CLEP Guides
American Government Biology College Mathematics General CLEP General Tips Human Growth And Development Humanities Introductory Psychology Principles Of Marketing Sociology US History 1 US History 22. Plant reproduction and development
Alternation of generations
Wiki on Alternation of generations
Wikipedia offers a good starting place to start learning about alternation of generations within plants, fungi and others.
This tutorial is very in depth but you will certainly understand the conifers life cycle after reading it. Interesting read and they include some good pictures to help you understand the entire life cycle.
Gamete formation and fertilization
You could just study this website alone and pass your CLEP exam but I try to mix it up by adding other resources. These pages are very helpful for the formation and hormonal parts of this section.
Tropisms and photoperiodicity
A small tutorial on how plants grow and what tropism is. The tutorial also continues onto some of the other subjects you will need for this section of the biology CLEP exam.
I know many links point to Wikipedia but they do have some great pages. This one is all about photoperiod and the difference between plants.