At the V—VIII stages resistance to a drought of cereals decreases, the crop falls due to reduction of quantity of cones and in an ear (. Drought resistance, as well as heat resistance of plants, sharply decreases with education at them generative bodies and to blossoming (the VII—IX stages) inclusive. According to F. D. Skazkin, cereals are most sensitive to moisture in the period of phases an exit in a tube — a kolosheniye. Therefore, during the critical period generative bodies are formed, there are a blossoming and fertilization.
In an of a plant are unequally sensitive to a lack of water. Plants are very sensitive to a lack of water during the periods of the greatest growth of concrete body or all plant. For each species of plants there are critical periods, i.e. the periods of the greatest sensitivity to supply with water. At the I—IV stages of an organogenesis cereals are rather steady against a though the crop decreases in this case due to reduction of number of the put cones in an ear.
During generative development of plants at early stages of development the drought results in sterility of flowers (to a cherezernitsa and a pustokolosye), and on later (dairy, wax ripeness) — to decline in quality and quantities of a crop of fruits and seeds, to formation of the puny grain which is insufficiently filled with nutritious spare substances with a weak germ. It is important to emphasize what exactly during the critical periods a most intensively grow and form hozyaystvenno bodies (fruits, seeds, etc.).