Effects of soil hypoxia and salinity on gas exchange and growth of Spartina patens

Laboratory expenments were conducted to evaluate the effects of increased so11 salinity on gas exchange functlonlng and growth of the braclush-marsh grass Spartlna patens (Alt) Muhl under controlled soil redox potentials (Eh) which were malntalned at either aerobic (+489 mV) or hypoxlc (-40 mV) conditions Plants were subjected to salinities of 0 5, 15 and 25 ppt gradually over a 7 d penod and leaf tissue chlorophyll content, gas exchange and growth responses were measured Leaf hssue chlorophyll content was not affected by the treatments Gas exchange of S patens was adversely influenced by increases in salinity Leaf conductance was reduced by 36 % and net photosynthesis by 23 % of control plants under aeration plus 25 ppt salinity and water use efficiency increased to 161 % of control plants When increased salinity accompanied hypoxia leaf conductance and net photosynthesis were reduced by 60 and 44 % of control plants respectively The Interaction between sallnity and hypoxla was not significant Sahnity of 25 ppt reduced root dry weight leaf dry weight and height growth sign~f~cantly Sallnlty and hypoxla combined affected various biomass components whlle hypoxla pnmanly affected root dry weights Elevated salinity and hypoxia also adversely affected gas exchange functions and growth Results presented suggested that saltwater intrusion is a malor factor contnbuting to the rapid rate of marsh deterioration in coastal Lolusiana (USA) brackish marshes which are dormnated by S patens