Structural changes of root, stem and leaf tissues in Tritichum aestivum cv. Mihan, under drought stress

Drought is the most challenging abiotic stress, which has irreversible effects on plant growth and development and reduces crop production worldwide. The effects of drought stress on the structure of leaves, roots, and stems of Tritichum aestivum cv. Mihan, were investigated under four different irrigation levels i.e. optimal irrigation or 100% of field capacity (FC), low stress (75% FC), mild stress (50% FC), and severe stress (25% FC). Microscopic sections from plant tissues were prepared, stained with Carmen Zaji and Methylene Blue, and studied using fluorescence and light microscopy. The results showed that in the roots, drought stress reduced the thickness of sclerenchyma tissue, cell walls and casparian strip in the endodermis, as well as the diameter of the root and metaxylems and the number of metaxylems. However, the lignin of the root's epidermal cell walls was increased. In stems, drought stress reduced the thickness of the cuticle layer and as well as cell walls diameter of sclerenchyma tissue, xylem and phloem. Reducing of chlorenchyma tissue area and ground parenchyma tissue cell size were also seen. In leaves, an increase in epidermal cell size, anthocyanin content, sclerenchyma cell size, and a decrease in xylem diameter were observed. Taking all together, structural changes indicate plant's effort to adapt to drought stress, possibly through metabolic processes.