Seed germination ecology of meadow knapweed (Centaurea x moncktonii) populations in New York State

Authors: DITOMMASO, ANTONIO - Cornell University; Milbrath, Lindsey; MARSCHNER, CAROLINE - Cornell University; MORRIS, SCOTT - Cornell University; Biazzo, Jeromy

Submitted to: Weed Science Society of America Meeting Abstracts
Publication Type: Abstract Only
Publication Acceptance Date: 1/8/2018
Publication Date: 1/29/2018
Citation: Ditommaso, A., Milbrath, L.R., Marschner, C.A., Morris, S.H., Biazzo, J. 2018. Seed germination ecology of meadow knapweed (Centaurea x moncktonii) populations in New York State. Weed Science Society of America Meeting Abstracts. No. 95 (http://www.wssaabstracts.com/public/54/proceedings.html).

Interpretive Summary:

Technical Abstract: The introduced meadow knapweed (Centaurea x moncktonii), a hybrid of black (C. nigra) and brown (C. jacea) knapweeds, appears to be common and expanding in New York agricultural lands, including pastures, meadows and waste areas. The biology and ecology of the hybrid is mostly unstudied, such as its germination characteristics which may influence the seasonal timing of seedling emergence. We evaluated the effect of temperature, light, seed stratification, scarification, and population on percentage germination in four experiments over two years. Temperature and light were factors in all experiments. Mature capitula were collected from four populations in August. Seeds were separated from dried capitula with a rubbing board (scarified) or gently removed by hand (non-scarified) and stored dry at 4ºC for 4-28 weeks prior to an experiment. Lots of 50 seeds were placed in sealed petri dishes with moist blotting paper and germinated immediately (non-stratified) or, for one experiment, held for 4 weeks at 4ºC before the test (cold-wet stratified). Dishes were uncovered (light) or covered with aluminum foil or placed in black bags (dark). Temperature treatments were 15:5ºC (day:night), 20:10ºC, 25:15ºC, or 30:20ºC using a 14:10 hr (day:night) photoperiod. Groups of 5 dishes per treatment were checked for germination over 4 weeks; dark-treated seeds were checked for germination in a dark room with a dim green light. Percentage germination was mostly similar among meadow knapweed populations for different treatments of temperature, light and stratification. Scarification did not increase percentage germination. Cold-wet stratification appeared to increase germination rates by 4-57% relative to non-stratified seeds, particularly at lower temperatures in either light treatment, but it was not necessary for germination to occur. Long durations (e.g., 28 weeks) of cold-dry storage also appeared to promote germination. Light significantly increased germination rates in the three lower temperature treatments by 15-86% compared to dark-treated seeds. Germination was most rapid at warmer temperatures (25:15 and 30:20ºC) and was 87-97% with light. Seeds in the dark treatment at the lowest temperature (15:5ºC) generally had the lowest germination (3-21%). Warm temperatures, light, and stratification stimulate germination in meadow knapweed.