141 research outputs found
Sensibilidade de respostas de fotossíntese foliar de cafeeiros após o experimento FACE: existe a memória?
No full textResumo: A hipótese deste trabalho foi que as respostas de fotossíntese de folhas de cafeeiros serão maiores em plantas que foram previamente cultivadas sob elevada concentração de CO2 (e[CO2]) do que nestas que sempre foram cultivadas sob a concentração atual de CO2 (a[CO2]), especialmente em condições de irrigação. Para estudar a existência de ?memória? positiva de e[CO2], o objetivo do estudo foi determinar variações de curvas de respostas de fotossíntese (A) na luz em folhas de café ao longo de perfil vertical de árvores, após um mês que o enriquecimento de CO2 foi encerrado no experimento FACE. As plantas previamente cultivadas sob e[CO2] apresentaram menor A comparadas com as que sempre foram cultivadas sob a[CO2]. O período transitório de rustificação (aclimatização) às condições de a[CO2] aumentou a sensibilidade das plantas cultivadas previamente sob e[CO2], especialmente estas sob irrigação. Em plantas continuamente cultivadas sob regime hídrico de campo e sob a[CO2], as folhas autossombreadas apresentaram maior resposta de A à concentração de CO2 de 590 ?L CO2 L-1 na câmara de medição na época de seca, como possível consequência de um ?estado de alerta?, para lidar com novos eventos de seca com sucesso. A hipótese de ?memória? em plantas previamente estimuladas com e[CO2] foi provada, mas ela induziu diminuição de A, por causa do aparelho fotossintético construído previamente no experimento FACE. ? Abstract: The hypothesis of this work was that the photosynthetic responses of coffee leaves would be promoted in plants that were previously cultivated under the elevated concentration of CO2 (e[CO2]) compared to those that were always cultivated under the current concentration of CO2 (a[CO2]), especially under irrigation conditions. To study the existence of positive ?memory? of e [CO2], the aim of this study was to determine variations in photosynthetic lightresponses curves of coffee leaves, estimated along the vertical tree profile, one month after the CO2 enrichment was terminated in the FACE experiment. Plants previously cultivated under e[CO2] showed lower leaf photosynthesis (A) compared to those always cultivated under a[CO2]. The transitional period of acclimatization (hardening) to the conditions of a[CO2] increased the sensitivity of plants previously cultivated under e[CO2], especially those ones under irrigation. In plants continuously cultivated under field water regime and under e[CO2], the self-shaded leaves showed higher A response to CO2 concentration of 590 ?L CO2 L-1 in the chamber during the dry season, as a possible consequence of a ?alertness? to successfully deal with new drought events. The hypothesis of ?memory? in plants previously stimulated with e[CO2] was proved, but it induced the reduction in A due to the photosynthetic apparatus previously built during the FACE experiment
Photosynthetic light curve parameters over vertical profile of Coffea arabica plants after five years of FACE experiment.
No full textTrends in climate changes indicate that the air [CO2] will continue to increase. The first plant response to elevated [CO2] (e[CO2]) is the increased photosynthetic rate. Photosynthetic rate dependence on light (A/PAR curves) is characterized by several parameters, often used to determine plant species responses to environment and phenological plasticity. The effects of water supply and phenological stage were expected, with no acclimation after long-term Coffea arabica L. cultivation under e[CO2]. The aim of the study was to determine variations in parameters of A/PAR curves in coffee leaves over a tree vertical profile after long-term cultivation under free-air-CO2-enrichment (FACE) system. The p arameters of A/PAR curves in C. arabica were estimated after five-years cultivation in FACE under two CO2 conditions, actual (a[CO2], ~390?L CO2 L-1) and e[CO2] (~590?L CO2 L-1), in two water regimes (rainfed and irrigation). The A/PAR curves were estimated in two phenological stages (grain formation - February 2016 and fruit maturation - May 2016). The A/PAR responses were determined by varying photosynthetic active radiation (PAR) from 1117 to 0 ?mol photons m?2 s?1 in four 50 cm-thick layers of vertical plant profile. The maximum photosynthesis (Amax), dark respiration (Rd), apparent quantum efficiency (?), and light compensation point (?) generally increased under e[CO2] compared to a[CO2], showing higher values during grain formation than during fruit maturation (Figure 1). The Rd and ? followed the progressive increase by layers only during the grain formation (Figures 1C and 1E). Continuation in e[CO2] stimulation indicated that leaf photosynthesis acclimation did not occur after five-years coffee cultivation under FACE. The lack of progressive increase in Amax, ? and ? over vertical profile indicates leaf plasticity to light availability, especially considering the high Amax of the two lowest layers. The compensation effects of e[CO2] to low water availability were observed in all A/PAR responses
Co-EP Banach algebra elements
No full text[EN] In this work, given a unital Banach algebra A and a \in A such that a has a Moore-Penrose inverse a^+, it will be characterized when a^+ a - a a^+ is invertible. A particular subset of this class of objects wil also be studied. In addition, perturbations of this class of elements will be studied. Finally, the Banach space operator case will also be consider.The third author is supported by Grant No. 174025 of the Ministry of Science, Technology and Development, Republic of Serbia.Benítez López, J.; Boasso, E.; Rakocevic, V. (2015). Co-EP Banach algebra elements. Banach Journal of Mathematical Analysis. 9(1):27-41. doi:10.15352/bjma/09-1-3S27419
Aspectos fotomorfogenéticos de plantas jovens de jatobá (Hymenaea courbaril L.).
No full textOrganizado por Patricia Póvoa de Mattos, Celso Garcia Auer, Rejane Stumpf Sberze, Katia Regina Pichelli e Paulo César Botosso
Impact of Kannan Contraction on Khan Contraction and its Generalizations
No full textCvetkovic, Marija/0000-0003-0691-3428; Rakocevic, Vladimir/0000-0002-4182-4458;Several concepts of rational contractions originated during the last 50 years with vivid discussion on possible applications and practical examples. The main topic of this article is a Khan contraction, its modifications and generalizations, with the emphasis on its relation to some well-known classes of contractive mappings. We prove that a Khan contraction is an example of Bianchini and, consequently, a Ciric contraction. Further, some of its generalizations present a special type of Kannan contraction.Ministry of Education, Science and Technological Development, Republic of Serbia [451-03-65/2024-03/200124]The first author is supported by Ministry of Education, Science and Technological Development, Republic of Serbia, no. 451-03-65/2024-03/200124
Estimations of leaf CO2 assimilation, stomatal conductance and transpiration in adult Arabic coffee plants after long-term FACE cultivation.
No full textThe air [CO2] can reach 600 ?L CO2 L-1 in the middle or the end of this century, depending on scenario. The first plant response to elevated CO2 (e[CO2]) is the increased leaf photosynthetic rate (A) occurring parallelly by mainly non-sensitive or decreased stomatal conductance (gs) and decreased transpiration (E). In Arabic coffee, A increases under e[CO2], especially during the dry growing season, while gs responses vary during years under free-air-CO2-enrichment (FACE). The aim of this study was to estimate A, gs and E over a coffee vertical profile after five years cultivation under FACE, including the responses to water availability. Coffee was cultivated under two CO2 conditions, actual (a[CO2], ~390?L CO2 L-1) and e[CO2] (~590?L CO2 L-1). The irrigation started at the end of the 4th year of experiment. The measurements were conducted in rainy season, in February 2016 (grain expansion). Values of photosynthetic active radiation (PAR) varied from 1131 to 0 ?mol photons m?2 s?1 to construct curves of A, gs and E dependence on PAR in four 50 cm-thick layers. Simultaneously, PAR was measured in the morning, midday and afternoon. Punctual values were estimated from nonrectangular hyperbola (A) and polynomial (gs and E) models. PAR reached ~1400 ?mol m?2 s ?1 at the highest plant layer at midday, while the transmitted PAR at soil level was about 4 ?mol m?2 s?1. The A diminished gradually from plant top to bottom, from 7.2 to -1 ?mol m?2 s?1. The A was positively impacted by e[CO2] in the highest and low layers. The gs and E showed similar trends in daily variation and in responses to CO2 and water availability treatments, showing lower values under e[CO2] than a[CO2] over the plant profile, with exception of the most shaded leaves. Results suggest better water economy under e[CO2] than a[CO2] under high light conditions
Elevated air CO2 conditions changes the metabolic profile of Arabic coffee leaves during vegetative and reproductive stages.
No full textEffects of drought, elevated air CO2 and temperature can change the quality of food. Arabic coffee is characterized by biannual phenological cycle constituted by six stages: vegetative that occurs under long days, maturation of reproductive buds (MRB), flowering and grain expansion (FGE), grain formation (GF), grain maturation (GM) and senescence. We expected that leaf metabolic profile of plants cultivated under elevated CO2 would differentiate among stages of vegetative and reproductive growth. The aim of this study was to analyze those variations in Free-Air-CO2-Enrichment (FACE) experiment. In the 2nd year of growing under rainfed conditions in FACE, fully expanded coffee leaves were collected in four periods: June 2012 (MRB1-transformation of vegetative to reproductive buds), July 2012 (MRB2-relative bud dormancy), December 2012 (FGE) and January 2013 (GF). GCMS datasets, coupled with multivariate statistical methods, were used to investigate 35 compounds identified in coffee leaves growing in two CO2 conditions, actual (a[CO2], ~ 390?L CO2 L-1) and elevated (e[CO2], ~590?L CO2 L-1). Mainly, the content of amino, fatty and organic acids besides phenolic compounds and sterols, diminished under e[CO2] (Table 1). Only the content of dodecanoic (GF) and citric (MRB1) acids increased. Under e[CO2], both reduction or increase in leaf carbohydrate contents occurred. Sugar alcohols as mannitol (FGE), galactitol (FGE) and pinitol (MRB1) showed 16, 22 and 37 times higher content under e[CO2] than a[CO2], respectively. The PCA showed an obvious separation in CO2 treatments, differing metabolites in all stages, not only vegetative from reproductive ones (Figure 1). The high leaf investments in carbohydrates, specifically sugar alcohols, indicates quick investments of carbon in metabolites under e[CO2]. Higher levels of citric and dodecanoic acids under e[CO2] than a[CO2] suggest the mitigation of various stress conditions under e[CO2], as drought, low/high temperatures and presence of coffee leaf rust attack, which were observed along the experimental period
Existence of a solution of integral equations via fixed point theorem
No full textIn this paper, we establish a solution to the following integral equation: u(t) = integral(T)(0) G(t, s)f(s, u(s)) ds for all t is an element of [0,T], (1) where T > 0, f : [0, T] x R -> R and G : [0, T] x [0, T] -> [0, infinity) are continuous functions. For this purpose, we also obtain some auxiliary fixed point results which generalize, improve and unify some fixed point theorems in the literature.Ministry of Science, Technology and Development, Republic of Serbia [174025]The authors thank the anonymous referees for their remarkable comments, suggestions and ideas that helped to improve this paper. The third author (V Rakocevic) is supported by Grant No. 174025 of the Ministry of Science, Technology and Development, Republic of Serbia
Elevated CO2 mitigates the effects of anomalous drought reducing the proportion of abnormal reproductive structures in Arabic coffee.
No full textThe increase in atmospheric carbon dioxide concentration [CO2] results in higher photosynthesis and growth of the upper layer structures in coffee trees. It was hypothesized that coffee trees would increase the reproductive investments of high plant layers under elevated [CO2](e[CO2]). The aim of this study was to estimate the dynamic in flowering intensity and quality at axis scale in free-air-CO2-enrichment (FACE) experiment over four years underrainfed conditions. The effects of actual [CO2](a[CO2], ~ 390 ?L CO2 L-1) and e[CO2] (~ 590 ?L CO2 L-1) on the flowering of Arabic coffee (cv. Red Catuaí IAC-144) were evaluated in completely randomized split-plot block design. Nonbranched second order plagiotropic axes from the upper layer, characterized by flower buds visually individualized on 13 to 16 metamers, were selected before the main flowering in 2012-2015. We used tulle bags to cover second order axes for reproductive structures collection. After abscission, buds and flowers were counted and classified as normal or abnormal. Flowering intensity and quality were impacted by e[CO2], varying by year. The coffee axes produced more reproductive structures in the first flowering year (2012) than later; this reproductive investment by axis was higher under e[CO2] than a[CO2] (Figure 1A-B). The % of dropped flower buds in 2012 was more than double compared to later years, without [CO2] impact (Figure 1C). High reproductive investments in the second-order axes in 2012 resulted from higher production of inflorescences per metamer compared to other years, with a positive e[CO2] effect. In 2014, drought in rainy period and high summer minimum temperatures (Figure 2) affected the inflorescences differentiation, increasing the proportion of abnormal reproductive structures compared to other years (Figure 1D). The e[CO2] reduced proportion of abnormal reproductive structures mitigating the anomalous drought effects
Discontinuity at fixed point and metric completeness
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