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C 3 and C 4 plants have two things in common, they both are found in hot and very dry areas and they both use photo respiration. However, the difference is the way they react toward water loss which will affect photosynthesis. If a C 3 plant starts to transpire rapidly because it is photosynthesizing and the stomata are open, then it will close the stomata, ending photosynthesis. What the plant does next is undergo a counterproductive cycle called photo respiration. In the C 3 plant photo respiration actually uses up 50 % of the CO 2 fixed by the Calvin cycle. What happens is the plant closes it s stomata and as a result stops transpiration and photosynthesis.
What happens is the O 2 level rises and the CO 2 drops. Then the plant must use O 2 in place of CO 2 to input into the Calvin cycle. A two carbon molecule comes out and is broken down by peroxisome's into CO 2. This just uses up CO 2 and doesn t benefit the plant because no energy or food is made in this process. In a C 4 plant it is different. When it needs to close it s stoma to stop transpiration, it undergoes photo respiration as well, however, it s photo respiration is productive.
Preceding the Calvin Cycle it incorporates CO 2 into an organic compound first, or the CO 2 into phosphoenolpyruvate to form oxaloacetate. PEP carboxylase has a higher affinity for CO 2 then rubicon does so PEP can fix CO 2 efficiently and rubicon can t. The O 2 starts to rise and the CO 2 drops. After the C 4 plant fixes CO 2, the mesophylls export there 4 carbon products to bundle sheath cells through plasmodesmata. Within the bundle sheath cells, the 4 carbon compounds release CO 2, which is re assimilated into an organic material by rubicon and the Calvin cycle.
In effect the mesophyll cells pump CO 2 into bundles heath cells keeping CO 2 high enough in the bundle sheath cells for rubicon to accept CO 2 instead of O 2. That is how the C 3 and C 4 plants react to desiccation. Plants are closer to humans then you would think. Plants reproduce, have a life span, respond to their environment, and even communicate.
Plants are able to do all these things because of evolution. Reproduction evolved from spores to uncovered seeds to fruit seeds and pollen and the use of stigmas and stamen. Evolution imbedded an internal clock into plants so they would know when to open and close there stomata and when to perform other functions like reproduction. Plants adapting and responding to there environment was all part of evolution to make the plants survive and change just like the desert, rainforest, and tundra plants. evolution was responsible for everything that the plant has.
Evolution gave the plants hormones to perform duties and to help the plant to carry out its task of passing down it s genes to the next generation and then mixing them up with other plants so the DNA wouldn t be wiped out in a massive plague. Evolution was responsible for everything. In the modern world evolution is being sped up at an alarming rate with all our new advances in the sciences and genetic engineering. We are making things we didn t even know we could like germ resistant seeds. The great thing about this biotechnology is that we are making good advances to help people like bean weevil resistant beans so that entire crops of beans will not be lost due to the bean weevil and that pretty much saved a whole village. Another great thing about these new genetically engineered plants that won t let bugs touch them is that we don t have to use pesticides because the plant defends itself.
Some more possibilities would be engineering a plant that was resistant to cold whether. The advantages of this would be plants in Russia because they could now survive the cold they could boost Russia s economy because they would have good crops to sell. The disadvantages of this would be putting this exotic plant in a different country could have serious economic repercussions. For example since there would be no natural predator this plant could grow out of control like the garlic mustard or Black Eyed Susan s. A seedless fruit would be a bad idea because seeds in the fruit are how the seeds get around, that is the entire point of fruit, to move the seeds. With all these new advances in biotechnology and genetic engineering we can make dozens and dozens of remarkable things that could help the worlds, but you have to weigh the disadvantages with the advantages first.
The repercussions of some of the genetically engineered plants that are introduced to a new economy could be devastating, and so with great power comes great responsibility.
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Research essay sample on Genetically Engineered Calvin Cycle
