AP BIOLOGY

Detailed explanation-1: -growth ring, in a cross section of the stem of a woody plant, the increment of wood added during a single growth period. In temperate regions the growth period is usually one year, in which case the growth ring may be called an “annual ring.” In tropical regions, growth rings may not be discernible or are not annual.

Detailed explanation-2: -Annual growth rings The vascular cambium ring is active during growing season and produces a new layer of xylem tissue or growth ring every year. This addition of a new lateral layer each year is called secondary growth and is exactly the same as in woody plants.

Detailed explanation-3: -The secondary phloem forms outside of the vascular cambium, and traces of primary phloem (protophloem) are visible above it. It is rich in fibers, and unlike the wood, it does not form annual rings.

Detailed explanation-4: -It is the result of cell division in the shoot apical meristem. Secondary growth is characterized by an increase in thickness or girth of the plant. It is caused by cell division in the lateral meristem.

Detailed explanation-5: -Secondary growth involves the thickening of the plant axis through the activity of lateral meristems. The end result of secondary growth is increased amounts of vascular tissue. As plants grow larger, more vascular tissue is needed for water conduction and the transport of nutrients.