Question

Why do plants not need an Oxygen carrier like the humans in whom Oxygen is carried by
Haemoglobin?

Answer 1

This is because plants synthesis oxygen during photosynthesis & they consume oxygen during respiration.All parts of plants perform respiration & gets oxygen directly.So,they do not need an additional carrier to transport oxygen. 

Answer 2

Answer:

Plants do not need an oxygen carrier like humans in whom oxygen is carried by haemoglobin because humans respire only through nostrils.

Since they get the oxygen throughout the body they do not require a special carrier system.