Nitrogen Variable Rate Influence on Photosynthetic Pigments in Wheat Flag Leaf

Abstract

The study evaluated the variation of photosynthetic pigments (chlorophyll, carotenoids) in wheat flag leaves in relation to the nitrogen variation rate. The PG102 winter wheat variety was cultivated, in non-irrigated conditions, on a chernozem type soil. Nitrogen was applied in doses of 0 - 280 kg ha-1 a.s., in a variation rate of 40 kg ha-1 a.s. (active substances). The field experiments took place in ULS "King Mihai I" from Timisoara, Romania. At the time of flowering (BBCH code 6), random samples of flag leaves were taken on each experimental variant. The chlorophyll content (Chl) varied between Chl = 43.73±1.04 (V1) and Chl = 58.92±1.21 (V6). The carotenoid content (Car) varied between Car = 10.12±0.59 (V1) and Car = 21.56±0.49 (V6). Based on the Chl and Car values, the Chl/Car and Car/Chl ratios were calculated for each experimental variant. According to Kruskal-Wallis test, resulted significant difference between sample medians (p (same) = 1.56E-05 in case of Chl data series; p (same) = 2.616E-09 in case of Car data series). The variation of Chl and Car pigments in relation to nitrogen (N) was described by polynomial equations of the 3rd degree, under statistical safety conditions (R2 = 0.981 in the case of Chl; R2 = 0.986 in the case of Car; p<0.001). The variation of Car in relation to Chl was described by a polynomial equation of degree 3 (R2 = 0.978, p<0.001).