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.
Too much nitrogen will cause beets to produce lots of greens but little roots. Soak beet seeds in water for 24 hours before planting to aid germination. Beets prefer cool weather. For an early summer crop, sow seeds in a sunny spot, 3 to 4 weeks before your last frost. Plant seeds 1/2-inch deep, 2 inches apart if growing for greens, 3 to 4 inches apart if growing for the roots (but you can still harvest the greens, too). Sow seeds again in late summer for a fall crop.