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Non-destructive real-time monitoring of leaf water status is important for precision irrigation practice to increase water productivity and reduce its use. To this end, we tested and validated a novel leaf sensor (Leaf Water Meter, LWM), based on the photon attenuation during the passage of the light through the leaf, to monitor plant water status. Four woody species were subjected to multiple cycles of dehydration and re-hydration, and the signals recorded by the LWM were compared with classical measurements of plant water relations (relative water content and water potential). A good agreement between the signals recorded by LWM sensor and the destructive measurements, throughout the repeated water stress and rewatering cycles, was found across all species. These results demonstrate that LWM sensor is a sensitive, non-destructive and easy-to-handle device to reliably monitor in continuous fashion leaf water status. In conclusion, this sensor may be considered a promising tool for smart irrigation scheduling in precision agriculture context to decrease water wastage in light of global change and increasing conflicts over water demand.

WOS: 000487646800001, The Mediterranean climate is characterized by hot dry summers and frequent droughts. Mediterranean crops are frequently subjected to high evapotranspiration demands, soil water deficits, high temperatures, and photo-oxidative stress. These conditions will become more severe due to global warming which poses major challenges to the sustainability of the agricultural sector in Mediterranean countries. Selection of crop varieties adapted to future climatic conditions and more tolerant to extreme climatic events is urgently required. Plant phenotyping is a crucial approach to address these challenges. High-throughput plant phenotyping (HTPP) helps to monitor the performance of improved genotypes and is one of the most effective strategies to improve the sustainability of agricultural production. In spite of the remarkable progress in basic knowledge and technology of plant phenotyping, there are still several practical, financial, and political constraints to implement HTPP approaches in field and controlled conditions across the Mediterranean. The European panorama of phenotyping is heterogeneous and integration of phenotyping data across different scales and translation of "phytotron research" to the field, and from model species to crops, remain major challenges. Moreover, solutions specifically tailored to Mediterranean agriculture (e.g., crops and environmental stresses) are in high demand, as the region is vulnerable to climate change and to desertification processes. The specific phenotyping requirements of Mediterranean crops have not yet been fully identified. The high cost of HTPP infrastructures is a major limiting factor, though the limited availability of skilled personnel may also impair its implementation in Mediterranean countries. We propose that the lack of suitable phenotyping infrastructures is hindering the development of new Mediterranean agricultural varieties and will negatively affect future competitiveness of the agricultural sector. We provide an overview of the heterogeneous panorama of phenotyping within Mediterranean countries, describing the state of the art of agricultural production, breeding initiatives, and phenotyping capabilities in five countries: Italy, Greece, Portugal, Spain, and Turkey. We characterize some of the main impediments for development of plant phenotyping in those countries and identify strategies to overcome barriers and maximize the benefits of phenotyping and modeling approaches to Mediterranean agriculture and related sustainability., Fundacao para a Ciencia e a Tecnologia (FCT, Portugal)Fundacao para a Ciencia e a Tecnologia (FCT) [UID/Multi/04551/2013]; FCTFundacao para a Ciencia e a Tecnologia (FCT) [UID/AGR/04129/2013, UID/MULTI/00612/2013, PEst-OE/BIA/UI4046/2014]; FCT R&D project INTERPHENO [PTDC/ASP-PLA/28726/2017]; FCT R&D project VitiRoots [PTDC/ASP-HOR/31907/2017]; COST Action PhenomenallEuropean Cooperation in Science and Technology (COST) [FA 1306]; Junta de AndaluciaJunta de Andalucia [P12-AGR-0370]; Ministerio de Ciencia, Innovacion y Universidades [RTI2018-094652-B-I00]; Ministerio de Ciencia, Innovacion y Universidades (MCIU/AEI/FEDER, UE); EU H2020 project EMPHASIS-PREP [739514]; EU-LIFE program [LIFE16 CCA/GR/000050], MO is thankful to Fundacao para a Ciencia e a Tecnologia (FCT, Portugal), for funding the R&D unit, UID/Multi/04551/2013 (GREEN-IT). JMC thanks the support of FCT for funding the R&D unit LEAF (UID/AGR/04129/2013). JMS is grateful to FCT for funding BioISI R&D unit, UID/MULTI/00612/2013, under the project PEst-OE/BIA/UI4046/2014 and the internal projects Optigrape I and II. Part of the work was also supported by the FCT R&D projects INTERPHENO (PTDC/ASP-PLA/28726/2017) and VitiRoots (PTDC/ASP-HOR/31907/2017). JMC, JMS, CP, PM, IT and BU acknowledge the COST Action Phenomenall FA 1306 - The quest for tolerant varieties - Phenotyping at plant and cellular level. MB is grateful to the financial support of grants from Junta de Andalucia (P12-AGR-0370) and Ministerio de Ciencia, Innovacion y Universidades (RTI2018-094652-B-I00 and MCIU/AEI/FEDER, UE). FL thanks the support of EU H2020 project EMPHASIS-PREP (grant agreement n. 739514). PM acknowledges the support of EU-LIFE program under the grant agreement LIFE16 CCA/GR/000050.

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Distinct photosynthetic physiologies are found within the Moricandia genus, both C3-type and C2-type representatives being known. As C2-physiology is an adaptation to drier environments, a study of physiology, biochemistry and transcriptomics was conducted to investigate whether plants with C2-physiology are more tolerant of low water availability and recover better from drought. Our data on Moricandia moricandioides (Mmo, C3), M. arvensis (Mav, C2) and M. suffruticosa (Msu, C2) show that C3 and C2-type Moricandias are metabolically distinct under all conditions tested (well-watered, severe drought, early drought recovery). Photosynthetic activity was found to be largely dependent upon the stomatal opening. The C2-type M. arvensis was able to secure 25–50% of photosynthesis under severe drought as compared to the C3-type M. moricandioides. Nevertheless, the C2-physiology does not seem to play a central role in M. arvensis drought responses and drought recovery. Instead, our biochemical data indicated metabolic differences in carbon and redox-related metabolism under the examined conditions. The cell wall dynamics and glucosinolate metabolism regulations were found to be major discriminators between M. arvensis and M. moricandioides at the transcription level.

The atmospheric concentration of carbon dioxide ([CO2]) and oxygen ([O2]) directly influence rates of photosynthesis (PN) and photorespiration (RPR) through the enzyme ribulose-1,5-bisphosphate carboxylase/oxygenase (RubisCO). Levels of [CO2] and [O2] have varied over Earth history affecting rates of both CO2 uptake and loss, alongside associated transpirative water-loss. The availability of CO2 has likely acted as a stronger selective pressure than [O2] due to the greater specificity of RubisCO for CO2. The role of [O2], and the interaction of [O2] and [CO2], in plant evolutionary history is less understood. We exposed twelve phylogenetically diverse species to combinations of sub-ambient, ambient and super-ambient [O2] and [CO2] to examine the biochemical and diffusive components of PN and the possible role of [O2] as a selective pressure. Photosynthesis, photosynthetic capacity and stomatal, mesophyll and total conductance to CO2 were higher in the derived eudicot and monocot angiosperms than the more basal ferns, gymnosperms and basal angiosperms which originated in atmospheres characterised by higher CO2:O2 ratios. The ratio of RPR:PN was lower in the monocots, consistent with greater carboxylation capacity and higher stomatal and mesophyll conductance making easier CO2 delivery to chloroplasts. The effect of [O2] and [CO2] on PN/RPR was less evident in more derived species with a higher conductance to CO2. The effect of [O2] was less apparent at high [CO2], suggesting that atmospheric [O2] may only have exerted a strong selective pressure on plant photosynthetic processes during periods characterised by low atmospheric CO2:O2 ratios. Current rising [CO2] will predominantly enhance PN rates in species with low diffusive conductance to CO2.

Drought compromises plant's ability to replace transpired water vapor with water absorbed from the soil, leading to extensive xylem dysfunction and causing plant desiccation and death. Short-term plant responses to drought rely on stomatal closure, and on the plant's ability to recover hydraulic functioning after drought relief. We hypothesize a key role for abscisic acid (ABA) not only in the control of stomatal aperture, but also in hydraulic recovery. Young plants of Populus nigra L. were used to investigate possible relationships among ABA, non-structural carbohydrates (NSC) and xylem hydraulic function under drought and after re-watering. In Populus nigra L. plants subjected to drought, water transport efficiency and hydraulic recovery after re-watering were monitored by measuring the percentage loss of hydraulic conductivity (PLC) and stem specific hydraulic conductivity (Kstem). In the same plants ABA and NSC were quantified in wood and bark. Drought severely reduced stomatal conductance (gL) and markedly increased the PLC. Leaf and stem water potential, and stem hydraulic efficiency fully recovered within 24 h after re-watering, but gL values remained low. After re-watering, we found significant correlations between changes in ABA content and hexoses concentration both in wood and bark. Our findings suggest a role for ABA in the regulation of stem carbohydrate metabolism and starch mobilization upon drought relief, possibly promoting the restoration of xylem transport capacity.

The response of broad bean (Vicia faba) plants to water stress alone and in combination with green stink bug (Nezara viridula) infestation was investigated through measurement of: (1) leaf gas exchange; (2) plant hormone titres of abscisic acid (ABA) and its metabolites, and of salicylic acid (SA); and (3) hydrogen peroxide (H2O2) content. Furthermore, we evaluated the effects of experimentally water-stressed broad-bean plants on N. viridula performance in terms of adult host–plant preference, and nymph growth and survival. Water stress significantly reduced both photosynthesis (A) and stomatal conductance (gs), while infestation by the green stink bug had no effects on photosynthesis but significantly altered partitioning of ABA between roots and shoots. Leaf ABA was decreased and root ABA increased as a result of herbivore attack, under both well-watered and water-deprived conditions. Water stress significantly impacted on SA content in leaves, but not on H2O2. However, infestation of N. viridula greatly increased both SA and H2O2 contents in leaves and roots, which suggests that endogenous SA and H2O2 have roles in plant responses to herbivore infestation. No significant differences were seen for green stink bug choice between well-watered and water-stressed plants. However, for green stink bug nymphs, plant water stress promoted significantly lower weight increases and significantly higher mortality, which indicates that highly water-stressed host plants are less suitable for N. viridula infestation. In conclusion two important findings emerged: (i) association of water stress with herbivore infestation largely changes plant response in terms of phytohormone contents; but (ii) water stress does not affect the preference of the infesting insects, although their performance was impaired.

We studied the high energy portion of solar light which reaches Earths’ surface, focusing on the interaction of UVB, UVA and blue light with plants, and investigating on plant response as BVOCs emission. We assessed the direct effects of high UVB radiation on both wild-type non-emitting and transgenic isoprene-emitting tobacco plants. We found that mechanisms regulating BVOC emissions were not very sensitive to high UVB intensities even if isoprene was able to mitigate UVB effect. The isoprene-induced protection was combined with an independent higher activation of antioxidant cycle as mechanism for ROS scavenging. We studied the effects of short-term, acute exposure to UVA, treating poplar plants in the middle of summer and then repeating it towards the end of the summer. In the middle of summer photosynthesis was inhibited by high doses of UVA radiation while isoprene bursted increasingly as the UVA dose increased. At the end of the summer, there were no longer significant differences in the time course of A and isoprene emission in response to high UVA radiation. The adaxial flavonoid level increased significantly over the period monitored, probably played a protective role against UVA radiation by shielding leaves. The relationship between isoprenoid emissions and diffusional limitation to photosynthesis were studied in response to blue light. We used three different plant species, a strong isoprene emitter (poplar), a strong monoterpene emitter with a small storage pool (holm oak) and a monoterpene emitter with a big storage pool (mandarin). Our results confirmed the strong effect of blue light on A and gm. Isoprene emission was also highly affected by blue light whereas monoterpenes emissions were in general not affected. Abbiamo studiato la parte di radiazione solare ad alta energia che raggiunge la superficie terrestre, osservando l’effetto di UVB, UVA e luce blu sulle piante. Abbiamo valutato gli effetti diretti degli UVB su tabacco: in piante wild type che non emettono isoprene ed in piante transgeniche che emettono isoprene. Abbiamo mostrato che i meccanismi che regolano le emissioni di BVOC non sono molto sensibili alle alte intensità di UVB e che, tuttavia, l’isoprene è in grado di mitigarne. La protezione indotta dall’isoprene è stata associata ad un’attivazione del ciclo degli antiossidanti come meccanismo di sequestro dei ROS. Abbiamo studiato gli effetti a breve termine di esposizione acuta agli UVA, irradiando piante di pioppo in piena estate e quindi ripetendo l’esperimento alla fine dell'estate. Inizialmente la fotosintesi è stata inibita da alte dosi di radiazioni UVA e picchi di isoprene si sono verificati ad applicazione di dosi crescenti di UVA. Nell’esperimento ripetuto alla fine dell’estate, gli UVA non hanno avuto effetti su A ed emissione di isoprene. Il livello di flavonoidi adassiale è aumentato notevolmente nel corso del periodo monitorato, giocando un ruolo protettivo contro i raggi UVA fungendo da schermo per le foglie. Abbiamo studiato il rapporto tra emissione di isoprenoidi e limitazione della fotosintesi dalla diffusione di CO2 in risposta alla luce blu in tre specie: una che emette isoprene (pioppo) e due specie che emettono monoterpeni con un modesto (leccio) ed un grande (mandarino) pool di monoterpeni immagazzinato. I nostri risultati hanno confermato il forte effetto della luce blu su A e gm così come sull’emissione di isoprene. Le emissioni di monoterpeni sono state invece influenzate in maniera meno evidente. Dottorato di ricerca in Ecologia forestale

Morpho-physiological traits that convey two years-old giant reed (Arundo donax) ecotypes (Moroccan and Northern Italy) high drought tolerance and water use efficiency (WUE) have been evaluated in large rhizotrons under semi-controlled environmental conditions. No large differences between the two ecotypes tested was evident in terms of plant height, number of tillers or biomass production. However, an interesting physiological parameter that distinguished both ecotypes under drought was the predawn leaf water potential (LWP), which was closely related to photosynthesis and stomatal conductance but not to the photochemical reactions of photosynthesis. Stomatal control and LWP could be important attributes to improve drought tolerance in giant reed., Proceedings of the 25th European Biomass Conference and Exhibition, 12-15 June 2017, Stockholm, Sweden, pp. 325-327