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Background and aims: A greenhouse experiment was conducted to analyze the physiological behavior of Acacia arabica in relation to concentration of phenolic compounds during drought and subsequent recovery. Methods: Seedlings were exposed to water shortage during 32 days and then rehydrated and allowed to recover during 15 days. Parameters related to plant water status, photosynthesis and oxidative stress were quantified after 7, 15 and 32 days of stress, and after 7 and 15 days of recovery. Phenolic acids, flavonoids and enzyme activities involved in their synthesis were quantified. Results: 88% of plants remained alive during the stress period and 10% died during recovery. Drought reduced water and osmotic potentials, stomatal conductance, net photosynthesis, instantaneous transpiration, non-photochemical quenching and flavanols concentration and increased proline, malondialdehyde, phenylalanine ammonia-lyase (PAL) and cinnamate 4-hydroxylase (C4H) activities, DPPH scavenging, hydroxycinnamic acids, hydroxybenzoic acids and flavonols concentration. Genes coding for PAL and chalcone synthase (CHS) were slightly downregulated at the end of drought while gene coding for C4H was upregulated at the beginning of drought. Parameters related to oxidative stress as well as hydroxybenzoic acids and flavonols remained at high values throughout the recovery period. Genes coding for C4H and CHS were up-regulated during recovery. Conclusions: Acacia arabica is resistant to water stress at the seedling stage and able to recover after stress relief. Recovery induces a specific physiological status in terms of transpiration rates and management of oxidative stress in relation to flavonols and hydroxybenzoic acids concentrations. [ABSTRACT FROM AUTHOR]

Background and aims: Proline and glycinebetaine are osmolytes playing a role in resistance to salt and water stress but their involvement in plant adaptation to heavy metals remain unclear. Methods: Young plants of the halophyte Kosteletzkya pentacarpos were grown in nutrient solution in the presence of Cd (20 or 40 μM) or Zn (200 or 400 μM), or a combination of both heavy metals and in the presence or absence of NaCl 50 mM for 48 h. Osmolytes concentrations, enzyme activities involved in their metabolism and expression of corresponding genes were determined in roots and leaves. Results: Cadmium but not zinc increased proline and glycinebetaine in the leaves. Salinity reduced proline content in Cd-treated plants but increased it in plants exposed to Cd + Zn. Proline was produced through both glutamate and ornithine pathways while proline dehydrogenase was inhibited in response to heavy metals. Correlation between enzyme activities and corresponding gene expression was significant in the leaves but not in the roots. Gene coding for proline transport (KvProT) was upregulated in response to heavy metals. Conclusion: Low NaCl dose (50 mM) afford protection to heavy metal stress in K. pentacarpos and its effect on osmolyte synthesis depends on considered metal and plant organ. [ABSTRACT FROM AUTHOR]

Background and aim: Cichorium intybus is a biennal species storing inulin in taproot during the first year and flowering after vernalization. Heat impact on sugar distribution and inulin yield remains poorly documented.Methods: Plants were cultivated under ambient or high (ambient+5 °C) temperature for 27 weeks. Plants were monthly harvested and morphological parameters, bolting rate, sugar translocation, soluble sugars and inulin content were determined.Results: Heat reduced shoot and root growth and unexpectedly induced precocious bolting. It increased fructose contents in roots and leaves, increased root myo-inositol and reduced leaf sucrose content. At harvest, inulin content was higher in heat-treated than in control roots but total amount of inulin produced per plant was lower. Heat inhibited sugar translocation from leaves to secondary roots. Total soluble sugar content was lower in leaves but higher in roots of bolted plants compared to non-bolted ones. Bolting induced an increase in the mean degree of polymerization of inulin and root lignification.Conclusion: High temperatures impaired inulin production as a result of root growth inhibition and reduced sugar translocation from the leaves to the roots. Heat induced precocious bolting on non-vernalized plants. Bolting reinforced root growth inhibition and thus inulin yield decrease. [ABSTRACT FROM AUTHOR]

To investigate whether Tilia trees are poisonous or valuable resources for bee visitors, we determined the nectar and pollen quantities and composition of the four main Tilia species planted in Western Europe (T. cordata, T. platyphyllos, T. tomentosa, and T. × europaea). We developed a new method to detect nicotine in nectars. We observed insect visitor diversity and abundance. We also assessed bumblebee death when individuals were only fed with Tilia flowers. No traces of mannose or nicotine, incriminated in the Tilia toxicity, have been detected in the nectars of the studied species. Huge numbers of insect visitors, mainly bees and syrphids, visited the trees which offer large numbers of flowers, plenty of sugar rich nectar, and protein-rich pollen. Bumblebees only fed with Tilia flowers did not present any particular mortality. We discuss the different hypotheses of the supposed toxicity and propose future research to solve this debate. [ABSTRACT FROM AUTHOR]

Key message: Genetic interactions of UFD gene support its specific function during reproductive development of tomato; in this process, UFD could play a pivotal role between inflorescence architecture and flower initiation genes. Abstract: Tomato ( Solanum lycopersicum L.) is a major vegetable crop that also constitutes a model species for the study of plant developmental processes. To gain insight into the control of flowering and floral development, a novel tomato mutant, unfinished flower development ( ufd), whose inflorescence and flowers were unable to complete their normal development was characterized using double mutant and gene expression analyses. Genetic interactions of ufd with mutations affecting inflorescence fate ( uniflora, jointless and single flower truss) were additive and resulted in double mutants displaying the inflorescence structure of the non- ufd parental mutant and the flower phenotype of the ufd mutant. In addition, ufd mutation promotes an earlier inflorescence meristem termination. Taken together, both results indicated that UFD is not involved in the maintenance of inflorescence meristem identity, although it could participate in the regulatory system that modulates the rate of meristem maturation. Regarding the floral meristem identity, the falsiflora mutation was epistatic to the ufd mutation even though FALSIFLORA was upregulated in ufd inflorescences. In terms of floral organ identity, the ufd mutation was epistatic to macrocalyx, and MACROCALYX expression was differently regulated depending on the inflorescence developmental stage. These results suggest that the UFD gene may play a pivotal role between the genes required for flowering initiation and inflorescence development (such as UNIFLORA, FALSIFLORA, JOINTLESS and SINGLE FLOWER TRUSS) and those required for further floral organ development such as the floral organ identity genes. [ABSTRACT FROM AUTHOR]

Urbanization affects the availability and diversity of floral resources (pollen and/or nectar) for wild pollinating insects. For example, urban green areas are characterized by an abundance of ornamental plant species. Increasingly, trees are planted to improve the aesthetics of urban streets and parks. These urban trees might offer important floral resources to pollinating insects. To examine the suitability of urban trees as resources for pollinating insects, we investigated the chemical composition of pollen and nectar as well as the amount of nectar produced by the nine major insect-pollinated tree species planted in cities of Western Europe, namely Acer pseudoplatanus, Aesculus carnea, A. hippocastanum, Robinia pseudoacacia, Tilia cordata, T. x euchlora, T. x europaea, T. platyphyllos and T. tomentosa. The analyses revealed that globally the Tilia trees provide pollen with lower contents of polypeptides, amino acids and phytosterols compared with the other species. Urban tree flowers offer abundant nectar with relatively high sugar contents (0.16-1.28 mg/flower); sucrose was the predominant sugar in all nectars. The investigated tree species could therefore be considered in future city plantings. [ABSTRACT FROM AUTHOR]

Background and aim: In numerous areas, rice cultivated under flooded conditions is exposed simultaneously to iron excess and arsenic contamination. The impact of these combined stresses on yield-related parameters and As distribution and speciation in various plant parts remains poorly documented. Methods: Rice (cv I Kong Pao) was exposed to iron excess (125 mg L FeSO), arsenic (50 and 100 μM NaHAsO.7HO) or a combination of those stressing agents in hydroponic culture until harvest. Plant growth, yield-related parameters, non protein thiols concentration and mineral nutrition were studied in roots and shoots. Arsenic speciation was determined by high-performance liquid chromatography-hydride generation-atomic fluorescence spectrometry. Key Results: Iron excess increased As retention by the roots in relation to the development of the root iron plaque but decreased As accumulation in the shoot. Arsenic concentration was lower in the grains than in the shoots. Iron stress reduced As accumulation in the husk but not in the dehusked grains. Iron excess decreased the proportion of extractable As(III) and As(V) in the grain while it increased the proportion of extractable As(III) in the shoot. Combined stresses (Fe+As) affected plant nutrition and significantly reduced the plant yield by limiting the number of grains per plant and the grain filling. Conclusions: Fe excess had an antagonist impact on shoot As concentration but an additive negative impact on several yield-related parameters. Iron stress influences both As distribution and As speciation in rice. [ABSTRACT FROM AUTHOR]

Kosteletzkya virginica is a wetland halophyte that is a good candidate for rehabilitation of degraded salt marshes and production of oil as biodiesel. Salt marshes are frequently contaminated by heavy metals. The distribution of Zn in vegetative and reproductive organs of adult plants, and the NaCl influence on this distribution remain unknown and were thus explored in the present study. Plants were cultivated in a nutrient film technique system, from seedling stage until seed maturation in a control, Zn (100 μM), NaCl (50 mM) or Zn + NaCl medium. Photosynthesis, ion nutrition, malondialdehyde and non-protein thiol concentrations were quantified. Zinc distribution in reproductive organs was estimated by a laser ablation-inductively coupled plasma-mass spectrometry procedure (LA-ICP-MS). Adult plants accumulated up to 2 mg g DW Zn in the shoots. Zinc reduced plant growth, inhibited photosynthesis and reduced seed yield. Zinc accumulation in the seeds was only two times higher in Zn-treated plants than in controls. Exogenous NaCl neutralized the damaging action of Zn and modified the Zn distribution through a preferential accumulation of toxic ions in older leaves. Zinc was present in seed testa, endosperm and, to a lower extent, in embryo. Additional NaCl induced a chalazal retention of Zn during seed maturation and reduced final Zn seed content. It is concluded that NaCl 50 mM had a positive impact on the response of K. virginica to Zn toxicity and acts through a modification in Zn distribution rather than a decrease in Zn absorption. [ABSTRACT FROM AUTHOR]