Drought tolerance of four vegetable crops during germination and initial seedling growth

Seeds of arugula (Eruca sativa Miller, cv. Cultivada), carrot (Daucus carota L., cv. Nantes), eggplant (Solanum melongena L., cv. Embú) and watermelon [Citrullus lanatus (Thunb.) Matsum. & Nakai cv. Crimson Sweet] were submitted to different osmotic potentials induced by polyethylene glycol (PEG) with the objective of evaluate the effects of drought stress on seed germination and initial seedling growth. Seeds were distributed in plastic boxes containing blotter paper, soaked with PEG solutions prepared with osmotic potentials 0.0 (control), -0.2, -0.4, and -0.8 MPa and kept into a seed germinator, at 25 °C for 14 days. A completely randomized design in a 4 × 4 factorial scheme with four replicates of 50 seeds each was used. The results showed that by increasing of the osmotic potential level, germinated seeds number, germination rate index, root and shoot length, shoot and root dry matter, and seedling vigor indices decreased, while mean germination time and root: shoot ratio increased in all four vegetable crops. Additionally, the carrot and watermelon are more susceptible than arugula and eggplant to drought stress, with germination response declining more rapidly with the rise of osmotic potential level. Arugula and eggplant crops tolerate water stress of up to -0.2 MPa, without reducing germination of the seeds; however, the growth of shoots and roots are inhibited. The germination process of eggplant and watermelon seeds are completely inhibited at -0.8 MPa osmotic potential, whereas germination of carrot seeds is completely inhibited at -0.4 MPa osmotic potential. Severe drought stress limits the process of seed germination and initial seedling growth of vegetable crops

Seed quality response of Urochloa humidicola cv. Llanero to drying surfaces and environments

The drying process and storage may interfere in the quality of creeping signalgrass seeds [Urochloa humidicola (Rendle.) Morrone & Zuloago, syn. Brachiaria humidicola (Rendle.) Schweick.]. This study aimed to evaluate the physical, physiological and sanitary quality of creeping signalgrass cv. Llanero seeds submitted to drying surfaces and environments and stored for two periods (1 and 8 months). The experiment was arranged in a completely randomized design, in a 4 × 2 × 2 + 2 factorial arrangement, with four drying surfaces (soil, asphalt, concrete and ceramic floor), two drying environments (seeds exposed to the sun or shade), two seed storage periods (1 and 8 months) and two additional treatments with drying in paper bags under laboratory conditions (control) and stored for 1 or 8 months, with four replicates. The water content, viability by the tetrazolium test, electrical conductivity, germination rate, germination rate index and seed sanitary quality were measured. Drying at full sun impaired the physiological quality of the seeds due to the high temperatures (46.8-51.0 ºC) of the drying surface; however, reduced the incidence of pathogens. The drying of seeds in paper bags under shade results in a higher physiological quality, but the sanitary quality is compromised. However, the pathogens present in the seeds did not inhibit their viability and vigor. The storage for eight months reduces the seed quality

Physiological and enzymatic changes in soybean seeds submitted to harvest delay

Harvest delay may affect the physiological quality of soybean seeds due to the occurrence of unfavorable environmental conditions in the field. This study was conducted to investigate the physiological and enzymatic changes in soybean seeds submitted to harvest delay. A randomized block design, with eight seed harvest periods (0; 5; 10; 15; 20; 25; 30; and 35 days after the R8 phenological stage - full maturity) of the BRS 820 RR® cultivar, with four replicates, was used. At each harvest period, the moisture content, 1,000-seed weight, germination, seedling emergence, emergence speed index, accelerated aging, vigor and viability (tetrazolium test), electrical conductivity, enzymatic expression and seed yield were measured. Harvest delay up to 35 days after the R8 phenological stage do not affect the 1,000-seed weight and seed yield. The delayed harvest from the R8 stage results in increased damage by stink bugs and moisture. The harvest delay of seeds from the 10th day after the R8 stage impairs the seed vigor and, from the 15th day, seed germination. Seeds harvested with a delay after the R8 stage have lower expressions of the following isoenzymatic systems: malate dehydrogenase, alcohol dehydrogenase, esterase, isocitrate lyase and superoxide dismutase, especially after 15 days of harvest delay

PHYSICAL CHARACTERIZATION OF FRUITS AND SEEDS OF JAMBOLAN [SYZYGIUM CUMINI (L.) SKEELS] (MYRTACEAE)

The main physical and biometric characteristics of fruits and seeds of Syzygium cumini (L.) Skeels, and correlation estimates between these characteristics were investigate in this study. Mature fruits of S. cumini were collected from ten matrices trees in Marechal Cândido Rondon, Paraná, Brazil. The longitudinal and transversal diameters of 100 fruits and 100 seeds were measured. The mass of fresh and dry matter, water content of fruits and seeds, and pulp yield of the fruits were quantified. Data were analyzed by using descriptive statistics, adjustment of statistical distributions, and Spearman's correlation analysis. The Syzygium cumini (L.) Skeels ("jambolan") presents variation in fruit, pulp and seed mass, which can be explored for breeding projects and should be considered in the formation of seed lots that are more homogeneous. There were significant positive correlations between the fruit pulp yield (FPY) and the fresh fruit mass (FFM), dry fruit mass (DFM) and fruit water content (FWC). The S. cumini fruits present great socioeconomic potential for the food industry in Brazil due to the high pulp yield of the fruits (72.93 ± 7.41%). The high fruit pulp yield can be optimized with the selection of plants with fruits of greater fresh mass or dry mass or water content due to the high degree of association between these characteristics and the pulp yield.The main physical and biometric characteristics of fruits and seeds of Syzygium cumini (L.) Skeels, and correlation estimates between these characteristics were investigate in this study. Mature fruits of S. cumini were collected from ten matrices trees in Marechal Cândido Rondon, Paraná, Brazil. The longitudinal and transversal diameters of 100 fruits and 100 seeds were measured. The mass of fresh and dry matter, water content of fruits and seeds, and pulp yield of the fruits were quantified. Data were analyzed by using descriptive statistics, adjustment of statistical distributions, and Spearman's correlation analysis. The Syzygium cumini (L.) Skeels ("jambolan") presents variation in fruit, pulp and seed mass, which can be explored for breeding projects and should be considered in the formation of seed lots that are more homogeneous. There were significant positive correlations between the fruit pulp yield (FPY) and the fresh fruit mass (FFM), dry fruit mass (DFM) and fruit water content (FWC). The S. cumini fruits present great socioeconomic potential for the food industry in Brazil due to the high pulp yield of the fruits (72.93 ± 7.41%). The high fruit pulp yield can be optimized with the selection of plants with fruits of greater fresh mass or dry mass or water content due to the high degree of association between these characteristics and the pulp yield

Quality of soybean seeds in response to nitrogen fertilization and inoculation with Bradyrhizobium japonicum

Nitrogen fertilization may interfere in the quality of soybean seeds. This study aimed to determine the physiological and sanitary quality of soybean seeds, in response to levels and times of nitrogen (N) application associated with Bradyrhizobium japonicum inoculation. Treatments were arranged in a randomized block design, in a 2 × 3 × 4 factorial arrangement [two soybean cultivars (BRS 1074 IPRO and ST 797 IPRO), three application times (sowing, 30 and 50 days after emergence) and four N levels (0 kg ha-1, 20 kg ha-1, 40 kg ha-1 and 60 kg ha-1), with four replicates. The 1,000-seed mass, moisture content, germination rate, seedling height, shoot length, primary root length, total seedling dry matter, electrical conductivity, mechanical damage, vigor and viability (tetrazolium test) and sanitary quality of the seeds were measured. The use of mineral N, associated with the inoculation of B. japonicum bacteria, does not prove to be consistent, in terms of its effects on the physiological quality of soybean seeds, although the incidence of pathogens may be reduced

Aplicação de calcário e de nitrogênio em cobertura melhora a qualidade das mudas de Peltophorum dubium (Sprengel) Taubert (Fabaceae–Caesalpinioideae)

The liming and mineral fertilization can improve the growth and quality of forest species seedlings. The effects of the application of nitrogen fertilizer rates and limestone on growth and quality of Peltophorum dubium (Sprengel) Taubert seedlings were investigated in this study. Peltophorum dubium plants were grown in 1.4-L polyethylene bags filled with sandy soil under greenhouse conditions. Treatments were arranged in a randomized block design in a 4 × 2 factorial: four of N application rates (0, 100, 200 and 300 mg mg dm–3) and application or non-application of limestone, with four replicates. The plant height, stem diameter, height/diameter ratio and number of leaves were measured at 30, 60, 90 and 120 days after emergence. At 120 days, root volume, shoot and root dry matter, N accumulation in shoots, shoot/root dry matter ratio, and Dickson quality index was also measured. The results reported that limestone and N fertilizer application have a positive effect on most of the growth and quality traits of Peltophorum dubium seedlings, and when Peltophorum dubium seedlings are produced in a substrate consisting of a sandy soil from Brazilian Cerrado, the limestone application and use of 200 mg N dm–3 in topdressing should be recommended to obtain high-quality seedlings.A calagem e adubação mineral podem melhorar o crescimento e a qualidade das mudas de espécies florestais. Os efeitos da aplicação de adubação nitrogenada e calcário sobre o crescimento e a qualidade das mudas de canafístula [Peltophorum dubium (Sprengel) Taubert] foram investigados neste estudo. Plantas de Peltophorum dubium foram cultivadas em sacos de polietileno de 1,4 L, preenchidos com solo arenoso e mantidos em condições de casa de vegetação. Os tratamentos foram arranjados em blocos casualizados em esquema fatorial 4 × 2: quatro doses de N (0, 100, 200 e 300 mg dm-3) e aplicação ou não de calcário, com quatro repetições. A altura da planta, diâmetro do caule, relação altura/diâmetro e número de folhas foram mensurados aos 30, 60, 90 e 120 dias após a emergência. Aos 120 dias, também foram determinados o volume radicular, massa seca da parte aérea e das raízes, acúmulo de N na parte aérea, relação entre matéria seca da parte aérea/raiz e o índice de qualidade de Dickson. Os resultados reportaram que a aplicação de calcário e de fertilizante nitrogenado tem efeito benéfico sobre a maioria das características da parte aérea e das raízes das mudas de Peltophorum dubium, e quando as mudas de Peltophorum dubium são produzidas em um substrato constituído de um solo arenoso da região do Cerrado, a aplicação de calcário e o uso de 200 mg N dm–3 aplicado em cobertura deve ser recomendado para a obtenção de mudas de alta qualidade

Potassium supplying capacity of some lowland soils under potassium fertilization and successive croppings

The effects of intense cropping and potassium fertilization on potassium (K) dynamics and non-exchangeable K release from three lowland soils of Paraná State, Brazil, were investigated in this study. Samples of three lowland soils were fertilized or not with K and subjected to six successive croppings (soybeans, pearl millet, wheat, common beans, soybeans, and maize). The crops were grown in 8-L pots for 45 days, and at the end of the sixth cropping, the soil from each pot was sampled to the determination of soil K pools. The lowland soils differ in the ability to K supply to the plants in the short to medium term due to the wide range of origin material and the concentration of K in solution, exchangeable K, non-exchangeable K, and structural K. When the soils were not fertilized with K, the successive cropping resulted in continuous depletion process of non-exchangeable and exchangeable K; however, this depletion was less pronounced in soils with a higher potential buffer capacity of K. Non-exchangeable and exchangeable K concentrations were increased with the addition of K fertilizer, indicating the occurrence of K fixation in soil. The non-exchangeable K contribution to K nutrition of plants ranged from 44 to 69% in the treatments without the addition of K fertilizer, reporting the importance of non-exchangeable K pools in the supply of this nutrient to plants in agricultural production systems

Silicate fertilization potentiates the nodule formation and symbiotic nitrogen fixation in soybean

The application of silicon (Si) to the soil can increase the grain yield of the soybean crop by improving the nitrogen biological fixation, due to its beneficial effect on the Bradyrhizobium-soybean symbiosis. This study aimed to investigate the effect of fertilization with calcium and magnesium silicate on plant growth, root nodulation and nitrogen (N) uptake, in two soybean cultivars [BRS 1074 IPRO (transgenic) and BRS-MG 800A (conventional)], under greenhouse conditions. The application of silicate significantly increased the number of root nodules only for the BRS-MG 800A, while the positive effects of the silicate addition on nodule size, chlorophyll level and leaf N concentration were observed in both cultivars. The soybean cultivars show distinct responses to the silicate application, with respect to growth and dry matter yield, being the BRS 1074 IPRO more responsive than the BRS-MG 800A. Therefore, Si may induce the formation of root nodules in soybean plants and lead to significant increases in the nitrogen biological fixation and plant growth. These results highlight that Si is not only involved in the improvement of plant growth, but it can be also considered a crucial element to improve the symbiotic performance of soybean plants. However, the physiological basis of how and where silicate exerts its influence on nodulation and nitrogen biological fixation still remains unknown

COINOCULAÇÃO DE Bradyrhizobium japonicum e Azospirillum brasilense EM SEMENTES DE AMENDOIM DE DIFERENTES TAMANHOS

O tamanho da semente é um importante indicador físico da qualidade fisiológica das sementes, pois pode afetar a taxa de germinação e o crescimento inicial das plântulas. Neste contexto, o presente estudo teve como objetivo avaliar os efeitos do tamanho das sementes e da inoculação de Bradyrhizobium japonicum e Azospirillum brasilense de forma isolada ou combinada na emergência das plântulas, nodulação das raízes e no crescimento inicial das plantas de amendoim (Arachis hypogaea L., cv. IAC Tatu ST). As plantas foram cultivadas em vasos plásticos de 8,0 L preenchidos com um solo arenoso do Cerrado e mantidas sob condições de casa-de-vegetação. O delineamento experimental utilizado foi o de blocos ao acaso em esquema fatorial 3 × 4 com quatro repetições. Os tratamentos foram constituídos por três tamanho de sementes (pequena, média e grande) e por quatro tratamentos de inoculação: i) controle (sem inoculação); ii) inoculação das sementes com Bradyrhizobium japonicum; iii) inoculação das sementes com Azospirillum brasilense; e, iv) coinoculação das sementes com B. japonicum e A. brasilense. Os resultados reportaram que a utilização de sementes grandes melhorou a nodulação das raízes, o crescimento das plantas, o acúmulo e a partição de matéria seca das plantas. Portanto, a implantação da cultura do amendoim deve ser realizada com a utilização de sementes de maior tamanho (grandes), por proporcionar sustentabilidade para o sistema de produção de amendoim, melhorando a fixação biológica de nitrogênio e o crescimento das plantas cultivadas em solos arenosos do Cerrado Sul-mato-grossense. A coinoculação das sementes com B. japonicum e A. brasilense melhorou a nodulação das raízes e a altura das plantas, no entanto, não teve efeito no crescimento, na partição de matéria seca e nos índices morfofisiológicos das plantas de amendoim, quando cultivadas em solos arenosos do Cerrado sob condições controladas

Molibdênio e coinoculação das sementes de amendoim com Bradyrhizobium e Azospirillum em solo do Cerrado

A adoção de práticas agrícolas sustentáveis que otimizem a fixação biológica de nitrogênio (FBN) pela cultura do amendoim são de extrema importância para assegurar elevados níveis de produção. Neste contexto, o presente estudo teve como objetivo avaliar a eficiência da coinoculação de Bradyrhizobium japonicum e Azospirillum brasilense e da aplicação de molibdênio na nodulação, no crescimento e na partição de matéria seca das plantas de amendoim (Arachis hypogaea L., cv. RUNNER IAC 886). As plantas de amendoim foram cultivadas em vasos de 5,5 L preenchidos com um Neossolo Quartzarênico em condições de casa-de-vegetação. Os tratamentos foram dispostos em um delineamento em blocos casualizados em um esquema fatorial 2 × 4: aplicação (+Mo) ou não de molibdênio (–Mo) na proporção de 10 g/50 kg de semente e de quatro tratamentos de inoculação das sementes: i) controle (sem inoculação); ii) inoculação com Bradyrhizobium japonicum; iii) inoculação com Azospirillum brasilense; e, iv) coinoculação com B. japonicum e A. brasilense, com quatro repetições. Aos 60 dias após a semeadura, foram avaliados nodulação das raízes, o crescimento e a partição de matéria seca das plantas. A coinoculação de Bradyrhizobium japonicum e Azospirillum brasilense não promoveu melhoria na nodulação e crescimento das plantas de amendoim, cultivado em condições de casa de vegetação. A aplicação de Mo via sementes, independente da coinoculação, incrementa o número de nódulos, a matéria seca dos nódulos e o número de folhas das plantas de amendoim