Frontiers in Plant Science (Aug 2015)
Physio-biochemical and morphological characters of halophyte legume shrub, Acacia ampliceps seedlings in response to salt stress under greenhouse
Abstract
Acacia ampliceps (salt wattle), a leguminous shrub, has been introduced in salt-affected areas in northeast of Thailand for remediation of saline soils. However, the defense mechanisms underlying salt tolerance A. ampliceps are unknown. We investigated various physio-biochemical and morphological attributes of A. ampliceps in response to varying levels of salt treatment (200 to 600 mM NaCl). Seedlings of A. ampliceps (252 cm in plant height) raised from seeds were treated with 200 mM (mild stress), 400 and 600 mM (extreme stress) of salt treatment (NaCl) under greenhouse conditions. Na+ and Ca2+ contents in the leaf tissues increased significantly under salt treatment, whereas K+ content declined in salt-stressed plants. Free proline and soluble sugar contents in plant grown under extreme salt stress (600 mM NaCl) for 9 days significantly increased by 28.7 (53.33 mol g1 FW) and 3.2 (42.11 mg g1 DW) folds, respectively over the control, thereby playing a major role as osmotic adjustment. Na+ enrichment in the phyllode tissues of salt-stressed seedlings positively related to total chlorophyll degradation (R2=0.72). Photosynthetic pigments and chlorophyll fluorescence in salt-stressed plants increased under mild salt stress (200 mM NaCl). However, these declined under high level of salinity (400-600 mM NaCl), consequently resulting in reduced net photosynthetic rate (R2=0.81) and plant dry weight (R2= 0.91). The study concludes that A. ampliceps has an osmotic adjustment and Na+ compartmentation as effective salt defense mechanisms, and thus it could be an excellent species to grow in salt-affected soils.
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