The role of abscisic acid and salination in the adaptive response of plants to reduced root aeration

Cessation of root aeration to tobacco plants (Nicotiana rustica) growing in half-Hoagland nutrient solution resulted in rapid wilting of the shoot. Plants growing in salinated solutions, however, retained their turgor despite lack of aeration. This resistance to aeration stress was associated with increased concentration of abscisic acid in the leaves. Maximum amounts of abscisic acid in leaves were reached by the 4th day of salination and coincided with the maximum resistance to lack of aeration. When the plants were returned to half-Hoagland, leaf-abscisic acid decreased to the presalination level. Resistance to lack of aeration also resulted when plants were pretreated with abscisic acid. We tentatively conclude that resistance to lack of root aeration reflects adaptation to osmotic stress and is partly due to an increase in the content of leaf-abscisic acid.