PHOTOPERIODIC ADAPTATIONS IN EUPATORIUM RUGOSUM

Racial differences based on flowering response to several photoperiods were detectable in two widely separated populations of white snakeroot, Eupatorium rugosum Houtt. The most favorable photoperiod for advanced flowering in Georgia stocks was 12 hr, for those from North Dakota, 14 hr. The difference in latitude between these populations was approximately 12° and represents a mean difference of 75 days in the frost-free season. Under noninductive photoperiod a 1-hr interruption of white light in the middle of 15 hr of darkness stimulated floral initiation in North Dakota plants, whereas the same application at the beginning or at the end of the dark period failed to produce flower buds. The effect of red light (660 mμ) for 10 min given in the middle of the long night was similar to white light on the northern strain, and was negated by far-red (730 mμ). Georgia stocks initiated flowering under 15 hr of darkness but were retarded by white light applied in the middle of the period, thus differing in basic response from North Dakota plants. Red light, in contrast to effects observed in North Dakota plants, retarded initiation of flower buds. This effect was offset by far-red light. When compared with other studies on long-day and short-day species our results suggest that photoperiodic adaptations related to latitudinal distribution occur in white snakeroot. The North Dakota strain showed correspondence to long-day types while short-day tendencies were exhibited by Georgia plants.     

Vereine,Anstalten, Unternehmungen

Ohne Zusammenfassung     

Vereine,Gesellschaften, Anstalten

Ohne Zusammenfassung