Introduction:
Algae, fungi, and submerged plants are organisms that do not possess stomata, which are specialized structures found in the epidermis of leaves and stems of most land plants. Stomata play a crucial role in the exchange of gases, such as oxygen and carbon dioxide, between the plant and its environment. However, these organisms have developed alternative mechanisms to facilitate gas exchange despite the absence of stomata.

Diffusion:
One of the primary mechanisms by which gases are transferred in algae, fungi, and submerged plants is diffusion. Diffusion is the passive movement of molecules from an area of higher concentration to an area of lower concentration. These organisms have adapted to rely on diffusion to exchange gases with their surroundings.

Gas Exchange in Algae:
1. Algae are simple photosynthetic organisms that inhabit aquatic environments. They lack specialized structures like stomata but have a large surface area exposed to the surrounding water, enabling efficient gas exchange.
2. Algae have thin cell walls and membranes that allow gases to readily diffuse in and out of their cells.
3. Additionally, some algae have gas-filled vesicles that aid in buoyancy control and enhance gas exchange.

Gas Exchange in Fungi:
1. Fungi are primarily terrestrial organisms that obtain nutrients through the decomposition of organic matter. They lack stomata but have a mycelium, a network of thread-like structures called hyphae, which facilitates gas exchange.
2. The mycelium of fungi is composed of thin-walled cells that allow gases to diffuse easily.
3. Fungi also have specialized structures called sporangia that help in the dispersal of spores. These sporangia often have openings or pores that allow for gas exchange.

Gas Exchange in Submerged Plants:
1. Submerged plants, as the name suggests, are aquatic plants that grow entirely or partially underwater. They lack stomata but have adaptations to facilitate gas exchange underwater.
2. Submerged plants have thin leaves with a large surface area that maximizes gas exchange with the surrounding water.
3. They also have specialized structures called lenticels that enable gas exchange through small openings in the stems and roots.

Conclusion:
While algae, fungi, and submerged plants do not possess stomata, they have evolved alternative mechanisms to facilitate gas exchange. These mechanisms primarily involve diffusion through thin cell walls, membranes, and specialized structures. Despite the absence of stomata, these organisms have successfully adapted to their respective environments and efficiently exchange gases to meet their metabolic needs.