Abstract Detail


Ramos, Sergio E. [1], Rzodkiewicz, Lacey [2], Turcotte, Martin [2], Ashman, Tia-Lynn [1].

Effects of herbicide on floral and vegetative traits in rapid Brassica rapa: implications for ecological interactions.

Off target exposure to herbicides is an anthropogenic stressor for natural plant communities that could alter eco-evolutionary dynamics. We investigated phenotypic changes in floral and vegetative traits that mediate important ecological interactions (i.e. pollination and herbivory) and seed production triggered by exposure to synthetic-auxin herbicide dicamba in fast-cycle Brassica rapa plants. We exposed seedlings to drift (0.5%, 1%) and splash (10%) concentrations of field application of dicamba, as well as controls, and recorded phenotypic responses in floral (flower size, ovule and pollen number) and vegetative traits (stem diameter, leaf mass and plant height) at two time points: when plants started producing flowers (‘early’ 18-25 days old), and when plants reached their flowering peak (‘late’, at 35-36 days old). Additionally, we performed hand-pollinations within treatments to evaluate effects on seed set, as well as final above-ground biomass, height and the total number of flowers produced. During the early-flowering stage, we found strong concentration-dependent effects of dicamba but the direction of effect varied among traits. Compared to controls, drift concentrations reduced flower size by 37-46%, ovule number by 59-78%, pollen number by 27-30%, and plant height by 17-30%. Splash concentration reduced flower size by 54%, ovule number by 85%, pollen number by 54%, and plant height by 81%. In contrast, stem diameter increased significantly by 33% and leaf mass by 41% but only in the splash concentration. Interestingly, at the late-flowering stage the phenotypic effects of dicamba on the same floral and vegetative traits attenuated, with plants from the drift concentration no longer differing from control plants. This apparent recovery, however did not occur in plants in the splash concentration, as they remained 68% shorter and produced 78% fewer flowers compared to controls. Nevertheless, total reproductive fitness (estimated as the product of final number of flowers and seeds per fruit) was still decreased in the drift concentrations by 40 and 41%, and up to 55% in the splash concentration compared to controls. The observed effects of dicamba in changing floral and vegetative traits could potentially affect interactions with pollinators and herbivores. The overall reduction of floral traits might negatively affect pollinator attraction and reproductive success, but a smaller plant size could be less apparent to insect herbivores and thus experience reduced herbivore damage. Also, the observed phenotypic recovery could be a mechanism of tolerance that might allow a rapid adaptation to dicamba.

1 - University of Pittsburgh, Pittsburgh, PA, USA
2 - University of Pittsburgh

none specified

Presentation Type: Oral Paper
Session: ECO7, Ecology 7: Species Interactions
Location: Virtual/Virtual
Date: Friday, July 31st, 2020
Time: 1:15 PM
Number: ECO7004
Abstract ID:647
Candidate for Awards:None

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