Search

Barbacenia graminifolia is a Velloziaceae species endemic to the campos rupestres in Serra do Cipó, Minas Gerais state (Brazil). This biome is characterised by high irradiance and limited water conditions. Unlike other resurrection plants, B. graminifolia can maintain a high hydric status (80%) after 28 days of water suppression before desiccation. We investigated the physiological and metabolic mechanisms associated with structural changes that allow B. graminifolia to maintain hydration under a prolonged water deficit and to recover after desiccation. After 30 days of water deficit, desiccated plants exhibited chlorophyll degradation, a 178.4% and 193.7% increase in total carotenoids and MDA, respectively, and twice the CAT and APX activity compared to hydrated plants. The metabolite profile showed increased amino acids, carbohydrates, saturated fatty acids and benzoic acids during dehydration, while trichloroacetic acid cycle acids were higher in hydrated and rehydrated plants. Anatomical and ultrastructural data corroborated the physiological and metabolic changes and revealed the presence of mucilaginous cells with high water retention capacity. Our data indicated that combined strategies of assimilatory metabolism shutdown, accumulation of compatible solutes and antioxidant compounds, increase in hydrophilic molecules, changes in the composition of membrane lipids and remodelling of cell organelles conditioned the efficiency of B. graminifolia in delaying water loss, tolerating further desiccation and quickly recovering after rehydration. These attributes evidence that this species is well adapted to cope with adverse environmental conditions, mainly directing the metabolism to an efficient antioxidant response and improving its capacity to retain water during the dry season. more...

Flooding negatively influences the growth and development of several plant species. Here, we show that the flood tolerance of young Handroanthus chrysotrichus plants involves growth deficit, carbon assimilation reductions, starch remobilization, and energy regulation. The effect of hypoxia was evaluated in a controlled experiment consisting of plants subjected to normoxia and water-logging, with later recovery. We measured morphological changes, gas exchange, photosynthetic pigments, soluble carbohydrates and starch contents, the activity of the enzymes alcohol dehydrogenase (ADH), and pyruvate decarboxylase (PDC), and ATP and ADP levels. While control plants showed normal appearance and growth, flooded plants exhibited a drastic decrease in growth, necrosis of some root tips, hypertrophic lenticels on the stems, and foliar chlorosis. Oxygen deprivation in root cells led to a significant decrease in stomatal conductance. The low A more...

Drought is considered the main abiotic stress because it influences the distribution of plant species and limits the productivity of ecosystems. The aim of this study was to evaluate the effects of drought on physiological and biochemical parameters during the initial development of Vatairea macrocarpa, a native cerrado species. Plants were subjected to daily watering (control); suppression of watering during 90 days with field capacity (fc) 50% and 25% and then followed by rewatering. Relative leaf water content (RWC), gas exchange, photosynthetic pigments content, carbohydrate and amino acids content, antioxidant activities and growth were recorded. The RWC decreased according to the soil water restriction, causing reduction in stomatal conductance and decrease of 76.4% in net photosynthesis in plants submitted to 25% fc. Water restriction decreased the chlorophyll content, however increased carotenoid content and also improved the antioxidant activities of superoxide dismutase (SOD), ascorbate peroxidase (APX) and catalase (CAT). In addition, high levels of sugars (sucrose, raffinose) and amino acids (proline, tryptophan, valine, glutamine and GABA) were detected in drought stressed plants, contributing to osmoregulation and as sources of carbon and nitrogen after rehydration. Decreases in carbon assimilation promoted a reduction of the leaf area, however an increase in the root surface area was observed. After rewatering, the analized parameters became similar to the control plants indicating that the severe water stress did not impair the survival of young plants. Instead, adjustments were made to protect them against drought such as the maintenance of the assimilatory metabolism at minimal levels. Made available in DSpace on 2017-11-14T23:19:58Z (GMT). No. of bitstreams: 1 Physiologicalandbiochemicalchanges.pdf: 1766127 bytes, checksum: 80711c8791f68e18ffe54688d0ba7d4c (MD5) Previous issue date: 2017-11-14 more...

Zinc (Zn) participates in numerous metabolic processes in plants under normal concentrations. In polluted environments, plants can develop different strategies to cope with Zn excess. Zinc stress can alter the photosynthetic metabolism and increase the production of reactive oxygen species (ROS). Therefore, this study aimed at evaluating the zinc tolerance of Handroanthus impetiginosus (Pink Ipe) and Tabebuia roseoalba (White ipe) under greenhouse conditions. We assessed the effects of different Zn concentrations on photosynthetic performance and maximum quantum yield (F v /F m ), pigment concentrations, antioxidant enzyme activities, content of macro and micronutrients in the tissues and growth parameters. Both species showed different strategies to tolerate Zn stress. Pink ipe plants accumulated larger amounts of zinc in the roots without showing severe damage in the aerial parts. Meanwhile, White ipe plants mobilized Zn to the aerial parts and showed less accumulation in the roots, with major effects on leaves. Growth was negatively affected in both plant species, which was evidenced by the decline in photosynthetic rates, most likely due the adverse effect of Zn on the electron transport chain. Upregulation of photoprotective mechanisms such as the increase in anthocyanin content and activities of antioxidant enzymes minimized the H 2 O 2 content and oxidative damage in the leaves. A decrease in nitrogen content in stems and leaves and in phosphorus and potassium concentrations in roots were observed especially in the White ipe plants. Our results demonstrated that roots and leaves of Ipe plants accumulate high concentrations of Zn, which evidences the potential of these species as candidates for bioremediation in Zn-polluted Cerrado areas. more...

Climatic change forecasts suggest an increase in the frequency and severity of droughts that would affect the plant water relations and the characteristics of terrestrial ecosystems. We examined how juvenile plants of D. alata use physiological and metabolic changes to resist the drought effects in the natural environment. This study was conducted in a remnant area of Cerrado, and the effect of seasonality was assessed by the end of the dry season, at the beginning of the rainy season and during the rainy season. The decrease in rainfall resulted in changes in the plant water status, with a significant decrease in the leaf RWC, Ψs, and Fv/Fm ratio, with a concomitant increase in the VPD. The increase in the carbohydrate content resulted from starch degradation contributed to osmotic adjustment, whereas increases in proline, tryptophan, aspartate, and other derived amino acids also promoted the balance in the C/N metabolism and the maintenance of energy homeostasis during dry season. The efficiency of ROS cleaning by the antioxidant enzymes related to the AsA-GSH cycle minimized the negative impact of dehydration and prevented oxidative and nitrosative damage to the leaves of D. alata, improving its performance to cope with water deficit. more...

Invasive grasses inhibit the growth of other plant species, and water deficit is one of the major competition problems for native vegetation. We evaluated whether the presence of Brachiaria brizantha cv. Piata has a negative influence on the competition for water and nutrients between Anadenanthera macrocarpa and Anadenanthera colubrina (Angico species). The interspecific competition was evaluated using a randomized experimental design with the following treatments: 1) free competition (FC), in which the native species were cultivated without the grass presence and 2) under competition (UC), in which the native species grew together with the invasive grass for 120 days. We analysed the water relationships in the two species, the effect of water limitation on the antioxidant stress, the nutritional content of shoots and roots, the relative competition intensity (RCI) and growth. The presence of Piata grass reduced the soil moisture causing a decrease of 21.9% and 29.5% in the relative water content (RWC) of leaves for A. macrocarpa and A. colubrina, respectively. For the two Angico species, the quantum efficiency of Photosystem II (ΦPSII) decreased with reduction of RWC leaf, resulting in the H2O2 increase (57.5% at day 30 for A. colubrina and 38.8% at day 120 for A. macrocarpa). The oxidative stress was evidenced by the increase in the superoxide dismutase (SOD), catalase (CAT) and ascorbate peroxidase (APX) activities in leaves and roots of both young native trees. In the UC treatment, reductions in water uptake also led to a decrease in root absorption of N, P, K, a Mg and low transport of these nutrients to the leaves of both Angico species. A. macrocarpa and A. colubrina showed less growth caused by limitation of water uptake, but the joint activity of the physiological and biochemical adjustments provided competitive ability. more...

Made available in DSpace on 2018-11-26T17:44:33Z (GMT). No. of bitstreams: 0 Previous issue date: 2017-12-01 Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) Rocky outcrops represent the diversity center of vascular desiccation tolerant (DT) plants. Vegetation in this environment is exposed to an extended dry season and extreme conditions due to rocky soils and high sun exposure. In this study, we demonstrated that Pitcairnia burchellii, a bromeliad from rocky outcrops, tolerates intense desiccation for about 90 days due to strategies as accumulation of compatible osmolytes and antioxidant substances together with leaf morphological changes. In dehydrated plants, an increase in antioxidant activity was observed and the vacuolization of parenchyma cells was accompanied by proline accumulation in leaves and rhizomes. Precursors related to phenylpropanoid pathway increased significantly during plant dehydration. Accordingly, increases in anthocyanin and phenolic contents as well as lignin deposition were observed in leaves of dehydrated plants. Cell divisions and a decrease in stored starch were observed in the rhizomes indicating starch mobilization. Anatomical analyses revealed the presence of a more developed water-storage tissue in dehydrated leaves. During desiccation, leaves curl upwards and the adaxial V deep water-storage tissue is supported by two larger lateral vascular bundles. Cell wall folding and an increased proportion of arabinose-containing polymers was observed in leaves under dehydration, suggesting increasing of cell wall flexibility during desiccation. Such biochemical and morphological changes are consistent with the ability of P. burchellii to tolerate intense desiccation and behave as a resurrection species. Inst Bot, Nucleo Pesquisa Fisiol & Bioquim Plantas, Sao Paulo, SP, Brazil Univ Estadual Paulista, Inst Biociencias, Dept Bot, Rio Claro, SP, Brazil Univ Estadual Campinas, Programa Posgrad Biol Celular & Estrutural, Campinas, SP, Brazil Univ Estadual Paulista, Inst Biociencias, Dept Bot, Rio Claro, SP, Brazil FAPESP: 2012/16332-0 FAPESP: 2012/14339-7 more...

Water availability in soil modulates plant acclimatisation responses in different habitats. In this study, we evaluated the effect of water deficit on the physiological, biochemical and growth responses of Vachellia farnesiana. Open environment experiment was conducted during 90 days and two conditions of hydration were tested: full hydration (H) and water deficit (WD) at 25% of field capacity. The relative water content (RWC) of the leaves under WD showed a 30.2% decrease (P < 0.01), compared with the hydrated plants at 30 days. A decrease in the RWC led to decrease in the osmotic potential (Ψs), quantum yield of PSII (Fv/Fm) and lesser content of chlorophylls a and b under WD. A greater carotenoid content and simultaneous increase in the content of proline, H2O2 and phenolic compounds of the leaves was also observed in WD. Water deficit also promoted differences in the nitrogen, phosphorus, and potassium content of the leaves when compared with hydrated plants. Although they showed growth deficit, plants of V. farnesiana demonstrated resistance to WD through physiological and biochemical adjustments. more...

Pitcairnia burchellii is a bromeliad found in Brazilian rocky outcrops. Given its capacity to cope with soil scarcity and extreme water deficit, this species is thought to behave as a resurrection plant. Herein, we evaluated water relations, gas exchange, the content of pigments, sugar and abscisic acid (ABA), and the metabolic profile of P. burchellii plants during desiccation and recovery after rehydration. During water withholding, the net photosynthesis rate, transpiration, and chlorophyll content decreased rapidly whereas leaf and root soluble carbohydrates increased presumably due to the starch breakdown. These drought-induced physiological changes were associated with a significant increase in leaf ABA content. Marked changes in amino acids, sugar alcohols such as galactinol and erythritol and dehydroascorbic acid levels were observed after desiccation. Our findings indicate that P. burchellii tolerates leaf protoplasmic dehydration and recovers its normal cellular metabolism within a short period after rehydration, as described for other resurrection species. However, plants of P. burchellii subjected to long-term desiccation presented a long delay in foliar tissue dehydration when compared with soil moisture loss, suggesting a cooperative role of the rhizome to cope with extreme water deficit. more...

O objetivo deste estudo foi realizar a análise florística e fitossociológica preliminar em um remanescente de vegetação na área de entorno do Córrego Criminoso, visando subsidiar futuros projetos de recomposição da vegetação. A área total do remanescente foi determinada com o auxílio de GPS e dos programas Pathfinder e Autocad. Amostragens de indivíduos com CAP maior ou igual a 20 cm foram realizadas em 20 parcelas de 300 m² distribuídas na área. Foram encontradas 26 famílias botânicas contendo 36 gêneros e 49 espécies. A família Leguminosae foi a mais rica em espécies, seguida da família Annonaceae. A espécie Xylopia aromatica foi a mais freqüente, apresentando valores de IVI e IVC de 99,77 e 85,73, respectivamente. Observou-se que mais de 50% das espécies presentes na área são pioneiras ou secundárias, sendo cinco consideradas típicas de matas ciliares: Tapirira guianenses, Cecropia pachystachya, Terminalia argentea, Ocotea pulchellae e Luehea grandiflora. O remanescente de vegetação do entorno do Córrego Criminoso encontra-se fortemente degradado, necessitando de ações de manejo específicos nos fragmentos vegetados e nas áreas destituídas de vegetação, cujas recomendações são propostas. The aim of this study was to complete a preliminary, floristic, phytosociological analyses of a vegetation remnant in the Criminoso Stream Basin, in order to provide data for future projects focusing on vegetation recovery. The total area of the remnant was determined using a GPS and the software Pathfinder and Autocad. Samples of individuals larger or equal to 20 cm CBH were made in 20 quadrats that were 300 m². Thirty-six genera and 49 species, within 26 botanical families, were found. The family Leguminosae was the richest in species, followed by the Annonaceae. Xylopia aromatica was the most frequent species, presenting values of IVI and IVC of 99.77 and 85.73, respectively. More than 50% of the species present in the area are pioneer or secondary taxa, and five of these species are considered typical of riparian forests: Tapirira guianenses, Cecropia pachystachya, Terminalia argentea, Ocotea pulchellae and Luehea grandiflora. The vegetation remnant of the Criminoso Stream Basin is strongly degraded and needs specific management plans for the fragments that have and lack vegetation, whose recommendations are proposed. more...

A composição das espécies de formigas dentro das comunidades é influenciada pela distribuição dos recursos a serem explorados, e também pelas estratégias utilizadas por esses indivíduos para a sua obtenção. O objetivo deste estudo foi investigar a importância da integridade do hábitat para a distribuição e diversidade da comunidade de formigas existentes em três fitofisionomias: Mata Ciliar, Cerrado Sensu Stricto e Cerradão. Foram utilizadas armadilhas do tipo pitfal com iscas, dispostas ordenadamente ao longo de um transecto nos três pontos escolhidos. Foram amostrados 60.266 indivíduos, distribuídos em 4 subfamílias com 14 morfoespécies. Foi observada diferença significativa entre o número de indivíduos e a época de coleta, com 29% capturados durante a seca e 71% no período chuvoso. Os maiores índices de diversidade foram obtidos para a área de Cerradão nos dois períodos de coleta denotando a maior riqueza de espécies desta fitofisionomia quando comparada aos dois outros pontos. more...

A seca é um dos mais severos estresses abióticos que influenciam a distribuição de espécies arbóreas e limitam a produtividade dos ecossistemas. O objetivo deste estudo foi avaliar o crescimento inicial de mudas de pau-terra-do-cerrado em diferentes regimes hídricos em casa de vegetação visando à produção de mudas para recuperação ambiental. O experimento foi conduzido em casa de vegetação da Universidade Estadual de Mato Grosso do Sul, Coxim-MS. Os tratamentos de estresse corresponderam a 100% da capacidade de campo (controle), estresse moderado (50% da capacidade de campo) e estresse severo (12,5% da capacidade de campo). Os parâmetros avaliados foram comprimento da parte aérea e parte radicular, diâmetro de colo, área foliar (AF), relação raiz/parte aérea (R/PA), matéria seca das raízes, parte aérea e total, TAL e TCR. Houve correlação significativa entre o crescimento e a disponibilidade hídrica do substrato, onde as plantas do tratamento estresse moderado apresentaram maiores taxas de crescimento quando comparados ao estresse severo. Foi observada alta razão parte aérea subterrânea principalmente em 12,5 de CC. Para as variáveis de AF, TAL e TCR, o tratamento de estresse severo foi o único que apresentou decréscimo linear de assimilação a partir de 60 dias refletindo no crescimento das plantas.&nbsp more...