The genetics of self-incompatibility inOenothera rhombipetala

Pollen tubes were grown under controlled temperatures in stigmas and styles which had been cut from the flowers at the point of juncture of the style with the ovary. At constant temperatures the tubes compatible with the styles grew rapidly at uniform rates. They showed accelerated growth with increase in temperature within the range 10°–30°C. Growth of incompatible tubes was irregular and slow and was neither measurably accelerated nor depressed within this range of temperatures. Routine tests for compatibility were conducted at 27°C; at this temperature compatible tubes grew through the entire length of the styles (ca. 58 mm) in 9 hours. Much of the incompatible pollen failed to germinate; that which did, grew to a maximum length ofca. 2 mm inca. 4 hours. The incompatible tubes did not even enter the styles but remained confined to the stigmas. ThreeS alleles were involved and conformed in their behavior to the gametophytic system of incompatibility. Colchicine-induced tetraploid derivatives of these plants showed no increase in compatibility.