Fourier transform infrared spectral analysis of maize (Zea mays) plants under zinc deficiency stress

【Objectives】Fourier transform infrared spectroscopy (FTIR) is a structural analysis technique based on the vibrations of functional group and polar bond in chemical components. The objective of this study was to reveal the component changes in different organs of maize plants with and without zinc(Zn) application using FTIR. It would provide some physiological evidences of maize plants subjected to Zn deficiency stress.【Methods】Two maize cultivars, Nongda108 and Zhengdan958, were chosen as tested crops. Hydroponic culture experiments were conducted with 0 and 10 mol/L Zn treatments. The plant shoot and root biomass were weighted. Dry plant samples were digested with HNO3-HClO4 (3∶1) for Zn determination by atomic absorption spectrophotometer. Root samples were stored in FAA solution (70% alcohol∶38% formaldehyde∶acetic acid = 90 ∶5∶5 parts by volume) prior to measurements. The root systems were then digitized with the EsponV700 scanner at 300 dpi resolution for further analysis. The total root length and root volume were measured with WinRHIZO root analysis software (Regent Instruments Inc., Canada). Dry samples of roots, stems and leaves were ground to through 0.2 mm sieve. A potassium bromide tablet method was used to detect spectral characteristics of different plant parts with FTIR (VERTEX 70, Bruker) and data were collected and analyzed by the OPUS 6.5 software. 【Results】The results show that Zn concentrations in maize plants without Zn application are below the critical level of 20 g/g, and the Zn deficiency stress significantly decreases shoot dry matter weight, root surface, root volume and total root length. The shoot biomass and root length of maize cultivar, Nongda108, are less than those of Zhengdan95 under the Zn deficiency, which indicates Nongda108 might be more sensitive to Zn deficiency. Compared with the 1.0 mol/L Zn treatment, plants with Zn deficiency show higher transmittance at peaks of 3410, 2920, 1650, 1380 and 1055 cm-1 in FTIR spectra of roots and leaves and lower transmittance in stems, which indicates the sugar, lipid and protein contents in roots and leaves are decreased, and the contents in stems are increased under the Zn deficiency stress. 【Conclusions】Zn deficiency has a great negative influence on plant growth and results in changes of organic components contents, including starch, lipids, protein, and nucleic acids in different parts of plants based on FTIR determinations. Nongda108 might be more sensitive to Zn deficiency compared with Zhengdan958.