Vitamin B₁and the Growth of Green Plants

The vitamin B1 content of pea plants kept in the dark does not increase, whereas in the light this content of the leaf rises rapidly. The root tips of plants whose leaves are in the light contain more vitamin B1 than do those of plants kept in the dark. This signifies that vitamin B1 is produced in leaves in the light and thence transported to the growing root tip. 2. It has been shown that when vitamin B1 is supplied in small amounts to the roots of plants grown in the dark, both shoot growth and root growth are increased. 3. Numerous species of plants have been grown in nutrient sand cultures in the greenhouse; that is, in the light. Addition of vitamin B1 (1, 0.1, and 0.01 mg. per liter of nutrient solution) was found to increase the shoot growth of species of plants which are normally slow growing. No additional growth response to added vitamin B1 was obtained under similar conditions when fast growing annual plants were used. 4. Organic manure contains appreciable amounts of vitamin B1. The beneficial effects of manure upon plant development may be owing in part to its content of vitamin B1. The vitamin B1 content of soils may be expected to be derived also from plant debris and from soil microflora.