Gargallo-Garriga A., Sardans J., Pérez-Trujillo M., Rivas-Ubach A., Oravec M., Vecerova K., Urban O., Jentsch A., Kreyling J., Beierkuhnlein C., Parella T., Peñuelas J. (2014) Opposite metabolic responses of shoots and roots to drought. Scientific Reports. 4: 0-0.EnllaçDoi: 10.1038/srep06829
Shoots and roots are autotrophic and heterotrophic organs of plants with different physiological functions. Do they have different metabolomes? Do their metabolisms respond differently to environmental changes such as drought? We used metabolomics and elemental analyses to answer these questions. First, we show that shoots and roots have different metabolomes and nutrient and elemental stoichiometries. Second, we show that the shoot metabolome is much more variable among species and seasons than is the root metabolome. Third, we show that the metabolic response of shoots to drought contrasts with that of roots; shoots decrease their growth metabolism (lower concentrations of sugars, amino acids, nucleosides, N, P, and K), and roots increase it in a mirrored response. Shoots are metabolically deactivated during drought to reduce the consumption of water and nutrients, whereas roots are metabolically activated to enhance the uptake of water and nutrients, together buffering the effects of drought, at least at the short term.
Rivas-Ubach A., Gargallo-Garriga A., Sardans J., Oravec M., Mateu-Castell L., Perez-Trujillo M., Parella T., Ogaya R., Urban O., Penuelas J. (2014) Drought enhances folivory by shifting foliar metabolomes in Quercus ilex trees. New Phytologist. 202: 874-885.EnllaçDoi: 10.1111/nph.12687
At the molecular level, folivory activity on plants has mainly been related to the foliar concentrations of nitrogen (N) and/or particular metabolites. We studied the responses of different nutrients and the whole metabolome of Quercus ilex to seasonal changes and to moderate field experimental conditions of drought, and how this drought may affect folivory activity, using stoichiometric and metabolomic techniques. Foliar potassium (K) concentrations increased in summer and consequently led to higher foliar K: phosphorus (P) and lower carbon (C): K and N: K ratios. Foliar N: P ratios were not lowest in spring as expected by the growth rate hypothesis. Trees exposed to moderate drought presented higher concentrations of total sugars and phenolics and these trees also experienced more severe folivory attack. The foliar increases in K, sugars and antioxidant concentrations in summer, the driest Mediterranean season, indicated enhanced osmoprotection under natural drought conditions. Trees under moderate drought also presented higher concentrations of sugars and phenolics; a plant response to avoid water loss. These shifts in metabolism produced an indirect relationship between increased drought and folivory activity. © 2014 New Phytologist Trust.
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