Evidence of Biologic Relationships Among Species of Chenopodiales.

Abstract

The differentiation of plants into species or larger groups is usually based upon gross or microscopic characteristics. Physiologic criteria are seldom emphasized and chemical ones are notoriously inadequate in the establishment of significant differences. The order Chenopodiales contains several genera which have been implicated in clinical allergy in man. The more important of these are Amaranthus, Atriplex, Chenopodium and Salsola. All, except the first, are included in the family Chenopodiaceae. There are many anatomic characteristics common to these genera although the gross appearances in the individual species differ enormously.

Approximately 300 allergic patients (62 in the Santa Fe group), drawn from the area commonly designated as the Pacific Southwest, have been tested with the same extract of pollen from one or more species of each genus listed above. A significant number of these patients, especially those from the desert sections, gave skin reactions to these extracts. The total number of Chenopodiales-sensitive patients in each of the 3 groups is essentially the same. Those from the Santa Fe Clinic, however, represent 74% of the total patients in that series as compared with 57% and 38%, respectively in the 2 remaining groups. The higher incidence of sensitivity to this type of flora among Santa Fe patients may be due to greater exposure to these pollens.

The object of this study is not to draw sweeping conclusions but rather to point out interesting possibilities, based on skin reactions, in the hope that others may confirm or nullify these suggestions. Amaranthus retroflexus seems to be rather closely related to all the species studied. The fact that it reacted alone on but 4 patients of the 144 sensitive to Chenopodiales—in a total of 278 patients— seems to indicate a high degree of specificity of the extract.