Figure 47. Metabolic conversions of pyruvic acid. This "key" 

 intemiediate in metabolism can be converted to a variety of end 

 products, depending on the organism and the electron acceptors 

 available (Nester et al. 1973). 



to shift from aerobic to anaerobic 

 (fennentation) metabolism. In one study, 

 enzymatic alcohol dehydrogenase (ADH) 

 activity, a measure of the cells' ability 

 to convert acetaldehyde to ethanol during 

 alcoholic fermentation, was much higher in 

 inland sites where the soil reduction 

 potential was intense than in a nearby 

 less-reduced streamside marsh (Table 17). 

 Alcohol did not accumulate in inland plant 



Table 17. Spartina al terni fl ora root 

 alcohol dehydrogenase (ADH) activity, 

 adenosine triphosphate (ATP) and ethanol 

 concentrations, and soil Eh in a Louisiana 

 salt marsh (Mendelssohn et al . 1982). 



Variable 



Unit 



Location 



Strediaside 



Inl and 



^71" 



ADH nmoles NADH oxi- 36 t 9 325 



dized/g fw/hr 



ATP umoles/g dw 218 -23 248 -25 



Ethanol umoles/g fw 1.17t .07 1.10* .08 



Eh mV 174 t30 -131 ^22 



Meantstandard error of mean. 



tissues in spite of the high ADH activity, 

 indicating that it was able to diffuse out 

 of the roots. 



In spite of these adaptations marsh 

 plants in highly reduced environments are 

 stressed, as shown by reduced growth rates, 

 and in severe cases, death. Comparison of 

 streamside to inland sites in the salt 

 marsh provides good examples of the 

 intensity of the stressing agents, their 

 relationship to tidal flooding, and their 

 effects on plant growth. Figure 48 shows 

 schematically a few of the transfonnations 

 that result from tidal action, and their 

 effects on plant growth. When the tide 

 rises it carries minerals, both 

 particulate and dissolved, onto the marsh. 

 Because the water slows as it crosses the 

 natural levee, most of the sediment is 

 deposited close to the stream bank, less 

 inland (Table 9). At the same time, 

 flooding water reduces the diffusion rate 

 of oxygen into the marsh soil. The result 

 is usually anoxic soils, especially where 

 organic concentration is high. The 

 streamside dred is flooded as regularly as 



52 



