The Physiology and Biochemistry of Flowering

With the two SDP, Xanthium canadense and Chenopodium Amaranticolor, it has been possible to separate more clearly the partial reactions of the photoperiodic response of SDP and in some degree to associate these processes with particular biochemical or physiological processes of the plant. Thus it has been shown that sugars and Krebs cycle acids are able to replace the high intensity light process. Further investigations have shown that substances formed during an inductive dark process are still susceptible to auxin inactivation even after exposure to several hours of high intensity light immediately following the dark period. It has been shown that the effect of a flash of light in inhibiting the dark process can be reversed by anti-auxins. Further experiments have confirmed earlier work which show that LD leaves on SD plants inhibit flowering. Hypotheses have been advanced 1) to explain the nature of this inhibition and 2) to explain the kinetics of the dark process. Experiments with a newly discovered LDP, Silene Armeria, have shown that its critical day length is reduced by increasing temperature. Studies on the auxin relations in the flowering of Silene and Hyoscyamus niger indicate that auxin causes flowering of these LDP under conditions in which the controls remain vegetative.