Michigan Test for Teacher Certification (MTTC) Secondary Integrated Science Practice test

What role does the endodermis play in plant physiology?

1. Photosynthesis

2. Storage of starch

3. Regulating movement in and out of the vascular system

4. Providing energy

The correct answer is: Regulating movement in and out of the vascular system

The endodermis serves a crucial role in plant physiology, particularly concerning the regulation of water and nutrient movement into the vascular system. It acts as a selective barrier, controlling which substances can enter the plant's vascular tissues (xylem and phloem). This regulation is achieved through the Casparian strip, a band of suberin (a waxy substance) that forms a barrier in the cell walls of the endodermal cells. As water and nutrients move from the soil, they must pass through the endodermis, which ensures that only essential substances are allowed to enter the vascular system while excluding potentially harmful materials. This function is vital for maintaining homeostasis within the plant and ensuring efficient nutrient uptake. In contrast, the other options relate to different functions within the plant. Photosynthesis is primarily conducted by chlorophyll-containing cells in the leaves, while starch storage is mainly associated with other tissues, such as parenchyma cells. Providing energy is a broader concept that encompasses various metabolic processes, but it does not directly pertain to the specific role of the endodermis in regulating vascular movement.