Effects of fire retardants on emergency and early growth of Handroanthus ochraceus (cham.) Mattos and Tabebuia roseoalba (Ridl.) Sandwith

ABSTRACT

The objective of this study was to evaluate the effects of short-term fire retardants and a water-retaining polymer on the emergence and initial growth of Handroanthus ochraceus and Tabebuia roseoalba, in protected environment conditions. Applications were made via substrate at sowing and at fortnightly intervals, of the following fire retardants and concentrations: Phos-Chek WD881® (0; 3.00; 6.00; 8.00; 10.00 mL L^-1), Hold Fire ® (0.7.00; 9.00; 12.00; 15.00 mL L^-1), and the water-retaining polymer Nutrigel® (0.25; 0.50; 0.75; 1.00 g L^-1), in a completely randomized design, with 10 replicates per treatment. At concentrations equal to 0, only water was used. Seedling emergence was assessed using the emergence speed index, percentage and average emergence time. Destructive growth analyzes were performed at 30, 45, 60, 90 and 120 days after sowing (DAS), while chlorophyll fluorescence analyzes were performed on 3 plants per treatment, starting at 60 DAS. The tested concentrations of Phos-Chek WD881, Hold Fire and Nutrigel did not influence the emergence of seedlings of the species Handroanthus ochraceus and Tabebuia roseoalba. Applications of Phos-Chek WD881 up to 5.00 mL ^-1 provide positive effects on the growth of both species. Hold Fire concentrations up to 8.00 mL L^-1 favor the initial growth of Tabebuia roseoalba. The growth in diameter of Handroanthus ochraceus shows a positive response from 9.60 mL L^-1 when subjected to the Hold Fire retardant. The range of 0.50 g L^-1 to 0.88 g L^-1 of the water-retaining polymer Nutrigel promotes growth in diameter of the two species. The fluorescence of chlorophyll a indicates that the photochemical step has fully functioned in the photosynthetic process of Handroanthus ochraceus and Tabebuia roseoalba in the presence of fire retardants and the water-retaining polymer.

Keywords:
Growth analysis; Fluorescence; Short term fire retardant; Hydrogel