Translocation of Solutes in Plants

Abstract

IN my experiments on the eradication of Dicha-petalum cymosum (Hook) Engl., one of the most toxic plants of the Transvaal, I was led to the following technique for introducing copper into the stem of the plant. The stem and branches of the plant are entirely underground and only the leaves emerge above the soil. The stem may be up to 100 ft. long. For the purpose of eradication, the stem is freed from the surrounding soil to a depth of about 9 in. and then ringbarked on a length of 2 in. for a 1 in. stem. Around this ringbarked region a mixture of the following substances is packed: calcium chloride, copper sulphate and soil in the proportion 2:1:2. The hole is then filled up again with soil. The circulation of the copper is very rapid; within twenty-four hours, leaves 15 ft. distant from the main stem are practically dead or dying. The downward movement is much slower ; it takes eighteen days to kill 104 inches of the stem. The movement of the copper was followed with the help of potassium ferrocyanide, and it was noticed that the trans-location takes place essentially in the phloem, although in the ringbarked region it is first taken up by the xylem. Only after about eight days does the xylem show copper in the same degree as the phloem does after twenty-four hours.