Is this a Multiple Post or did you not find these answers in the Websites I gave you?
1. Bracts = this where a flower or new stalk will originate. http://www.wikieducator.org/Bamboo_and_Rattan/Rattan/Course-1_Unit-2
2. This must be the culm:
The above-ground portion of bamboo has several names depending on the stage of growth. When it forms on the rhizome node, it is a bud. As it emerges from the ground and until it develops side branches, it is called a shoot. Once the side branches form, it is called a culm. Once the culm is cut or harvested, it is called a pole or cane. Bud, shoot, culm, cane and pole all refer to the same individual above-ground plant. A single culm with rhizome and roots attached is usually referred to as a plant. Before being removed, it is a culm of the grove. If you plant a single bamboo plant, as it expands the new culms are all attached to the original plant by the rhizomes. The culm has the same design as the rhizome, nodes and internode sections. Most of the internode sections of the culm are hollow, but in a few varieties the internodes are almost solid. Branches form only at the nodes and have the same basic structure as the culm with leaves and side branches forming only at the nodes of the main branch or culm.
Now to the growth habits of bamboo: All bamboo culms normally shoot and grow to their full height and diameter in one growing season, usually in 60 to 90 days. In succeeding years the wood of the bamboo culms will increase in strength and silica content and the plant will put out new leaves, but the culm will never grow taller or increase in diameter after the first growing season. If you top a bamboo culm at 4 feet, that culm will always be 4 feet tall, year after year until it dies. This makes bamboo an excellent choice for hedges. The culms have a life span of 5 to 15 years.
3. What do you mean by "graffiti?" People carve graffiti on the stems of bamboo. Is that what you mean? Please clarify.