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Auxin and making more cytoplasm
I am teaching the botany part of second semester biology at the college
level and have come across something that may contradict what I've been teaching. In the 8th edition of the Campbell, Reese, etc. of Biology, on page 828, the last paragraph, under the heading of "The role of auxin in cell elongation"reads: Auxin also rapidly alters gene expression, causing cells in the region of elongation to produce new proteins within minutes. Some of these proteins are short-lived transcription factors that repress or activate the expression of other genes. For sustained growth after this initial spurt, cells must make more cytoplasm and wall material. Auxin also stimulates this sustained growth response. Does the last sentence mean that auxin stimulates the cell to make more cytoplasm and wall material OR does it simply mean that it stimulates the sustain growth response, but does not stimulate the cell to make more cytoplasm and cell wall material. I have always taught that auxin increases cell growth, but does not stimulate the cell to make more cytoplasm nor does it have anything to do with making more cell wall material. Furthermore, When I go to the Mastering Biology web page that is set up to be used for this text, there is a question that reads: Which of the following has not been established as an aspect of auxin's role in cell elongation?... The answer choices we Auxin increases the quantity of cytoplasm in the cell. Auxin activity permits an increase in turgor pressure. Auxin stimulates proton pumps. Auxin instigates a loosening of cell wall fibers. Through auxin activity, vacuoles increase in size The answer Mastering Biology gives is the first choice, "auxin increases the quantity of cytoplasm in the cell". So am I correct in saying that perhaps the wording in the last paragraph, in the text, is ambiguous and that auxin has nothing to do with increasing the quantity of cytoplasm in the cell? Thanks for any comments on this question. |
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