Hello! The interaction between the two system is an inter-dependent relationship. An example of this is that the heart pumps arterial blood to the circulation. The deoxygenated or venous blood returns to the lung where blood is oxygenated. Then the blood flows into the heart chambers and the cycle continues on.
<em>The two main process by which plant cells absorb, release, and use energy are Photosynthesis and respiration.</em>
This is referring to meiosis, which happens just once to make reproductive cells, unlike mitosis which is just simple copying.
In mitosis, one cell splits into two, but the number of chromosomes doesn't change. The original cell makes two copies of its chromosomes and divides them up.

In <em>meiosis</em>, however, our cell doesn't bother making those two copies. It just takes what it has and divides it between two new cells.