Stomata are small openings or pores found on the surface of leaves and stems of plants. They are responsible for the exchange of gases, such as oxygen and carbon dioxide, between the plant and its environment. In dicot plants, stomata are primarily found on the lower surface of the leaf.

Reasons for stomata being found on the lower surface of the leaf:

1. Minimizing water loss: The placement of stomata on the lower surface of the leaf helps to reduce water loss through transpiration. The lower surface is often shaded and cooler, which reduces the rate of evaporation and helps to conserve water within the plant.

2. Protection from excessive sunlight: The lower surface of the leaf is typically more protected from direct sunlight compared to the upper surface. Placing stomata on the lower surface helps to shield them from excessive sunlight, which can lead to excessive water loss and damage to the plant.

3. Reducing heat stress: The lower surface of the leaf is also better suited for reducing heat stress. As hot air rises, placing stomata on the lower surface allows for the intake of cooler air, which helps to regulate the temperature of the leaf and prevent overheating.

4. Avoiding dust deposition: Stomata on the lower surface of the leaf are less likely to become clogged with dust and pollutants compared to those on the upper surface. This reduces the risk of blockage and ensures effective gas exchange.

5. Guarding against herbivory: Placing stomata on the lower surface also provides some protection against herbivory. Many herbivorous insects and animals tend to feed on the upper surface of the leaf, and having stomata on the lower surface makes them less accessible to these herbivores.

In conclusion, stomata are primarily found on the lower surface of dicot plant leaves for several reasons, including reducing water loss, protecting against excessive sunlight and heat, avoiding dust deposition, and guarding against herbivory. This placement helps to optimize gas exchange while minimizing potential damage to the plant.