1962 Volume 27 Issue 3 Pages 122-128
Several salts of ethylene-bis-dithiocarbamate (EDC), such as disodium-(NaEDC), zinc-(ZnEDC), manganese-(MnEDC), and diammonium-ethylene-bis-dithiocarbamate (NH4EDC, ) were applied to tomato seedlings through soil or by spraying on leaves, and their behavior in the plant was examined.
Tomato seedlings were grown in soil in 21cm pots, one plant in each pot, and 500ml per single plant of 1/5, 000 solution of ZnEDC or NH4EDC was applied to the soil every day, for seven days. Leaves were then detached, inoculated with Phytophthora infestans, and incubated for five days at 20°C in moist petri dish. Enlargement of lesions was very much retarded by the pretreatment with the chemicals. The leaf juice was found to contain a substance which inhibits the germination of conidia of Cochliobolus miyabeanus.
Lower leaves of tomato plants were sprayed with Zn-, Mn-, or NH4EDC while upper leaves were left unsprayed. After 24 hours, the leaves were washed with water and their juices were assayed on C. miyabeanus conidia. Lower leaves contained a similar inhibitory substance, while the upper unsprayed leaves did not.
Leaves of tomato plants which had been treated through soil with EDC compounds, especially with NH4EDC, contained a higher amount of non-protein N and total acids, including inorganic acids and some of the TCA members, as compared with leaves of non-treated plants.
Cuttings of treated plants were put into 1/15M solution of sodium succinate. After 24 hours, the content of malic acid was determined. The acid content in the treated leaves was much lower than that in the non-treated leaves, suggesting that the malic acid metabolism was stimulated by the treatment. The O2 uptake of the leaf was also stimulated by the same treatment.
Dilute NaEDC and MnEDC solutions were stored at room temperature, and change in ultraviolet absorption curve was examined. After one or two days storage, a single peak at 277mμ appeared, indicating the formation of ethylene thiuram monosulphide (ETM) or ethylene thiuram disulphide (ETD). Tomato leaves were sprayed with Na-, Mn-, Zn-, or NH4-EDC. After 4, 24 hours, and 3 days, they were washed with water or with dilute NaOH, and the UV-absorption of the washings were examined. ETM formation was observed after three days. Dilute NH4EDC solution (1/10, 000 at final concentration) was added to the culture of C. miyabeanus, and the UV-absorption of the supernatant solution was examined. ETM was found within 24 hours, while no trace of ETM was detected in the NH4EDC solution without the fungus mycelium.