Factors affecting Photosynthesis;
http://www.marietta.edu/~spilatrs/biol103/photolab/globexpl.html
http://library.thinkquest.org/22016/photo/rate.html (watch for typos) Will tell you in general what affects photosynthesis, and how the effects of increasing or decreasing components are exerted.
Methanotrophic bacteria are by necessity anaerobic. Thus the answer to your second question as you stated and amended it is zero.
For methanotrophs, try:
http://www.nature.com/cgi-taf/DynaPage.taf?file=/nature/journal/v356/n6368/abs/356421a0.html http://www1.dupont.com/NASApp/dupontglobal/corp/index.jsp?page=/content/US/en_US/science/sharpe.html http://www.newscientist.com/conferences/confarticle.jsp?conf=amgun200006&id=22421100 http://www.pubmedcentral.nih.gov/articlerender.fcgi?artid=91497 http://www.spacedaily.com/news/life-04zzzu.html (again a typo alert in this one)
Beam me up, Scotty.
I'm sorry to disappoint you but there is no methane-consuming plant life on this planet anymore. It all died out when the oxygen level in the air got too high.
