Water Weeds have a main extra feature that plant cells have is a cell wall on the outside. So it's mostly made of cellulose, which gives a tough covering on the outside of the cell membrane. And therefore, gives plant cells a distinctive polygonal outline. And the reason why Onion cells aren't green is that cells deep within the structure of plants are not green. Second, not all onion cells are lacking in green color. The bulb of the onion lacks green, but the stem and leaves of the onion plant are green. The reason the bulb is white, and not green is that it has no chlorophyll.
These belong to legumes and legumes have a mutualistic relationship relationship with bacteria which allows them to add atmospheric nitrogen into the soil by a process called nitrogen fixation.<span />
