This is a hard question to address with so many variables such as what nutrients are you considering more important than others. Wheat grass is a good start, it's packed with nutrients.
The plant that consumes the most CO2 is the giant sequoia tree.
Aspen tree
Moringa is considered as the most nutritional food, It is a very healthy food, full of vitamins and minerals, that are good for your body. It has lots of nutrients that can help keep you well. youtu.be/slB7GLHU6AA
Olive tree (the answerer)
No, a plant is only considered a plant when it meets the biological classification criteria for being a plant, such as having chlorophyll and the ability to undergo photosynthesis. If something does not possess these characteristics, it would not be classified as a plant.
The eucalyptus tree.
The widely cultivated tree for its fruit is the apple tree. Apples are a popular fruit worldwide and are grown in many regions due to their versatility in culinary uses and high nutritional value. The apple tree belongs to the Rosaceae family and is native to Central Asia.
If you mean what plant can live on top of another plant, epiphytes are a good example (e.g. orchids). Here the plant attaches it's self to the bark of a tree, but does not derive any nutritional benefit from the tree. If you mean what plant lives off another then you are referring to parasitic plants, where the plant derives direct nutritional benefit from the host plant i.e. it gets its nutrients and water from the host plant. An example of this is the Dodder plant/ vine
A plant a plant is a tree
Most paper is made from various plant and tree fibers.
Most of the time it's an evergreen or a spruce
plant a tree