Avaliação das alterações de crescimento e do perfil bioquímico por espectroscopia no infravermelho de plântulas de Lactuca sativa L. expostas a sulfato de níquel

Abstract

Nickel despite being an essential micronutrient for several organisms, in certain concentrations can have a negative impact on biodiversity. In this work, spectroscopy in the mid-infrared region (MID) was used with statistical treatments to identify changes in growth and changes in the biochemical profile of lettuce seedlings induced by nickel sulfate (NiSO4) grown in microenvironments and to correlate with biometric data and physiological (germination percentage (%G), germination speed index (VGI), radicle length (RL) and hypocotyl length (HL), vigor index (IV) and nickel tolerance index (TI)). Lettuce seeds were germinated in different environments (distilled water (control) and NiSO4 at concentrations of 0.081; 0.161 and 0.323 mmolL-1). Cotyledon leaves of lettuce seedlings (CLLs) were subjected to MID spectroscopic analysis by attenuated total reflection (ATR). The values of RL, VI and TI significantly reduced (P < 0.05) in NiSO4 0.161 mmolL-1 and 0.323 mmolL-1 treatments when compared to the control. The principal component analysis (PCA) of the spectral data of the CLLs allowed explaining 98.91% of the total variance using three principal components. Considering the analysis of the peaks in the spectrum, significant changes (P < 0.05, ANOVA and Tukey's test) were noted in the intensity of molecular vibration between wave numbers 1100 cm–1 – 1231 cm–1; 1355 cm–1 – 1366 cm–1 and 1738 cm–1, plus significant peak shifts (P < 0.05, Kruskall-Wallis test) between wave numbers 2845 cm–1 – 2930 cm–1. Together, the data suggest an increase in the biosynthesis of carbohydrates (pectin, cellulose) and structural lipids in CLLs at a concentration of 0.081mmolL-1 when compared to the control due to the availability of the SO4 2- ion as an activator of biosynthesis metabolic pathways and at the same time, Ni+2 concentration dependent decrease in the vibrational intensity of functional groups of these biomolecules at higher NiSO4 concentrations, as a consequence of increased Ni+2 bioaccumulation. Peak shifts may be related to the formation of Ni+2 complexes with biomolecules. The use of MID enabled the evaluation of the composition and intensity of the bands, and when associated with statistical treatments, it proved to be a promising and complementary tool to studies of the effect of toxic metals on plant germination.