Morphological and Physiological Responses of Carnation and Tomato to Organic Phosphorus Insecticides and Inorganic Soil Phosphorus.

During the last few years considerable attention has been focused upon the use of the organic phosphorus compounds hexaethyl tetraphosphate and tetraethyl pyrophosphate as the active components of certain commercial insecticides. These substances are known to be toxic not only to insects but to other organisms in general as well. As the names of hexaethyl tetraphosphate and tetraethyl pyrophosphate are generally abbreviated HETP and TEPP, respectively, they will be referred to as such in this paper. HALL and JACOBSEN (11) concluded that HETP does not possess a definite structure by demonstrating that it is essentially a mixture of esters containing ethyl metaphosphate, triethyl orthophosphate, and tetraethyl pyrophosphate. These workers believe that the biological potency of the so-called HETP is actually due to the TEPP that it contains, although in a later publication, HALL (10) implied that HETP contains other toxic principles in addition to TEPP. These compounds become of interest to the plant scientist through the formative effects that they elicit in particular sensitive species and this paper reports some of the fundamental effects that these compounds, or their degradation products, have on plant metabolism. The formative effects produced in plants by these compounds so strikingly resemble, in most cases, those of the hormone-type phytocides that a number of workers have attributed the symptoms to 2,4-D contamination of either the insecticides or spray equipment. Carefully controlled experiments have demonstrated, however, that these characteristic symptoms can be initiated consistently by HETP and TEPP in carnation, tomato, and sunflower. This has been the case generally when slightly higher concentrations than recommended for insect control were employed. Other reports (24, 26, 27, 34) have appeared confirming this result for the same and other species. SMITH et al. (26, 27) have noted that tomatoes, roses, chrysanthemums and carnations are susceptible to HETP and TEPP and they cite many grower reports of formative effects appearing in greenhouse ornamentals treated with these compounds. ZIMMERMAN and HARTZELL (34) have noted that epinasty was produced in more than 20 species when exposed to HETP and TEPP. The report of MCILRATH (24), as well as many Texas grower reports of 2,4-D-