Spatial Flowering Patterns in Dactylis glomerata Populations

Background:

Dactylis glomerata is thought to be one of the major contributors to the annual grass pollen load in temperate regions due to wide distribution, high abundance and high pollen production. Detailed information about its flowering dynamics may therefore help in assessing the severity of the grass pollen season. Grass flora estimates of the flowering period are not enough to determine when the species is capable or most likely to release pollen. Observing multiple grass populations over time would enhance the detail and understanding of the flowering dynamics and reveal the variation in flowering events within a region.

Methods:

Eight populations were chosen in Worcestershire, UK in 2018, with minimum 150 individual tillers each to secure full variation within each population. Flowering progression was determined from the BBCH scale adapted from cereal monitoring. The phenology was focused on the percentage of extruded anthers, with equal intervals of 25, 50, 75 and 100%. Senescence was considered reached with the detachment of the last anther to avoid ambiguity in terms of pollen emission. The two main populations were observed every second day while the six secondary populations were observed ten times during the season.

Results:

A total of 2672 tillers were observed. The spatial investigation highlighted the uniformity of flowering progression between both main and secondary populations, with a mean seasonal difference of less than 1/10th of a phase. Both main populations started to flower on May 29th. The main populations reached peak flowering on June 14th while the average population reached full flowering on June 20th. Peak flowering is reached earlier than average full flowering in all populations due to the divergent growth progression of individual Dactylis tillers. The flowering ended on Aug 9th, 73 days later.

Conclusion:

This study highlights that Dactylis glomerata flowering is uniform over an entire region. There is little to no difference between populations in the timing of crucial flowering events such as start, peak and full flowering. It also notes the difference between peak and full flowering, which will be of importance in the aspect of pollen release.