Respiration in plants involves the process of converting stored energy in the form of glucose into a usable form of energy called ATP (adenosine triphosphate). There are two major pathways of respiration in plants: aerobic respiration and anaerobic respiration.

Aerobic Respiration:
Aerobic respiration occurs in the presence of oxygen and is the most common pathway of respiration in plants. It takes place in the mitochondria of plant cells and involves a series of chemical reactions that break down glucose molecules to produce ATP.

1. Glycolysis:
Glycolysis is the first step of aerobic respiration. It occurs in the cytoplasm of plant cells and involves the breakdown of glucose into two molecules of pyruvate. This process also generates a small amount of ATP.

2. Krebs Cycle:
After glycolysis, pyruvate molecules enter the mitochondria where they undergo further breakdown in the Krebs cycle. This cycle generates ATP, NADH, and FADH2, which carry high-energy electrons.

3. Electron Transport Chain:
The high-energy electrons carried by NADH and FADH2 are transferred to the electron transport chain located in the inner membrane of the mitochondria. This process generates a large amount of ATP through oxidative phosphorylation.

Anaerobic Respiration:
Anaerobic respiration occurs in the absence of oxygen and is less efficient than aerobic respiration. It is commonly observed in plants under conditions of low oxygen availability.

1. Alcoholic Fermentation:
In alcoholic fermentation, pyruvate molecules are converted into ethanol and carbon dioxide. This process occurs in the cytoplasm and generates a small amount of ATP.

2. Lactic Acid Fermentation:
In lactic acid fermentation, pyruvate molecules are converted into lactic acid. This process also occurs in the cytoplasm and generates a small amount of ATP.

The choice between aerobic and anaerobic respiration in plants depends on the availability of oxygen. Under normal conditions, plants primarily undergo aerobic respiration to generate ATP efficiently. However, when oxygen is limited, plants resort to anaerobic respiration to sustain energy production, although at a lower efficiency.