Question

Carbon dioxide is present to the extent of only 0.03 % in air, yet it is very important for plants. Why ?

Answer 1

Air

• Air is a mixture of many gases like Nitrogen $\left({\mathrm{N}}_2\right)$, Oxygen $\left({\mathrm{O}}_2\right)$ , Carbon-dioxide $\left({\mathrm{CO}}_2\right)$, Argon $\left(\mathrm{Ar}\right)$ etc .
• Composition of these gases in atmosphere is different for different gases like-

1. Nitrogen $\left({\mathrm{N}}_2\right)$ - 78 %
2. Oxygen$\left({\mathrm{O}}_2\right)$ - 21 %
3. Carbon- dioxide$\left({\mathrm{CO}}_2\right)$ - 0.03 %
4. Other gases $(\mathrm{Argon}(\mathrm{Ar}),\mathrm{Neon}(\mathrm{Ne}),\mathrm{Hydrogen}(\mathrm{H}),\mathrm{Krypton}(\mathrm{Kr})\mathrm{etc})$ - 0.96 %

Importance of Carbon dioxide $\left({\mathrm{CO}}_2\right)$

• Although the amount of Carbon dioxide in air is 0.03% in air, yet it is very very important for photosynthesis in plants.
• Plants use Carbon dioxide, water, sunlight, and chlorophyll for the process of photosynthesis.
• Carbon dioxide is reduced to $\left({\mathrm{C}}_6{\mathrm{H}}_{12}{\mathrm{O}}_6\right)$.
• Water is oxidised to give Oxygen $\left({\mathrm{O}}_2\right)$.

$\underset{\mathrm{Carbon}-\mathrm{dioxide}}{6{\mathrm{CO}}_2\left(\mathrm{g}\right)}+\underset{\mathrm{Water}}{12{\mathrm{H}}_2\mathrm{O}\left(\mathrm{l}\right)}\underset{\mathrm{Chlorophyll}}{\overset{\mathrm{Sunlight}}{\to }}\underset{\mathrm{Glucose}}{{\mathrm{C}}_6{\mathrm{H}}_{12}{\mathrm{O}}_6\left(\mathrm{s}\right)}+\underset{\mathrm{Oxygen}}{6{\mathrm{O}}_2\left(\mathrm{g}\right)}+\underset{\mathrm{Water}}{6{\mathrm{H}}_2\mathrm{O}\left(\mathrm{l}\right)}$

• Hence, Carbon-dioxide is very important for plants for the process of photosynthesis.