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Hiroshi Shimizu and Royal D. Heins

The effects of photoperiod and the difference between day temperature (DT) and night temperature (NT) (DIF) on stem elongation in Verbena bonariensis L. (tall verbena) were investigated. Plants were exposed to nine treatment combinations of -10, 0, or 10 °C DIF and 8-, 12-, or 16-hour photoperiods. Stem elongation was measured and analyzed by a noncontact computer-vision-based system. Total daily elongation increased as DIF increased; it also increased as photoperiod increased under positive DIF (DT > NT) and zero DIF (DT = NT), but not under negative DIF. Under positive DIF, daily elongation was 90% greater under the 16-hour photoperiod than under the 8-hour photoperiod. DIF affected elongation rate during the daily light span but not during the daily dark span. Total light-span elongation increased as DIF or photoperiod increased. Total dark-span elongation was not influenced by DIF or photoperiod. Elongation rates per hour in the light and dark were not significantly affected by photoperiod but increased in the light as DIF increased. Therefore, for a particular DIF, total elongation during 16-hour photoperiods (long days) was greater than that under 8-hour photoperiods (short days) because there were more hours of light under long days.

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Margaret G. Aiken, Holly L. Scoggins and Joyce G. Latimer

starting substrate pH. Materials and Methods Two perennial plant species were studied. Verbena bonariensis L. ‘Lollipop’ (purpletopvervain) and Veronica spicata L. ‘Goodness Grows’ (spiked speedwell), based on their response to foliar applications of

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Hiroshi Shimizu and Royal D. Heins

A computer vision system for noncontact growth analysis was developed. Front and side images of a plant were captured simultaneously using a mirror system and CCD camera and were magnetically stored on a magneto-optical disk. Images acquired at night were obtained by irradiating plants with incandescent light filtered to wavelengths of 850 nm and greater. Images were automatically captured and saved every 12 minutes. After images were collected, outlines of plant shape were extracted from stored images, a three-dimensional center line of the plant was extracted from the outline, and the elongation rate was computed. The outline extraction algorithm was modified to improve spatial resolution of images, and the thinning algorithm created a representative line of the plant by calculating a center line of the stem so the three-dimensional length could be calculated. Results of growth analysis on Verbena bonariensis L. plants grown under three photoperiods (8, 12, and 16 hours) and three day/night air-temperature combinations (15/25, 20/20, and 25/15) will be presented.

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Christopher J. Currey, Kenneth G. McCabe and Kellie J. Walters

10 d after transplanting at Michigan State. Aiken et al. (2015) reported that while veronica ( Veronica spicata ) flowering was unaffected by ethephon drenches, verbena ( Verbena bonariensis ) flowered up to ≈2 weeks later than untreated plants

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Anderson Machado de Mello, Nereu Augusto Streck, Erin E. Blankenship and Ellen T. Paparozzi

’ penstemon. Similar increases in germination when seeds were soaked at similar concentrations as those used in this research have been shown to effectively increase seed germination for a wide variety of seeds such as Verbena bonariensis ( Kornegay and