancy, enabling the germination of all viable seeds. Host infection (i.e. protrusion of parasite haustoria from host tissue) was heavily influenced by host growth stage. Tropism towards a host was due to the perception of light transmitted by green parts of sugarbeet plants. Insertion of a transparent glass sheet between host leaves and parasite seedlings did not modify this response. This phototropism permitted Cuscuta to identify host plants with high chlorophyll content as a function of the lower red/far red ratio of transmitted light.

Notes: This paper presents a review of weed dynamics in the Mediterranean urban ecosystem, seen both in an ecological and biological perspective and also in relation to the interaction between human activity and the survival strategies of the various phytocoenoses. Although generalizations on urban weeds cannot easily be drawn on account of the wide range of microenvironments, anemochoric dissemination mechanisms (Asteraceae), resilience (grasses) and perennation are of particular importance. The reasons underlying the undesirability of weeds in the urban environment are investigated. Not only are weeds considered unsightly, but they may also give rise to ‘functional’ obstacles, damaging sidewalks or clogging storm drains. Furthermore, they may adversely affect human health by releasing allergenic pollen into the atmosphere. Management of urban weeds is based almost exclusively on mechanical control, as chemical measures may involve a toxicity risk for man. Paradoxically, certain weeds species may however have a positive effect if they are linked to fauna (butterflies, birds, etc.) considered to give a favourable impression in the cityscape. Finally, the possibility of favouring the biodiversity of the urban ecosystem by introducing some wildflowers typically associated with the degree of biodiversity of the surrounding environment is discussed.

Notes: Trials were carried out to investigate the effects of light and temperature on germination of Rumex obtusifolius L. After several months of storage, seeds gradually lost dormancy and became photosensitive. Thermal optima for germination were between 20 °C and 25 °C in light or in darkness. At lower temperatures there was a greater demand for light, so that the greatest differences in germination percentage (between low and high temperatures) were found within the 10–15 °C temperature range. The calculated thermal minima (x-intercept method) in light and darkness were 8.3 °C and 6.1 °C respectively. Daily temperature fluctuation increased germination even after seed irradiation with far-red light, suggesting a lower demand for the far-red-absorbing form of phytochrome. Seed burial inhibited germination in proportion to depth; however, germination inhibition was independent of seed phytochrome photo-equilibrium, which had been diversified by seed pretreatment with light. Seedlings did not emerge when seeds were buried 〉8 cm deep. Recovery of ungerminated seeds showed that excessive burial did not impede seedling emergence but rather prevented seed germination. However, this induction of dormancy was lost once germination processes were activated (24–48 h at 20 °C) that made germination irreversible. Temperature was also involved in inhibition, and low temperature (〈15 °C) induced the least inhibition. This is discussed in terms of processes of respiration and fermentation in buried seeds.

Notes: Leptochloa chinensis is a new weed that has been found with increasing frequency in Italian rice paddies. The germination ecology of L. chinensis seeds was studied in order to investigate the development mechanisms and survival strategy of this weed in rice paddies of northern Italy. Leptochloa chinensis seeds showed no dormancy and exhibited germination even in anoxic conditions. Germination was strongly influenced by temperature (minimum around 15°C; optimal 25–35°C) and light (phytochrome dependent). Temperature fluctuation caused an increase of seed germination in the dark. Seed burial also strongly inhibited germination and emergence of this species. At 5 cm seed burial only 5% of seedlings emerged in flooded conditions, while at the same depth, but with no flooding, no seedling emergence was observed. This phenomenon was not due to oxygen depletion, as germination was not inhibited by complete anoxia, as demonstrated by the fact that some seedlings did emerge in flooding conditions when water was no deeper than 6 cm. Seed burial and concomitant flooding induced an unusual germination: first coleoptile emergence and subsequently emergence of the radicle was observed. The possible exploitation of this knowledge for weed management is discussed.

Notes: Trials were carried out in order to investigate the effect of hypoxia on seed germination of Datura stramonium L. in Petri dishes and when buried at various depths in soil. Hypoxia was found to cause a decrease in germination capacity and germination rate. This inhibition was partially alleviated by daily exchange of hypoxic gas surrounding the seeds during incubation. Similarly, seed scarification allowed maintenance of a higher germination capacity under conditions of low oxygen availability, showing that the seed coat was only partially gas permeable. Oxygen deficiency led to a decrease in respiratory capacity. However, this was probably compensated for by induction of fermentation metabolism. The possibility of removing the final products of fermentation exerts a decisive influence on seed germination, especially in an environment such as soil, where their diffusion into the surrounding environment is restricted. Thus daily nitrogen flushing partially eliminated this inhibition, even under conditions of low external oxygen availability. It was therefore postulated that the main depth–derived inhibition was not caused directly by oxygen deficiency but by the increasing difficulty in eliminating toxic fermentation products, which was found to be proportional to the degree of hypoxia. Finally, incubation for several days under completely anaerobic conditions induced secondary dormancy. This was probably due to an ecological adaptation mechanism that prevents germination under conditions that are unfavourable for survival.

Notes: Relations between availability of light and reproductive activity in several of the most damaging summer weeds (Abutilon theophrasti Medicus, Datura stramonium L., Sorghum halepense L. Pers.) were studied, in order to investigate seed production capacity of these weed species in the unfavourable conditions occurring under a crop canopy simulated by shade cloths. Decrease in seed production under shading appeared to be due to a decrease in the number of fruits per plant, while the quantity of seed per fruit proved to be fairly stable. Biomass partitioning within the plant reduced the percentage of dry matter accumulated in reproductive organs, leading to a marked decrease in the harvest index. Further-more, shading caused a species-dependent delay in onset of the flowering and ripening stages. In Datura stramonium shading led to a greater de-crease in seed production and, consequently, in the harvest index than in the other species examined. Finally, laboratory tests demonstrated that the percentage of dormant seeds remained unmodified in all species examined. Effet de l'ombragesur la reproduction et quelques caracteristiques morphologiques de Abutilon theophrasti Medicus, Datura stramonium E. et Sorghum halepense L. Pers. Les relations entre la fourniture de lumière et l'activité reproductrice de quelques unes des mauvaises herbes les plus importantes (Abutilon tiieophrasti Medicus, Datura stramonium L., Sorghum halepense L. Pers.) ont étéétudiées en vue de déterminer leur capacitéà produire des graines dans les conditions défavorables qui prévalent sous les couverts végétaux. La diminution de la production de graines était due à une diminution du nombre de fruit par plante, alors que la quantité de graines par fruits restait à peu près stable. La distribution de la biomasse dans la plante conduisait à une diminution du pour-centage de matière seche accumulée dans les organes reproducteurs, ce qui se traduisait par une diminution de l'indice de récolte. De plus, l'ombrage causait un retard (variable selon l'espece) du début de la floraison et de la maturation. Chez Datura stramonium, l'ombrage conduisait à la réduction la plus importante de la production de graines (et par conséquent de l'indice de récolte). Enfin, des tests en laboratoire ont montré que le pourcentage de graines dormantes n'était modifie chez aucune des espèces testées. Einfluß von Beschattung auf Vermehrung und morphologische Eigenschaften von Abutilon theophrasti Medicus, Datura stramonium E. und Sorghum halepense (E.) Pers. An einigen sommerannuellen Unkräutem (Abutilon theophrasti Medicus, Datura stramonium L. und Sorghum halepense (L.) Pers.) wurde die Beziehung zwischen der Lichtverfügbarkeit und der Samenproduktion dieser Arten unter den ungünstigen Bedingungen der Beschattung in einem Kulturpflanzenbestand, die durch Beschattungsgewebe simuliert wurde, untersucht. Die Abnahme der Samenproduktion bei Beschattung ist durch die geringere Fruchtzahl pro Pflanze bedingt; die Samenzahl pro Frucht erwies sich als ziemlich stabil. Die Biomasseverteilung in den Pflanzen führte zu einer Abnahme der Trockenmasse der Reproduktionsorgane und damit zu einem deutlich kleineren Ertragsindex. Außerdem wurden durch die Beschattung der Blühbeginn und das Reifestadium verzögert. Bei Datura stramonitim war die Abnahme der Samenbildung und somit des Ertragsindex stärker als bei den anderen Arten. Der Anteil dormanter Samen blieb bei alien Arten durch die Beschattung einbeeinflußt.