Responses of Ulmus americana seedlings to flooding of soil

Abstract

Flooding of soil induced several physiological, morphological, and growth changes in 12- or 13-week-old Ulmus americana L. seedlings. Among the early responses to flooding was stomatal closure, without subsequent reopening, in leaves that were fully expanded by the time flooding was initiated. However, flooding did not induce stomatal closure of leaves that completed expansion during the flooding period. Flooding greatly accelerated production of ethylene by stems. Other responses to flooding included stem swelling; production of hypertrophied lenticels and abundant adventitious roots on submerged portions of the stem; reduction in leaf formation and expansion; and inhibition of dry weight increment of leaves, stems, and roots. Some of the morphological responses to flooding appeared to be associated with accelerated ethylene production. The much greater reduction in root growth over leaf growth in flooded seedlings will create leaf water deficits and predispose seedlings to drought injury after the flood waters recede.