Investigation of microstructural analyses of wheat grown in in vitro condition by spectroscopic and microscopic methods

In this thesis, it was aimed to investigate the changes in the microstructure of of the four-week-old wheat seedlings of Selimiye variety grown in tissue culture medium (in-vitro conditions) by exposing to different concentrations of salt stress factor by biochemical, spectroscopic and microscopic methods. Wheat (Triticum aestivum L.) is systematically a member of the Poaceae family and is the third most important cereal crop worldwide. It is the main food source of approximately 35% of the world's population as well as meets 20% of the calorie and protein needs. In addition, wheat constitutes a large part of the grain production in Turkey. In order to obtain high yield from the plant, it must meet the optimal environmental demands. Any deviation from optimal demands causes stress in the plant. A stress impacts the plant metabolism, it can prevent its growth and development; then, product and yield loss may occur. Salinity is one of the major abiotic stress factors affecting growth and crop productivity of plants. There are many scientific studies showing that both terrestrial and irrigated areas are greatly affected by salt stressor. Therefore, the current studies to evaluate the effects of salt stressor on plants are increasing. In the process of examining the effects of a stress factor on the plant, it is also important to create in-vitro environments that allow it to be applied in homogeneous concentrations and under controlled conditions. Selimiye wheats were grown in tissue culture environments containing MS (Murashige and Skoog) media as one (1) control group without salt and four (4) groups under different salt concentrations (50 mM, 100 mM, 150 mM, 200 mM NaCl). In the first step, biochemical methods based on UV-Visible Spectroscopy technique were used in the measurement of malondialdehyde (MDA), chlorophyll and carotenoid values, which are frequently used as bioindicators in the determination of the damage caused by the applied salt stressor to the plant samples. In the second step, the effects of salt stress factor on the microstructure of leaf samples of grown wheats were aimed to be revealed by performing Raman Spectroscopy (RS) and Scanning Acoustic Microscopy (SAM). Raman spectra of the samples examined have been obtained in the wavenumber range of 200−2200 cm−1 and vibrational bands have been assigned. The variation of the intensities of vibration modes attributed to each band has been analyzed. Two-dimensional surface acoustic images of the investigated samples without disturbing the surface morphology and without any preliminary preparation have been mapped by SAM technique, and the average acoustic impedance values have been calculated. Changes in surface microhardness, elasticity have been determined depending on diseases/damages in microstructure of soft and hard tissues of wheats. In line with the purpose of this thesis study; in the determination of the effects of applied salt stressor on wheat samples, it has been demonstrated that Raman and TAM techniques can be used as stressor determination methods that are faster as well as less manpower requirement and time loss compared to the biochemical techniques that are frequently used today.