BackgroundCarotenoids are the most widespread group of pigments found in nature. In addition to their role in the physiology of the plant, carotenoids also have nutritional relevance as their incorporation in the human diet provides health benefits. In non-photosynthetic tissues, carotenoids are synthesized and stored in specialized plastids called chromoplasts. At present very little is known about the origin of the metabolic precursors and cofactors required to sustain the high rate of carotenoid biosynthesis in these plastids. Recent proteomic data have revealed a number of biochemical and metabolic processes potentially operating in fruit chromoplasts. However, considering that chloroplast to chromoplast differentiation is a very rapid process during fruit ripening, there is the possibility that some of the proteins identified in the proteomic analysis could represent remnants no longer having a functional role in chromoplasts. Therefore, experimental validation is necessary to prove whether these predicted processes are actually operative in chromoplasts.ResultsA method has been established for high-yield purification of tomato fruit chromoplasts suitable for metabolic studies. Radiolabeled precursors were efficiently incorporated and further metabolized in isolated chromoplast. Analysis of labeled lipophilic compounds has revealed that lipid biosynthesis is a very efficient process in chromoplasts, while the relatively low incorporation levels found in carotenoids suggest that lipid production may represent a competing pathway for carotenoid biosynthesis. Malate and pyruvate are efficiently converted into acetyl-CoA, in agreement with the active operation of the malic enzyme and the pyruvate dehydrogenase complex in the chromoplast. Our results have also shown that isolated chromoplasts can actively sustain anabolic processes without the exogenous supply of ATP, thus suggesting that these organelles may generate this energetic cofactor in an autonomous way.ConclusionsWe have set up a method for high yield purification of intact tomato fruit chromoplasts suitable for precursor uptake assays and metabolic analyses. Using targeted radiolabeled precursors we have been able to unravel novel biochemical and metabolic aspects related with carotenoid and lipid biosynthesis in tomato fruit chromoplasts. The reported chromoplast system could represent a valuable platform to address the validation and characterization of functional processes predicted from recent transcriptomic and proteomic data.

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In most African urban areas, Particulate Matters (PM) concentration exceeds by far the WHO limits. In these areas, plants can play a key role in removing particles. In this study, we evaluated three ornamental species (Jatropha interrigima, Ficus benjamina, Barleria prionitis) used in Abidjan (Ivory Coast). Leaf-encapsulated saturation isothermal remnant magnetisation (SIRM) were measured and the relationship between PM captured and leaf wettability were done. The sampling were performed at roadsides and Parks. Firstly, Leaf-encapsulated and total leaf SIRM were quantified and the wettability was determined by drop contact angles (DCA). Secondly, the relationship between leaf SIRM and wettability was found. Results showed that leaf SIRM was two to ten times higher at roadsides than in Parks. Total leaf SIRM was also higher on mature leaves in Main roads suggesting a particle accumulation in leaves over time especially in waxy species (Ficus benjamina). This species encapsulated other than 20% of total leaf SIRM. All tested species were highly-wettable (40° < DCA < 90°). Thus, Jatropha interrigima with its leaf trichomes and F. benjamina with its leaf waxes were more wettable. A significantly positive correlation was found between wettability intensity and leaf SIRM.

Weeds are the most important biological constraint reducing rice production. This study was conducted to know the physiological characteristics and the germinative behavior of the seeds of Rottboellia cochinchinensis, Euphorbia heterophylla and Porophyllum ruderale, three major weeds of rice field in Côte d'Ivoire. Seed characteristics were determined according to ISTA's standards. These three weeds had orthodox seeds with low moisture content (< 15%). These weeds raise better when they were sown on the surface (0-0.5 cm) or slightly buried in the ground. E. heterophylla and P. ruderale germinated well when their seeding density is high (150 seeds/Petri dish). For R. cochinchinensis, when the seedling density is low (25 seeds/Petri dish). The germination was maximum after five to nine days. RésuméLes mauvaises herbes constituent l'une des contraintes biologiques les plus importantes entrainant une baisse de la production du riz. Cette étude a été menée en vue de connaître les caractéristiques physiologiques et le comportement germinatif des semences de Rottboellia cochinchinensis, de Euphorbia heterophylla et de Porophyllum ruderale, trois adventices majeures des rizières de la Côte d'Ivoire. Les caractéristiques physiologiques ont été déterminés selon les normes de ISTA. Ces trois adventices possèdent des semences orthodoxes qui ont une teneur en eau inférieure à 15 %. Ces graines lèvent mieux lorsqu'elles sont semées en surface (0 cm) ou à une faible profondeur de 0,5 cm. E. heterophylla et P. ruderale germent mieux lorsque leur densité de semis est forte (150 graines/boîte de Pétri). Par contre les semences de R. cochinchinensis germent mieux lorsque la densité de semis est faible (25 graines/boîte de Pétri). Pour ces trois adventices, la germination est maximale au bout de cinq à neuf jours.