Seed Quality and Vigor of Germination of Moringa oleífera Lam. in Saline Stress

Abstract Moringa oleifera Lam., is a tree species that has several purposes of use, standing out in the recovery of degraded areas and the use of seeds as biodsorbents in water clarification. However, ony a little is known about the behavior of seed germination under saline conditions, common in soils and water in the Brazilian Northeast. Thus, the objective was to evaluate the increment of water during the soaking and seed germination of M. oleífera that were submitted to different electrical conductivity of the irrigation water. The work was developed following a completely randomized design, with stress simulation employing saline solutions at the concentrations of 0.0; 3.0; 6.0 and 9.0 dS m-1. To determine the soaking curve, the water increment of the soaked seeds in the different saline solutions was monitored at regular intervals with four replications per treatment. To characterize the physiological quality of the seeds, the percentage, first count, speed index, average time and average germination speed were evaluated. The M. oleífera is tolerant to the effect of salinity during the germination phase, however seed vigor is reduced as a function of increased salinity. Soaking the seeds makes begin the phase II of the germination process around 10 hours and extends for up to 50 hours, when phase III begins, they absorb approximately 0.2 g of water and require 86 hours for germination. Salinity reduces the absorption and increase of water in the seeds.

Monopotassium phosphate (KH2PO4) and salicylic acid (SA) as seed priming in Vicia faba L. and Vicia sativa L. / Fosfato de monopotássio (KH2PO4) e ácido salicílico (SA) como primagem de sementes em Vicia faba L. e Vicia sativa L.

The first experiment was conducted to evaluate the impact of seed priming on germination behavior and seedling establishment in Vicia faba and Vicia sativa, for that, seeds priming was done using SA (100 µM) and KH2PO4. In order to determine the optimal concentration of KH2PO4 for improving germination, different concentrations were used: 25 µM, 50 µM, and 100 µM. The best germination behavior and seedling establishment were obtained with 25 and 50 µM KH2PO4, respectively for Vicia faba and Vicia sativa. Moreover, data showed that 100 µM of SA improved seed germination as well as the seedling establishment for both species. The second experiment was carried out to investigate the influence of seed priming for improving phosphorous (P) deficiency tolerance. To do, seedling obtained from primed and nonprimed seeds were grown in a hydroponic culture system with three different treatments: control (C, medium containing sufficient P concentration: 360 µM KH2PO4), direct phosphorus-deficient (DD, medium containing only 10 µM KH2PO4), and induced P deficiency by bicarbonate (ID, medium containing sufficient P concentration: 360 µM KH2PO4 + 0.5 g L-1 CaCO3 + 10 mM NaHCO3). Furthermore, the role of exogenous SA applied to P deficiency tolerance enhancement was explored. Seed priming or the exogenous application of SA significantly reduced the severity effect of P deficiency. In fact, the pretreated plants were observed more tolerant to P deficiency as reflected from the significant increase in plant biomass, P uptake, and an efficient antioxidant system. Overall, this paper highlights the beneficial effect of seeds priming or the exogenous application of SA in the improvement of plant tolerance to phosphorus deficiency.

A deficiência de fósforo (P) é um fator ambiental adverso comum que limita a produção agrícola em todo o mundo. Este estudo é uma avaliação do efeito benéfico da técnica de priming de sementes para tolerância à deficiência de P em Vicia faba e Vicia sativa. Para avaliar o impacto do condicionamento das sementes no comportamento germinativo de Vicia faba e Vicia sativa, suas sementes foram imersas em diferentes concentrações de KH2PO4 (25 µM, 50 µM e 100 µM) e em 100 µM de ácido salicílico (SA) por 24 h. Os resultados obtidos definiram KH2PO4 50 µM (para Vicia sativa) e KH2PO4 25 µM (para Vicia faba) como as concentrações ótimas que garantem uma melhor germinação das sementes. Além disso, os dados mostraram que a SA melhora a germinação de sementes e o estabelecimento de mudas. Posteriormente, para investigar a contribuição dessa técnica no aumento da tolerância à deficiência de P, sementes preparadas e não preparadas foram cultivadas em solução hidropônica com três tratamentos diferentes: controle (C, meio contendo concentração suficiente de P: KH2PO4 360 µM), deficiente em fósforo direto (DD, meio contendo apenas 10 µM de KH2PO4) e deficiência induzida de P por bicarbonato (ID, meio contendo concentração suficiente de P: 360 µM de KH2PO4 + 0,5 g l-1 de CaCO3 + 10 mM de NaHCO3). Além disso, o papel da SA exógeno aplicada no aumento da tolerância à deficiência de P foi explorado. A preparação das sementes ou a aplicação exógena de SA reduziu significativamente o efeito da severidade da deficiência de P. De fato, as plantas pré-tratadas foram observadas mais tolerantes à deficiência de P, refletidas no aumento significativo da biomassa da planta, na absorção de P e em um eficiente sistema antioxidante. No geral, este artigo destaca o efeito benéfico da priming de sementes ou a aplicação exógena de SA na melhoria da tolerância das plantas à deficiência de fósforo.

Vigor and tolerance of cowpea (Vigna unguiculata) genotypes under salt stress / Vigor e tolerância de genótipos de feijão-caupi (Vigna unguiculata) sob estresse salino

Saline stress is a frequent phenomenon in the arid and semi-arid regions of the globe, affecting the agricultural production of these regions, and it is necessary to use strategies that minimize the impacts of saline stress under agriculture. This requires the incorporation of species, variety and genotypes tolerant to increase agricultural production in those regions. This study aimed to evaluate germination and initial growth of cowpea genotypes under salt stress. The experimental design was completely randomized in 19 x 3 factorial scheme, composed of nineteen cowpea cultivars and three osmotic potentials, with four replicates of 50 seeds each. The germination test lasted for eight days, when the seeds were evaluated for germination percentage, germination speed index, length of shoot and root, accumulation of dry mass of shoot and root. The increase in salinity affected germination and initial growth of the cowpea genotypes. The genotypes 6 - MNCO2-689F-2-8, 10 - MNCO2-675F-4-10, 12 - MNCO3-737F-5-9, 16 - MNCO2-677F-2, 18 - BRS-Pajeú and 19 ­ Paulistinha exhibited higher tolerance to salt stress in the stage of germination and initial growth. The genotypes 11 - MNCO2-675F-9-5, 13 - BRS-Tumucumaque, 15 - MNCO3-736F-7 and 17 - BR17-Gurgueia were more susceptible to the effects of salt stress in the stage of germination and initial growth.

O estresse salino é um fenômeno frequente em regiões áridas e semiáridas do globo, afetando a produção agrícola dessas regiões, sendo necessário lançar mão de estratégias que minimizem os impactos do estresse salino sob agricultura, para isso é necessário a incorporação de espécies, variedade e genótipos tolerantes para aumentar a produção nessas regiões. Assim, objetivou-se com esse trabalho avaliar a germinação e o crescimento inicial de genótipos de feijão-caupi sob estresse salino. Utilizou-se de um delineamento experimental inteiramente casualizado em esquema fatorial 19 x 3, constituído de dezenove cultivares de feijão-caupi e três potenciais osmóticos, com quatro repetições de 50 sementes cada. O teste de germinação teve duração de oito dias, quando as sementes foram avaliadas a quanto à percentagem de germinação, índice de velocidade de germinação, comprimento da parte aérea e da raiz, acúmulo de massa seca da parte aérea e da raiz. O aumento da salinidade afetou a germinação e o crescimento inicial dos genótipos de feijãocaupi. Os genótipos 6 - MNCO2-689F-2-8, 10 - MNCO2-675F-4-10, 12 - MNCO3-737F-5-9; 16 - MNCO2-677F-2; 18 - BRS-Pajeú e 19 ­ Paulistinha apresentaram maior tolerância ao estresse salino na fase de germinação e crescimento inicial. Os genótipos 11 - MNCO2-675F-9-5, 13 - BRS-Tumucumaque; 15 - MNCO3-736F-7 e 17 - BR17-Gurgueia foram mais suscetíveis aos efeitos do estresse salino na fase de germinação e crescimento inicial

Ação inibitória do endosperma na germinação in vitro de embrião zigótico de pinhão manso / Inhibitory action of endosperm on in vitro germination of physic nut zygotic embryo

A busca por protocolos de micropropagação de pinhão manso tem resultado em relatos sobre dificuldades na germinação in vitro de sementes recém colhidas. Nesse sentido, levantou-se a hipótese da dormência estar relacionada com a presença do endosperma. Objetivando investigar a influência do endosperma no desenvolvimento in vitro de embriões zigóticos de pinhão manso, extratos puros e filtrados de endosperma de sementes recém colhidas e armazenadas por 50 e 100 dias foram adicionados ao meio MS, no qual foram colocados embriões zigóticos isolados ou contendo endosperma. Foi possível observar que a presença do endosperma junto ao embrião exerce uma inibição à retomada do desenvolvimento do embrião. Ademais, a adição de extratos do endosperma no meio de cultivo reduziu sobremaneira o desenvolvimento dos embriões, evidenciando que além de provável inibição física, o endosperma pode contribuir com inibidores químicos no processo de germinação. Essas observações estão baseadas no perfeito desenvolvimento dos embriões, quando estes foram adicionados isolados ao meio MS, desprovido do extrato.

Researches on physic nut micropropagation have resulted in reports about difficulties in the process of in vitro germination of fresh seeds, and we hypothesized that this dormancy is related to endosperm presence. Aiming to investigate the influence of the endosperm presence on in vitro development of zygotic embryos of physic nut, pure and filtered extracts of the endosperm of newly harvested and stored seeds for up to 100 days were added to MS medium, in which zygotic embryos were added alone or attached to the endosperm. It was observed that the endosperm presence attached to the embryo seems to establish dormancy to the restart of the embryo development. Moreover, addition of endosperm extracts into the MS medium greatly reduced the embryos development, supporting the idea that in addition to probable inhibition physics, the endosperm may contribute to chemical inhibitors in the germination process. All these idea were supported by perfect embryo development when it was added to MS medium without endosperm structure or extract.

Detection of lipid peroxidation and cytotoxicity induced by aluminium (Al) and cobalt (Co) ions in barbunia root tip cells.

The aim of this study was to investigate the cytotoxic effects of different concentrations of Aluminium (Al) and Cobalt (Co) heavy metal ions on Phaseolus vulgaris L. cv. Barbunia (Fabaceae) root tips. We used the germination percentage (GP), root length (RL), weight gain (WG) and micronucleus (MN) frequency as indicators of cytotoxicity, and correlated these data with statistical parameters. Additionally to the cytogenetic analysis, lipid peroxidation and DNA analyses were performed in root tips of barbunia seeds treated with Al and Co metals. The seeds were divided into five groups as control, Al and Co treatment groups. They were treated with 25 and 50 ppm doses of Al and Co during 7 days. The results indicated that there was an alteration in the GP, RL, WG and MN frequency depending on the treatment dose in the seeds exposed to Al and Co metal ions when compared with the controls. Al and Co metal ions at both the doses significantly reduced the GP, RL and WG in seeds of all the treatment groups. The highest GP was observed in seeds of the control group (in proportion as 96%). 25 and 50 ppm doses of Co and Al caused 30 , 50 and 42, 64% decrease of seed germination, respectively. In the control group, the final weights of all the seeds increased about 1.31 g when compared to initial weight. The mean RL of control seeds were measured as 3.71 cm at the end of experimental period. In Co and Al groups, the final weights of seeds increased about 0.34 g and 0.19 g according to initial weight at 50 ppm dose, respectively. But, Al and Co ions caused a dose-dependent increase in the frequency of MN. The highest frequency of MN was observed at 50 ppm dose of Al and least frequency of MN was observed at 25 ppm dose of Co. Besides, 25 and 50 ppm concentrations of Al and Co significantly enhanced the lipid peroxidation and caused an increase in malondialdehyde (MDA) levels at both the doses. In roots treated with 25 and 50 ppm doses of Al, the increase of MDA was about 62 and 136% according to control, respectively. In Co-treated roots, the increase of MDA was about 31 and 91% according to the control at 25 and 50 ppm doses, respectively. The investigated parameters (except MN and MDA) were higher in the seeds exposed to Co than the seeds treated with Al. Moreover, it was observed that the yields of DNA in the seeds treated with Al and Co metals were lower than recorded in the controls. Hence, DNA yields exposed to Al and Co were run ahead on agarose gel according to the control group. The results of the present study indicate that Al and Co metal ions have toxic effects on barbunia root tip cells, and the selected parameters such as the GP, RL, WG, MN and MDA are very sensitive and useful biomarkers for biomonitoring these effects.

Viabilidade e superação da dormência em sementes de Araçá-boi (Eugenia stipitata ssp. sororia)

Eugenia stipitata ssp. sororia McVaugh - Myrtaceae is a small Amazonian fruit tree with considerable economic potential. The present work investigated the effects of dehydration on seed viability and evaluated methods of overcoming seed dormancy by mechanical scarification (by peeling and sanding). The physiological quality of seeds is affected by reduction in moisture content. Seeds show recalcitrant behaviour with a critical moisture content between 58,8 and 47,1 %. No seeds survived dehydration to moisture contents of less than or equal to 25,76%. In view of the detrimental effects of drying, seeds should preferably be sown immediately after being extracted and cleaned. The seed integument offers mechanical resistance to expansion of the embryo. Total removal of the integument proved to be the most efficient method of overcoming dormancy since it eliminates resistance in the region where the embryo normally breaks through. The average time for emergence was 66 days and the final percentage emergence was 96%. Simple abrasion of the integument caused mechanical injury to the seeds with adverse consequences on emergence and vigour.

O araçá-boi (Eugenia stipitata ssp. sororia McVaugh - Myrtaceae) é uma frutífera amazônica com potencial agroindustrial. O presente trabalho verificou os efeitos da desidratação sobre a viabilidade de sementes e avaliou métodos de escarificação mecânica (por descascamento e lixamento) na superação da dormência de sementes dessa espécie. A qualidade fisiológica das sementes é afetada pela redução do teor de água. As sementes apresentam comportamento recalcitrante, sendo que o nível crítico de umidade pode estar situado entre 58,8 e 47,1%. A desidratação a níveis iguais ou inferiores a 25,76% de água provocou a morte em 100% das sementes. As sementes devem ser semeadas, preferencialmente, logo após a extração e limpeza. O tegumento das sementes apresenta resistência mecânica à expansão do embrião. A remoção total do tegumento foi o método mais eficiente na superação da dormência, pois elimina a resistência na região onde ocorrerá a ruptura pelo embrião, com tempo médio de emergência de 66 dias e percentagem final de emergência de 96%. Os lixamentos provocaram injúrias mecânicas nas sementes, tendo consequências diretas na emergência e vigor.