In general salt, or sodium chloride, increases the osmotic pressure and inhibits the growth of Baker's yeast, Saccharomyces cerevisiae. Agave nectar contains mostly fructose and honey contains fructose and glucose. Both of these monosaccharides can be used as a source of energy by yeast to product energy and carbon dioxide.
Here is a website that includes useful general information on yeast metabolism, including energy production:http://biochemie.web.med.uni-muenchen.d ... bolism.pdf
The Wikipedia articles on agave and honey include information and references for these sugar sources:http://en.wikipedia.org/wiki/Agavehttp://en.wikipedia.org/wiki/Honey
Here is a reference that describes the optimum growth of Saccharomyces on molasses. The authors define the optimum salt, sugar, temperature, and pH for yeast growth. http://www.doiserbia.nb.rs/img/doi/1451 ... 00029S.pdf
These are just examples of sources of information. You should do additional internet searches for "yeast metabolism," and "optimum growth conditions for Saccharomyces," to find more scientific sources of information and look at the references in the Wikipedia articles.
Please note that for your experiment, if you are comparing the effect of different sugar sources, you should keep all other experimental parameters controlled. So the salt concentration, pH, temperature and other conditions should be identical, and you should only vary the source of sugar.
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