A presente pesquisa teve por objetivo avaliar o efeito de agentes indutores de estresse hídrico e salino na germinação, crescimento e resposta antioxidante de plântulas de girassol. Sementes da cv. M735 foram germinadas em papel umedecido com soluções osmóticas nos potenciais de 0,0; -0,2; -0,4 e -0,8 MPa, induzidos com PEG 6000 e NaCl. O teste de germinação foi conduzido com quatro subamostras de 100 sementes e quatro repetições por tratamento, em câmara de germinação sob temperatura média de 25 ºC, na ausência de luz. Foram avaliados a porcentagem final e índice de velocidade de germinação das sementes, além do crescimento inicial e atividade de enzimas antioxidantes das plântulas. O estresse hídrico induzido por PEG 6000 aumentou a porcentagem de sementes germinadas no potencial de -0,2 MPa, por outro lado, para o NaCl no potencial de -0,8 MPa, houve significativa redução. Para este mesmo potencial, também houve redução no índice de velocidade de germinação das sementes para ambos os agentes condicionantes. Para os parâmetros de crescimento, o comprimento da parte aérea reduziu linearmente com o aumento das concentrações de PEG 6000 e NaCl. Já para a massa seca de folhas e raízes e o comprimento das raízes, este efeito foi mais expressivo somente no potencial de -0,8 MPa. As enzimas SOD, APX e CAT apresentaram tendência de menor atividade nas plântulas oriundas de sementes acondicionadas em PEG 6000. Na presença do NaCl, a atividade da SOD nas folhas aumentou significativamente nos três potenciais testados em relação a testemunha. Para a APX e CAT este aumento foi observado nos potenciais de -0,2 e -0,4 MPa. Nas raízes não foi observada diferença significativa. A análise conjunta dos parâmetros avaliados indica que a cv de girassol M735, nas condições testadas, apresenta tolerância ao estresse hídrico e salino até o potencial de -0,4 MPa.

The objective of this research was to assess the manner in which the presence of green soybean seeds affects their physiological quality. In this study, six lots of soybean seeds of cultivar 5958RSF IPRO with 0, 0, 7, 8, 16 and 18% of green seeds were examined. The tests done included the first germination count, germination, electrical conductivity, field emergence, accelerated aging, emergence speed index, Tetrazolium, length, dry mass and seedling growth curve. Results were tested employing the normality test and analysis of variance, and the means were compared by the Tukey test at 5% probability level, employing the Rbio statistical program. Growth data were analyzed by the nonlinear regression analytical method, using the SigmaPlot 12.0 software. The viability and vigor of the greenish seeds were confirmed to reveal higher deterioration, proportional to the percentage of seeds in which the cotyledons had green pigmentation, indicating that the presence of chlorophyll caused the physiological quality of the soybean seeds to decrease.

Seed coat cracking is a “physiological defect” that occurs in soybean seeds, affecting their integrity. The objective of this study was to evaluate the effect of seed coat cracking on the physiological quality and storability of soybean seeds. Seeds from three lots were used: one from the NS 7209 IPRO cultivar and two from the 8473 RSF cultivar, produced in the states of Goiás and Mato Grosso, Brazil. Each lot was manually segregated into three portions: the original lot (OL), seeds with an intact seed coat (IS), and seeds with a cracked seed coat (CS), which were stored at temperatures of 15 °C and 28 °C for 270 days. The experiment was carried out in a completely randomized design. Vigor and viability were evaluated using the tetrazolium test, first germination count, germination test, accelerated aging, and electrical conductivity at 0, 45, 90, 135, 180, 225, and 270 days of storage, as well as seedling emergence in a seedbed after 0, 90, 180, and 270 days of storage. Seed coat cracking in soybean reduced the physiological quality of the lots in all the tests compared to seeds with intact seed coats, and this effect was more pronounced when seeds were stored at 28 °C. Seed coat cracking contributes to increased seed deterioration in soybean when seeds are stored under high-temperature conditions.

Non-structural carbohydrates (NSC) accumulation and photosynthesis traits were studied in two rice (Oryza sativa L.) genotypes maintained under control (22/30 °C - night/day) and at high night temperatures (HNT) (28/30 °C) conditions from heading to milk stage. Rice cultivars were Nagina22 - N22 and BRS Querência - Quer, which are tolerant and sensitive to high temperatures, respectively. The source-sink flow related attributes were tested to understand the nature of NSC accumulation and translocation. Compared to N22, Quer maintained higher stem starch in glucose on seventh day after heading and at milk stage independently of imposed temperatures. However, the levels of starch in glucose were lower for N22 meanwhile their total sugar concentration (TSC) were higher at control and at HNT at milk stage as compared to Quer. N22 maintained unaltered the spikelet sterility and 1000-grain weight across environments showing a consistent trend with its stem NSC translocation. Both genotypes showed similarity in some gas exchange and chlorophyll fluorescence performance suggesting unaffected photosystem II photochemistry, linear electron flux, and CO2 assimilation. Beyond indicating that source functioning was not the limiting factor for low TSC and starch in glucose levels found in N22 on seventh day after heading stage. Moreover, our data suggest that the higher translocation capacity shown by N22 can be involved in their lower spikelet sterility and 1000-grain weight stability across the environments. These results indicate that selecting genotypes with higher capacity to stem NSC translocation at HNT could lead to more grain yield stability in future climate scenarios.

The present study had as the aim to analyze the performance of soybean seeds treated different products on the germination test using the substrates described by the “Rules for seed analysis” and alternative substrates. Two steps were carried out, in the first the products (fungicides and insecticides) were used individually and in the second in combinations (fungicide + insecticide, with or without polymer). Seeds were treated and sown on paper rolls, sand, vermiculite between paper rolls and sand between paper rolls. The variables evaluated were: first count, abnormal seedlings and germination. In the first step, imidacloprid+thiodicarb presented as the most problematic treatment in the paper substrate, with improved results in sand and in the alternative substrates proposed. It is possible to observe the low influence of the polymer in the results obtained in the second step. Lower results were observed for seeds treated with fludioxonil+metalaxyl-M+thiabendazole + imidacloprid+thiodicarb. Lower percentages of normal seedlings in the first count and germination, and higher percentage of abnormal seedlings, were observed in the paper substrate when the products were used individually. Sand was superior to the paper substrate, and vermiculite between paper stands out as a good alternative.