Tree-ring Porosity Forms in Hardwoods

One growth increment of a tree, commonly called a “growth ring,” is composed of structural, conducting, and defensive components. In a cross-section, the largest conducting vessels can be visible to the unaided eye or can be minutely small. Due to shoot growth rates and timing, and leaf expansion periods, different growth conditions affect vessel size and xylem composition.

The link address is: http://warnell.forestry.uga.edu/service/library/for99-018/for99-018.pdf