Chlorophyll fluorescence in sweet pepper subjected to N:K ratios and biostimulant doses

Abstract Sweet pepper are a vegetable of great economic importance in Brazil. This vegetable is widely cultivated and consumed throughout the country, with an estimated planting area of 19 thousand hectares and production of over 420 thousand tons. Analysis of chlorophyll content in leaves is therefore a method commonly adopted in agriculture, with the function of monitoring plant development, providing important information on the physiological state, nitrogen content in leaves and the photosynthetic potential of plants. In this research, chlorophyll fluorescence was evaluated a, b and total chlorophyll was evaluated in bell pepper plants subjected to N:K ratio and doses of biostimulant. The experiment was carried out from March to July 2020, at Engenho Triunfo, rural area of the municipality of Areia - PB, using a randomized block design, arranged in subdivided plots, in a 5 × 5 factorial scheme, with five N:K ratios in the main plot (1:1, 1:2, 2:1, 1:3; 3:1) and five doses of biostimulant in the subplot (0; 1.12; 2.25; 3.37 and 4.5 mL L-1). The variables analyzed were chlorophyll fluorescence: initial, maximum, variable fluorescence. The chlorophyll indices were also analyzed: chlorophylls a, b and total. The analysis of variance showed no significant effect in the interaction of factors, biostimulant doses and N:K ratios, and no significant effect for both factors alone on the photochemical activity and photosynthetic pigments of pepper at 30 and 60 days after planting (DAP). In this sense, confidence intervals (bands) were performed to demonstrate the average effect of each N:K ratio as a function of the increase in the biostimulant concentration for the variables studied. The use of N:K ratios 1:2 and 2:1 did not require the use of the biostimulant for greater chlorophyll fluorescence and synthesis of photosynthetic pigments.