We have already discussed how organisms get rid of gaseous wastes generated during photosynthesis or respiration.
- Other metabolic activities generate nitrogenous materials which need to be removed. The biological process involved in the removal of these harmful metabolic wastes from the body is called excretion.
- Different organisms use varied strategies to do this.
- Many unicellular organisms remove these wastes by simple diffusion from the body surface into the surrounding water.
- As we have seen in other processes, complex multi-cellular organisms use specialised organs to perform the same function.
Excretion in Plants
- Plants use completely different strategies for excretion than those of animals. Oxygen itself can be thought of as a waste product generated during photosynthesis!
- We have discussed earlier how plants deal with oxygen as well as CO2.
- They can get rid of excess water by transpiration.
- For other wastes, plants use the fact that many of their tissues consist of dead cells, and that they can even lose some parts such as leaves.
- Many plant waste products are stored in cellular vacuoles. Waste products may be stored in leaves that fall off.
- Other waste products are stored as resins and gums, especially in old xylem.
- Plants also excrete some waste substances into the soil around them.