During the day, plants carry out photosynthesis releasing carbon dioxide. During the night, there isn't any sunlight so the plants carry out cellular respiration releasing oxygen.
I believe the answer you're looking for is cellular respiration.
Methanogens can be found in B.human intestines
Roots of plants and synthetic fertilizers can contain oxygen or come into contact with oxygen.
I have searched everywhere, but I have not found the proposals of the question, but I will explain to you what is the endoplasmic reticulum so that you can answer it.
The endoplasmic reticulum is a eukaryotic organelle located in the cytoplasm.
The endoplasmic reticulum is a network of membrane tubules (often interconnected) scattered throughout the cytoplasm of eukaryotic cells. Its membrane, which alone represents more than half of the cellular membrane system, is in contact with the nuclear envelope.
The endoplasmic reticulum can be:
Granular (or rough) (RER) that is to say associated with ribosomes.
Smooth (SER).
The granular endoplasmic reticulum is the place of synthesis (in the associated ribosomes) of the proteins secreted outside the cell and of the proteins and lipids constituting the membranes of the cellular organelles. Golgi, lysosomes, mitochondria, nucleus, ribosomes, vesicles ...). It participates in the correct folding of the proteins that have just been synthesized.
The smooth endoplasmic reticulum participates in cellular metabolism, synthesizing lipids and storing calcium.
