Variability of leaf pubescence characteristics in transgenic tobacco lines with partial proline dehydrogenase gene suppression

Proline plays an important role in plant ontogenesis and stress response (Dar et al. 2016, Trovato et al. 2019). The proline content in plant cells increases manifold in response to an increase or decrease in temperature, to drought, soil salinity, nutrient deficiency, increased UV radiation, or exposure to heavy metals resulting in plant osmotic stress (Kuznetsov and Shevyakova 1999). An increase in cell proline leads to the modulation of cell pressure potential, thereby creating an osmotic balance, stabilizes cell membranes, protein and enzyme structures, preventing electrolyte leakage in the cell and oxidative stress. Thus, proline acts as a signalling molecule of stress response in plants (Hayat et al. 2012). Changes in proline content are just one of many plant stress responses: physiological, morphological, and anatomical (Hameed et al. 2010, Ilyas et al. 2020). One of the characteristic morphological changes is associated with leaf pubescence. Leaf pubescence is formed by