Dario Munt de Moraes

Qualidade fisiológica de sementes de arroz submetidas a estresse salino

Experiments were conducted to evaluate the physiological quality of the rice seed cultivars BRS Bojuru and IAS 12-9 Formosa (salt tolerant) and BRS Agrisul and BRS 6 Chui (salt sensitive). Seeds were soaked in salt solutions with zero, 25, 50, 75 and 100 mM NaCl for one hour. The seeds viability and vigour of the cultivars BRS Agrisul and IAS 12-9 Formosa were reduced as the NaCl concentration increased whereas the speed germination index was not affected by salinity.

Respiratory activity for the differentiation of vigor on soybean seeds lots

Currently, the highest interest with respect to the assessment of seed physiological quality is to obtain reliable results in a relatively short period of time. This initiative allows for prompt decisions during different phases of seed production primarily after physiological maturity. This research was performed to verify the efficiency and rapidity of the method of Pettenkofer to determine the respiratory activity and to differentiate vigor levels of soybean seed lots. Three lots of soybean seeds cv. 8000 were used. Seed performance was determined by respiratory activity, compared to the following tests: standard germination, germination first count, electrical conductivity, seedling emergence, seedling shoot and root length and total dry mass. Results ranked seed lots according to defferences in physiological quality. Seed imbibition and conditioning period in Pettenkofers equipment were enough to detect differences in vigor among seed lots, showing that the determination of the respiratory activity is a promising procedure to identify differences in vigor levels among soybean seed lots.

Alterações fisiológicas em sementes de arroz expostas ao frio na fase de germinação

Cold is one of the main problems for rice cultivation in Rio Grande do Sul because the vast majority of cultivars in use are of tropical origin. The occurrence of low temperatures combined with the susceptibility of the materials used can cause serious damage to the establishment of the crop reducing the plant stand. The objective of this study was to evaluate the physiological changes in different rice cultivars, when exposed to low temperature during germination. Seeds from four cultivars, BRS Agrisul, BRS Chui, Lemont and Oro were used and evaluated regarding low temperature tolerance by the cold test. To evaluate the physiological changes, isoenzyme analyses of alcohol dehydrogenase and esterase were performed at temperatures of 25 oC (ideal for germination) and 13 oC (low temperature). The other characteristics evaluated were germination, germination speed, coleoptile length and dry weight at 25 oC and 13 oC. According to cold test results, seeds of the Lemont and Oro cultivars presented better tolerance to the low temperature. In the isoenzyme analysis, the cold caused an increase in the expression of the isoenzyme alcohol dehydrogenase and reduction in the esterase isoenzyme expression. For the other ratings, the cold caused damage to all the characteristics evaluated, especially in the BRS Agrisul and BRS Chui cultivars.

Physiological quality of barley seeds submitted to saline stress

The objective of the experiments was to determine the influence of the effects of different salt levels (zero, 15, 30, 45 and 60mM NaCl) on the physiological quality of seeds of two barley cultivars (BRS 195 and AF 98067). Assays were conducted to evaluate salt stress on germination and vigor. The germination and germination rate of the barley seeds decreased as salt levels increased, reducing the seed viability and vigor. The salinity affected the membrane integrity, mainly in AF 98067 that showed more sensitivity to salt stress.

Physiological performance of soybean seeds from conventional and transgenic cultivars treated with glyphosate

The objective of this study was to evaluate the physiological quality of seeds from conventional (cultivar CD 216) and transgenic (cultivar CD 212RR) soybeans treated with glyphosate. Seeds were soaked in dosages of zero; 1.8; 3.6; 5.4 and 7.2 g.L-1 of acid equivalent of glyphosate for 30 minutes. Seed quality was evaluated from the tests of first count germination, germination, electrical conductivity, emergence speed index, seedling emergence, root and shoot length and total dry matter. It was concluded that the physiological quality of the CD 212RR seeds seeds is affected by glyphosate and as dosages increased, soybean seed quality decreased. Based on this conclusion, it is important that care be taken to avoid problems with seed germination and soybean field establishment when glyphosate is used in burndown or for the control of cover crops. A certain period of time between the control of weeds or of cover plants should be respected to reduce the glyphosate transfer from target to non-target plants, thus avoiding problems with germination and soybean crop establishment.

Alterações fisiológicas e bioquímicas em sementes de arroz submetidas ao estresse térmico

The purpose of this research was to analyze the effect of different temperatures on the respiratory activity, enzymatic and in process related to the physiological quality of rice seeds, and use the relationship between these parameters to characterize the beginning of the deterioration process of seeds. The seeds were exposed during 24 h and conducted tests for germination, first count germination, index the germination speed, length and dry weight of shoot and roots, electrical conductivity, respiratory activity and activity of the enzymes. The experiment was completely randomized with four replicates and the averages compared by Tukey test (p i 0.05) with subsequent analysis of regression. Rice seeds showed that the germination and vigor were reduced above 25 oC temperatures. Respiratory activity increased with increasing temperature, the same occurred with study enzymes activity in at five days after sowing (ranging from 14.55 at 59.86 µmol of NAD + g -1 MF min -1 for at malate dehydrogenase and 0.25 at 0.57 µmol of at NADPH g -1 MF min -1 for glucose-6-phosphate dehydrogenase). Therefore, it can be concluded that the evaluated biochemical tests can be used to identify the beginning of the deteriorating process of rice seeds and that temperatures above 25 oC can depreciate the quality of these seeds.

Teste de respiração para avaliar a qualidade fisiológica de sementes de girassol

The increased demand for high quality oilseeds, such as sunflower, has encouraged interest in faster tests to distinguish seed lots, and allow prompt decisions during different stages of seed production, storage, and marketing. The objective of this study was to evaluate the efficiency of the Pettenkofer method for determining respiratory activity, which can be used to differentiate the vigor of different cv. MG2 sunflower seed lots. Besides determining respiratory activity, the germination, electrical conductivity, total dry weight, fresh weight and seedling length were measured. The results permitted the classification of seed lots according to their potential performance. The Pettenkofer apparatus provided an efficient and fast separation of seed lots and the measurement of respiratory activity is promising for identifying differences in the physiological quality of sunflower seeds.

Antioxidant activity of corn seeds after thermal stress

The aim of this research was to analyze the effect of different temperatures on physiological quality and relate the responses with the antioxidant activity of three lots of corn seeds. The seeds from three lots were exposed for 24h at temperatures of 15, 25, 35 and 40°C and then evaluated for percentage, speed index and first germination count, as well as early growth and activity of antioxidant enzymes in the seedlings. The experimental design was completely randomized with four replications, with subsequent polynomial regression analysis. The results showed that the seeds from the three lots of corn exposed to temperatures of 15 and 40°C, were of better high physiological quality (vigor), which explains the low activity of enzymes of the antioxidant defense system in these same temperatures. The antioxidant defense system is related to the physiological quality of corn seeds exposed to thermal stress.

Respostas na germinação e no crescimento inicial de rabanete sob ação de extrato aquoso de Piper mikanianum (Kunth) Steudel

This study evaluated the allelopathic effects of an extract from P. mikanianum leaves on the germination and early growth of radish (Raphanus sativus L.). Leaf extracts were prepared at concentrations of 2, 4 and 8%. The pH and osmotic potential of the extracts were determined. Germination bioassay consisted of five replicates of 25 radish seeds distributed in Petri dishes with germitest paper and 7 mL of extract or water, and were kept at 25oC in B.O.D. for five days. Germination percentage (PG), germination speed (VG), germination speed index (IVG) and index of allelopathic effect (RI) were determined. For bioassay initial growth, seeds were germinated until the protrusion of the radicle was 2 mm and transferred to Gerbox boxes containing germitest paper and 15 mL of extract or water, which were kept for seven days at 25oC in B.O.D. to evaluate the length of the radicle and hypocotyl, fresh and dry mass, water content and chlorophyll content (a, b ​​and total). Leaf extracts from P. mikanianum negatively affected all parameters examined for germination (PG, VG, IVG and RI). The extracts affected the initial growth, causing reduction of the radicle length and stimulating the growth of the hypocotyl. In addition, the extracts at 8% concentration reduced fresh weight and water content. Extracts at concentrations of 2 and 4% increased the content of chlorophyll b and total chlorophyll. Thus, Piper mikanianum exerted an allelopathic effect on radish.

Composição química de sementes de trigo (Triticum aestivum L.) submetidas a estresse salino na germinação

The objective of the experiment was to determine some biochemical changes in two wheat cultivars (BRS 177 and BRA 179) under the influence of different salt levels ( zero, 15, 30, 45, and 60mM NaCl). The experiment was carried out to evaluate the effect of saline stress on a-amylase activity and starch, sugar reducers, total soluble carbohydrates and protein contents. The a-amylase activity and the contents of total soluble carbohydrates, sugar reducers and proteins decreased but starch content increased with the increase in salinity for both cultivars. At all NaCl concentrations, the chemical components in the seeds of the BRS 179 cultivar were higher than the ones of the BRS 177 cultivar, showing that the BRS 179 cultivar is more tolerant to salinity.