Plant cells, tissues and organs are composed of various biomolecules arranged as structurally diverse units, which represent heterogeneity at microscopic levels. Molecular knowledge about those constituents with their localization in such complexity is very crucial for both basic and applied plant sciences. In this context, infrared imaging techniques have advantages over conventional methods to investigate heterogeneous plant structures in providing quantitative and qualitative analyses with spatial distribution of the components. Thus, particularly, with the use of proper analytical approaches and sampling methods, these technologies offer significant information for the studies on plant classification, physiology, ecology, genetics, pathology and other related disciplines. This review aims to present a general perspective about near-infrared and mid-infrared imaging/microspectroscopy in plant research. It is addressed to compare potentialities of these methodologies with their advantages and limitations. With regard to the organization of the document, the first section will introduce the respective underlying principles followed by instrumentation, sampling techniques, sample preparations, measurement, and an overview of spectral pre-processing and multivariate analysis. The last section will review selected applications in the literature.

Infrared (IR) spectroscopy, as one the most common spectroscopic techniques, has been developed in terms of both instrumentation and analysis methods. This allows the wide applications of infrared spectroscopy in all branches of basic and applied research. Especially, its ability for direct identification of chemical changes without the addition of contrast agents enables the examination of a large variety of biological samples, including biological fluids, isolated cells, tissues, and sections. This review focuses on in vitro and in vivo applications of Fourier transform infrared (FTIR) spectroscopy and Fourier transform infrared microspectroscopy (FTIRM) to analyze the biochemical and structural changes associated with neurological diseases such as Alzheimer's disease, Parkinson's disease, transmissible spongiform encephalopathies, multiple sclerosis, as well as epilepsy. With the application of FTIR and FTIRM, successful discrimination of pathological states of these diseases could be achieved. Hence, the high capacity of these methods offers insight into disease-induced alterations underlying pathogenesis of the diseases, which provides early diagnostic information and the improvement of therapeutic approaches.

There is significant increasing interest in phosphodiesterase-4 (PDE4) inhibition in treatment of cardiovascular diseases. Related with this, research has focused on cellular, biochemical, molecular and structural changes in heart tissue induced by PDE4s inhibitors. However, for their clinical applicability additional studies are still needed. Fourier transform infrared spectroscopy offers promising approach to contribute such issue due to its ability in detection the changes in biomolecules. By utilizing this method, we examined the effects of PDE4 inhibition by rolipram at 0.05 mg/kg and 0.1 mg/kg doses on content of lipids and proteins, and fluidity, order and packing of membranes in naive mice heart. In treated groups, there was a significant decrease in unsaturated, saturated lipids, cholesterol esters, fatty acids, phospholipids and triacylgylcerols obtained from CH2, C=O, olefinic=CH, and COO- areas, and CH2/lipid, C=O/lipid, olefinic=CH/lipid, and COO-/lipid ratios. Additionally, olefinic=CH area and olefinic=CH/lipid ratio may suggest decreased lipid per oxidation, confirmed by thiobarbituric acid assay. Also, a higher degree of membrane order, slight increase in membrane fluidity and differences in membrane packing were obtained. Amide I and II areas and RNA/protein ratios showed that variation in protein content is not correlated with applied concentration. Analysis of amide I mode predicted alterations in secondary structures like an increase in random coils and decrease in alpha-helices. Moreover, all groups were successfully discriminated by cluster analysis. The corresponding results may help to understand the potential effects of PDE4 inhibition by rolipram.