Fourier transform infrared spectroscopic analysis of maize (Zea mays) subjected to progressive drought reveals involvement of lipids, amides and carbohydrates

Changing climate means that there will be more episodes of drought, especially in arid regions. Drought stress is an important environmental factor that reduces crop productivity. Despite the vast amount of literature on drought stress in plants, there are still many uncertainties concerning the molecular responses under water deficit. In particular, if we wish to breed plants that are able to tolerate stress, identifying novel traits that contribute to this is desirable. In this study, Fourier transform infrared (FTIR) spectroscopy was used to investigate the response of maize to progressive drought. The objective was to determine whether FTIR spectroscopy is a technique that might be used in monitoring the molecular processes involved in drought responses in plants. Maize seeds were grown for three weeks in a controlled environment before drought was imposed by withdrawing water for up to 12 days. Principal component-discriminant function analysis (PC-DFA) indicated that water deficit elicited changes in the FTIR spectra within the wavenumber ranges of 3050 to 2800, 1750 to 1250 and 1250 to 900 cm-1. With water deficit, the intensities of the absorption bands were reduced. PC-DFA loadings confirmed that the signals to the changes were lipids, amides and carbohydrates, respectively. This work shows that FTIR spectroscopy can provide valuable insights into drought responses of plants and maybe useful for identifying novel drought tolerance traits.   Key words: Metabolic fingerprint, molecular changes, multivariate analysis, principal component-discriminant function analysis (PC-DFA), principal component analysis (PCA).