A Comparison of the Mode of Floral Abscission in Two Varieties of Nicotiana tabacum

Oat plants were sprayed with gibberellic acid in con- centrations of 10 ppm, 100 ppm, 1000 ppm, and 2,500 ppm at 24 hours before and 24 and 144 hours after anthesis. The application 24 hours before or after anthesis caused 10 percent to 50 percent elongation of the upper internodes. Weight of the primary kernels was depressed approximately 10 percent and that of the secondary 15 percent. The effect upon seed size was independent of time of application or concentration