Temperatures just below the optimum range also induce a condition called "bolting" in certain valuable vegetable crops, e.g., cabbage, collards, celery, onions, and beets. These kinds are biennials. Under favorable temperatures the plants develop the storage structure during the first year and flowering stalks, flowers, fruit, and seed during the second. If seedling plants of these crops are subjected to temperatures somewhat below the optimum range, that is between 40° and 50°F, for four to eight weeks depending on the kind and variety, they produce flowering stalks and seeds instead of producing the storage structure, e.g., the head in cabbage, the fleshy leaves in collards, the fleshy petioles in celery, the bulb in onion, and the fleshy root in beets. Why does bolting take place at temperatures just below the optimum range? In general, the rate of photosynthesis is fairly high and at the same time the rate of respiration and the rate of cell division is low. As a result, relatively low quantities of carbohydrates are stored. This more or less rapid accumulation of carbohydrates is associated with the formation of flower-forming hormones and the initiation of flower buds which, with the onset of warm weather, develop into flowering stalks which bear the fruit and seed. Thus, these biennials become annuals when the seedling plants are subjected to relatively low temperatures for a sufficient period of time.