botany help...?

go to answers.com at search of site ,type heterocyst  , spawns , Koch's postulates  , chlorosis  , necrosis , spore , for each of these ,you find detailed information  , for cleisothecium  type cleisothecium you get links  some of them are good , hope this helps you  .

Heterocyst - When cyanobacteria are both anaerobic and lacking nitrogen they can alter in response to the environment then they fix nitrogen for themselves. However they do this at a cost as they can no longer photosynthesize in they same way. They revert to an older photosynthetic pathway that will not release oxygen but does supply them with energy.
Oxygen in their area would stop them from fixing the nitrogen they need. The enzymes required to fix nitrogen are in the nitrogenase operon (gene series regulated as one to keep them in order & proportion).  The operon is only released from down regulation if there is no oxygen.

Koch related specific bacteria to specific diseases.
http://www.cps-scp.ca/kochspostulates.htm

Chlorosis is the result of pigment loss when chlorophyll is missing. Many causes can contribute notably pH not being neutral so soil nutrients are not available to the plant.

Necrosis is cell or tissue death, when plants cells die other than in planned turn over & replacement. When they die from climate extremes, injury or sickness the leaves or the stem's cambium layer discolor.

Cleistothecium is one of four types of ascocarp or fruiting body produced by some fungus. Spawn are fungal mycelium used to inoculate fresh growth medium to produce more cultured mushrooms. A spore is the single haploid cell that will grow and develop into a new organism. If it is indigenous it is resident not introduced.
http://www.botany.hawaii.edu/faculty/wong/Bot201/Ascomycota/lab_02b.htm
http://www.mansfield.ohio-state.edu/~sabedon/campbl31.htm

Gardengallivant skipped two:

- spawns are when fish, molluscs, or other aquatic organisms reproduce

- "indigenous" means native, so that would be a spore from plants (ferns) or fungi native to that area

I'd also add that Kock's postulates are what are used to determine (experimentally) the causes of "new" diseases.  By infecting organisms which previously were unaffected with possible pathogens, a doctor can determine if any are the actual cause of the illness if the characteristic symptoms/signs appear.