Effect of Sucrose and Gibberellic Acid on Floral Induction of Xanthium

Application of gibberellic acid (GA₃) before and sucrose after the inductive dark period promotes flowering in Xanthium. The promotive effects of these two compounds are independent but additive. Sucrose application either before or utter the dark period has promotive effect on the flowering response. These effects are additive. The roles of pre- and post-induction high-intensity light period and of GA₃ in the promotion of flowering have been discussed. It has been suggested that sucrose application promotes flowering by increasing translocation of the flowering stimulus and by promoting the rate of development of the terminal male inflorescence. It has also been suggested that GA₃-induced promotion of flowering is due to the increased synthesis as well as translocation of the flowering hormone.     

Photoperiodic sensitivity of the cotyledon and first true leaf of Xanthium

Three days after germination of Xanthium seeds, the seedlingswith only the first pair of opposite leaves attained full photoperiodicsensitivity and flowered in response to a 16-hr dark periodtreatment. The cotyledons of three- to six-day-old seedlingswere completely insensitive to inductive dark treatment. Six-day-oldseedlings could not be induced to flower with a 9-hr dark period.But with a dark period of 10 hr or longer, floral inductionoccurred and the optimum dark period was 15 hr. Developmentof the flowering apices started within 2 days after the inductivedark treatment and was completed by 9 to 11 days. ¹This work was supported by the United States Atomic EnergyCommission Contract AT (11-1)-1338. ²Present address: Plant Physiology Section, Crops Research Institute,P.O. Box 3785, Kumasi, Ghana, West Africa. (Received March 28, 1974; )     

Genotypic differences in potassium response and proline accumulation in maize during wilting

When leaf discs of six experimental hybrids of maize (Zea maysL.) grown with high as well as low levels of potassium weretreated with 5 mM KCl for 2 hr in light before exposure to long-term(43 hr) mild wilting conditions, a stimulating effect of potassiumtreatment ("potassium effect") on water-stress-induced prolineaccumulation was observed. This effect was greater in the discsgrown at a high level of potassium. Marked differences in prolineaccumulation due to wilting were observed in the different genotypes.Genotypic differences in the ‘potassium effect’were also evident. Use of potassium uptake as an index for screeningcultivars for drought tolerance may be possible. Present address: Department of Plant Science, School of Agriculture,University of Zambia. P.O. Box 2379, Lusaka, Zambia. (Received September 11, 1979; )