Growth and energy status of arrowhead tubers, pondweed turions and rice seedlings under anoxic conditions

Abstract

The responses of two aquatic plants, arrowhead ( Sagittaria pygmaea Miq.) and pondweed ( Potamogeton distinctus A. Benn), to anoxia were compared with those of rice ( Oryza sativa L.). Shoot elongation of arrowhead tubers was enhanced at around 1 kPa O 2 , whereas that of pondweed turions was slight in air and reached a maximum in the absence of O 2 . Anaerobic enhancement of alcohol dehydrogenase (ADH) activity took place in rice coleoptiles but not in arrowhead and pondweed shoots. Shoots of both arrowhead and pondweed maintained a more stable energy status than did the rice coleoptile under anaerobic conditions. Total adenylate nucleotide contents of arrowhead and pondweed shoots were constant under anaerobic conditions. Adenylate energy charge in both shoots remained at a high and stable level of more than 0·8 for at least 8 d. Three forms of ADH from arrowhead shoots were separated by starch gel electrophoresis, showing that the activity of each ADH form was different under aerobic and anaerobic conditions. The incorporation of 35 S‐labelled Cys and Met into soluble proteins in arrowhead shoots showed active protein biosynthesis and an involvement of a special set of polypeptides in the anaerobiosis.