Greenhouse studies showed that eastern white cedar (Thuja occidentalis L.) exhibited yellowing and necrosis of foliage and browning of roots in response to high salt concentrations in soil and nutrient solution. Foliar spray showed injury symptoms to the foliage but the root system was not affected. Water stress as measured by water saturation deficit of the leaves also increased with increased concentration of salt in the soil. The damage to white cedar foliage occurred when the concentration of Na was 3 mg/g (0.3%) of dry matter. The toxic concentration of Cl was 8 mg/g (0.8%) of dry foliage. White cedar trees grown in muck soil treated with salt exhibited less injury than those grown in loam, sandy, or greenhouse soils receiving the same treatment.

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Extensive greenhouse and field experiments on the effects of DDT, BHC, and certain other insecticides upon plant growth when mixed with the soil have been in progress at the Plant Industry Station at Beltsville, Md., since late in the summer of 1945. This circular summarizes the results obtained primarily in studies with DDT but includes some data on BHC, chlordane, toxaphene, and 1 The author acknowledges the assistance of Victor R. Boswell, principal horticulturist and assistant head of the Division, in connection with the planning of the work, the analysis of data, and the preparation of the manuscript for publication; of Drs.

Analysis of snow and soil samples showed that the concentrations of Na and Cl were higher near the road and decreased with increasing distance from the pavement. The level of calcium in soil did not change with distance. The concentration of calcium in the foliage of eastern white cedar trees (Thuja occidentalis L.) facing the highway was not significantly different from the concentration in the foliage on the opposite side. The filter paper discs attached to the foliage accumulated significantly high amounts of salts on days with freezing rain or snow storms. A strong correlation was found between element levels in the foliage and the levels found in filter paper discs.

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