Leaf Conductance, Growth, and Survival of Willow and Deciduous Fruit Tree Species under Flooded Soil Conditions

Potted seedlings and cuttings of various tree species were submerged to 5–10 cm above the soil level for up to 20 months in order to determine flood tolerance based on leaf conductance (kl), growth, and survival. Flooding induced a decline in kl at soil oxygen diffusion rates of 30, 22, 20, and 15 × 10 −8 g cm −2 min −1 for Prunus persica (L.) Batsch, Halford seedlings (peach), Pyrus communis L. cv. Bartlett (Bart), Pyrus calleryana Decne (Call), and Pyrus betulaefolia Bunge (Bet), respectively. The leaves of some species, particularly Pyrus communis L. cv. Old Home × Farmingdale 97 (OH × F 97), abscised shortly after a decline in kl, yet leaves of most other Pyrus species did not abscise despite months of maintaining a kl near zero. Growth rates were reduced for all fruit tree species except Bet and Call after one month of spring flooding. One month of fall flooding reduced the growth of all fruit tree species the following spring. Bet survived 20 months of continuous submergence; however, only Salix discolor Muhl. (willow) grew well under these conditions. Flooding promoted adventitious rooting of willow, Cydonia oblonga Mill. cv. Provence BA 29 (quince) and Malus domestica Borkh. cv. MM 106 (apple); anthocyanin pigmentation in leaves of apple and all Pyrus species; leaf chlorosis of quince, apple, and peach; and hypertrophied lenticels on the submerged stems and roots of all species. The tolerance, based upon kl, growth, and survival, was: willow > Bet > Call = quince > Bart > OH × F 97 = Pyrus pyrifolia (Burm.) Nak. (Pyri) = Pyrus ussuriensis Maxim. (Ussuri) = apple > peach. Although the survival of pear rootstocks with and without a ‘Bartlett’ scion were similar, flooding symptoms often were quite different.