The genus Physalis belongs to the family Solanaceae, Physalis peruviana L. being the most cultivated species. As a newly explored crop in Brazil, little is known about its germination ecology and emergence under local conditions. The aim of the present study was to determine the effect of temperature, photoperiod, planting depth and seed dormancy on the establishment of Physalis seedlings. Tests were conducted on two Physalis biotypes from Sertão (Rio Grande do Sul state-RS) and Capelinha (Minas Gerais state). Seeds incubated at 27 °C and 32 °C exhibited high germination percentages of 98% and 96%, respectively. Germination declined when seeds were incubated at 12, 17, 22 and 37 °C. Photoperiods longer than 8 h are sufficient for seed germination, while the absence of light significantly reduces the germination percentage. Seeds should be planted at a depth of 1-2 cm to ensure better seedling emergence. After 18 months of field work, 81% of seeds had germinated and/or been predated prior to assessment, indicating low seed dormancy. As such, ideal conditions for Physalis seedling establishment are planting depth between 1 cm and 2 cm, temperatures ranging from 27 °C to 32 °C and a photoperiod longer than 8 h, with a postharvest seed shelf life of 12 months.
The evapotranspiration (ETc) and crop coefficient (Kc) of lettuce were determined in two growing seasons (winter and autumn) using percolation lysimeters. During the winter and autumn growing seasons, total ETc average observed was, respectively, 162 mm and 181 mm. The Kc reached in both growing seasons its maximum in the moment of harvest. In winter and autumn the maximum value of Kc was nearly 1.40. This value is bigger than Kc suggested by FAO (1.00). By linear regression was ascertained what Kc values seemed to be strongly related to plant development.
The herbicide nicosulfuron is an important tool for weed control in maize crops; however, its incorrect use can cause yield losses to crops due to its high toxicity. The objective of this work was to evaluate the efficiency of using herbicide safener to increase selectivity of nicosulfuron to maize crops. The experiment was conducted in field conditions, and the treatments consisted of dose-response curves, using nicosulfuron at rates of 0, 15, 30, 45, and 60 g ha-1, applied with safener and/or malathion to maize crops at the V5-V6 stage. The use of organophosphorus insecticides such as malathion decrease the selectivity of nicosulfuron to maize crops. Rates of up to 60 g ha-1 were selective to the maize crops when using nicosulfuron or nicosulfuron + safener. However, plant height decreased 0.19 and 0.91 cm for each gram of nicosulfuron in the treatments nicosulfuron + safener + malathion, and nicosulfuron + malathion, respectively, at 28 days after the application. The phytotoxicity increased 0.19% and 0.97% in the treatments nicosulfuron + safener + malathion and nicosulfuron + malathion, respectively. The number of grains per row and grain yield were affected by the treatments with nicosulfuron + malathion, presenting decreases of 0.09 grains and 52 kg ha-1, respectively. Thus, adding safener to the herbicide mixture increases the selectivity of nicosulfuron to maize crops, decreases damages regarding plant height and phytotoxicity, and prevents effects of the herbicide on the number of grains per row and grain yield, up to the rate of 60 g ha-1.
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Genetic variability is the basis of plant breeding. In corn, a large and diverse genetic pool permits manipulation of different genotypes, but the genetic diversity of tropical
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