Three sources of carbon dioxide in plant photosynthesis

Plants need carbon dioxide as a raw material for photosynthesis, and there are three sources of carbon dioxide.

First, carbon dioxide in the atmosphere. The atmosphere contains carbon dioxide, although the proportion is not high, it is an important source for plants to obtain carbon dioxide. The stomata of leaves open and close like a portal. The carbon dioxide in the outside atmosphere passes through this stomata and enters the interstitial space of mesophyll cells, and then reaches the chloroplast to participate in the dark reaction of photosynthesis. This is the most common carbon dioxide uptake path for plants in the natural environment.

Second, carbon dioxide produced by plant respiration. Plants themselves respire day and night, consuming oxygen and releasing carbon dioxide. During the day, when photosynthesis is strong, the carbon dioxide produced can be immediately used by photosynthesis and recycled in the plant body. This carbon dioxide is produced from the mitochondria through cellular respiration, and then diffuses within the cells and enters the chloroplast for photosynthesis.

Third, soil microorganisms release carbon dioxide from decomposing organic matter. There are a large number of microorganisms in the soil, which release carbon dioxide when decomposing animal and plant residues, humus and other organic matter. This carbon dioxide diffuses in the pores of the soil, and part of it can be absorbed by plant roots, transported through the tissues in the plant body, and transported to the leaves for photosynthesis. Especially in fertile soils, where microbial activity is strong, the contribution of carbon dioxide released to plant photosynthesis cannot be underestimated.

These three, the carbon dioxide supplied by the atmosphere, plant respiration and soil microbial decomposition, and the coordinated maintenance of plant photosynthesis are of key significance in plant growth and development and ecosystem carbon cycle.