Green foxtail millet (Setaria viridis) has NADP-ME type of C4 photosynthesis. Because of its short life cycle, small genome size of ~515？Mb, small plant stature, high number of seed set, simple growth requirements, and wide adaptability, this diploid ( ) weed is proposed to be a model species for the study of C4 photosynthesis. It is also a representative of bioenergy grasses and a model for genetic study of invasive weeds. Despite having all traits of a model species, it is difficult to cross-pollinate because its flowering behavior is not well studied. We used time lapse digital recording to study the flowering time and pattern along a single panicle. We found that flowering in Setaria was triggered by the darkness of the night and when the temperature was lower than 35°C. The anthesis of all the spikelets in a panicle took up-to three nights flowering from 9:30 pm to 10:00 am in the morning. Each spikelet has three phases of anthesis during which pollination occurs. A spikelet remains open for less than three hours. The pollination time for each spikelet is less than 60 minutes. Information from this study will facilitate the geneticists and plant breeders to plan for efficient crossing of Setaria. 1. Introduction A common weed, green foxtail millet (Setaria viridis (L.) P. Beauv.), which belongs to family Poaceae, has gained the attention of plant scientists due mainly to its inherent C4 traits. Brutnell et al., (2010) proposed to make this weed a model species for C4 photosynthesis research [1], and there is a progressive support and acceptance to the proposal [2, 3]. About 125 species are identified under genus Setaria [4], and S. viridis is considered the ancestral stock of this genus. Allozyme assay has shown that foxtail millet (S. italica) was the domesticated form of the S. viridis [5]. S. italica was grown as early as 6,000 years ago and was one of the oldest cultivated cereals of China [6]. Today, several species of millet belonging to the family Poaceae are widely cultivated. The major cultivated species of millet include: Pennisetum glaucum (pearl millet), Setaria italica (foxtail millet), Panicum miliaceum (proso millet), and Eleusine coracana (finger millet) [7]. The green foxtail millet is an invasive weed because of its short life span and its ability to produce seeds with long life [8]. Recently, it was reported that S. viridis also showed repeated evolution to herbicide resistance [9]. This finding opens a new dimension to uncover the genetic basis of the evolution of herbicide resistance. A model plant species should have rapid
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