El rol dels terpens en la competència entre plantes invasores i natives a Hawaii

Els terpens, hidrocarburs derivats de l'isoprè, són emesos i emmagatzemats per moltes plantes. La seva funció biològica i ecològica és estudiada des de fa uns anys, havent estat proposades diverses possibles funcions, com per exemple la protecció davant dels herbívors o com a mecanisme antiestrès metabòlic. Investigacions realitzades per científics del CREAF a les illes Hawaii han permès detectar diferències en l'acumulació foliar de terpens entre les espècies nadiues i invasives a través de l'screening efectuat en una àmplia mostra de les principals espècies forestals natives i invasives a l'illa d'Oahu. Aquests resultats aporten noves pistes per conèixer els mecanismes que expliquen l'èxit competitiu que permet que moltes espècies introduïdes en un nou hàbitat esdevinguin un problema ecològic per la seva expansió i exclusió competitiva d'espècies nadiues.Los terpenos, hidrocarburos derivados del isopreno, son emitidos y almacenados por muchas plantas. Su función biológica y ecológica está siendo estudiada desde hace unos años, habiendo sido propuestas varias posibles funciones, como por ejemplo la protección frente a los herbívoros o como mecanismo antiestrés metabólico. Investigaciones realizadas por científicos del CREAF en las islas Hawai han permitido detectar diferencias en la acumulación foliar de terpenos entre las especies nativas e invasivas a través del screening efectuado en una amplia muestra de las principales especies forestales nativas y invasivas en la Isla de Oahu. Estos resultados aportan nuevas pistas para conocer los mecanismos que explican el éxito competitivo que permite que muchas especies introducidas en un nuevo hábitat se conviertan en un problema ecológico por su expansión y exclusión competitiva de especies nativas

Highly Diverse Phytophthora infestans Populations Infecting Potato Crops in Pskov Region, North-West Russia

There is limited understanding of the genetic variability in Phytophthora infestans in the major potato cultivation region of north-western Russia, where potato is grown primarily by small households with limited chemical treatment of late blight. In this study, the mating type, sensitivity to metalaxyl, and genotype and population genetic diversity (based on 12 simple sequence repeat (SSR) markers) of 238 isolates of P. infestans from the Pskov region during the years 2010–2013 were characterized. The aim was to examine the population structure, phenotypic and genotypic diversity, and the prevalent reproductive mode of P. infestans, as well as the influence of the location, time, and agricultural management practices on the pathogen population. The frequency of the A2 mating was stable over the four seasons and ranged from 33 to 48% of the sampled population. Both mating types occurred simultaneously in 90% of studied fields, suggesting the presence of sexual reproduction and oospore production in P. infestans in the Pskov region. Metalaxyl-sensitive isolates prevailed in all four years (72%), however, significantly fewer sensitive isolates were found in samples from large-scale conventional fields. A total of 50 alleles were detected in the 141 P. infestans isolates analyzed for genetic diversity. Amongst the 83 SSR multilocus genotypes (MLGs) detected, 65% were unique and the number of MLGs varied between locations from 3 to 20. These results, together with the high genotypic diversity observed in all the locations and the lack of significance of linkage disequilibrium, suggest that sexual recombination is likely responsible for the unique MLGs and the high genetic diversity found in the Pskov region population, resembling those of north-eastern European populations

Synthesis of phenolics and flavonoids in ginger (Zingiber officinale Roscoe) and their effects on photosynthesis rate

The relationship between phenolics and flavonoids synthesis/accumulation and photosynthesis rate was investigated for two Malaysian ginger (Zingiber officinale) varieties grown under four levels of glasshouse light intensity, namely 310, 460, 630 and 790 μmol m 2s 1. High performance liquid chromatography (HPLC) was employed to identify and quantify the polyphenolic components. The results of HPLC analysis indicated that synthesis and partitioning of quercetin, rutin, catechin, epicatechin and naringenin were high in plants grown under 310 μmol m 2s 1. The average value of flavonoids synthesis in leaves for both varieties increased (Halia Bentong 26.1%; Halia Bara 19.5%) when light intensity decreased. Photosynthetic rate and plant biomass increased in both varieties with increasing light intensity. More specifically, a high photosynthesis rate (12.25 μmol CO 2 m 2s 1 in Halia Bara) and plant biomass (79.47 g in Halia Bentong) were observed at 790 μmol m 2s 1. Furthermore, plants with the lowest rate of photosynthesis had highest flavonoids content. Previous studies have shown that quercetin inhibits and salicylic acid induces the electron transport rate in photosynthesis photosystems. In the current study, quercetin was an abundant flavonoid in both ginger varieties. Moreover, higher concentration of quercetin (1.12 mg/g dry weight) was found in Halia Bara leaves grown under 310 μmol m 2s 1 with a low photosynthesis rate. Furthermore, a high content of salicylic acid (0.673 mg/g dry weight) was detected in Halia Bara leaves exposed under 790 μmol m 2s 1 with a high photosynthesis rate. No salicylic acid was detected in gingers grown under 310 μmol m 2s 1. Ginger is a semi-shade loving plant that does not require high light intensity for photosynthesis. Different photosynthesis rates at different light intensities may be related to the absence or presence of some flavonoid and phenolic compounds

The Coordination of Leaf Photosynthesis Links C and N Fluxes in C3 Plant Species

Photosynthetic capacity is one of the most sensitive parameters in vegetation models and its relationship to leaf nitrogen content links the carbon and nitrogen cycles. Process understanding for reliably predicting photosynthetic capacity is still missing. To advance this understanding we have tested across C3 plant species the coordination hypothesis, which assumes nitrogen allocation to photosynthetic processes such that photosynthesis tends to be co-limited by ribulose-1,5-bisphosphate (RuBP) carboxylation and regeneration. The coordination hypothesis yields an analytical solution to predict photosynthetic capacity and calculate area-based leaf nitrogen content (Na). The resulting model linking leaf photosynthesis, stomata conductance and nitrogen investment provides testable hypotheses about the physiological regulation of these processes. Based on a dataset of 293 observations for 31 species grown under a range of environmental conditions, we confirm the coordination hypothesis: under mean environmental conditions experienced by leaves during the preceding month, RuBP carboxylation equals RuBP regeneration. We identify three key parameters for photosynthetic coordination: specific leaf area and two photosynthetic traits (k3, which modulates N investment and is the ratio of RuBP carboxylation/oxygenation capacity () to leaf photosynthetic N content (Npa); and Jfac, which modulates photosynthesis for a given k3 and is the ratio of RuBP regeneration capacity (Jmax) to). With species-specific parameter values of SLA, k3 and Jfac, our leaf photosynthesis coordination model accounts for 93% of the total variance in Na across species and environmental conditions. A calibration by plant functional type of k3 and Jfac still leads to accurate model prediction of Na, while SLA calibration is essentially required at species level. Observed variations in k3 and Jfac are partly explained by environmental and phylogenetic constraints, while SLA variation is partly explained by phylogeny. These results open a new avenue for predicting photosynthetic capacity and leaf nitrogen content in vegetation models