Tress and plant release carbon and respiratory
I suppose it is the density, having more pockets of air in between the granules of sawdust. Air has oxygen. What does a fire need to strive? Oxygen.
The word that would fit the blank is vascular. You are consuming the vascular tissues of a plant when consuming a celery stick. This part of the celery is called the petiole. This is the stalk that joins a leaf and a stem. This part is made up largely of vascular tissues.
