The effect of potassium on the production of proteins, sugars, and starch in cowpea and in sugar beet plants and the relation of potassium to plant growth

The investigation described in foregoing pages deals with a study of the relation between sugars, starch, and nitrogen distribution of cowpea and sugar beet plants which had been grown on high- and low-potassium nutrient solutions. An anatomical study of these plants was also made. 1. It shows that the greatest percentage of potassium is taken up in plants which were given the heavier potassium application. 2. Analyses for carbohydrates has shown that cowpea plants grown in a low-potassium nutrient solution, as a rule, were higher in reducing sugars and total sugars and lower in starch than those grown in high-potassium nutrient solutions. 3. The total percentage of nitrogen was usually greater in the low-potassium plants than in the high-potassium plants. The percentage of protein nitrogen also was usually greater for the potassium-deficient plants than in the high-potassium plants. This was particularly true in the case of stems. 4. From the results presented, it appears that nitrogen, sugars, and starch are not limiting factors for growth in potassium-deficient plants. The percentages of these compounds were usually as high in potassium-deficient plants as in high-potassium plants. 5. In nearly all instances the percentage of amino nitrogen in the low-potassium plants was as great as or greater than that in the high-potassium plants. 6. The anatomical study of cowpeas and soybeans shows that thick cell walls are associated with low-potassium in the plant. In general, there seems to be a greater development of the sclerenchyma cells and mechanical tissue of the vascular system and a smaller development of the cortex cells, both in number and size, in the low-potassium plants than in the high-potassium plants. 7. In the sugar beet, it appears that the cell walls of the mechanical tissue of the vascular system are thicker and more numerous in the low-potassium plants than in the high-potassium plants; also that the pericycle activity was reduced in the former plants.