Ultrastructural Changes of Organelles in Root Cap Cells of Tobacco Under Salinity

We investigated how an abiotic factor, i.e. salinity, affects specific intracellular organelles of cells of the root cap. We focused on: 1) amyloplasts, which are specific plastids of the cap that perform important metabolic and sensory functions; and 2) mitochondria, which protect cells from ROS damage by changing their ultrastructure. In our work we studied the ultrastructural changes of these organelles in different areas of the root cap under NaCl and Na₂SO₄ impact. We showed that the amyloplasts (statoliths) and mitochondria of the columella and the peripheral zone of the cap change their structural organisation in the presence of NaCl. Under action of Na₂SO₄, in plastids of columella the number of starch grains decreases dramatically, the cells of the peripheral part of the cap do not contain the amyloplasts, and the proplastids that do not store or store a little starch grains, which is attributed to leucoplasts with typical lamellae characteristic for root cortex cells. Thus, Na₂SO₄ influence has the most significant effect on the plastids of the root cap, and plastids of the cells of the peripheral zone of the cap are subjected to the most significant changes under salinity stress.