There are many different cell types and sub-types involved in the immune system. Some of the main types include: Lymphocytes: are white cells which circulate between blood and lymph. They play an important role in fighting infection.
After about 50 to 60 days, beets are ready to harvest. Not only can the roots be dug up and chopped to add flavor to a meal, but the greens of the beets can be harvested periodically and put in salads. Given how well these beets fare in different weather conditions, they can be grown several times in a summer.
First, you may harvest beet greens as you thin the seedlings in the beginning and continue until the greens are too tough. Also, you may indeed harvest some of the greens before you take the root, but not all of them. Just one or two per plant. Otherwise, the root will not mature.