|MadSci Network: General Biology|
Hi there, I think your question is about plant respiration. You are right that stomata are open during the day, when the plant is photosynthesizing, and closed at night, as in when sunlight is absent. Gas exchange at the stomatal pores is to allow CO2 to diffuse in, and for the by-product oxygen to diffuse out for the process of photosynthesis. Plant respiration uses up oxygen and produces carbon dioxide. Oxygen is dissolved in aqueous solutions (at 25C, the concentration is 250uM) and is available in the intercellular spaces of the plant. The amount of oxygen required in respiration is around 1uM so there is no lack of oxygen for the plant cells in daytime or nighttime. Thanks for your question! Evelyne my references came from textbooks and the internet: 1.(oxygen concentrations) Taiz & Zeiger "Plant Physiology" 1991. 2.(general overview) ht tp://www.ultranet.com/~jkimball/BiologyPages/G/GasExchange.html 3.(in-depth lecture) http://www.bio.fsu.edu/courses/bot- 4503/gas_exchange-96.html
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