Response of oilseed rape leaves to sulfur and boron foliar application

Oilseed rape ( Brassica napus L.) reacts differently to foliar application of sulfur (S) and boron (B), and for that reason it is important to find an early indicator that would inform about the direction of this reaction. This study aimed at evaluating the early response of two double-low cultivars of winter oilseed rape: hybrid (Nelson) and open pollinated (Digger) on the foliar fertilization with S and B in two terms: fall and spring, based on the rate of leaf greenness index (SPAD) and seven indicators of chlorophyll a fluorescence (FL). On 7th or 9th day after the application of liquid fertilizers, the selected parameters of FL and SPAD were determined on the leaves of rape. As a result, a significant effect of foliar B and S supplementation on the yield of oilseed rape was found. Principal component analysis (PCA) allowed for a separation for each of the cultivars the two parameters of FL, namely Tfm and Fv/F0, which are sensitive indicators of a physiological state of the rape plants shortly after foliar S and B dressing.