Environmental feedbacks in temperate aquatic ecosystems under global change: why do we need to consider chemical stressors?

Regional Environmental Change - Globally increasing temperature and modifications in precipitation patterns induce major environmental alterations in aquatic ecosystems. Particularly profound...     

Generality of relationships between leaf pigment contents and spectral vegetation indices in Mallorca (Spain)

Vegetation indices are calculated from reflectance data of discrete spectral bands. The reflectance signal in the visible spectral range is dominated by the optical properties of photosynthetic pigments in plant leaves. Numerous spectral indices have been proposed for the estimation of leaf pigment contents, but the efficacy of different indices for prediction of pigment content and composition for species-rich communities is unknown. Assessing the ability of different vegetation indices to predict leaf pigment content we identify the most suitable spectral indices from an experimental dataset consisting of field-grown high light exposed leaves of 33 angiosperm species collected in two sites in Mallorca (Spain) with contrasting leaf anatomy and pigment composition. Leaf-level reflectance spectra were recorded over the wavelength range of 400 – 900 nm and contents of chlorophyll a, chlorophyll b, total carotenoids, and anthocyanins were measured in 33 species from different plant functional types, covering a wide range of leaf structures and pigment content, five-fold to more than 10-fold for different traits. The best spectral region for estimation of leaf total chlorophyll content with least interference from carotenoids and anthocyanins was the beginning of near-infrared plateau well beyond 700 nm. Leaves of parallel-veined monocots and pinnate-veined dicots had different relationships between vegetation indices and pigments. We suggest that the nature and role of “far-red” chlorophylls which absorb light at longer wavelengths than 700 nm constitute a promising target for future remote sensing studies.

     

Modeling the temporal dynamics of monoterpene emission by isotopic labeling in Quercus ilex leaves

A mathematical model to study the temporal dynamics of stable isotope ¹³C incorporation into monoterpene molecules, emitted from Mediterranean evergreen sclerophyll oak Quercus ilex L. leaves, was developed. The box model uses leaf level gas exchange and monoterpene emission data to assess biochemical and diffusional processes of the light-dependent monoterpene biosynthesis and emission within the leaf tissues. We estimated total leaf monoterpene pool exchange half-lifes against these processes. The slowest response took up to 38 h, while the fastest response occurred within 1 h, taking the sum of the lumped processes time constants into account. Separately, the turnover half-lives of the biochemical processes ranged between 26 min up to more than 4 h. The diffusional processes turnover times, driven by the physico-chemical properties of the monoterpene molecule, have been found to range between 32 min and 3 h, depending on the number of ¹³C-labeled carbon atoms. As a consequence, the steady-state assumption that is used in many larger scale emission models, may not hold in all cases and the application of process-based algorithms is beneficial to overcome such long transient pool dynamics of light-dependent monoterpene emission.     

Interacting environmental and chemical stresses under global change in temperate aquatic ecosystems: stress responses,adaptation, and scaling

Regional Environmental Change - Unfavorable environmental conditions—abiotic stress—constitute one of the key drivers of evolution leading to environmental adaptation. Since the start...     

Indicators of climate change adaptation from molecules to ecosystems

Regional Environmental Change -     

Instantaneous and historical temperature effects on alpha-pinene emissions in Pinus halepensis and Quercus ilex

We compared the role of instantaneous temperature and temperature history in the determination of alpha-pinene emissions in Mediterranean conifer Pinus halepensis that stores monoterpenes in resin ducts, and in Mediterranean broad-leaved evergreen Quercus ilex that lacks such specialized storage structures. In both species, alpha-pinene emission rates (E) exhibited a significant exponential correlation with leaf temperature and the rates of photosynthetic electron transport (Jco2+o2) started to decrease after an optimum at approximately 35 degrees C. However, there was a higher dependence of E on mean temperature of previous days than on mean temperature of current day for P. halepensis but not for Q. ilex. Jco2+o2 showed a maximum relationship to mean temperature of previous 3 and 5 days for P. halepensis and Q. ilex respectively. We conclude that although the best correlation of emission rates were found for instantaneous foliar temperatures, the effect of accumulated previous temperature conditions should also be considered in models of monoterpene emission, especially for terpene (see text) species.     

Salting-in and salting-out effects of ionic and neutral osmotica on limonene and linalool Henry's law constants and octanol/water partition coefficients

Foliar emission rates of plant-generated volatile monoterpenes depend on monoterpene partitioning between air, aqueous and lipid-phases in the leaves. While Henry's law constants (H pc, equilibrium gas/water partition coefficient) and octanol/water partition coefficients (K OW) for pure water have been previously used to simulate monoterpene emissions from the leaves, aqueous phase in plants is a complex solution of electrolytes and neutral osmotica. We studied the effects of dissociated compounds KCl and glycine and sugars glucose, sorbitol and sucrose with concentrations between 0 and 1M on H pc and K OW values for limonene and linalool. Linalool with ca. 1500-fold lower H(pc) (2.62 Pa m(3)mol(-1) for pure water at 30 degrees C) and ca. 30-fold lower K OW (955 mol mol(-1) for pure water at 25 degrees C) is the more hydrophilic compound of the two monoterpenes. H pc of both monoterpenes increased with increasing concentration of both ionic compounds and sorbitol, but decreased with increasing glucose and sucrose concentrations. The salting-out coefficients for H pc (kH) were ca. an order of magnitude larger for more hydrophilic compound linalool than for more hydrophobic limonene. For linalool, co-solutes modified H pc by 30-50% at the highest concentration (1M) tested. The effect of temperature on the salting-out coefficient of KCl was minor. As with H pc, K OW increased with increasing the concentration of KCl, glycine and sorbitol, and decreased with increasing glucose and sucrose concentrations. For limonene, co-solutes modified K OW by 20-50% at the highest concentration used. For linalool, the corresponding range was 10-35%. Salting-out coefficients for H pc and K OW were correlated, but the lipid-solubility was more strongly affected than aqueous solubility in the case of limonene. Overall, these data demonstrate physiologically important effects of co-solutes on H pc and K OW for hydrophilic monoterpenes and on K OW for hydrophobic monoterpenes that should be included in current emission models.     

Temperature dependencies of Henry's law constants and octanol/water partition coefficients for key plant volatile monoterpenoids

To model the emission dynamics and changes in fractional composition of monoterpenoids from plant leaves, temperature dependencies of equilibrium coefficients must be known. Henry's law constants (H(pc), Pa m3 mol(-1) and octanol/water partition coefficients (K(OW), mol mol(-1)) were determined for 10 important plant monoterpenes at physiological temperature ranges (25-50 degrees C for H(pc) and 20-50 degrees C for K(OW)). A standard EPICS procedure was established to determine H(pc) and a shake flask method was used for the measurements of K(OW). The enthalpy of volatilization (deltaH(vol)) varied from 18.0 to 44.3 kJ mol(-1) among the monoterpenes, corresponding to a range of temperature-dependent increase in H(pc) between 1.3- and 1.8-fold per 10 degrees C rise in temperature. The enthalpy of water-octanol phase change varied from -11.0 to -23.8 kJ mol(-1), corresponding to a decrease of K(OW) between 1.15- and 1.32-fold per 10 degrees C increase in temperature. Correlations among physico-chemical characteristics of a wide range of monoterpenes were analyzed to seek the ways of derivation of H(pc) and K(OW) values from other monoterpene physico-chemical characteristics. H(pc) was strongly correlated with monoterpene saturated vapor pressure (P(v)), and for lipophilic monoterpenes, deltaH(vol) scaled positively with the enthalpy of vaporization that characterizes the temperature dependence of P(v) Thus, P(v) versus temperature relations may be employed to derive the temperature relations of H(pc) for these monoterpenes. These data collectively indicate that monoterpene differences in H(pc) and K(OW) temperature relations can importantly modify monoterpene emissions from and deposition on plant leaves.