Why does plants need carbon dioxide

1 Plant scientists have observed that when levels of carbon dioxide in the atmosphere rise, most plants do something unusual: They thicken. This increase in carbon dioxide directly increases plant photosynthesis up The stomata open and close according to the physiological needs of the leaf. 20 thg 7, Plants take in – or 'fix' – carbon dioxide from the atmosphere during photosynthesis. Some of the carbon is used for plant growth, and some of.