1,721,039 research outputs found
POSSIBLE ROLE OF MANNITOL AS AN OXYGEN RADICAL SCAVENGER IN OLIVE
No full textAlong with mannose and sucrose, olive produces large amounts of mannitol in
photosynthesizing leaves. Leaf mannitol shows large variation among olive genotypes
and Sicilian cultivars with different leaf mannitol content were used in our trials to see
whether mannitol may function as an additional non-enzymatic system to protect cells
from oxygen radicals and photosystem damage. In one experiment, entire shoots of
‘Passulunara’, ‘Castriciana’, ‘Nocellara del Belice’, and ‘Moresca’ olive trees were
taken to a greenhouse, and mature leaves were treated with paraquat solution, which
generates oxygen radicals in presence of light. After 48 hours leaves were sampled,
photographed and percent of necrosis was quantified by digital image analysis.
Mannitol content was determined in control non-treated leaves positioned in the same
node as the paraquat-treated ones. The same experiment was repeated using fieldgrown
trees under full sun light. In both cases, a significant inverse relation was found
between leaf necrosis and mannitol content suggesting that mannitol may provide
some scavenging action on paraquat-generated oxygen radicals. In another experiment,
leaf gas exchange and chlorophyll fluorescence were measured on field-grown
‘Castriciana’ (higher mannitol) and ‘Nocellara del Belice’ (lower mannitol) trees in the
morning, at noon, and in the afternoon to quantify partitioning of absorbed energy
among net photosynthesis (JCO2), photoprotection by heat dissipation (non-photochemical
quenching, JNPQ) and by alternative electron transport and photorespiration
(JNC), formation of reactive oxygen species (ROS) and heat re-emission inactive
photosystem (PSII). ‘Nocellara’ reported higher JCO2 and JNC than ‘Castriciana’,
whereas JNPQ was similar in the two cultivars. Despite a greater amount of energy for
ROS formation, ‘Castriciana’ yielded a smaller percentage of inactive photosystems
compared to ‘Nocellara’. Also in this case mannitol may act as an additional oxygen
radical scavenger and explain the differences in photosystem inactivation between the
two olive cultivars
Evaluation of three modelling approaches for almond blooming in Mediterranean climate conditions
No full textChilling and heat requirements for breaking dormancy and flowering were studied in seven almond cultivars in Southern Italy. Chilling portions (CP), computed through the Dynamic model, and growing degree hours (GDH) were used to determine chill and heat accumulation, respectively. Then, using full bloom dates and temperature data from nine seasons (2003/2004-2007/2008 and 2009/2010-2012/2013), three sequential methods for the estimation of thermal requirements were compared: 1) the Ashcroft Method (AM), where chilling and heat requirements were selected considering the lowest variability of the GDH at several intervals of CP, and two variations: 2) modified Ashcroft Method (AMm) that took into consideration the lowest variability in both CP and GDH, and 3) reverse Ashcroft Method (AMr) opposite to AM. All methods were effective in predicting full bloom dates; however the modified Ashcroft method was the most accurate under Mediterranean conditions and allowed to classify almond cultivars for their thermal requirements. The results from AMm, showed chilling requirements ranging between 24–62 CP and heat requirements between 3263 and 6699 GDH, respectively
Effects of rootstock on pear photosynthetic efficiency
No full textThe effect of rootstock on scion photosynthesis can be quite marked. Reduced hydraulic conductivity at the graft union can negatively affect stomata conductance, which in turn may diminish gas exchanges and photosynthesis. Under high light intensities this condition can worsen, as a proportionally smaller fraction of intercepted photons can be utilized in the photosynthetic process. The excess photons are dissipated either via photoprotective mechanisms (Non-Photochemical-Quenching; Alternative Transports; Photorespiration), or photooxidation, with the production of Active Oxygen Species (AOS). Under reduced photosynthetic activity, the defense mechanisms and photooxidation reactions increase, to cope with excess energy which cannot be utilized for carboxylation. This paper reports a study conducted on leaves of the pear ‘Bosc’ grafted on seedling and quince EMC rootstocks, detailing their behavior under conditions of same light and temperature. Stomata conductance and transpiration were consistently higher in the trees on seedling than on EMC, which resulted in greater photosynthetic activity in the leaves of the former. Because of the stomata limitation, trees on EMC allocated less energy to the photosynthetic process, as a greater proportion of intercepted photons was dissipated via the Non-Photochemical Quenching (NPQ) cycle and leaded the Photosystem II (PSII) damage. Somewhat surprisingly Alternative Transports (Water-Water Cycle; Cyclic Transport around PSI; Glutathione-Ascorbate Cycle) and Photorespiration in quince was consistently lower than in seedling-grafted trees during the first measurement. In conclusion, rootstocks can affect the photosynthetic potential of the grafted tree, in relation to their graft compatibility, although more work is needed to understand the degree of reduction due to photo-oxidative stress
Quenching partitioning through light-modulated chlorophyll fluorescence: A quantitative analysis to assess the fate of the absorbed light in the field
No full textPlants use a small part of the total absorbed light energy for net carboxylation, while the remaining amount is dissipated via alternative pathways involving thermal processes, fluorescence and non- carboxylation photochemistry in order to limit the formation of reactive oxygen species (ROS) and other photooxidative risks. The commonly used analysis of the Photosystem II (PSII) fluorescence signals gives qualitative information about absorbed light energy management by plants, but it is difficult to appreciate the relative contribution of each pathway in energy partitioning. This study reports the application of quenching partitioning through a chlorophyll fluorescence approach performed on peach leaves subjected to three different light intensities for four durations of exposure in absence of recovery from photo-damage. This methodology was compared with the P700 redox kinetic method for determining the functional PSII fraction in leaves. In the absence of recovery processes the active PSII concentration decayed with an increase in photon exposure (the product of irradiance and the time of exposure), following an exponential pattern according to the reciprocity law. The photoprotective thermal dissipation ( ̊NPQ ) was proportional to irradiance up to 30 min of photoin- hibitory treatment. Afterwards ̊NPQ was limited by the increasing competition for the absorbed energy re-emitted by the inactive PSII ( ̊NF ). ̊NF increased with the photon exposure dissipating up to 70% of the total incoming energy. The energy funnelled to photochemistry ( ̊PSII ) decreased with increasing exposure time or intensity, becoming zero after 120 min of photoinhibitory treatment at the maximum irradiance (2100 mol photon m−2 s−1 ). The relation between the fraction of energy dissipated by the inactive PSII (derived from the quenching partitioning) and the inactive PSII fraction (measured with the P700 redox kinetic method) was linear. The quenching partitioning through light-modulated chlorophyll fluorescence is a useful tool to anal- yse plant energy management and gives also a reasonable estimation of the active PSII fraction. This methodology can easily be used in the field as measurements are rapid, non-destructive and detection devices are portable
Scouting ecophysiological variables to monitor regulated deficit irrigation in almond
No full textIn semi-arid regions, almond orchards face significant challenges from climate change, necessitating sustainable
irrigation strategies and advanced monitoring methods to enhance water use efficiency. This study investigated
key ecophysiological variables to identify the most relevant physiological variables for future threshold definition
in irrigation management (Prunus dulcis Mill., cv. Guara). The experiment included three irrigation treatments
during the kernel-filling phase: 100 % (CTRL), 80 % (MRDI), and 60 % (SRDI) of crop evapotranspiration
(ETc), with full irrigation provided during fruit growth and post-harvest periods. Key physiological variables,
including stomatal conductance (gs), stem water potential (Ψs), photosynthesis (Pn), and PKO/KC (reflecting
electron flux from PSII and RuBisCO carboxylative activity) were monitored weekly during a single growing
season and showed clear seasonal dynamics: peaking during fruit growth, declining during kernel filling, and
partially recovering post-harvest. During kernel filling, MRDI values for gs, Ψs, Pn, and PKO/KC were lower than
CTRL but higher than SRDI. Strong correlations were observed between Pn and gs, PKO/KC, as well as between gs
and Ψs. Pn, gs, and PKO/KC were significantly influenced by air temperature and vapor pressure deficit, whereas
Ψs was more closely linked to soil water content. Yield, fruit fresh weight, and seed dry weight were similar
across treatments, although SRDI produced a higher proportion of tight-hull fruits. Variables such as gs, Ψs, Pn,
and PKO/KC effectively captured plant water status and microclimatic variations. The MRDI treatment achieved
significant water savings while maintaining yield and fruit quality, suggesting that Ψs, Pn, gs, and PKO/KC are
reliable indicators of plant performance under reduced irrigation, with potential to inform the development of
simplified, decision-support tools for growers. Advances in sensor technologies could facilitate the adoption of
plant-based irrigation thresholds, improving water resource efficiency
Detection and distribution of two dominant alleles associated with the sweet kernel phenotype in almond cultivated germplasm
Full text linkAlmond [Prunus dulcis Miller (D. A. Webb), syn. Prunus amygdalus L.)] is the major tree nut crop worldwide in terms of production and cultivated area. Almond domestication was enabled by the selection of individuals bearing sweet kernels, which do not accumulate high levels of the toxic cyanogenic glucoside amygdalin. Previously, we showed that the Sweet kernel (Sk) gene, controlling the kernel taste in almond, encodes a basic helix loop helix (bHLH) transcription factor regulating the amygdalin biosynthetic pathway. In addition, we characterized a dominant allele of this gene, further referred to as Sk-1, which originates from a C1036!T missense mutation and confers the sweet kernel phenotype. Here we provide evidence indicating that the allele further referred to as Sk-2, originally detected in the cultivar “Atocha” and arising from a T989!G missense mutation, is also dominantly inherited and confers the sweet kernel phenotype in almond cultivated germplasm. The use of single nucleotide polymorphism (SNP) data from genotyping by sequencing (GBS) for population structure and hierarchical clustering analyses indicated that Sk-2 occurs in a group of related genotypes, including the widespread cultivar “Texas”, descending from the same ancestral population. KASP and dual label functional markers were developed for the accurate and high-throughput selection of the Sk-1 and Sk-2 alleles, and the genotyping of a panel of 134 almond cultivars. Overall, our results provide further insights on the understanding of the almond cultivation history. In addition, molecular marker assays and genotypic data presented in this study are expected to be of major interest for the conduction of almond breeding programs, which often need to select sweet kernel individuals in segregant populationsThis study was carried out within the framework of: 1) the Agritech National Research Center, receiving funding from the European Union Next-GenerationEU (PIANO NAZIONALE DI RIPRESA E RESILIENZA (PNRR) – MISSIONE 4 COMPONENTE 2, INVESTIMENTO 1.4 – D.D. 1032 17/06/2022, CN00000022); 2) The project “Recupero e valorizzazione del germoplasma frutticolo pugliese” “Re.Ge.Frup.2.1”, receiving funds from “PSR Puglia 2014- 2020. Misura 10 - Sottomis. 10.2 - Operazione 10.2.1 - Progetti per la conservazione e valorizzazione delle risorse genetiche in agricoltura”; 3) the project “ALmond ADaptation in NOvel Environments: Multiscale Approach from Genome to Function PrediCtion: ALADINO MAGIC” (MINECO-Spain). This manuscript reflects only the authors’ views and opinions, neither the European Union nor the European Commission can be considered responsible for themPeer reviewe
EFFECT OF MODERATE LIGHT REDUCTION ON ABSORBED ENERGY MANAGEMENT, WATER USE, PHOTOPROTECTION AND PHOTO-DAMAGE IN PEACH
No full textNet carbon assimilation increases with irradiance to a saturation point, above which absorbed light is in excess. Besides the temperature increase, with attendant water losses, light excess can increase the photoinhibition risks due to Reactive Oxygen Species (ROS) production. Plants developed a multi-pronged and synergistic photoprotective strategy involving the thermal dissipation, via the xanthophylls cycle, and the photochemistry transports (alternative electron transports and photorespiration). Plants, however, cannot completely avoid photo-damage, and have developed an effective, efficient and energy-dependent recovery system to repair the damaged photosystem II (PSII). This study reports the effect of 40% neutral shading of peach leaves on their gas exchange parameters, the absorbed energy management, and the PSII damage susceptibility during the day. Light reduction did not affect net carboxylation but, decreasing stomatal conductance and temperature under the highest daily irradiance, it increased water use efficiency (WUE). During the same time of the day the xanthophylls cycle quenched more energy in CTRL than in SHD, dissipating 65 and 50% of the absorbed energy, respectively. On the contrary SHD funnelled more energy to photochemistry than CTRL probably because at medium-low irradiance the xanthophylls cycle is pH limited. The susceptibility of PSII to photoinhibition was similar between the two treatments as the same exponential decay of the active PSII against the photon exposure (light intensity × time of exposure) was recorded. The maximal amount of active PSII damaged by a photon unit (Quantum yield of photoinactivation, Qy) was also not influenced by light reduction therefore, the more the absorbed photons, the more the photo-damage to be repaired (at energy cost). These preliminary results suggests that optimizing light interception can ameliorate the plant water use efficiency, without affecting net carbon assimilation and reducing carbon and energy costs for photosystems recovery
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