What is the role of the endodermis in nutrient absorption?

Answer to q. 1

Because of the Casparian strip, the endodermis forces the nutrients to enter the cytoplasm in order to
pass. This is beneficial for two reasons. First, it allows the plant a higher level of regulation as to
what gets into the xylem. Most small ions could diffuse through the walls of the cortex cells, but only
the materials taken into the cytoplasm can pass the endodermis. Second, this allows the plant to
accumulate high levels of ions in the region of the xylem, creating a hypertonic environment that will
draw water into the root.

Answer to q. 2

A root nodule is an example of mutualism. The plant provides carbohydrates and an oxygen-free
environment (necessary for nitrogen fixation) while the bacteria provide nitrogen (commonly limiting
in soils) for the plant partner.

Thank you so much for the answer