Anatomical responses to waterlogging in Chrysanthemum zawadskii

The purpose of this study was to investigate the anatomical adaptations of Chrysanthemum zawadskii to waterlogged conditions. Compared with the comparable tissues prior to waterlogging treatments, waterlogging caused the thicknesses of the upper epidermis, lower epidermis, leaf, palisade parenchyma, and spongy parenchyma to increase by 27.1%, 67.6%, 33.8%, 47.7%, and 12.4%, respectively. After waterlogging, the ratio of the thickness of the palisade mesophyll to the thickness of the spongy mesophyll, palisade cell length, and palisade cell width increased by 40.0%. 62.2% and 15.9%, respectively. However, after 10 d of exposure to waterlogged conditions, stomatal aperture decreased to 44.4% of that observed in control plants. The stomatal density increased initially after the onset of exposure to waterlogged conditions, reaching levels 126.8% higher than those in control plants after 6 d of exposure to waterlogged conditions, after which it decreased. The amount of intercellular space in root cortex tissue increased 8.9-fold over the course of a 10-d waterlogging treatment. The area of aerenchyma in the stem increased 4.5-fold over the course of a 10-d waterlogging treatment. These substantial changes in leaf anatomy following prolonged immersion come at the cost of reduced rates of photosynthesis. The nature of the changes in leaf, root and stem anatomy suggest that C. zawadskii exhibits anatomical adaptations to cope with waterlogged conditions. (C) 2012 Elsevier B.V. All rights reserved.