Abstract

This research was designed to study induction and floral initiation of 11 cultivars of Kentucky bluegrass (Poa pratensis L.). Spring-seeded plants were in the vegetative condition when exposed in autumn to inductive environment (cool temperatures and short photoperiods). Floral initiation was determined by 1) biweekly dissection of tillers and by 2) biweekly transfer to warm temperature and long photoperiod to force panicle production.

Dissection of tillers showed no transition to floral development from early November, 1974, to 4 Jan., 1975. Transition to floral primordia was. apparent for ‘Merion’ and ‘Newport’ on 27 January, six cultivars on 10 February, and all 11 cultivars on 25 February. ‘Cougar’, ‘Fylking’, and ‘Glade’ require a longer induction period than the other cultivars before floral initiation.

Transfer of plant material from field inductive conditions to warm temperature and long photoperiod in a greenhouse indicated that induction had not occurred before 18 November. Panicles were produced by ‘Arista’, ‘Baron’, ‘Garfield’, and Newport when transferred on 2 December and by an additional four cultivars when transferred on 16 December. Glade and Fylking did not produce panicles until the transfer was made on 27 January, again indicating the longer induction period necessary for these cultivars. Induction and floral initiation, as measured by panicle production, increased in linear association (r = 0.98**) with duration of time plants were left under inductive conditions.

Either method of study, tiller dissection or transfer to artificial environment, has advantages and disadvantages. This research indicates that the two methods are complementary and valuable to understanding induction and development of floral primordia when used concurrently.

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