Physiological and Morphological Changes in Maize Plants Under Various Flooding Conditions

Abstract

Physiological and structural changes were determined in shoots and in uneven-aged roots of maize (Zea mays L.cv. Odess-kaya 10) plants after exposure to waterlogging (the roots and lower part of the stem) for different periods of time. Waterlogging, especially in short-term experiments, promoted water exudation. In adventitious roots and in stem base tissues flooding enhanced respiration. The total volume of xylem and the primary cortex area increased in adventitious roots and a formation of aerenchyma was observed. In the conducting bundles of the stem base central region waterlogging promoted vessel expansion and weakening of the sclerenchyma. The enhancement of physiological activity in adventitious roots, as compared with the main root, and rearrangements in their structural organization are considered adaptive responses of plants to flooding. Simultaneously the growth and structural peculiarities of adventitious roots and stem base after exposure of whole plants to flooding were examined. The treatment period lasted for 24, 48 and 72 h. The growth of shoots and roots was retarded under flooding conditions. The rate of exudation from adventitious roots and the oxygen uptake in all organs decreased in comparison with the control. The data show that flooding promoted vessel expansion and weakened mechanical elements. The adaptive responses in flooded plants appeared only if the period of flooding lasted for about 24-36 h. The adaptive reactions to hypoxia depend primarily on whether the cessation of oxygen supply affected the whole plant or the root system alone.