Aspectos morfológicos e fisiológicos de cultivares de girassol sob diferentes regimes hídricos.

Abstract

Currently sunflower cultivation has increased sharply due to its multiple use as human food, animal feed, ornamentation and biodiesel production. When exposed to abiotic factors such as water restriction there are considerable reductions in its production. Aiming to expand the knowledge on the effects of water restriction on growth characteristics, physiological and sunflower production, this study was conducted in pots containing 100 liters of substrate in a greenhouse located in the Academic Unit of Agricultural Engineering Federal University of Campina Grande, Campina Grande, PB. The experimental design was completely randomized in a 3x4 factorial design (3 cultivars x 4 water regimes), with four replications. The cultivars were BRS Turns 26, Agrobel 962 and Embrapa 122 and the water regimes 40, 60, 80 and 100% of field capacity. The variables evaluated were: plant height, stem diameter, number of leaves and leaf area measured at 20, 50 and 80 DAS; absolute growth rates and relative plant height and stem diameter, early flowering, physiological maturity, dry matter of shoots, number and weight of achenes for each chapter, relative chlorophyll content, chlorophyll fluorescence, content of chlorophyll a, b, and total carotenoids. Were also evaluated the correlations between relative chlorophyll index and chlorophyll a, chlorophyll b, total chlorophyll and carotenoids There was not statistical significant difference among cultivars for the number of leaves at 50 DAS, leaf area at 20 and 50 DAS, relative chlorophyll index at 60 DAS, chlorophyll fluorescence and contents of chlorophyll a, b and total. Plant height, stem diameter, number of leaves, leaf area, absolute growth rate of plant height and stem diameter, dry weight of shoots, number and weight of achenes per chapter and contents of chlorophyll b and total increased with the soil water content. It was observed correlation only between the relative index of chlorophyll and total chlorophyll content. Embrapa 122 had greatest stem diameter and plant height at 20 and 50 DAT, respectively, and presented the shortest phenological cycle. The BRS Gira 26 had the highest plant height, leaf number and leaf area at 80 DAS, while Agrobel 962 provided better results for the stem diameter at 50 and 80 DAS, number of leaves at 20 DAS, higher biomass of shoots, number of achenes and carotenoids content. ABSTRACT XV