CAUSES OF INJURY TO PLANTS RESULTING FROM FLOODING OF THE SOIL

Abstract

Flooding is followed by a rapid reduction in transpiration and the water absorbing capacity of roots, and usually is followed by more or less wilting of shoots. Within 3 or 4 days the lower leaves begin to turn yellow and die, the middle leaves of tomato and yellow poplar show epinasty, and adventitious roots begin to develop on some spp. Injury to the shoots was found to be more severe when the pots were surrounded by soil and flooded than when they were simply submerged in water. Plants potted in soil were injured more than plants potted in sand. Tobacco was most injured by flooding, sunflower least, and tomato was intermediate in amt. of injury. Those plants which produced adventitious roots most rapidly after flooding suffered least injury and showed the greatest degree of recovery. While lack of water might explain the death of the leaves, it cannot explain such characteristic effects of flooding as curvature of the leaf petioles, hypertrophy of stems at the water line, nor development of adventitious roots. Flooding probably stops downward translocation of carbohydrate and auxin, and possibly their accumulation at the water line is responsible for hypertrophy and development of adventitious roots. Accumulation of auxin in the lower part of the stem might also be responsible for the epinastic curvature of the leaves and petioles. The injury and death of the leaves may be caused at least in part by toxic substances moving up from the dead roots or even from the surrounding soil. It is believed that injury to the shoots of flooded plants is complex in origin and has several causes rather than resulting simply from interference with water absorption.