I used the internet to do a little research on the subject and found there are two separate things.
First is daytime photosynthesis where the plants uses the co2 and produces o2. The second thing is respiration where the plant uses o2 as well as co2. Here's a quote.
"Plants consume CO2 in the process of photosynthesis and convert it to sugar. Oxygen is a waste product of this reaction, in that water is split to form hydrogen and oxygen. The plant uses the hydrogen to produce ATP. This process is only occuring in the day when there is light. However, at all times, the plant is respiring, just like people. They need oxygen for the metabolic process and produce CO2 as a waste product."
Source(s):
PhD in botany, and taught it for 7 years.
So I look into respiration,
"Cellular respiration (process that uses oxygen to break sugar into energy for life functions) and photosynthesis (green plants converting sunlight energy into sugars using water and carbon dioxide) are distinct and separate processes. Animals only use cellular respiration. Plants do not have muscles and the other functions necessary in animals functioning that require a high levels of oxygen. Plants also CAN NOT take the energy directly for their energy needs from photosynthesis. Photosynthesis produces a far greater amount of oxygen and sugars, etc. then the small amount the plant requires to produce its energy needs. OK - but only during the day when the sun light is available! During the night, the plant actually uses oxygen it has left over from the daylight photosynthesis or takes the oxygen from the air surrounding the plant to meet its energy needs. This is not nearly the amount of oxygen an animal needs over the same period of time."
Question, Do plants use o2? If so when and how. (yahoo answers)
Yes, all green or vascular plants consume oxygen all the time. Green plants release oxygen through photosynthesis but they still consume oxygen at the same time. The primary way plants use oxygen is through their root cells. In order for a plant to take up water and nutrients from the soil, it must continually grow new root hairs. The cells that make up these hairs are living cells that do not carry out photosynthesis. They are similar to the cells of animals in that they require oxygen and give off carbon dioxide as they burn carbohydrates to obtain the energy they need to function. This is why you can "drown" a house plant by watering it too much. If the soil gets too saturated with water, the plants root cells can't get enough oxygen from the air. There are vascular plants such as cypress trees and cattails that are adapted to living in saturated soil. These plants have root hairs that grow out of the stems above the soil and/or water surface so that they can take in oxygen.
It sounds to me like its primarily the roots that absorb o2 and a few hours with a high amount of co2 at the canopy shouldn't hurt them. I still think gassing them at sunrise is best but I just thought I would share that.
.. AND it talks.
