Influence of the Chloride Ion on the Content of Chlorophyll in the Leaves of Potatoes.

The color of plants depends to a great extent on the conditions of nutrition. Approximately fifty years ago VILLE (7) attempted to determine the proper provision of plants with elements of nutrition by their color from the amount of chlorophyll produced. The pale color of plants may depend on various causes. In some cases it is called forth by an actual reduction of the amount of chlorophyll owing to the depressive action of one or another factor on the formation of chlorophyll. However, very often the pale color is conditioned not by the decrease of the amount of chlorophyll, but by other factors, such as the accumulation of colored substances, increase of water content, and so on. The ability to determine these factors is of great importance when studying the changes in color called forth by potassium salts, especially by chlorides, which greatly increase the water content of plants. In the work of MAWALD (4) the reduction of the content of chlorophyll under the influence of potassium salts has been sharply made apparent in potatoes. MAIWALD considers the paler color of the leaves as an incipient chlorosis called forth by the inactivation of iron in the plants by superfluously accumulated ions of potassium and chlorine. The experiments of IIESEGANG (6) with potatoes have confirmed, as to essentials, the observations of MAWALD on the sharp action of the chlorides. RgmY (6) advances an opinion as to the possibility of the influence of the ratio of green and yellow pigments on color. MAIWALD (5), in his controversy with RET1⁄2M on the change of ratio of green and yellow pigments, alludes to the work of DEUBER (1), who found that changes in the content of carotinoids in the soy bean advances parallel with the changes in the content of chlorophyll, and that therefore the ratio of yellow and green pigments remains constant. DHEIN (2) was the first to note that, when studying potassium salts, it is necessary to take into account the fact that they increase the amount of water in plants. He distinguishes the "apparent" content of chlorophyll (the content in a unit of fresh leaves which determines the color of the leaf) from the "true" content in a unit of dry substance, which provides the possibility of judging the formation of chlorophyll. DHEIN has observed an actual reduction of the amount of chlorophyll only with large doses of KCI.