COPPER AS AN ESSENTIAL FOR PLANT GROWTH

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Abstract
Sunflowers, tomatoes and flax were grown in water cultures prepared with re-distilled water and repurified salts, and containing KNO3, KH2PO4, MgSO4 . 7H2O, CaSO4, FeSO4 and SiO2. The sunflowers received traces of Mn, Al, I, F, Na, Cl and B. In addition to these the tomatoes and flax received traces of Sn, Rb, Li, Ba, Hg, Ni, Co, As and Pb. Sunflowers receiving 3 additions of 0.125 mgm. and one of 0.06 mgm. CuSO4 had at flowering an average dry weight of 4.2 gm., while plant without Cu had 0.31 gm. A 2nd experiment with sunflowers was unsuccessful due to either high temp. or the higher purity of the salts in which some essential element was lacking. Tomatoes receiving 0.06 mgm. of Cu grew well for 9 weeks, except one plant, and had an average green weight of 31.3 gm. and dry weight of 2.6 gm. The plants without Cu made poor growth, 3 dying early. Those still living had an average green weight of 2.9 gm. and dry weight of 0.3 gm. Flax, making poor growth, received after 3 weeks a second addition of 0.06 mgm. of Cu, but made no response, and a 2nd addition of the elements was made. Those with Cu made improved growth, those without Cu did not, 6 dying before harvest. The remaining plants were harvested at the end of 52 days, 18 plants with Cu having a dry weight of 4.5 gm. and 18 without Cu 1.4 gm.