Metabolic and Ultrastructural Changes Associated with Flooding at Low Temperature in Winter Wheat and Barley

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Abstract
Cold-hardened winter wheat (T. aestivum L. cv. Fredrick) and winter barley (H. vulgare L. cv. Dover) were exposed to total flooding at 2.degree. C. ''Dover'' seedlings were damaged more quickly than ''Fredrick'', and after 3 wk of flooding the survival of ''Dover'' was reduced to 10% and ''Fredrick'' to about 50%. Tissue moisture was slightly greater in ''Dover'' than ''Fredrick'' throughout the 4 wk flooding period. CO2 and ethanol accumulated throughout the 4 wk flooding period in both cultivars. Lactic acid increased rapidly during the 1st wk of flooding, and remained relatively constant during the remainder of the flooding period. O2 consumption of seedling shoot tissue after exposure to flooding declined abruptly after only 1 day of flooding, but recovered somewhat during the subsequent 2 wk. The effect of flooding was more pronounced on the ultrastructure of ''Dover'' than ''Fredrick''. Although proliferation of endoplasmic reticulum was observed in the early stages of flooding in both cultivars, the occurrence of distinct parallel arrays and concentric whorls of membranes was prevalent in the flooded barley. Severe ultrastructural damage to a large proportion of apical cells in both cultivars was observed after 2-3 wk of flooding.