Growth, Morphology, Stem Anatomy, and Ethylene Production in Flooded Alnus Japonica Seedlings

Flooding of soil of potted, 24-month-old Alnus japonica seedlings for 24 days altered growth, morphology, stem anatomy, and ethylene production. This species exhibited high adaptability to soil flooding by forming adventitious roots that grew through hypertrophied lenticels. Aerenchyma tissues were observed in the bark of the adventitious roots. Flooding slightly reduced height growth and greatly stimulated diameter growth of submerged portions of stems in comparison with unflooded seedlings. Diameter growth in flooded seedlings was largely due to increases in both the number and size of wood fibres produeed during the flooding period. Flooding did not affect biomass increment of leaves and stems but reduced the total dry weight increment of the root system even though abundant adventitious roots had formed. Ethylene production in the submerged portions of stems was greatly increased by flooding. Morphological and anatomical responses of Alnus japonica seedlings to flooding are discussed.