Photosynthesis makes a sugar for the plant, in order for photosynthesis to occur the plant needs carbon dioxide and water, and with the use of the sunlight it produces oxygen and glucose. For respiration you need glucose and oxygen which produces carbon dioxide, water and ATP(energy) for the cell. I hope this helps, I only know the first half of the question.
I think its because so the plants can absorb more nutrients from the soil while being sturdy and wide so when the plant gets snowed on it doesn't break<span />
