Flowering behaviour of populations of Dactylis glomerata under field conditions in Britain.
Reproductive behaviour was recorded in 23 populations of D. glomerata grown under uniform field conditions. In most populations some plants headed in the year of sowing; the wild populations, and those from areas of less severe winters, tended to head more freely. Heading date in spring varied between populations and appeared to be controlled by genetic differences in the daylength required for the elongation of culms. Late sowing in one year was associated with delayed heading in the following year. In some populations inflorescences could be initiated throughout the winter, suggesting that initiation has a lower daylength threshold than elongation of the culm. In many populations a high proportion of the plants produced heads during aftermath regrowth, and heading in the year of sowing and in the aftermath were correlated. [See also H.A, 34: 1882.] F. s.-R.B.