Ground level isoprenoid exchanges associated with Pinus pinea trees in a Mediterranean turf

The emissions of isoprenoids, a kind of biogenic volatile organic compounds (BVOCs), from soils is not well characterized. We quantified the exchange of isoprenoids between soil with litter and atmosphere along a horizontal gradient from the trunks of the trees, in a Mediterranean Pinus pinea plantation with dry and green needle litter to open herbaceous turf during mornings at mid-summer. Further, potential associated drivers were identified. Isoprenoid emissions were greatest and most diverse, and also can be roughly estimated by litter dry weight near the trunk, where the needle litter was denser. The composition of emitted isoprenoid by needle litter was different than the composition previously described for green needles. Low exchange rates of isoprenoids were recorded in open turf. Isoprenoid exchange rates were correlated positively with soil temperature and negatively with soil moisture. Given the variations in ground emissions with soil, vegetation, microorganisms, and associated interactions, we recommend widespread extensive spatio-temporal analysis of ground level BVOC exchanges in the different ecosystem types

Bidirectional interaction between phyllospheric microbiotas and plant volatile emissions

Due to their antimicrobial effects and their potential role as carbon sources, plant volatile organic compound (VOC) emissions play significant roles in determining the characteristics of the microbial communities that can establish on plant surfaces. Furthermore, epiphytic microorganisms, including bacteria and fungi, can affect plant VOC emissions in different ways: by producing and emitting their own VOCs, which are added to and mixed with the plant VOC blend; by affecting plant physiology and modifying the production and emission of VOCs; and by metabolizing the VOCs emitted by the plant. The study of the interactions between plant VOC emissions and phyllospheric microbiotas is thus of great interest and deserves more attention

L'alzina podria perdre la seva hegemonia en el bosc mediterrani a causa del canvi climàtic

Les baixes temperatures de l'hivern i la baixa disponibilitat d'aigua són els dos factors principals que poden inhibir o danyar l'aparell fotosintètic de les espècies mediterrànies. Amb l'augment de les temperatures i la disminució de la disponibilitat d'aigua associades al canvi climàtic, hi ha un seguit d'espècies arbustives, com el fals aladern, que podrien competir amb avantatge amb l'alzina, l'actual espècie dominant dels boscos mediterranis.Las bajas temperaturas invernales y la baja disponibilidad de agua son los dos factores principales que pueden inhibir o dañar el aparato fotosintético de las especies mediterráneas. Con el aumento de las temperaturas y la disminución de la disponibilidad de agua asociadas al cambio climático, hay algunas especies arbustivas, como el labiérnago negro, que podrían competir ventajosamente con la encina, la actual especie dominante de los bosques mediterráneos

β-Ocimene, a key floral and foliar volatile involved in multiple interactions between plants and other organisms

β-Ocimene is a very common plant volatile released in important amounts from the leaves and flowers of many plant species. This acyclic monoterpene can play several biological functions in plants, by potentially affecting floral visitors and also by mediating defensive responses to herbivory. The ubiquity and high relative abundance of β-ocimene in the floral scents of species from most plant families and from different pollination syndromes (ranging from generalism to specialism) strongly suggest that this terpenoid may play an important role in the attraction of pollinators to flowers. We compiled abundant evidence from published studies that supports β-ocimene as a generalist attractant of a wide spectrum of pollinators. We found no studies testing behavioural responses of pollinators to β-ocimene, that could directly demonstrate or deny the function of β-ocimene in pollinator attraction; but several case studies support that the emissions of β-ocimene in flowers of different species follow marked temporal and spatial patterns of emission, which are typical from floral volatile organic compound (VOC) emissions that are involved in pollinator attraction. Furthermore, important β-ocimene emissions are induced from vegetative plant tissues after herbivory in many species, which have relevant functions in the establishment of tritrophic interactions. We thus conclude that β-ocimene is a key plant volatile with multiple relevant functions in plants, depending on the organ and the time of emission. Experimental behavioural studies on pure β-ocimene conducted with pollinating insects will be necessary to prove the assumptions made here

Photosynthesis, stomatal conductance and terpene emission response to water availability in dry and mesic Mediterranean forests

Water stress results in a reduction of the metabolism of plants and in a reorganization of their use of resources geared to survival. In the Mediterranean region, periods of drought accompanied by high temperatures and high irradiance occur in summer. Plants have developed various mechanisms to survive in these conditions by resisting, tolerating or preventing stress. We used three typical Mediterranean tree species in Israel, Pinus halepensis L., Quercus calliprinos and Quercus ithaburensis Webb, as models for studying some of these adaptive mechanisms. We measured their photosynthetic rates (A), stomatal conductance (g s), and terpene emission rates during spring and summer in a geophysical gradient from extremely dry to mesic from Yatir (south, arid) to Birya (north, moist) with intermediate conditions in Solelim. A and g s of P. halepensis were threefold higher in Birya than in Yatir where they remained very low both seasons. Quercus species presented 2-3-fold higher A and g s but with much more variability between seasons, especially for Q. ithaburensis with A and g s that decreased 10-30-fold from spring to summer. Terpene emission rates for pine were not different regionally in spring but they were 5-8-fold higher in Birya than in Yatir in summer (P < 0.05). Higher emissions were also observed in Solelim for the drought resistant Q. ithaburensis (P < 0.001) but not for Q. calliprinos. α-Pinene followed by limonene and 3-carene were the dominant terpenes. Warmer summer conditions result in increased Terpene emission rates except under severe drought, in which case they strongly decreas

Leaf carotenoid concentrations and monoterpene emission capacity under acclimation of the light reactions of photosynthesis

Factors controlling the seasonal dynamics (days-weeks) in leaf monoterpene emission capacity are not yet well understood. Volatile isoprenoids, such as monoterpenes, and higher isoprenoids such as carotenoids share the initial steps of their synthesis pathways, therefore, interaction between the pool size of leaf carotenoids and its acclimation and leaf monoterpene emission capacity could be expected. Our aim was to examine this interaction in evergreen foliage using the non-storing Holm oak (Quercus ilex L.), as a model species. We modified the light environment of a number of potted trees in order to induce acclimation in leaf carotenoid contents, and study the effects on leaf monoterpene emission capacity. We followed chlorophyll fluorescence, photosynthetic capacity, chlorophyll and carotenoid contents, and monoterpene emission capacity. The results indicate that monoterpene emission capacity and photosynthetic pigment metabolism are coupled in Holm oak seedlings growing at or acclimating to different light levels

Les plantes s'avisen del perill imminent

Les plantes envien senyals a l'atmosfera per comunicar-se amb altres plantes i amb els animals: quan una planta és atacada per un patogen o per un herbívor allibera certs compostos a l'aire que "avisen" les altres del perill imminent, de manera que puguin preparar-se per rebre'l. Són substàncies que activen el metabolisme defensiu de les plantes com l'emissió de compostos repel·lents contra els herbívors, de reclam pels parasitoides dels herbívors o la segregació d'antioxidants o estabilitzadors de les membranes cel·lulars. Investigadors de la UAB han investigat si el metanol podria comptar-se entre aquestes substàncies de comunicació ja que s'ha detectat que en la sega dels camps de cultiu o en l'atac per herbívors s'alliberen grans quantitats d'aquest compost a l'atmosfera detectables per les plantes de la rodalia.Las plantas envían señales a la atmósfera para comunicarse con otras plantas y con los animales: cuando una planta es atacada por un patógeno o por un herbívoro libera ciertos compuestos en el aire que "avisan" a las demás del peligro inminente, de manera que puedan prepararse para recibirlo. Son sustancias que activan el metabolismo defensivo de las plantas como la emisión de compuestos repelentes contra los herbívoros, de reclamo para los parasitoides de los herbívoros o la segregación de antioxidantes o estabilizadores de las membranas celulares. Investigadores de la UAB han investigado si el metanol podría estar entre estas sustancias de comunicación ya que se ha detectado que en la siega de los campos de cultivo o en el ataque por herbívoros se liberan grandes cantidades de este compuesto a la atmósfera detectables por las plantas de los alrededores