(Dandelions are example of plants that use the C3 pathway. This picture is taken from this site: http://www.google.com/imgres?q=dandelion&num=10&hl=en&gbv=2&biw=1024&bih=610&tbm=isch&tbnid=ZGn9W6PPMOALHM:&imgrefurl=http://www.manataka.org/page1126.html&docid=766naOQmHrWzVM&imgurl=http://www.manataka.org/images/dandelion.jpg&w=425&h=319&ei=eTCqTrLNBdLQiALO5_GuCw&zoom=1&iact=rc&dur=249&sig=110919301459896358943&sqi=2&page=1&tbnh=115&tbnw=153&start=0&ndsp=15&ved=1t:429,r:5,s:0&tx=80&ty=74)
C3 Plants: When it is hot or dry, C3 plants close their stomata to prevent water loss. Because of this, photorespiration occurs when the carbon dioxide is less concentrated in the air spaces in the leaf, which slows down the Calvin Cycle. Oxygen and carbon dioxide accumulate in the leaf and rubisco adds oxygen to the RuBP. The product is broken down and a two-carbon compound is broken down, releasing carbon dioxide. Cactus is an example of C3 plants.
(Corn is an example of a plant that uses the C4 pathway. This picture is taken from this site: http://www.google.com/imgres?q=c4+plants+examples&num=10&um=1&hl=en&biw=1024&bih=610&tbm=isch&tbnid=7WCZi_3MfDP0FM:&imgrefurl=http://fhs-bio-wiki.pbworks.com/w/page/12145744/CAM%2520and%2520C4%2520plants&docid=dXcRfJ_0a06RsM&imgurl=http://fhs-bio-wiki.pbworks.com/w/page/12145744/f/corn.jpg&w=2304&h=3072&ei=PS6qTtbtA4riiALW-uiYCw&zoom=1&iact=hc&vpx=424&vpy=114&dur=2383&hovh=259&hovw=194&tx=35&ty=276&sig=110919301459896358943&sqi=2&page=1&tbnh=128&tbnw=93&start=0&ndsp=15&ved=1t:429,r:2,s:0)
C4 Plants: Before the Calvin Cycle begins, PEP carboxylase (an enzyme) helps add carbon dioxide is to PEP (a 3-carbon compound). The product is a four-carbon compound that is made in the leaf's mesophyll cells and is transported to the bundle-sheath cells (located around veins of the leaf). The four-carbon compound is broken down, releasing carbon dioxide and initiating the Calvin Cycle.
(Pineapples are an example of plants that use the CAM pathway. This picture is taken from this site: http://www.google.com/imgres?q=pineapple+tree&hl=en&gbv=2&biw=1024&bih=610&tbm=isch&tbnid=yrwJi6IcL45PpM:&imgrefurl=http://www.mrbigben.com/food/pineapple.html&docid=OvrVOWQ13DdWwM&imgurl=http://www.mrbigben.com/food/twin-fruit-pineapple-719390.JPG&w=640&h=480&ei=KS-qTtvAGse0iQLB66G1Cw&zoom=1&iact=hc&vpx=526&vpy=177&dur=2051&hovh=194&hovw=259&tx=158&ty=214&sig=110919301459896358943&page=1&tbnh=118&tbnw=153&start=0&ndsp=20&ved=1t:429,r:4,s:0)
CAM Plants: These plants may also close their stomata to prevent water loss and beak down compounds to release carbon dioxide during the day. However, the crassulacean acid metabolism (CAM) pathway doesn't separate the process of carbon fixation from the Calvin Cycle, unlike the C4 pathway.
Source: Campbell and Reece's Biology, Sixth Edition
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