No abstract

No abstract

No abstract

The objective of this study was to: first, evaluate the infection effects caused by Colletotrichum lindemuthianum pathogen (race 2047) on photosynthetic pigments and gas exchanges in Phaseolus vulgaris plants (cv. Mexico 222); and, second, determine infection effects on leaf pigments and their consequences on photosynthesis rate. A completely randomized design with a factorial scheme was used, combining two treatments (control and inoculated) and three evaluation periods (4th, 8th and 12th day). Carotenoid levels presented decreases of 28.3% and 35% during the 8th and 12th day after infection, when control and inoculated plants were compared. Correlation analysis demonstrated the direct relationship between carotenoids and photosynthesis rate (r 00.84). Total chlorophyll in infected plants had progressive reductions of 6.4%, 20.6% and 21.3% on the 4th, 8th and 12th day, respectively, when treated and untreated plants were compared. Total chlorophyll with photosynthesis (r 00.85) also revealed a significant and linear correlation. The photosynthetic rate in infected plants decreased by 22%, 49.9% and 77.3% on the 4th, 8th and 12th days after the inoculation, respectively. Anthracnose infection also induced negative effects concerning stomatal conductance, transpiration, photosynthesis and water use efficiency. Our results demonstrate that leaf pigment reduction as a result of pathogens was the main cause of lower gaseous exchanges in infected plants.

Effect of plant growth regulator on germination and vigor of soybean seedsPlant growth regulators can enhance growth and development of plants and induce cell division. They can also interfere in seed germination. The objective of this study was to evaluate the physiological quality of seeds treated with a plant growth regulator. Seeds of nine soybean (Glycine max (L.) Merrill) commercial cultivars were treated with four concentrations (400; 500 and 600 mL 100 kg -1 seeds) of the plant growth regulator Stimulate®, in addition to a control treated with distilled water. Tests of seed germination and vigor were carried out: it was calculated the germination percentage (first counting and final counting), percentage of normal seedlings; and speed of germination, length of the primary root and the aerial part and dry weight of seedlings were recorded. The experiment was arranged in a completely randomized design with four treatments and four or five repetitions depending on the test. Increasing doses of the plant growth regulator did not influence the germination and the dry weight of the seeds, however, they can increase the speed of germination depending on the cultivar.