Abstract
ABSTRACT Soil water saturation requires different adaptative strategies by tree species that live under such conditions. We aimed to study the responses that ensure flooding tolerance by tree species and so provide support for recovery projects with degraded areas subject to flooding. We evaluated the ecophysiology of Cedrela fissilis under different water saturations, including anatomical traits, gas exchange parameters, antioxidant system analysis and growth. We subjected 100 day-old plants to three treatments: Control (FC) where the substrate was kept at field capacity; Flooded Roots (FR), where the substrate remained submerged but with no surface layer of water, and Flooded Stem (FS), with a water layer accumulation of around 3.0 cm over the substrate, flooding part of the stems. The plants were kept under such conditions for 90 days. Plants survived in all treatments due to a marked development of cortical intercellular spaces in flooded plants. However, photosynthesis and other gaseous exchange were limited under FR and FS treatments. In addition, the periderm thickness was reduce by flooding and there was an accumulation of starch grains in the parenchyma cells of the xylem, cortex and pith of the stem. There was also a significant lipid peroxidation on the leaves under FR and FS treatments. The superoxide dismutase activity was decreased, but the activities of the ascorbate perioxidases and catalase in the leaves were increased. We concluded that young Cedrela fissilis plants partially tolerate flooding since they developed ecophysiological changes in order to survive in this condition. Consequently, this species is a good candidate for the reforestation projects in environments where intermittent flooding occurs, such as riverside and riparian forests.
Highlights
Climate change has affected the water cycle around the world impacting on the availability of water resources in ecosystems (Marengo et al, 2011)
All C. fissilis plants survived for the experimental period of 90 days, regardless the treatment
C. fissilis plants grown under flooding showed significant decrease in shoot growth with a 44% decrease of this variable in the Flooded roots (FR) treatment and 64% for plants of Flooded stem (FS) treatment
Summary
Climate change has affected the water cycle around the world impacting on the availability of water resources in ecosystems (Marengo et al, 2011). A great oscillation of water availability is estimated to occur in tropical forests, promoting unusual periods of rainfall which may affect and the occurrence and duration of flooding events (IPCC, 2014). In this scenario, in which flooding events are likely to increase, plant life may be impaired once soil water saturation decreases oxygen availability (Loreti et al, 2016). Low oxygen availability may trigger several disorders in plants, such as reduced growth, chlorosis, premature abscission of leaves, decreased water potential and leaf expansion, among other effects and may even, in some cases, result in plant death (Jackson and Colmer, 2005; Medri et al, 2012). Flooding causes changes in the biomass allocation among the plants organs and changes in carbohydrate storage (Ferreira et al, 2009), hypertrophy of lenticels, and development of adventitious roots and aerenchyma (Arruda and Colbo, 2004; Medri et al, 2007; Voesenek and Bailey-Serres, 2015)
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