﻿COPPER SPRAYS ON IKISII POTATO TUBERS. 5 



Working with a large number of greenhouse plants, Zucker (52) 

 concluded that plants sprayed with Bordeaux have greater resistance 

 to etiolation than the unsprayed plants. The sprayed plants also 

 showed an increase of chlorophyll and an increased power of assimi- 

 lation, and their shoots lived longer. All of the sprayed plants 

 transpired more than the unsprayed plants or those sprayed with 

 lime alone. 



Harrison (2£) found that Bordeaux-sprayed plum, peach, and pear 

 leaves were slightly thickened and that a marked development of 

 chlorophyll granules occurred in their cells. 



According to Chuard and Porchet (6), copper spray causes a 

 slight increase in the sugar content of matured fruits. Injection of 

 solutions of copper salts into the tissues of such plants as the grape- 

 vine produced more vigorous growth, more intense color, and greater 

 persistence of the leaves. The copper seemed to act as a stimulant to 

 all the cells of the organism. Other metals, such as cadmium and 

 iron, are said to give a similar effect. Injecting small quantities of 

 copper salts into the branches of a currant bush caused an acceler- 

 ation in the maturation of the fruit identical with that obtained by 

 the application of Bordeaux to the leaves. If the quantity of copper 

 introduced-into the vegetable organism was increased, the toxic action 

 of the metal was brought into play. These investigators attribute 

 the stimulus, as shown by the earlier maturation of the fruit, to a 

 greater activity of all the cells of the organism and not to an excita- 

 tion of the chlorophyll functions alone. 



Treboux (49), in 1903, demonstrated the harmful effect of solu- 

 tions of copper salts on leaves, measuring the activity of photosyn- 

 thesis by a determination of the rate of emission of bubbles of oxygen. 



Kanda (25) undertook to ascertain whether copper had a stimu- 

 lating action on plants. He found that very small amounts of copper 

 sulphate were toxic to peas grown in distilled water. 



Schander (J^l) believes that the copper in a Bordeaux spray pene- 

 trates the leaf to a very small extent, perhaps less than one in a 

 hundred million parts, and that the copper there produces changes 

 in assimilation and in transpiration. He considers that the shading 

 effect of the Bordeaux spray on the leaves is beneficial to the absorp- 

 tion of carbon dioxid. 



Ewert (17) states that in the morning Bordeaux-sprayed potato 

 plants contain more starch than the unsprayed plants, not because 

 they are making more starch, but because they are unable to get rid 

 of it as rapidly. The starch is piled up in the chlorophyll bodies 

 as the minute amount of copper absorbed checks the diastase action. 

 Bordeaux spraying, shading the plants with cloth, and a combination 

 of the two procedures diminish the yield of tubers. This author 

 demonstrated by its effect on diastase that copper is present in the 

 sprayed leaf in minute amount and concludes that the organic life 

 of the plant is hindered rather than stimulated by the application 

 of Bordeaux sprays. 



Von Schrenk (50), working with cauliflower, also observed that 

 swellings were formed on the leaves owing to the action of copper 

 salts. 



Amos (1) studied the effect of Bordeaux mixture on the assimila- 

 tion of carbon dioxid by the leaves of plants to determine whether any 



