Aerenchyma formation in seminal roots of <em>Hordeum vulgare</em> in hydroponic conditions

Hypoxia is a severe stress factor which negatively affects plant growth. One of the adaptations to hypoxia is formation of aerenchyma. Lysigenous aerenchy ma was found in many species, including barley (Hordeum vulgare L.). At what moment of root development and in which part of it the lysigenous cavities are formed is not completely clear. For this, barley plants were grown hydroponically with and without aeration for 30 and 40 days, respectively. Every 5 days seminal roots from barley plants were detached from the seedlings, and were divided into 4 equal parts characterizing the age gradient of cells from the apical (1) to its base (4) part. Under hypoxic conditions, aerenchyma in barley roots was formed in two stages — to the 10th day of growth (1st stage) and to the 30th day of growth. Lysigenous cavities were mostly formed in the parts with the most mature cells (in the 3rd and 4th parts). Accumulation of H2O2 in basal part of roots could be considered as a trigger for the aerenchyma formation at the first stage, but not at the second one. Aerenchymal lacunae were absent in seminal roots of aerated plants.