EFFECTS OF SEAWATER SALINITY ON HYPOCOTYL GROWTH IN TWO MANGROVE SPECIES
海水盐度对两种红树植物胚轴萌发的影响

The quality of Bruguiera gymnorrhiza and Rhizophora sty losahypocotyl budding and rooting in water of different salinities (expressed relative to normal sea water) was studied in seeds from the Guangxi coast. Seaw ater salinity lower than 10‰ promoted the budding and rooting of B. gymnorrhi za hypocotyls. Relative to those grown in water with salinity levels higher th an 20‰ and 30‰ these began rooting about 6 days earlier and mean rooting was 7 .1-4.8 days earlier. Rooting rates were 20%-30%. The best seawater salinity co ndition for R. stylosa hypocotyl rooting was about 20‰ at which the rooting rate and mean rooting rate were 90% and 68% respectively. The rooting rate was only 40% in freshwater. A novel bimodal phenomenon in the continuous rooting rat e of B. gymnorrhiza hypocotyles was also observed. Budding of R. stylosa hypocotyls appears to be limited when their base is exposed to light.