Mobilização de água e conservação da viabilidade de embriões de sementes recalcitrantes de ingá (Inga vera Willd. subsp. affinis (DC.) T. D. Pennington)

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Influência do estresse hídrico e salino na germinação de urochloa decumbens e urochloa ruziziensis

Studies of the germination response of seeds subjected to artificial stresses are provided tools for better understanding of the survivability and adaptation of these species in natural stress conditions such as drought or saline soils, common in agricultural and forest regions, contributing significantly to the development of management strategies. Thus, the purpose of this study was to evaluate the possible effects of water and salt stress on germination of Urochloa decumbens and Urochloa ruziziensis. The test was conducted at the Faculty of Technology of São Paulo, campus of Capon Bonito. The seeds were sown with four replicates of 50 seeds in paper soaked in solutions with the potentials of 0.0, -0.2, -0.4 and -0.8 MPa, induced with polyethylene glycol (PEG 6000) and NaCl. The germination test was conducted at 25 degrees C in the presence of light, evaluating the first test score at seven days after sowing, and weekly germination (normal seedlings) until 35 days. We calculated the index of germination rate. The results allowed the conclusion that water stress causes a greater reduction in force, speed of germination and cumulative germination of seeds of U. decumbens and U. ruziziensis than salt stress. The species U. decumbens showed higher tolerance to water and salt stresses.

Osmocondicionamento de sementes de salsa (Petroselinum sativum Hoffm.) em diferentes potenciais hídricos

A germinação de sementes de salsa (Petroselinum sativum Hoffm.) é lenta e desuniforme, sendo a contagem do teste padrão de germinação recomendada aos 10 e 28 dias e a emergência em campo é relativamente longa, justificando o uso de técnicas que acelerem e uniformizem o processo germinativo: um método promissor é o osmocondicionamento. No presente trabalho, objetivou-se avaliar os efeitos dos diferentes potenciais de osmocondicionamento, com PEG 6000, na germinação de sementes de salsa e identificar o potencial osmótico ótimo para aumentar a germinação destas sementes. Sementes das cultivares Lisa e Portuguesa de dois lotes, adquiridas no comércio local foram osmocondicionadas pelo método de imersão direta das mesmas em soluções aquosas com potencial hídrico: 0,0, -0,5, -1,0 e -1,5 MPa, obtidos com a adição de PEG 6.000, sob aeração constante a 25ºC por 144 horas, como testemunha utilizaram-se sementes não osmocondicionadas. As variáveis analisadas foram: porcentagem de germinação (10 e 28 dias), velocidade de germinação e índice de velocidade de germinação. O osmocondicionamento aumenta a porcentagem e a velocidade de germinação de sementes de salsa, sendo que, o potencial osmótico indicado situa-se entre -1,0 e -1,5 MPa.

Fotossíntese e relações hídricas de duas cultivares jovens de seringueira

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Dimorphic cypsela germination and plant growth in Synedrella nodiflora (L.) Gaertn. (Asteraceae)

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Efeitos de extratos aquosos de assa-peixe sobre a germinação de três espécies de braquiária

Examinou-se o potencial alelopático da planta invasora de pastagem assa-peixe (Vernonia polyanthes), através dos efeitos dos extratos aquosos (concentração de 10%) da parte aérea, de raízes e de sementes sobre a germinação (porcentagem e velocidade) e o alongamento da radícula das gramíneas forrageiras Brachiaria humidicola, Brachiaria decumbens e Brachiaria brizantha cv. Marandu. O pH, a condutividade e o potencial osmótico foram determinados em cada extrato. A contribuição do potencial osmótico foi isolada através de cálculo, tendo por base os potenciais osmóticos dos extratos e da água e a equação de regressão que se ajustou a cada parâmetros, em função da variação do potencial osmótico na faixa de 0,0 a 0,4 MPa. Os bioensaios foram desenvolvidos em câmaras do tipo BOD, com temperatura controlada para 35/15oC (diurna/noturna) e fotoperíodo de 12 horas-luz (bioensaios de germinação), e temperatura constante de 35oC e fotoperíodo de 24 horas-luz (bioensaios de alongamento da radícula). Os resultados indicaram que tanto o pH como a concentração de cátions não contribuíram para os resultados encontrado. O assa-peixe evidenciou potencialidade alelopáticas que variaram em função da espécie receptora e da parte da planta doadora do extrato. A velocidade de germinação foi o indicador mais sensível aos efeitos dos extratos aquosos da assa-peixe.

Efeito alelopático de plantas daninhas e concentrações de capim-braquiária (Brachiaria decumbens) no desenvolvimento inicial de eucalipto (Eucalyptus grandis)

Com o objetivo de verificar possível efeito alelopático de 18 espécies de plantas daninhas sobre o crescimento inicial de Eucalyptus grandis, realizaram-se dois experimentos em casa de vegetação. No primeiro experimento, dentre 18 espécies de plantas daninhas testadas, Brachiaria decumbens (BRADC) demonstrou acentuada capacidade de reduzir o crescimento de Eucalyptus grandis, quando incorporada ao solo. No segundo experimento avaliou-se o efeito da adição no substrato de concentrações de matéria seca de BRADC sobre o crescimento inicial de mudas de E. grandis. A matéria seca triturada de BRADC foi incorporada ao solo nas concentrações de 0% (testemunha), 0,5%, 1,0%, 2,0% e 3,0% (p/p). Instalou-se também uma réplica do experimento, com adição de idênticas quantidades totais de carbono entre os tratamentos. O ajuste da quantidade de carbono foi feito através da adição de Sphagnum. Extraiu-se a solução do solo por meio de cápsulas de porcelana introduzidas nos vasos quando do transplante das mudas de eucalipto. As soluções foram coletadas ao final do experimento (39 dias após o transplante das mudas), sendo utilizadas para a determinação de pH, condutividade elétrica, potencial osmótico e para análise de teores de nutrientes. As mínimas proporções de BRADC, com efeito inibitório, foram de 0,5 e 1,0%, com e sem Sphagnum, respectivamente. Nestas duas condições, a área foliar média do eucalipto foi reduzida em 24 e 23%, respectivamente. As análises de solução do solo dos tratamentos permitiram concluir que os teores de nutrientes e as características químicas destes foram pouco alterados pelos tratamentos, sendo pouco provável que a redução do crescimento do E. grandis se deva às restrições nas quantidades de nutrientes disponíveis.

Germinação de sementes de Stryphnodendron Mart. osmocondicionadas

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Effect of calcium and magnesium silicate on the growth of the castor oil plant subjected to salinity levels

Salt stress decreases the osmotic potential of soil solution causing water stress, causing toxic effects in the plants resulting in injuries on the metabolism and nutritional disorders, thus compromising the plant growth, resulting in lower production. The calcium silicate and magnesium can perform the same function as limestone, besides providing silicon to plants, may also contribute to the resistance of plants to salt stress. Thus, the objective of this study was to evaluate the effect of calcium and magnesium silicate on the growth of the castor oil plant BRS Energia cultivated under saline conditions. This study evaluated plant height, stem diameter, number of leaves, leaf area, dry weight of shoot and root, and soil chemical characteristics. There was no interaction between factors of salinity level and of silicate level regarding the evaluated variables. There was a direct relationship between salinity levels and plant growth in height and stem diameter. The K concentration in soil were affected by salinity levels.

Efeitos do potencial alelopático de três leguminosas forrageiras sobre três invasoras de pastagens

Bioassays were carried out to identify and characterize the allelopathic potential effects of forage legumes leucena (Leucaena leucocephala), mineirão (Stylosanthes guianensis cv. Mineirão) and calopogônio (Calopogonium mucunoides) on germination and radicle elongation of the pasture weeds desmódio (Desmodium adscendens), guanxuma (Sida rhombifolia) and assa-peixe (Vernonia polyanthes). Aqueous seeds and shoot extracts were prepared in a concentration of 10% (w/v). The pH and osmotic potential were measured in each extract. The effects of the osmotic potential on the results were calculated considering the regression equations adjusted to the variations of osmotic potential in each parameter and the osmotic potential of the extracts. The results showed that the pH did not constitute in a source of variation of the results. The donor species indicated allelopathic potential that varied in function of donor and receiver species and part of the donor plant. The aqueous shoot extract of mineirão and calopogônio showed inhibition potential higher than the extract from seeds, while for leucena the effects more evident were obtained with the extract from seeds. Comparatively, the radicle elongation was a more sensitive indicator than germination to the effects of the extracts.The receiver species assa-peixe was the less sensitive to the effects of the extract.

Germinação de sementes de pinho-cuiabano sob deficiência hídrica com diferentes agentes osmóticos

The species Schizolobium amazonicum (Huber ex Ducke) commonly known as pinho-cuiabano or paricá, is one of the trees in Amazonian area used for plantings in degraded areas, reforestations and agroforestry systems. The present work evaluated the germinative behaviour of seeds of Schizolobium amazonicum in relation to the hydric stress, defining their levels of tolerance to those limitations in the environment. The seeds were collected from 30 trees in Alta Floresta-MT and submitted the dormancy treatment by submersion into water at 100°C for 1 minute; followed by treatment with fungicide Ridomil and Cercobin 0,25% each, then being left to germinate in a BOD camera at 30°C under a photoperiod of 12 hours. For evaluating the effect of different water potentials in the germinative process, polyethylene glicol (PEG 6000) was used and the salts NaCI and CaCl 2 used to simulate saline stress. The seeds were put to soak in potentials of 0 (control); -0.1 ; -0.2; -0.3; -0.4 and -0.5MPa. For each treatment 5 repetitions of 20 seeds were used in gerbox, placed between filter paper moistened with 20 mL of PEG, NaCI and CaCl 2 solutions. The solutions were changed at intervals of 24 hours for maintenance of the potential. The evaluations of percentages and germination speed were carry out daily for 8 days, being considered germinated the seeds that presented a 2mm root extension or longer. The data were submitted to analysis of variance and averages compared by the Tukey test at 5% probability. It was concluded that osmotic potentials between -0.4 and -0.5MPa inhibited the germination of seeds of Schizolobium amazonicum completely. The osmotic stress caused by CaCl 2, and PEG injured the germination more than did the stress caused by NaCl.

Germinação e vigor de sementes de crambe sob estresse hídrico

This study aimed to evaluate crambe seeds germination and vigor under water stress conditions induced by polyethylene glycol solutions. The seeds were germinated on substrate moistened with polyethylene glycol solutions, using the osmotic potentials of 0 (control), -0.2, -0.4, -0.6, -0.8, -1.0, -1.2 and -1.4 MPa. The seeds germination was evaluated by normal seedlings and root emission percentages. Vigor was evaluated by germination average time, relative frequency, velocity and synchronization index. It was observed that more negative osmotic potential caused significant reduction in crambe seed germination and vigor, and no normal seedlings was observed at potentials below -0.6 MPa.

O modelo 'hydrotime' pode descrever a resposta de sementes de feijão comum (phaseolus vulgaris l.) à temperatura e potenciais de água reduzidos

Germination parameters of the response to temperature and water potential from four common bean (Phaseolus vulgaris) lines based on thermal-time and hydrotime concepts were estimated to verify to what extent they can predict germination under different thermal and water conditions. The cultivars IPR Uirapuru and IAPAR 81 (drought-tolerant), and Grauna and Carioca (not tolerant) were used. The isothermal assays were performed in a temperature gradient block, and the assays with different osmotic potentials (PEG 6000) were performed in germination chambers. Seeds from drought-tolerant cultivars spent less time to germinate at supra-optimum temperatures than non-tolerant ones, and the cultivar Uirapuru (drought-tolerant) germinated faster in response to reduced Ψ and low temperatures. The parameter Ψb(50) did not discriminate between drought-tolerant and non-tolerant lines at the infraoptimum temperature range, but it can be used to identify drought-tolerant lines at high temperatures. In general, the hydrotime model reproduced the actual germination data relatively well, chiefly at higher temperatures. This study evidenced that the hydrotime model can be used to describe the germination of common bean seeds under reduced water potentials, and as a screening tool for drought-tolerant bean genotypes.

Influence of potassium and sodium nutrition on leaf area components in Eucalyptus grandis trees

Background and Aims: Recent studies showed a positive tree response to Na addition in K-depleted tropical soils. Our study aimed to gain insight into the effects of K and Na fertilizations on leaf area components for a widely planted tree species. Methods: Leaf expansion rates, as well as nutrient, polyol and soluble sugar concentrations, were measured from emergence to abscission of tagged leaves in 1-year-old Eucalyptus grandis plantations. Leaf cell size and water status parameters were compared 1 and 2 months after leaf emergence in plots with KCl application (+K), NaCl application (+Na) and control plots (C). Results: K and Na applications enhanced tree leaf area by increasing both leaf longevity and the mean area of individual leaves. Higher cell turgor in treatments +K and +Na than in the C treatment resulting from higher concentrations of osmotica contributed to increasing both palisade cell diameters and the size of fully expanded leaves. Conclusions: Intermediate total tree leaf area in treatment +Na compared to treatments C and +K might result from the capacity of Na to substitute K in osmoregulatory functions, whereas it seemed unable to accomplish other important K functions that contribute to delaying leaf senescence. © 2013 Springer Science+Business Media Dordrecht.

Condicionamento fisiológico de sementes, componentes produção e produtividade de soja

Pós-graduação em Agronomia (Agricultura) - FCA