Flowering characteristics of annual bluegrass (Poa annua L.)

Abstract

Annual bluegrass (Poa annua L.) seeds, which were collected from an orchard in the experimental farm of Utsunomiya University, were sown in a pot filled with upland soil and then were grown in a grasshouse. In the following season, flowering characteristics of the weed were measured in terms of 4 following parameters, regarding a spikelet attached on the top of inflorescence, as 1 inflorescence per 1 plant. The results are summarized as below. (1) The number of female and hermaphrodite floret consisting of spikelet. Although most of the spikelet consisted of 1 female floret and 2 and/or 3 hermaphrodite florets, spikelet only consisting of hermaphrodite florets or spikelet having two female florets was observed. (2) The order of flowering of lemma in spikelet. In spikelet having female floret, female floret flowered first followed by the 1st. hermaphrodite florets. However, in spikelet having only hermaphrodite florets, regular flowering order was not found. (3) The time for flowering or closing of lemma in floret. Most of the female and hermaphrodite florets flowered at midnight, but some florets flowered from early morning to afternoon daytime in female florets. In addition, both female and hermaphrodite florets closed between early in the morning and in the afternoon. (4) The time from flowering to closing of lemma in floret. The flowering time of female was about 44 hours; it is longer than that of hermaphrodite florets. Moreover, in female floret, time from flowering to stigmatic development or from stigmatic development to closing took 21 hours or 23 hours, respectively, and in hermaphrodite floret, time from flowering of lemma to anther protruding or from anther protruding to closing lemma took less than 1 hour or 7 hours, respectively.