Analysis of growth of potted ornamental sunflower and application of nitrogen

摘要

This study aimed at comparing the growth of potted ornamental sunflowers submitted to doses of nitrogen by fertirrigation in greenhouse, using the technique of growth analysis. The experiment was carried out at the Department of Natural Resources - Soil Science, on the Experimental Farm Lageado, which belongs to FCA, UNESP, Botucatu (S?o Paulo, Brazil), in a greenhouse, from August 21 to October 22, 2008. We adopted the randomized block design with four doses of nitrogen (75%, 100%, 125% and 150%), using a 100% reference dose of 0.035 g L-1 during the vegetative stage and 1.66 g L-1 in the reproductive phase, with the ammonium nitrate as a source. Seeds of ornamental sunflower, cultivar Sumbrite Supreme Sunflower F1, from SAKATA ?, were sown in trays with 128 cells and then transplanted into plastic pots with a capacity of 1.3 L, filled with substrate. Every fortnight, collections of plants were examined for growth analysis, with assessments of leaf area and total dry weight. These were transformed into physiological data of relative growth rate, net assimilation rate and leaf area ratio. The results show that plant photosynthesis was more efficient with increasing doses of nitrogen applied to the sunflowers.