Abstract
Twelve species of Avena, including 15 varieties, were used for the observation of the time when flowers begin to bloom every day. The observed plants were grown in pots under natural conditions, and the blooming time was observed every 30 minutes from April 19 to June 1, 1969.
Based on the mean time of blooming they were divided into four groups, afternoon-blooming type (4:00-4:30 p.m.), evening-blooming type (7-9 p.m.), night-blooming type (about 10 p.m.) and morning-blooming type (about 4 a.m. of the next day). A. pilosa, A. clauda, A. ventricosa, A. magna and hexaploid species belong to the afternoon type, diploid species with AA genomes to the evening type. A. barbata and A. longiglumis represent night and morning types, respectively.
Temperature, rainfall and sunshine are evidently associated with flowering. Temperature, however, seems to exert the most important meteorological influence. Avena flowers usually begin to open during a continuous fall of temperature from the highest point on each day, and only A. longiglumis blooms at nearly the lowest temperature next morning. Temperature fall ranging from 0.5° to 1.5° or 2.0°C per hour seems to be very favorable for initiating the opening of flowers, but on the contrary such steep fall, especially successive falls, as of 2-4°C per hour checked the blooming or sometimes postponed it in the evening and night types until next morning.
The time and manner of blooming in Avena, Triticum and Haynaldia were discussed and a preliminary mechanism of blooming was proposed.
