Atributos estruturais foliares de três espécies de Qualea Mart. (Vochysiaceae) em uma área de cerradão na transição Cerrado-Floresta Amazônica

Qualea genus is commonly found in different phytophysiognomies of the Brazilian Cerrado, growing in open ecosystems to closed forest areas, under high irradiances, fires, low availability of nutrients and seasonal water deficit. We compared the leaf structural traits of Qualea grandiflora Mart., Qualea multiflora Mart., and Qualea parviflora Mart., in a cerradão area in the Cerrado-Amazonian forest transition. Leaf samples were collected at Mário Viana Municipal Biological Reserve, in Nova Xavantina, Mato Grosso state, Brasil, and processed according to the usual techniques for optical microscopy. Thick cuticle, stomatal ridges, stomata distributed between the stomatal crypts, density and distribution of tector trichomes, hypodermis, isobilateral mesophyll with few intercellular spaces, abundance of sclerenchyma associated to vascular bundles and the presence of vascular bundle sheath extensions are typical anatomic traits of xerophytic environments. We found qualitative structural differences among the species, with Qualea grandiflora having stomata with ridges distributed among stomatal crypts, and the presence of a hypodermis in Qualea multiflora, and Qualea parviflora. The results suggest that the species are xeromorphic in the region of Cerrado-Amazonian transition having leaf adaptive traits to deal with the environmental variations of their habitat.Qualea é um gênero comumente encontrado em diferentes fisionomias do cerrado brasileiro, crescendo em ecossistemas abertos até áreas florestais fechadas, sujeitos à alta irradiância, incêndios, baixa disponibilidade de nutrientes e deficit hídrico sazonal. Comparam-se aqui, atributos estruturais foliares de Qualea grandiflora Mart., Qualea multiflora Mart., e Qualea parviflora Mart., em uma área de cerradão na transição entre os biomas Cerrado-Amazônia. Amostras foliares foram coletadas na Reserva Biológica Municipal Mário Viana, Nova Xavantina, Mato Grosso – Brasil, e processadas segundo as técnicas usuais para microscopia óptica. Cutícula espessa, cristas estomáticas, estômatos distribuídos entre as criptas estomáticas, densidade e distribuição dos tricomas tectores, hipoderme, mesofilo isobilateral com poucos espaços intercelulares, abundância de esclerênquima associado aos feixes vasculares e presença de extensões de bainha do feixe vascular são atributos anatômicos típicos de ambientes xerófilos. Encontraram-se diferenças estruturais qualitativas entre as espécies, com Qualea grandiflora apresentando estômatos com cristas distribuídos entre criptas estomáticas, e a presença de hipoderme em Qualea multiflora, e Qualea parviflora.  Os resultados sugerem que as espécies são xeromórficas na região de transição Cerrado-Amazônia e que possuem atributos foliares adaptativos para lidar com as variações ambientais do seu habitat

Biomass and leaf acclimations to ultraviolet solar radiation in juvenile plants of Coffea arabica and C. Canephora

E-26/202.323/2017 E-26/202.759/2018 E-26/210.309/2018 E-26/210.037/2020 PV 312959/2019-2 PQ 300996/2016 PVS 00583/20 UID/04129/2020 Funding Information: The authors acknowledge Funda??o Carlos Chagas de Apoio ? Pesquisa do Estado do Rio de Janeiro (FAPERJ) (Grants E-26/202.323/2017, WPR; E-26/202.759/2018, E-26/210.309/2018 and E-26/210.037/2020, EC), CNPq (awarded the fellowships: PV 312959/2019-2, MR; PQ 300996/2016, EC), and PVS 00583/20, EC FAPEMA (Funda??o de Amparo ? Pesquisa e ao Desenvolvimento Cient?fico e Tecnol?gico do Maranh?o), all from Brazil. Support from Funda??o para a Ci?ncia e a Tecnologia I.P., Portugal, to J.C.R. through the units UID/04129/2020 (CEF) and UIDP/04035/2020 (GeoBioTec) is also greatly acknowledged. Publisher Copyright: © 2021 by the authors. Licensee MDPI, Basel, Switzerland.Despite the negative impacts of increased ultraviolet radiation intensity on plants, these organisms continue to grow and produce under the increased environmental UV levels. We hypothe-sized that ambient UV intensity can generate acclimations in plant growth, leaf morphology, and photochemical functioning in modern genotypes of Coffea arabica and C. canephora. Coffee plants were cultivated for ca. six months in a mini greenhouse under either near ambient (UVam) or reduced (UVre) ultraviolet regimes. At the plant scale, C. canephora was substantially more impacted by UVam when compared to C. arabica, investing more carbon in all juvenile plant components than under UVre. When subjected to UVam, both species showed anatomic adjustments at the leaf scale, such as increases in stomatal density in C. canephora, at the abaxial and adaxial cuticles in both species, and abaxial epidermal thickening in C. arabica, although without apparent impact on the thickness of palisade and spongy parenchyma. Surprisingly, C. arabica showed more efficient energy dissipation mechanism under UVam than C. canephora. UVam promoted elevated protective carotenoid content and a greater use of energy through photochemistry in both species, as reflected in the photochemical quenching increases. This was associated with an altered chlorophyll a/b ratio (significantly only in C. arabica) that likely promoted a greater capability to light energy capture. Therefore, UV levels promoted different modifications between the two Coffea sp. regarding plant biomass production and leaf morphology, including a few photochemical differences between species, suggesting that modifications at plant and leaf scale acted as an acclimation response to actual UV intensity.publishersversionpublishe

Morphology, ultrastructure and immunocytochemistry of Hypnea cervicornis and Hypnea musciformis-(Hypneaceae, Rhodophyta) from the coastal waters of Ceará, Brazil

AbstractBased on their morphological and physiological features, red algae comprise a complex and variable group of multiple genera, including Hypnea. In particular, the genus Hypnea J.V. Lamouroux (Cystocloniaceae, Rhodophyta) consists of approximately 54 species, including Hypnea cervicornis and H. musciformis. Lectins were described for both species; however, the localization of these proteins is still unclear. Therefore, this work aimed to characterize the morphology and ultrastructure of Hypnea cervicornis and H. musciformis, as well as localize their lectins at the subcellular level. Samples were collected at Praia do Pacheco (Fortaleza-CE) and processed for light, scanning and transmission electron microscopy, in addition to immunocytochemistry. The studied species presented cortical cell layers, subcortical cells and medullary cells. Based on ultrastructural analysis, these species presented vacuolated cortical cells, with a dense cytoplasm containing chloroplasts. The cell wall consisted of concentric microfibrils embedded in an amorphous matrix. Immunochemistry analysis showed the expression of lectins in the cytoplasm and cell walls. While the structure of the studied algae was similar to the description of other species of the genera under different conditions, this is the first record of algae lectin localization

Outer cell wall structure and the secretion mechanism of colleters of Bathysa nicholsonii K. Schum. (Rubiaceae)

ABSTRACT Secretory structures are formed by many types of plants and are present on numerous different organs. Among the many types of known secretory structures, colleters are predominant on plants of the Rubiaceae. One remarkable characteristic of secretory tissues is the export of exudates; however, the precise mechanism involved in this process is still unclear. To better understand the mechanisms of exudate externalization it is necessary to understand the ultrastructure and dynamics of the outer cell wall of the secretory structures during the secretory process, and so we investigated these aspects of the colleters of Bathysa nicholsonii. The outer cell wall (OCW) exhibits multiple layers: a basal polysaccharide rich layer; a cuticular membrane, which is subdivided into arborescent and reticulated layers; and a thin cuticle proper. The structural organization of the OCW is changed during secretion passage, which is mainly related to the development of a secretion accumulation site on the polysaccharide rich layer. Secretion dynamics is driven by the organization and disruption of the secretion accumulation site. The results show that the OCW of the colleters of B. nicholsonii is a dynamic structure with an active role in secretion externalization via constant structural reorganization directly related to secretion passage

Biomass and leaf acclimation to ultraviolet solar radiation in juvenile plants of Coffea arabica and C. canephora

Despite the negative impacts of increased ultraviolet radiation intensity on plants, these organisms continue to grow and produce under the increased environmental UV levels. We hypothesized that ambient UV intensity can generate acclimations in plant growth, leaf morphology, and photochemical functioning in modern genotypes of Coffea arabica and C. canephora. Coffee plants were cultivated for ca. six months in a mini greenhouse under either near ambient (UVam) or reduced (UVre) ultraviolet regimes. At the plant scale, C. canephora was substantially more impacted by UVam when compared to C. arabica, investing more carbon in all juvenile plant components than under UVre. When subjected to UVam, both species showed anatomic adjustments at the leaf scale, such as increases in stomatal density in C. canephora, at the abaxial and adaxial cuticles in both species, and abaxial epidermal thickening in C. arabica, although without apparent impact on the thickness of palisade and spongy parenchyma. Surprisingly, C. arabica showed more efficient energy dissipation mechanism under UVam than C. canephora. UVam promoted elevated protective carotenoid content and a greater use of energy through photochemistry in both species, as reflected in the photochemical quenching increases. This was associated with an altered chlorophyll a/b ratio (significantly only in C. arabica) that likely promoted a greater capability to light energy capture. Therefore, UV levels promoted different modifications between the two Coffea sp. regarding plant biomass production and leaf morphology, including a few photochemical differences between species, suggesting that modifications at plant and leaf scale acted as an acclimation response to actual UV intensityinfo:eu-repo/semantics/publishedVersio

Mitochondrial dysfunction associated with ascorbate synthesis in plants

International audienceMitochondria are the major organelles of energy production; however, active mitochondria can decline their energetic role and show a dysfunctional status. Mitochondrial dysfunction was induced by high nonphysiological level of L-galactone-1,4-lactone (L-GalL), the precursor of ascorbate (AsA), in plant mitochondria. The dysfunction induced by L-GalL was associated with the fault in the mitochondrial electron partition and reactive oxygen species (ROS) over-production. Using mitochondria from RNAi-plant lines harbouring silenced Lgalactone-1,4-lactone dehydrogenase (L-GalLDH) activity, it was demonstrated that such dysfunction is dependent on this enzyme activity. The capacity of alternative respiration was strongly decreased by L-GalL, probably mediated by redox-inactivation of the alternative oxidase (AOX) enzyme. Although, alternative respiration was shown to be the key factor that helps support AsA synthesis in dysfunctional mitochondria. Experiments with respiratory inhibitors showed that ROS formation and mitochondrial dysfunction were more associated with the decline in the activities of COX (cytochrome oxidase) and particularly AOX than with the lower activities of respiratory complexes I and III. The application of high L-GalL concentrations induced proteomic changes that indicated alterations in proteins related to oxidative stress and energetic status. However, supra-optimal L-GalL concentration was not deleterious for plants. Instead, the L-GalLDH activity could be positive. Indeed, it was found that wild type plants performed better growth than L-GalLDH-RNAi plants in response to high nonphysiological L-GalL concentrations

Mitochondrial ascorbate synthesis acts as a pro-oxidant pathway and down-regulate energy supply in plants

Attempts to improve the ascorbate (AsA) content of plants are still dealing with the limited understanding of why exists a wide variability of this powerful anti-oxidant molecule in different plant sources, species and environmental situations. In plant mitochondria, the last step of AsA synthesis is catalyzed by the enzyme L-galactone-1,4-lactone dehydrogenase (L-GalLDH). By using GalLDH-RNAi silencing plant lines, biochemical and proteomic approaches, we here discovered that, in addition to accumulate this antioxidant, mitochondria synthesize AsA to down-regulate the respiratory activity and the cellular energy provision. The work reveals that the AsA synthesis pathway within mitochondria is a branched electron transfer process that channels electrons towards the alternative oxidase, interfering with conventional electron transport. It was unexpectedly found that significant hydrogen peroxide is generated during AsA synthesis, which affects the AsA level. The induced AsA synthesis shows proteomic alterations of mitochondrial and extra-mitochondrial proteins related to oxidative and energetic metabolism. The most identified proteins were known components of plant responses to high light acclimation, programmed cell death, oxidative stress, senescence, cell expansion, iron and phosphorus starvation, different abiotic stress/pathogen attack responses and others. We propose that changing the electron flux associated with AsA synthesis might be part of a new mechanism by which the L-GalLDH enzyme would adapt plant mitochondria to fluctuating energy demands and redox status occurring under different physiological contexts.Instituto de Fisiología Vegeta