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In this study, we present the complete mitochondrial DNA sequences of Epinephelus areolatus for the first time, which is 16,893 bp in length and contains 13 protein-coding genes, 2 rRNA genes, 22 tRNA genes, and a putative control region. The overall base composition of the H-strand is 27.0% T, 28.0% C, 28.6% A, and 16.3% G. The CO1 gene is initiated by GTG codon and ATP6 gene is initiated by TTG codon. The tRNA-Ser2 cannot be folded into the typical cloverleaf secondary structure because its dihydrouridine arm is replaced by a simple loop. A long-tandem repeat motif (76 bp), repeated six times, is found in the control region.

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From August 2004 to August 2005, three replicate experimental platforms were constructed in a section of the tidal flats in Yingluo Bay, Guangxi Province to study the growth and physiological responses of Rhizophora stylosa Griff seedlings to tidal waterlogging stress in a diurnal tidal zone. A total of eight tidal flat elevation (TFE) treatments, i.e., 320, 330, 340, 350, 360, 370, 380 and 390 cm above Yellow Sea Datum (YSD), were created on each platform. The results showed that lower TFEs (320-330 cm YSD) slightly increased the seedling stem height of 1-year old seedlings, while higher TFEs ( > 340 cm YSD) increased the seedling growth significantly. Moderate TFEs (350-370 cm YSD) favored the development of knots. Number of leaves, leaf conservation rate and leaf area per seedling all decreased dramatically with decreasing TFE. Lower TFEs caused large damage to Chl a, but Chl b was less affected. The Chl a/b ratio decreased with decreasing TFE. Prolonged waterlogging induced higher SOD activity in roots, while moderate TFE inhibited the SOD activity in leaves. The POD activity in roots and leaves increased with decreasing TFE. Waterlogging stress decreased the biomass of individual organs and entire seedlings. With increasing waterlogging, the biomass partitioning in 1-year old seedlings increased from leaf to stem. The survival rate decreased sharply from 88.9% to 40.0% as TFE decreased, while more than 80% of the seedlings were able to survive at the TFE level of 370 cm YSD and above. We propose that the local mean sea level should be adopted as the critical tidal level for forestation with hypocotyls of R. stylosa along the Guangxi coast.