Water stress and temperature on germination and vigor of Handroanthus impetiginosus (Mart. ex DC)

ABSTRACT Water availability and temperature are among the main abiotic factors that influence seed germination and vigor, since they act directly on biochemical and physiological processes, which result in the production of the primary root. The objective of this study was to verify the effects of stress on germination and vigor of H. impetiginosus (‘ipê-roxo’) seeds under different temperatures and osmotic agents. The experimental design was completely randomized, in a 6 x 2 factorial scheme (osmotic potentials x temperatures) with four replicates of 25 seeds for each osmotic agent. In order to simulate water stress, polyethylene glycol (PEG 6000) and mannitol solutions were used and distilled water was used as control. Osmotic potentials of 0, -0.2, -0.4, -0.6, -0.8 and -1.0 MPa were evaluated at temperatures of 25 and 30 °C, under 8 h photoperiod. The variables analyzed were: germination, germination speed index, shoot length, root length, and total dry matter of seedlings. Simulated water stress affected seed germination and seed vigor of H. impetiginosus at both temperatures and osmotic agents from -0.6 MPa

Tolerance of castor bean cultivars under salt stress

ABSTRACT This study aimed to evaluate the tolerance of castor bean cultivars under salt stress during the initial growth stage. The experiment was set in randomized blocks, in a 5 x 4 factorial scheme, resulting in 20 treatments, 5 salinity levels (0.6-control, 1.2, 1.8, 2.4 and 3.0 dS m-1) and 4 castor bean cultivars (BRS Energy, LA Guarani, BRS Gabriela and IAC 028)] with 3 replicates. At 30 days after sowing, plants were evaluated for growth, dry matter accumulation and salt tolerance. Increased salinity levels in the water used for irrigation reduced the growth of all the studied cultivars. The salt tolerance of the studied castor bean cultivars follows the following order: BRS Energia > BRS Gabriela = IAC 028 > LA Guarani

Crescimento e produção da mamoneira BRS Paraguaçu sob irrigação, cobertura do solo e adubação orgânica

RESUMOObjetivou-se, neste trabalho, avaliar o crescimento e produção da mamona cv. BRS-188 Paraguaçu que tem sido recomendada para a região Nordeste do Brasil em relação à adubação orgânica, cobertura morta e níveis de reposição de água. Para isto foi desenvolvido o experimento em condições de campo, na cidade de Catolé do Rocha, PB, usando-se um delineamento experimental em blocos casualizados com fatorial 2 x 2 x 4, constituído de dois níveis de reposição de água em função da evapotranspiração da cultura - ETc de 100 e 50% no solo sem e com cobertura morta (Cenchrus ciliares L) e quatro níveis de biofertilizante bovino (0; 1,2; 2,4 e 3,6 L planta-1), aplicados ao solo totalizando 16 tratamentos com três repetições e dez plantas por tratamento totalizando 48 parcelas experimentais. As plantas irrigadas com 50% da ETc, no solo com cobertura morta e biofertilizante bovino na dose de 3,6 L planta-1atingiram áreas foliares e produções semelhantes às plantas cultivadas em sistema convencional sem cobertura e irrigadas com 100% da ETc

Tolerance of guava rootstocks under salt stress

ABSTRACT This study aimed to evaluate the tolerance of guava rootstocks under salt stress in the initial development stage. The experiment was conducted in a greenhouse in a randomized block design in a 5 x 3 factorial, consisting of five levels of irrigation water salinity (0.6, 1.2, 1.8, 2.4 and 3.0 dS m-1) and three guava rootstocks (‘Crioula’, ‘Paluma’ and ‘Ogawa’), with four replicates and four plants per replicate. Emergence, growth and phytomass accumulation were evaluated 30 days after sowing. Increased salinity restricts guava emergence, growth and phytomass accumulation, and the most drastic effects occur at levels higher than 1.8 dS m-1. The cultivar ‘Crioula’ is more tolerant to salinity in relation to ‘Paluma’ and ‘Ogawa’, and can be indicated as rootstock

Water salinity, nitrogen and phosphorus on photochemical efficiency and growth of west indian cherry

ABSTRACT The objective of this study was to evaluate the interaction between water salinity and doses of nitrogen and phosphorus on chlorophyll a fluorescence and on the growth of West Indian Cherry (‘acerola’) plants in the initial growth stage. The research was carried out in a protected environment, in lysimeters filled with Regolithic Neosol of loamy clay texture and low initial phosphorus content. The experiment was conducted in a randomized block design, arranged in a factorial scheme with two factors, five levels of electrical conductivity of the irrigation water - ECw (0.6, 1.4, 2.2, 3.0 and 3.8 dS m-1) and four proportions of the recommendation of phosphorus/nitrogen - P/N (100:100, 140:100, 100:140 and 140:140% P/N of recommendation), with three replicates, and each plot consisted of one plant. Water salinity above 2.2 dS m-1 decreases the quantum efficiency of photosystem II and the growth of west indian cherry plants. Increase in nitrogen and/or phosphorus supply improves the energy stability of west indian cherry plants by reducing the effects of salt stress on the quantum efficiency of photosystem II. The increase of 40% in the nitrogen dose increased the chlorophyll a fluorescence, but did not influence the plant growth

Germination and tolerance of cowpea (Vigna unguiculata) cultivars to water stress

ABSTRACT The objective of this study was to evaluate the tolerance of cowpea cultivars to water stress, during seed germination and seedling establishment. For this, a completely randomized experimental design was used in a factorial scheme consisting of nine cultivars of cowpea (BRS Guariba, BRS Potengi, BRS Itaim, BRS 17 Gurguéia, BRS Aracê, Paulistinha, Maratanã, Costela-de-Vaca and Canapu-Branco) and two levels of osmotic potential induced by PEG 6000 (0.0 MPa (control) and -0.4 MPa) in four replicates of 50 seeds. The variables analysed were germination, germination first count, root and shoot lengths, and dry matter accumulation of shoots and roots. The dissimilarity between the genotypes was also determined by Euclidean distance. Germination and initial development of cowpea cultivars are impaired by the reduction in the potential to -0.4 MPa. The cultivars BRS Guariba, BRS Aracê, Paulistinha and Canapu-Branco are the most tolerant to water stress, while BRS Potengi, BRS Itaim, BRS 17 Gurguéia, BRS Maratanã and Costela-de-Vaca are the most sensitive in the early development stage

Growth and production of dwarf coconut in saline-sodic soil under doses of potassium sulfate

ABSTRACT The objective was to study the influence of potassium sulfate doses applied to the soil on the growth and production of green dwarf coconut (Cocos nucifera L.) grown in saline-sodic soil. The experiment was conducted from January 2013 to January 2016, in a commercial plantation in the Sector 7 of the ‘Várzeas de Sousa’ Irrigation District, PB, Brazil, in saline-sodic Ebanic Vertisol. The experiment used coconut plants belonging to green dwarf variety, arranged in a 7.0 x 7.0 m rectangular shape, starting the third year in the production stabilization stage. The adopted experimental design was randomized blocks, evaluating five doses of potassium sulfate (K2SO4) (0, 0.52, 1.04, 2.08 and 4.16 kg plant-1 year-1), with four replicates of four plants each, totaling 20 experimental units. The K2SO4 doses positively influenced the growth and production of green dwarf coconut trees in saline-sodic soil. The highest growth in height and diameter of this coconut variety was obtained at the K2SO4 dose of 4.16 kg plant-1 year-1. The largest fruits and water volume in the first year of production were obtained with K2SO4 doses from 2.08 to 2.81 kg plant-1 year-1