Stimulatory Effects of Radiation from a Quartz Mercury Vapor Arc Upon Higher Plants

Abstract

The deleterious effects of ultra-violet radiation upon plants have been known since the work of Bailey ('94), who found that electric arc discharges caused the collapse and the loss of color of epidermal cells of Coleus plants. Since Bailey many other workers have studied the reactions of plants to ultra-violet radiation, in the majority of cases, that from an unscreened mercury vapor arc or an unscreened iron or carbon arc. Green ('97) found ultraviolet rays destructive to diastase in leaves. Hertel ('05) found a retardation of cyclosis and finally death in leaf cells of Elodea, and lethal effects on bacteria and other micro-organisms. Maquenne and Demoussy ('09) showed a killing and blackening effect of ultra-violet rays on plant epidermises. Schulze in the following year, studying the reactions of individual cells to the mercury arc radiation, found disorganization of cytoplasmic and nuclear structures and a repressive effect upon the germination of fungous spores. Stoklasa ('12) carried out lengthy investigations on many types of plants and found only lethal effects. Kluyver ('11) verified the work of Bailey and others and studied in addition the relative effects of ultra-violet rays on various individual organs and tissues of plants; he found the most marked injury in the shorter ultra-violet rays, those below 290 mv. and he failed to discover any resistance on the part of the plant to these rays. Chauchard and Mazou6 ('11) found that ultra-violet radiations were destructive to many enzymes in vitro. Bovie ('16), investigating the effects of the Schumann region on both plants and animals, found a marked increase in lethal effects in direct proportion to decreasing wave length. Ursprung and Blum ('17) used deplasmolysis as an indicator of injury and found that the wave-lengths below 290 mp. caused the greatest damage, that the presence of some pigments evidently increases the absorptive