Biologia Vegetal
URI permanente desta comunidadehttps://locus.ufv.br/handle/123456789/11836
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Resultados da Pesquisa
Item Photosynthetic induction and activity of enzymes related to carbon metabolism: insights into the varying net photosynthesis rates of coffee sun and shade leaves(Theoretical and Experimental Plant Physiology, 2013) Martins, Samuel Cordeiro Vitor; Detmann, Kelly Coutinho; Reis, Josimar Vieira dos; Pereira, Lucas Felisberto; Sanglard, Lílian Maria Vincis Pereira; Rogalski, Marcelo; DaMatta, Fábio MuriloThe shade leaves of coffee (Coffea arabica L.) apparently retain a robust photosynthetic machinery that is comparable to that of sun leaves and can fix CO2 at high rates when subjected to high light intensities. This raises the question of why the coffee plant would construct such a robust photosynthetic machinery despite the low photosynthetic rates achieved by the shade leaves at low light supply. Here, we grew coffee plants at 100% or 10% full sunlight and demonstrated that the shade leaves exhibited faster photosynthetic induction compared with their sun counterparts, in parallel with lower loss of induction states under dim light, and were well protected against short-term sudden increases in light supply (mimicking sunflecks). These findings were linked to similar photosynthetic capacities on a per mass basis (assessed under nonlimiting light), as well as similar extractable activities of some enzymes of the Calvin cycle, including Rubisco, when comparing the shade and sun leaves. On the one hand, these responses might represent an overinvestment of resources given the low photosynthetic rates of the shade leaves when light is limiting; on the other hand, such responses might be associated with a conservative behavior linked to the origin of the species as a shade-dwelling plant, allowing it to maximize the use of the energy from sunflecks and thus ultimately contributing to a positive carbon balance under conditions of intense shading.Item Crescimento vegetativo sazonal do cafeeiro e sua relação com fotoperíodo, frutificação, resistência estomática e fotossíntese(Pesquisa Agropecuária Brasileira, 2006-03) Rena, Alemar Braga; Amaral, José Augusto Teixeira do; Amaral, José Francisco Teixeira doO objetivo deste trabalho foi avaliar as flutuações sazonais do crescimento vegetativo do cafeeiro (Coffea arabica L.) e suas relações com o fotoperíodo, a remoção dos frutos, a fotossíntese e a resistência estomática. Os tratamentos foram constituídos por dois regimes fotoperiódicos – natural e estendido para 14 horas – em plantas com frutos e sem frutos. O crescimento de ramos e da área foliar decresceu a partir de meados de março, atingindo taxas mínimas nos meses de maio e junho, quando foram registradas as menores temperaturas. Esse modelo de crescimento não foi modificado pela extensão do fotoperíodo para 14 horas, nem pela remoção dos frutos, ainda que os cafeeiros sem frutos exibissem maiores taxas de crescimento dessas variáveis (ramo e área foliar). Não foi observada diferença significativa na fotossíntese potencial decorrente da presença de frutos, nem a extensão do fotoperíodo afetou taxas fotossintéticas. As taxas fotossintéticas potenciais não explicam os declínios do crescimento vegetativo, mas a temperatura mínima do ar correlacionou-se com as quedas do crescimento. A resistência estomática às 14h apresentou valores relativamente elevados, de meados de março a início de maio, coincidindo com elevadas quedas no crescimento de ramos e da área foliar. O declínio inicial no crescimento vegetativo pode estar associado a temperaturas em torno de 14ºC.Item Aspectos morfofisiológicos das cultivares de cafeeiro Catuaí-Vermelho e Conilon(Pesquisa Agropecuária Brasileira, 2001-03) Carvalho, Luciana Marques de; Silva, Eldo Antônio Monteiro da; Azevedo, Aristéa Alves; Mosquim, Paulo Roberto; Cecon, Paulo RobertoO objetivo deste trabalho foi comparar cafeeiros das espécies Coffea arabica L. cv. Catuaí- Vermelho e C. canephora Pierre cv. Conilon quanto à fotossíntese líquida e a aspectos da anatomia foliar a esta relacionados. Verificaram-se taxas fotossintética líquida, transpiratória e de condutância estomática maiores em plantas de C. canephora. As plantas de C. arabica apresentaram menor eficiência do sistema "antena", e folhas menores, porém mais espessas. As duas espécies diferiram, ainda, quanto ao tipo, dimensões e número dos estômatos presentes na epiderme foliar: paracíticos em C. arabica e actinocíticos em C. canephora, e maiores, mas em menor número, em C. arabica.Item Matter accumulation and photosynthetic responses of macaw palm to cyclical drought(Revista Caatinga, 2016-10) Mota, Clenilso Sehnen; Cano, Marco Antonio OlivaThe objective of this work was to evaluate the plant-water relations, photosynthetic parameters and growth of macaw (Acrocomia aculeata (Jacp.) Lodd. ex Mart.) plants, thus, ten plants were subjected to three successive drought and rehydration cycles and ten other plants were irrigated normally as control. The drought cycles consisted of a suspension of irrigation until the net CO2 assimilation rate (A) reach values lower than 5% of the control, and a rehydration until a plants recover at least 85% of A of the control plants. Reductions in A, stomatal conductance (gs ) and transpiration (E), above 95%, were found with predawn leaf water potential (Ψpd) of -1.85 MPa. After rehydration, the gs and E of plants with and without water stress was not different, however, A presented a significant difference. Leaf water potentials below -0.5 MPa reduced the intracellular and atmospheric CO2 ratio and increased water use efficiency, and values of -1.85 MPa, when both showed an increase and decrease, respectively. The reduction of A and gs was linear and proportional to Ψpd. Total dry matter accumulation reduced by 50% in the plants subjected to drought. The cyclic water stress resulted in reduction of gas exchange and matter accumulation in macaw palm plants; a stomatal limitation of A occurred until Ψpd of -1.85 MPa, and then a non-stomatal limitation.Item Modulation of auxin signalling through DIAGETROPICA and ENTIRE differentially affects tomato plant growth via changes in photosynthetic and mitochondrial metabolism(Plant, Cell & Environment, 2019-02) Batista‐ Silva, Willian; Medeiros, David B.; Rodrigues‐ Salvador, Acácio; Daloso, Danilo M.; Omena‐ Garcia, Rebeca P.; Oliveira, Franciele Santos; Pino, Lilian Ellen; Peres, Lázaro Eustáquio Pereira; Nunes‐ Nesi, Adriano; Fernie, Alisdair R.; Zsögön, Agustín; Araújo, Wagner L.Auxin modulates a range of plant developmental processes including embryogenesis, organogenesis, and shoot and root development. Recent studies have shown that plant hormones also strongly influence metabolic networks, which results in altered growth phenotypes. Modulating auxin signalling pathways may therefore provide an opportunity to alter crop performance. Here, we performed a detailed physiological and metabolic characterization of tomato (Solanum lycopersicum) mutants with either increased (entire) or reduced (diageotropica—dgt) auxin signalling to investigate the consequences of altered auxin signalling on photosynthesis, water use, and primary metabolism. We show that reduced auxin sensitivity in dgt led to anatomical and physiological modifications, including altered stomatal distribution along the leaf blade and reduced stomatal conductance, resulting in clear reductions in both photosynthesis and water loss in detached leaves. By contrast, plants with higher auxin sensitivity (entire) increased the photosynthetic capacity, as deduced by higher Vcmax and Jmax coupled with reduced stomatal limitation. Remarkably, our results demonstrate that auxin‐sensitive mutants (dgt) are characterized by impairments in the usage of starch that led to lower growth, most likely associated with decreased respiration. Collectively, our findings suggest that mutations in different components of the auxin signalling pathway specifically modulate photosynthetic and respiratory processes.Item Picolinic acid spray stimulates the antioxidative metabolism and minimizes impairments on photosynthesis on wheat leaves infected by Pyricularia oryzae(Physiologia Plantarum, 2019-04) Aucique- Pérez, Carlos Eduardo; Resende, Renata Sousa; Cruz Neto, Lara Beatriz; Dornelas, Fernanda; DaMatta, Fábio Murilo; Rodrigues, Fabrício ÁvilaFungal pathogens produce toxins that are important for their pathogenesis and/or aggressiveness towards their hosts. Picolinic acid (PA), a non‐host selective toxin, causes lesions on rice leaves resembling those originated from Pyricularia oryzae infection. Considering that non‐host selective toxins can be useful for plant diseases control, this study investigated whether the foliar spray with PA on wheat (Triticum aestivum L.) plants, in a non‐phytotoxic concentration, could increase their resistance to blast, stimulate the anti‐oxidative metabolism, and minimize alterations in photosynthesis. The PA spray at concentrations greater than 0.1 mg ml−1 caused foliar lesions, compromised the photosynthesis and was linked with greater accumulation of hydrogen peroxide (H2O2) and superoxide anion radical (O2•−). Fungal mycelial growth, conidia production and germination decreased by PA at 0.3 mg ml−1. Blast severity was significantly reduced by 59 and 23%, respectively, at 72 and 96 h after inoculation for plants sprayed with PA (0.1 mg ml−1) at 24 h before fungal inoculation compared to non‐sprayed plants. Reduction on blast symptoms was linked with increases on ascorbate peroxidase (EC 1.11.1.11), catalase (EC 1.11.1.6), glutathione peroxidase (EC 1.11.1.9), glutathione reductase (EC 1.8.1.7), glutathione‐S‐transferase (EC 2.5.1.18), peroxidase (EC 1.11.1.7), and superoxide dismutase (EC 1.15.1.1) activities, lower H2O2 and O2•− accumulation, reduced malondialdehyde production as well as less impairments to the photosynthetic apparatus. A more efficient antioxidative metabolism that rapidly scavenges the reactive oxygen species generated during P. oryzae infection, without dramatically decreasing the photosynthetic performance, was a remarkable effect obtained with PA spray.Item On the role of plant mitochondrial metabolism and its impact on photosynthesis in both optimal and sub-optimal growth conditions(Photosynthesis Research, 2014-02) Araújo, Wagner L.; Nunes-Nesi, Adriano; Fernie, Alisdair R.Given that the pathways of photosynthesis and respiration catalyze partially opposing processes, it follows that their relative activities must be carefully regulated within plant cells. Recent evidence has shown that the components of the mitochondrial electron transport chain are essential for the proper maintenance of intracellular redox gradients, to allow considerable rates of photorespiration and in turn efficient photosynthesis. Thus considerable advances have been made in understanding the interaction between respiration and photosynthesis during the last decades and the potential mechanisms linking mitochondrial function and photosynthetic efficiency will be reviewed. Despite the fact that manipulation of various steps of mitochondrial metabolism has been demonstrated to alter photosynthesis under optimal growth conditions, it is likely that these changes will, by and large, not be maintained under sub-optimal situations. Therefore producing plants to meet this aim remains a critical challenge. It is clear, however, that although there have been a range of studies analysing changes in respiratory and photosynthetic rates in response to light, temperature and CO2, our knowledge of the environmental impact on these processes and its linkage still remains fragmented. We will also discuss the metabolic changes associated to plant respiration and photosynthesis as important components of the survival strategy as they considerably extend the period that a plant can withstand to a stress situation.Item Seasonal changes in photoprotective mechanisms of leaves from shaded and unshaded field-grown coffee (Coffea arabica L.) trees(Trees, 2008-06) Chaves, Agnaldo R. M.; Ten-Caten, Angela; Pinheiro, Hugo A.; Ribeiro, Aristides; DaMatta, Fábio M.Coffee is native to shady environments, but often grows and yields better without shade. Thus, it may be reasoned that coffee leaves should display enough plasticity to acclimate themselves to contrasting light environments. However, little is known about mechanisms associated with such plasticity in coffee. This work aimed, therefore, to explore differences in leaf photoprotective mechanisms. Plants were grown in the field and received either 48 or 100% natural light. Evaluations were made using outer leaves from the sun-facing sides of the coffee hedgerow in Viçosa (Brazil) in August and October, when growth and photosynthetic rates are expected to be minimal and maximal, respectively, and in December, when temporary depressions in those variables are common. Regardless of light treatments, coffee leaves showed: (1) very low photosynthetic rates (generally below 2.5 μmol m−2 s−1), (2) chronic photoinhibition in August (dry, cool season) that was accompanied by strong loss of pigment concentration, and (3) discrete, dynamic photoinhibition in October and December (rainy, warm season). Compared with shaded leaves, sunlit leaves generally exhibited lower pigment concentration, lower quantum yield of electron transport, steeper inclinations and similar electron transport rate. Total ascorbate pool tended to be larger in sunlit than in shaded leaves (but with similar redox state), whereas activities of key antioxidant enzymes, as well as malondialdehyde accumulation and electrolyte leakage, were similar between those leaf types. As a whole, the photosynthetic apparatus of the coffee tree showed a low phenotypic plasticity to varying irradiance.Item A reliable methodology for assessing the in vitro photosynthetic competence of two brazilian savanna species: Hyptis marrubioides and Hancornia speciosa(Plant Cell, Tissue and Organ Culture (PCTOC), 2014-03-20) Otoni, Wagner Campos; Pereira, Flávia Dionisio; Costa, Alan Carlos; Rosa, Márcio; Megguer, Clarice Aparecida; Silva, Fabiano GuimarãesEvaluation of photosynthetic efficiency is critical for studies on plant responses to environmental conditions as well as for genotype selection; however, there is a lack of reliable and functional protocols for such assessments of plants cultured in vitro. In this study, we aimed to adapt the conventional methodology for measuring gas exchange of plants grown in vitro to analyze the effects of irradiance, flow rate, and air humidity on the photosynthetic rate in cultured plantlets of two ‘Cerrado’ species, namely Hyptis marrubioides and Hancornia speciosa plantlets. Chlorophyll (chl) a fluorescence and chloroplastidic pigment content were also assessed. The highest photosynthetic rates were observed at a photon flux density of 600 μmol m^−2 s^−1, with tube inlet airflow rates between 100 and 300 mL min^−1 and 80 % relative humidity in the inlet air. The electron transport rate curve, by means of chl a fluorescence, was similar to the photosynthetic rate response curve obtained with the infrared gas analyzer. These results demonstrate that both H. marrubioides and H. speciosa seedlings grown in vitro have a functional photosynthetic apparatus and respond to variations in measurement conditions, exhibiting substantial rates of CO2 assimilation under saturating irradiance conditions. The methodology proposed here can be adapted and applied to other species growing in vitro.Item Phenotypic plasticity in response to light in the coffee tree(Environmental and Experimental Botany, 2009-12) DaMatta, Fábio M.; Matos, Fábio S.; Wolfgramm, Ricardo; Gonçalves, Fábio V.; Cavatte, Paulo C.; Ventrella, Marília C.Phenotypic plasticity to light availability was examined at the leaf level in field-grown coffee trees (Coffea arabica). This species has been traditionally considered as shade-demanding, although it performs well without shade and even out-yields shaded coffee. Specifically, we focused our attention on the morpho-anatomical plasticity, the balance between light capture and excess light energy dissipation, as well as on physiological traits associated with carbon gain. A wide natural light gradient, i.e., a diurnal intercepted photon irradiance differing by a factor of 25 between the deepest shade leaves and the more exposed leaves in the canopy, was explored. Responses of most traits to light were non-linear, revealing the classic leaf sun vs. leaf shade dichotomy (e.g., compared with sun leaves, shade leaves had a lower stomatal density, a thinner palisade mesophyll, a higher specific leaf area, an improved light capture, a lower respiration rate, a lower light compensating point and a limited capacity for photoprotection). The light-saturated rates of net photosynthesis were higher in sunlit than in shade leaves, although sun leaves were not efficient enough to use the extra light supply. However, sun leaves showed well-developed photoprotection mechanisms in comparison to shade leaves, which proved sufficient for avoiding photoinhibition. Specifically, a higher non-photochemical quenching coefficient was found in parallel to increases in: (i) zeaxanthin pools, (ii) de-epoxidation state of the xanthophyll cycle, and (iii) activities of some antioxidant enzymes. Intracanopy plasticity depended on the suite of traits considered, and was high for some physiological traits associated with photoprotection and maintenance of a positive carbon balance under low light, but low for most morpho-anatomical features. Our data largely explain the successful cultivation of the coffee tree in both exposed and shade environments, although with a poor resource-use efficiency in high light.