Seedless plants produce spores.Spores can develop into an adult without fusing with another cell.Seed plants produce seeds.Seeds are formed when the female reproductive structure matures; this occurs after fertilization.
That is the answer (:
Answer: THEY ARE INVOLVED IN THE DISASSEMBLY OF THE NUCLEAR ENVELOPE
Explanation: The disassembly of the nuclear envelope is triggered by the cyclin‐dependent kinase at the onset of mitosis. At this point, Integral nuclear membrane proteins diffuse/move into the endoplasmic reticulum (ER) after nuclear envelope breakdown. The nuclear envelope reassembles around compact chromosome mass at late anaphase/telophase and the chromosomes condenses and become visible.
There are plenty of plants producing oxygen by photosynthesis.
Also, human's only use 5% of the oxygen in the air in respiration, there is 21% in the air.