Uso do regulador de crescimento daminozide no cultivo de pimenta (Capsicum annuum L.) e girassol (Helianthus annuus l.) ornamental em vasos com fibra de côco e areia.

Abstract

The culture of sunflower and pepper as potted ornamental plants has been highlighted in flower farming by being innovative products of great attractiveness. And there is no record on the production and researches with these species under climatic conditions of Fortaleza and Ceará State. Aiming the manipulation of plant architecture and the search for species with lower heights and suitable ornamental traits for the culture in pots it is necessary to use growth-reducing substances and substrates that maximize their production. With this, two experiments were performed with the purpose to evaluate, under the climatic conditions of Fortaleza, the effect of three applications of different levels of the growth regulator daminozide in ornamental plants of pepper and sunflower in pots containing coconut fiber (FC) and sand. The experiments were conducted in greenhouse and distributed into a completely randomized design in a factorial scheme 2x5 composed of two types of substrate (FC and sand) and five levels of daminozide (0 (control), 2, 4, 6 and 8 g.L-1) in which were applied three times at fortnightly intervals. In relation to the ornamental pepper, the first application of the regulator was performed at 25 DAS, being analyzed the following variables: relative chlorophyll index (spad) and leaf gas exchange, at 80 DAS, plant height (cm), stem diameter (mm), dry matter (g) of leaf, stem, root, and fruit, leaf area (cm²), leaf area ratio (cm².g-1), specific leaf area (cm².g-1), dry root: dry shoot ratio, number, width, length (mm) and length:width ratio of fruits , at 83 DAS. In the experiment with the sunflower, the first application was made at 15 DAS, being analyzed the variables: relative chlorophyll index and leaf gas exchange, at 37 DAS, plant height (cm), stem diameter (mm), internal diameter of the head (mm), days from sowing to anthesis, number of head per plant, dry matter of leaf, stem and root (g), leaf area (cm²), leaf area ratio (cm².g-1), specific leaf area (cm².g1), dry root: dry shoot ratio, at 53 DAS. Both for pepper and sunflower, the levels of the growth regulator were effective to reduce the size of the plants in the two substrates, but in the sand, the plants have had lower height, vigor and development compared with the plants on the FC. In pepper plants, increased levels led to increased stem diameter, reduction in the number, width and length of fruit, in leaf area, increase in leaf thickness, which had intense green color. A significant interaction was detected between the substrates and the levels of daminozide in the stomatal conductance of pepper plants, and the transpiration rate and net photosynthesis were only influenced by the levels of the growth regulator. In sunflower plants, higher levels caused reduction in stem diameter, in internal diameter of head, late anthesis, thicker leaves with intense green color, and reduced leaf area. Stomatal conductance, transpiration, and net photosynthesis of sunflower plants were only affected by substrates, with the plants grown on FC presenting a higher photosynthetic rate.