Citricultura. El cuajado del fruto. Polinización y partenocarpia. Las giberelinas

El objeto de aprendizaje describe la relación entre el cuajado, bien sea sexual o asexual, y las giberelinas.Mesejo Conejos, C. (2012). Citricultura. El cuajado del fruto. Polinización y partenocarpia. Las giberelinas. http://hdl.handle.net/10251/1689

A Review of Symbolic, Subsymbolic and Hybrid Methods for Sequential Decision Making

The field of Sequential Decision Making (SDM) provides tools for solving Sequential Decision Processes (SDPs), where an agent must make a series of decisions in order to complete a task or achieve a goal. Historically, two competing SDM paradigms have view for supremacy. Automated Planning (AP) proposes to solve SDPs by performing a reasoning process over a model of the world, often represented symbolically. Conversely, Reinforcement Learning (RL) proposes to learn the solution of the SDP from data, without a world model, and represent the learned knowledge subsymbolically. In the spirit of reconciliation, we provide a review of symbolic, subsymbolic and hybrid methods for SDM. We cover both methods for solving SDPs (e.g., AP, RL and techniques that learn to plan) and for learning aspects of their structure (e.g., world models, state invariants and landmarks). To the best of our knowledge, no other review in the field provides the same scope. As an additional contribution, we discuss what properties an ideal method for SDM should exhibit and argue that neurosymbolic AI is the current approach which most closely resembles this ideal method. Finally, we outline several proposals to advance the field of SDM via the integration of symbolic and subsymbolic AI

NeSIG: A Neuro-Symbolic Method for Learning to Generate Planning Problems

In the field of Automated Planning there is often the need for a set of planning problems from a particular domain, e.g., to be used as training data for Machine Learning or as benchmarks in planning competitions. In most cases, these problems are created either by hand or by a domain-specific generator, putting a burden on the human designers. In this paper we propose NeSIG, to the best of our knowledge the first domain-independent method for automatically generating planning problems that are valid, diverse and difficult to solve. We formulate problem generation as a Markov Decision Process and train two generative policies with Deep Reinforcement Learning to generate problems with the desired properties. We conduct experiments on several classical domains, comparing our method with handcrafted domain-specific generators that generate valid and diverse problems but do not optimize difficulty. The results show NeSIG is able to automatically generate valid problems of greater difficulty than the competitor approaches, while maintaining good diversity

The flower to fruit transition in Citrus is partially sustained by autonomous carbohydrate synthesis in the ovary

[EN] Why evergreen fruit tree species accumulate starch in the ovary during flower bud differentiation in spring, as deciduous species do during flower bud dormancy, is not fully understood. This is because in evergreen species carbon supply is assured by leaves during flower development. We suggest the existence of an autonomous mechanism in the flowers which counteracts the competition for photoassimilates with new leaves, until they become source organs. Our hypothesis is that starch accumulated during Citrus ovary ontogeny originates from 1) its own photosynthetic capacity and 2) the mobilization of reserves. Through defoliation experiments, we found that ovaries accumulate starch during flower ontogeny using a dual mechanism: 1) the autotrophic route of source organs activating Rubisco (RbcS) genes expression, and 2) the heterotrophic route of sink organs that hydrolyze sucrose in the cytosol. Defoliation 40 days before anthesis did not significantly reduce ovary growth, flower abscission or starch concentration up to 20 days after anthesis (i.e. 60 days later). Control flowers activated the energy depletion signaling system (i.e. SnRK1) and RbcS gene expression around athesis. Defoliation accelerated and boosted both activities, increasing SPS gene expression (sucrose synthesis), and SUS1, SUS3 and cwINV (sucrose hydrolysis) to maintain a glucose threshold which satisfied its need to avoid abscission.Mesejo Conejos, C.; Martinez Fuentes, A.; Reig Valor, C.; Agustí Fonfría, M. (2019). The flower to fruit transition in Citrus is partially sustained by autonomous carbohydrate synthesis in the ovary. Plant Science. 285:224-229. https://doi.org/10.1016/j.plantsci.2019.05.014S22422928

Examining the impact of dry climates temperature on citrus fruit internal ripening

[EN] High temperatures alter the ripening process of citrus fruit, affecting quality, flavor, harvest time and marketing period. For example, citrus fruits ripen faster and are sweeter in tropical hot-humid climates than in Mediterranean warm-dry climates due to higher sugar accumulation and organic acid catabolism. Considering that: 1) over 60 % of the world's citrus exports come from countries with warm Mediterranean climates, and 2) the Mediterranean region is warming 20 % faster than the global average, the citrus industry will face significant challenges in the coming years. The range of high temperatures and the timing at which they determine sugar and acid content in dry climates have not been studied under field conditions. Therefore, a study was undertaken over 6 years to determine the relationship between high temperature and citrus ripening in two dry macroclimates, hot (Arid, in Morocco) and warm (Mediterranean, in Spain), and 5 microclimates of the Mediterranean region. Heat stress in these dry climates correlates with changes in fruit quality (lower juice and sugar content, and higher organic acids), depending on the maximum temperature threshold and the time of onset and duration of heat. In the arid climate, the heat stress threshold was found to be a significant number of days above 35 degrees C. This was particularly important at the beginning of summer (July in the northern hemisphere). However, in the current Mediterranean climate of Spain, the percentage of summer days above 35 degrees C is still low indicating that other microclimatic conditions are involved in determining fruit quality. In particular, an increase in the number of days with temperatures between 27 degrees C and 33 degrees C in late summer and early autumn was found to correlate with reduced citric acid concentration. Microclimate did not determine sucrose, fructose, and glucose concentrations.Mesejo Conejos, C.; Martinez Fuentes, A.; Reig, C.; El-Otmani, M.; Agustí Fonfría, M. (2024). Examining the impact of dry climates temperature on citrus fruit internal ripening. Scientia Horticulturae. 337. https://doi.org/10.1016/j.scienta.2024.11350133

Warm temperature during floral bud transition turns off EjTFL1 gene expression and promotes flowering in Loquat (Eriobotrya japonica Lindl)

[EN] The Rosaceae family includes several deciduous woody species whose flower development extends over two consecutive growing seasons with a winter dormant period in between. Loquat (Eriobotrya japonica Lindl.) belongs to this family, but it is an evergreen species whose flower bud initiation and flowering occur within the same growing year. Vegetative growth dominates from spring to late summer when terminal buds bloom as panicles. Thus, its floral buds do not undergo winter dormancy until flowering, but a summer heat period of dormancy is required for floral bud differentiation, and that is why we used loquat to study the mechanism by which this summer rest period contributes to floral differentiation of Rosaceae species. As for the deciduous species, the bud transition to the generative stage is initiated by the floral integrator genes. There is evidence that combinations of environmental signals and internal cues (plant hormones) control the expression of TFL1, but the mechanism by which this gene regulates its expression in loquat needs to be clarified for a better understanding of its floral initiation and seasonal growth cycles. Under high temperatures (>25 & DEG;C) after floral bud inductive period, EjTFL1 expression decreases during meristem transition to the reproductive stage, and the promoters of flowering (EjAP1 and EjLFY) increase, indicating that the floral bud differentiation is affected by high temperatures. Monitoring the apical meristem of loquat in June-August of two consecutive years under ambient and thermal controlled conditions showed that under lower temperatures (<25 & DEG;C) during the same period, shoot apex did not stop growing and a higher EjTFL1 expression was recorded, preventing the bud to flower. Likewise, temperature directly affects ABA content in the meristem paralleling EjTFL1 expression, suggesting signaling cascades could converge to refine the expression of EjTFL1 under specific conditions (T<25 & DEG;C) during the floral transition stage.García-Lorca, A.; Reig Valor, C.; Martinez Fuentes, A.; Agustí Fonfría, M.; Mesejo Conejos, C. (2023). Warm temperature during floral bud transition turns off EjTFL1 gene expression and promotes flowering in Loquat (Eriobotrya japonica Lindl). Plant Science. 335. https://doi.org/10.1016/j.plantsci.2023.11181033

Loquat Fruit Lacks a Ripening-Associated Autocatalytic Rise in Ethylene Production

[EN] Loquat is considered as a non-climacteric fruit; however, there is an evidence of a climacteric-like maturation. Therefore, it seems its ripening behavior has yet to be satisfactory classified. Because autocatalytic regulation of ethylene production during fruit ripening is one of the primary features defining climacteric-like fruit maturation, we examined its ability of autocatalysis during ripening by applying the ethylene-releasing compound ethephon to the on-tree-fruit or ethylene to detached fruit of 'Algerie' loquat and measuring its ethylene and CO2 production. We also analyzed indoleacetic acid (IAA), gibberellin, cytokinin, and abscisic acid (ABA) contents as plant hormones involved in fruit ripening. The fruit response to ethephon (500 mg l(-1)) applied at color change was immediate producing increasing amounts of ethylene during the 4 h following the treatment, but 24 h after treatment onward values were similar to those produced by untreated fruit. Similar results were obtained when applying ethylene to detached fruit (10 mu l l(-1)). Accordingly, applying ethephon (200 mg l(-1)) did not advance harvest; neither the color nor the percentage of fruit harvested at the first picking date differed significantly from the untreated fruit. Flesh firmness, total soluble solid concentration, and acidity of juice were not significantly altered either. IAA concentration reached the maximum value when fruit stopped growing, declining sharply at fruit color change; active gibberellins and cytokinins declined continuously during the fruit growth period, and ABA content sharply increased during ripening, peaking after fruit color break. Results indicate that 'Algerie' loquat lacks a ripening-associated autocatalytic rise in ethylene production, and suggest that a decline in gibberellin, cytokinin, and IAA concentrations might be needed to allow its ripening process to proceed.Reig Valor, C.; Martínez Fuentes, A.; Mesejo Conejos, C.; Rodrigo, M.; Zacarias Garcia, L.; Agustí Fonfría, M. (2016). Loquat Fruit Lacks a Ripening-Associated Autocatalytic Rise in Ethylene Production. Journal of Plant Growth Regulation. 35(1):232-244. doi:10.1007/s00344-015-9528-3S232244351Agustí M, Guardiola JL, Almela V (1981) The regulation of fruit cropping in mandarins through the use of growth regulators. Proc Int Soc Citric 1:216–220Amorós A, Zapata P, Pretel MT, Botella MA, Serrano M (2003) Physicochemical and physiological changes during fruit development and ripening of five loquat (Eriobotrya japonica Lindl.) cultivars. 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Ethylene biosynthesis and perception during ripening of loquat fruit (Eriobotrya japonica Lindl.)

[EN] In order to gain insights into the controversial ripening behavior of loquat fruits, in the present study we have analyzed the expression of three genes related to ethylene biosynthesis (ACS1, ACO1 and ACO2), two ethylene receptors (ERS1a and ERS1b), one signal transduction component (CTR1) and one transcription factor (EIL1) in peel and pulp of loquat fruit during natural ripening and also in fruits treated with ethylene (10 mu LL-1) and 1-MCP (10 mu LL-1), an ethylene action inhibitor. In fruits attached to or detached from the tree, a slight increase in ethylene production was detected at the yellow stage, but the respiration rate declined progressively during ripening. Accumulation of transcripts of ethylene biosynthetic genes did not correlate with changes in ethylene production, since the maximum accumulation of ACS1 and ACO1 mRNA was detected in fully coloured fruits. Expression of ethylene receptor and signaling genes followed a different pattern in peel and pulp tissues. After fruit detachment and incubation at 20 degrees C for up to 6 days, ACS1 mRNA slightly increased, ACO1 experienced a substantial increment and ACO2 declined. In the peel, these changes were advanced by exogenous ethylene and partially inhibited by 1-MCP. In the pulp, 1-MCP repressed most of the changes in the expression of biosynthetic genes, while ethylene had almost no effects. Expression of ethylene perception and signaling genes was barely affected by ethylene or 1-MCP. Collectively, a differential transcriptional regulation of ethylene biosynthetic genes operates in peel and pulp, and support the notion of non-climacteric ripening in loquat fruits. Ethylene action, however, appears to be required to sustain or maintain the expression of specific genes. (C) 2016 Published by Elsevier GmbH.Enriqueta Alos was recipient of a post-doctoral contract JAE-DocCSIC (Fondo Social Europeo). The financial support of the researchgrants FP7-PEOPLE-2011-CIG-2011-303652 (Marie Curie Actions, European Union), AGL-2009-11558 and AGL-2012-34573 (Ministerio Economia y Competitividad, Spain), GV/2012/036 (Generalitat Valenciana, Spain) and PROMETEOII 2014/27 (Generalitat Valenciana) is gratefully acknowledged.Alós, E.; Martinez Fuentes, A.; Reig Valor, C.; Mesejo Conejos, C.; Rodrigo, M.; Agustí Fonfría, M.; Zacarias, L. (2017). Ethylene biosynthesis and perception during ripening of loquat fruit (Eriobotrya japonica Lindl.). Journal of Plant Physiology. 210:64-71. https://doi.org/10.1016/j.jplph.2016.12.008S647121

Tree water status influences fruit splitting in Citrus

[EN] Fruit splitting or cracking is a major physiological disorder in fruit trees markedly influenced by environmental conditions, but conclusive data still are required to provide a definite explanation and preventive measures. Changes in climatic conditions critically influence fruit splitting incidence. We studied plant-soil-ambient water relations in splitting-prone citrus grown under 4 contrasting environmental conditions (climate type and soil), in Spain and Uruguay, over a six years period. Automatic trunk and fruit diameter measurements (trunk and fruit growth rate and maximum daily trunk shrinkage), which are a tree water status indicator, together with factors modifying the tree and fruit water relationship (temperature, ET, rainfall, soil texture, soil moisture, rootstock and xylem anatomy) were studied and correlated with splitting. A close fruit splitting and soil texture relationship was found, inversely correlated with clay and silt percentages, and positively with those for sand. Under 85%-sand soil conditions, slight changes in soil moisture due to fluctuations in temperature, ET, or rainfall changed trunk and fruit growth rate patterns during few hours and induced splitting. Splitting incidence was higher in trees with larger xylem vessels in the fruit peduncle due to rootstock ('Carrizo' and 'C-35' citrange being higher than 'FA-5', 'Cleopatra' and Poncirus trifoliata). Finally, reducing the frequency of irrigation by half increased midday canopy temperatures (similar to 5 degrees C) and splitting (+15%). We conclude that irregularities in the tree water status, due to interactions among soil moisture, rootstock and climatic conditions, leads to a number of substantial changes in fruit growth rate increasing the incidence of fruit splitting. (C) 2016 Elsevier B.V. All rights reserved.Mesejo Conejos, C.; Reig Valor, C.; Martinez Fuentes, A.; Gambetta, G.; Gravina Telechea, A.; Agustí Fonfría, M. (2016). Tree water status influences fruit splitting in Citrus. Scientia Horticulturae. 209:96-104. doi:10.1016/j.scienta.2016.06.009S9610420

Cuajado y Desarrollo de los Frutos Cítricos

El fruto de los cítricos es una baya típica llamada hesperidio. En él se pueden distinguir las siguientes partes (Foto 1) (González-Sicilia, 1968; Schneider, 1968): - Exocarpo o flavedo, que es la región más externa y constituye la parte visible de la corteza, formada por células epidérmicas de color verde cuando el fruto es inmaduro y naranja o amarillo, según la especie, en la madurez. - Mesocarpo o albedo, que es la región situada debajo del exocarpo, formado por un tejido blanco esponjoso de células parenquimáticas. - Endocarpo, que es la región más interna y está constituido por los lóculos o gajos. Los lóculos contienen las vesículas de zumo, formadas por un cuerpo de células completamente vacuolizadas y un pedúnculo que las mantiene unidas a la epidermis dorsal de los carpelos y limitadas lateralmente por los septos. El exocarpo y mesocarpo constituyen la corteza del fruto propiamente dicha. Dentro de los lóculos del endocarpo se encuentran las semillas