With the two SDP, Xanthium canadense and ChenopodiumAmaranticolor, it has been possible to separate more clearly thepartial reactions of the photoperiodic response of SDP and in somedegree to associate these processes with particular biochemical orphysiological processes of the plant. Thus it has been shown thatsugars and Krebs cycle acids are able to replace the high intensitylight process. Further investigations have shown that substancesformed during an inductive dark process are still susceptible toauxin inactivation even after exposure to several hours of highintensity light immediately following the dark period. It has beenshown that the effect of a flash of light in inhibiting the darkprocess can be reversed by anti-auxins. Further experiments have confirmed earlier work which show that LD leaves on SD plantsinhibit flowering. Hypotheses have been advanced 1) to explainthe nature of this inhibition and 2) to explain the kinetics of thedark process.
Experiments with a newly discovered LDP, SileneArmeria, have shown that its critical day length is reduced byincreasing temperature. Studies on the auxin relations in theflowering of Silene and Hyoscyamus niger indicate that auxincauses flowering of these LDP under conditions in which thecontrols remain vegetative.
