•Tomato fruit mass, color, taste, flavor, texture and health value drive purchasing.•Main traits of quality show a broad range of responses to environmental factors.•Many QTLs of quality traits have ...been identified, part of them depends on environment.•Process-based models of quality can predict genotype by environment interactions.
Tomato quality is a multi-faceted trait, involving many processes at the plant and fruit level, which depend on interactions between cultural practices, genetic and environmental factors. This review focusses on tomato quality as influenced by pre-harvest factors, and quality is defined from the consumer’s point of view, i.e. through fruit size or fresh mass, colour, taste, flavour, texture and health value. Tomato is a model plant for biologist and the second fruit consumed worldwide. The mechanisms involved in tomato fruit quality have been extensively investigated by physiologists and geneticists, and the responses to climatic and cultural practices have been widely described. Yet, our ability to manage and improve fruit quality in a context of global change will rely on our capacity to integrate knowledge’s and anticipate interactions among genotype, environment and cultural practices. The recent development of process-based models of fruit quality may help us for this challenging issue. Several models of tomato growth and quality are reviewed here, as well as their potential application for the design of ideotypes, i.e. conceptual plants that are expected to perform in specific environments.
The objective of this study was to determine the impact of lowering nitrogen supply from 12 to 6 or 4 mM NO3 − on tomato fruit yield and quality during the growing season. Lowering nitrogen supply ...had a low impact on fruit commercial yield (−7.5%), but it reduced plant vegetative growth and increased fruit dry matter content, improving consequently fruit quality. Fruit quality was improved due to lower acid (10−16%) and increased soluble sugar content (5−17%). The content of some phenolic compounds (rutin, a caffeic acid glycoside, and a caffeic acid derivate) and total ascorbic acid tended to be higher in fruit with the lowest nitrogen supply, but differences were significant in only a few cases (trusses). With regard to carotenoids, data did not show significant and univocal differences related to different levels of nitrogen supply. Thus, reducing nitrogen fertilization limited environmental pollution, on the one hand, and may improve, on the other hand, both growers’ profits, by limiting nitrogen inputs, and fruit quality for consumers, by increasing tomato sugars content. It was concluded that primary and secondary metabolites could be affected as a result of a specific response to low nitrogen, combined with a lower degree of vegetative development, increasing fruit irradiance, and therefore modifying fruit composition.
The growth of plant organs is a complex process powered by osmosis that attracts water inside the cells; this influx induces simultaneously an elastic extension of the walls and pressure in the ...cells, called turgor pressure; above a threshold, the walls yield and the cells grow. Based on Lockhart's seminal work, various models of plant morphogenesis have been proposed, either for single cells, or focusing on the wall mechanical properties. However, the synergistic coupling of fluxes and wall mechanics has not yet been fully addressed in a multicellular model. This work lays the foundations of such a model, by simplifying as much as possible each process and putting emphasis on the coupling itself. Its emergent properties are rich and can help to understand plant morphogenesis. In particular, we show that the model can display a new type of lateral inhibitory mechanism that amplifies growth heterogeneities due e.g to cell wall loosening.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
In this study the sensitivity of peach tree (Prunus persica L.) to three water stress levels from mid-pit hardening until harvest was assessed. Seasonal patterns of shoot and fruit growth, gas ...exchange (leaf photosynthesis, stomatal conductance and transpiration) as well as carbon (C) storage/mobilization were evaluated in relation to plant water status. A simple C balance model was also developed to investigate sink-source relationship in relation to plant water status at the tree level. The C source was estimated through the leaf area dynamics and leaf photosynthesis rate along the season. The C sink was estimated for maintenance respiration and growth of shoots and fruits. Water stress significantly reduced gas exchange, and fruit, and shoot growth, but increased fruit dry matter concentration. Growth was more affected by water deficit than photosynthesis, and shoot growth was more sensitive to water deficit than fruit growth. Reduction of shoot growth was associated with a decrease of shoot elongation, emergence, and high shoot mortality. Water scarcity affected tree C assimilation due to two interacting factors: (i) reduction in leaf photosynthesis (-23% and -50% under moderate (MS) and severe (SS) water stress compared to low (LS) stress during growth season) and (ii) reduction in total leaf area (-57% and -79% under MS and SS compared to LS at harvest). Our field data analysis suggested a Ψstem threshold of -1.5 MPa below which daily net C gain became negative, i.e. C assimilation became lower than C needed for respiration and growth. Negative C balance under MS and SS associated with decline of trunk carbohydrate reserves--may have led to drought-induced vegetative mortality.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
Epigenetic variations are involved in the control of plant developmental processes and participate in shaping phenotypic plasticity to the environment. Intense breeding has eroded genetic diversity, ...and epigenetic diversity now emerge as a new source of phenotypic variations to improve adaptation to changing environments and ensure the yield and quality of crops. Here, we review how the characterization of the stability and heritability of epigenetic variations is required to drive breeding strategies, which can be assisted by process-based models. We propose future directions to hasten the elucidation of complex epigenetic regulatory networks that should help crop modelers to take epigenetic modifications into account and assist breeding strategies for specific agronomical traits.
Broadening crop phenotypic diversity is a key issue facing the challenge of sustainable food security and crop adaptation to ongoing climate changes.
Chromatin marks and epigenetic regulatory mechanisms are essential to the control of plant developmental processes and in shaping plant phenotypic plasticity, including adaptive responses to environmental stresses.
Stability and heritability features of epigenetic marks and knowledge of epigenetic regulatory mechanisms are crucial for breeding applications.
Modeling epigenetic variations requires understanding epigenetic regulatory mechanisms to further predict their impact on plant performances.
Modeling epigenetic variations with a process-based approach could help to assess and quantify their impacts on plant performances and then to guide the decision to either induce or repress them. This modeling feedback is central to model-driven breeding strategies.
Crop modelers are urged to take epigenetic variations into account to assist breeding strategies.
•Study of the effects of fluctuating shading on an apple orchard using agrivoltaism.•Shading in orchard allowed a less stressful environment and reduced water needs.•Shading increased specific leaf ...area and reduced leaf photosynthetic rates.•Strong shading over 3 years reduced floribundity and alternate bearing behaviour.•Shading has low impact on fruit size due to higher water content in shaded fruits.
The installation of dynamic photovoltaic panels over apple orchards could meet the challenges of protecting orchards from climate change and drive the energetic transition. However, the impact of solar panel's shading on apple performance needs to be investigated before being commercially adopted. A dynamic agrivoltaic system was installed in the south of France over a 10-year-old 'Golden Delicious' apple orchard and studied during three experimental seasons (2019–2021). This study aimed to evaluate the impact of fluctuating shading (photovoltaic panel orientation to maximise panel light interception) on water relations, leaf morphophysiological characteristics and yield determinants. With the selected photovoltaic design and strategy, trees were grown under a fluctuating shading (variable shading between 4% and 88% during the day) with a mean shading rate of 50–55%. On average, the air temperature was reduced by 3.8 °C, while relative humidity was increased by 14% under shading conditions. Depending on the season, the lower radiation and stressful microclimate decreased the irrigation between 6% and 31%. Fluctuating shading reduced the photosynthetic capacity of leaves and increased their specific leaf area (thinner leaves). The reduction in carbohydrate assimilation under shading was associated with lower starch reserve accumulation in the shoots (-7%), lower flower intensity at the shoot scale (-31%) and a lower proportion of trees with a high floribundity in 2020 (-45%). However, less alternate bearing was observed under shading, and better frost protection resulted in a higher proportion of trees bearing fruit under photovoltaic panels (+31%) and number of fruits per fruit-bearing tree (+44%) in 2021. Fruit size was less sensitive than fruit number to shading. Fruit size was reduced by 17% in 2019 but maintained in 2020 and 2021, probably due to a better water status of shaded trees that accumulated more water. Fruit dry matter content under shading was reduced by an average of 24%. In conclusion, agrivoltaic systems may reduce alternate bearing behaviour in apple trees, showing the importance of carrying out a multi-year study. However, the fluctuating shading strategy tested in this study did not maintain sufficient yields, with yields below 40 t/ha in all three years of study. Identifying the positive and negative effects of shading in this study may be useful for the development of sustainable apple orchard shading strategies.
To assess the influence of the environment on fruit metabolism, tomato (Solatium lycopersicum 'Moneymaker') plants were grown under contrasting conditions (optimal for commercial, water limited, or ...shaded production) and locations. Samples were harvested at nine stages of development, and 36 enzyme activities of central metabolism were measured as well as protein, starch, and major metabolites, such as hexoses, sucrose, organic acids, and amino acids. The most remarkable result was the high reproducibility of enzyme activities throughout development, irrespective of conditions or location. Hierarchical clustering of enzyme activities also revealed tight relationships between metabolic pathways and phases of development. Thus, cell division was characterized by high activities of fructokinase, glucokinase, pyruvate kinase, and tricarboxylic acid cycle enzymes, indicating ATP production as a priority, whereas cell expansion was characterized by enzymes involved in the lower part of glycolysis, suggesting a metabolic reprogramming to anaplerosis. As expected, enzymes involved in the accumulation of sugars, citrate, and glutamate were strongly increased during ripening. However, a group of enzymes involved in ATP production, which is probably fueled by starch degradation, was also increased. Metabolites levels seemed more sensitive than enzymes to the environment, although such differences tended to decrease at ripening. The integration of enzyme and metabolite data obtained under contrasting growth conditions using principal component analysis suggests that, with the exceptions of alanine amino transferase and glutamate and malate dehydrogenase and malate, there are no links between single enzyme activities and metabolite time courses or levels.
Little is known about the light regulation of vitamin C synthesis in fruits. In contrast, previous studies in leaves revealed that VTC2 (coding for GDP-l-galactose phosphorylase) was one of the key ...genes up-regulated by light in leaves. Our objective was to determine how the expression of ascorbate (AsA) synthesis genes in tomato (Solanum lycopersicum) was modified according to light irradiance in both leaves and fruits. Seven days of shading strongly decreased total ascorbate (reduced and oxidized form) content in leaves (50%) and to a lesser extent in fruits (10%). Among the last six steps of AsA biosynthesis, only two genes, VTC2 and GPP1 (one of the two unigenes coding for l-galactose-1-P phosphatase in tomato), were down-regulated by long-term shading in red ripe fruits, compared to seven genes regulated in leaves. This underlines that light affects AsA-related gene expression more in leaves than in ripening fruits. Moreover, this study reveals strong daily changes in transcript levels of enzymes of the AsA biosynthetic pathway in leaves (11 of the 12 studied genes showed significant changes in their expression pattern). Among those genes, we found that diurnal variation in transcript levels of VTC2 and GME1 correlated to leaf AsA content measured 8 h later. This study provides a new hypothesis on the role of GME1 in addition to VTC2 in light-regulated AsA biosynthesis.
Regulation of water flow in the pedicel–fruit system may generate a diurnally regulated uptake of sugar and prevent water loss by a system of fruit xylem-to-phloem and phloem-to-apoplast ...recirculation.
Abstract
We develop a model based on the biophysical representation of water and sugar flows between the pedicel, fruit xylem and phloem, and the fruit apoplast and symplast in order to identify diurnal patterns of transport in the pedicel–fruit system of peach. The model predicts that during the night water is mainly imported to the fruit through the xylem, and that fruit phloem–xylem transfer of water allows sugar concentrations in the phloem to be higher in the fruit than in the pedicel. This results in relatively high sugar transport to the fruit apoplast, leading to relatively high sugar uptake by the fruit symplast despite low sugar concentrations in the pedicel. At midday, the model predicts a xylem backflow of water driven by a lower pressure potential in the xylem than in the fruit apoplast. In addition, fruit xylem-to-phloem transfer of water decreases the fruit phloem sugar concentration, resulting in moderate sugar uptake by the fruit symplast, despite the high sugar concentration in the pedicel. Globally, the predicted fruit xylem–phloem water transfers buffer the sugar concentrations in the fruit phloem and apoplast, leading to a diurnally regulated uptake of sugar. A possible fruit xylem-to-apoplast recirculation of water through the fruit phloem reduces water lost by xylem backflow at midday.
Ecosystem services in orchards. A review Demestihas, Constance; Plénet, Daniel; Génard, Michel ...
Agronomy for sustainable development,
04/2017, Letnik:
37, Številka:
2
Journal Article
Recenzirano
Odprti dostop
Arboriculture must maintain acceptable fruit production levels while preserving natural resources. This duality can be analyzed with the concept of ecosystem service. We reviewed the literature on ...orchards to explain how ecological functions modified by agricultural practices provide six ecosystem services - fruit production, climate regulation, soil nitrogen availability, water regulation, pest and disease control, and pollination
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and which indicators could describe them. The major points are, first, that orchards have a high potential of multiple services. They can sequester from 2.4 to 12.5 t C/ha/year. Their perennial character and multi-strata habitat, as well as the opportunity of creating diversified hedgerows and cover crops in alleys, may contribute to a high level of biodiversity and related services. Second, every service depends on many functions. Fruit yield, which could reach up to 140 t/ha in apple orchards, is increased by light interception, carbon allocation, and nitrogen and water uptake. Third, agricultural practices in orchards have a strong impact on ecosystem functions and, consequently, on ecosystem services. Overfertilization enhances nitrogen leaching, which reduces soil nitrogen availability for the plant and deteriorates the quality of drained water. Groundcover increases humification and reduces denitrification and runoff, thus enhancing soil nitrogen availability and water regulation. It also enhances biotic interactions responsible for pest control and pollination. Pruning may increase fruit quality trough a better carbon allocation but decreases pest control by fostering the dynamics of aphids.
To study multiple ecosystem services in orchards, we suggest using models capable of simulating service profiles and their variation according to management scenarios. We then refer to the available literature to show that conflicts between provisioning and regulating services can be mitigated by agricultural practices. Improved knowledge of soil processes and carbon balance as well as new models that address multiple services are necessary to foster research on ecosystem service relationships in orchards.
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