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Arthur Villordon, Christopher Clark, Don Ferrin, and Don LaBonte

; Jenni et al., 1998 ; Perry and Wehner, 1996 ; Viator et al., 2005 ). Heat unit summations or growing degree days (GDD) for vegetable production has been used for many years on crops with limited life span of quality in the field ( Dufault, 1997 ). Heat

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Gil Simmons and Bill B. Dean

Carrot (Daucus carota) L.) seed quality is affected by the environment in which it matures. Substantial differences in germination from year to year and from field to field have been recognized for many years for umbelliferae seed. Part of the explanation for low germination appears to be the harvest of immature seed. Data was collected for two years, from fields of the cultivars Chantenay and Nantes. Approximately 550 growing degree days were accumulated from anthesis until maturity for seed from the primary umbel. Growing degree days were calculated using a 10°C base temperature and without truncating for temperatures in excess of 35°C. Secondary, tertiary, and quaternary umbel seed maturity sequentially followed primary umbel seed. Secondary and tertiary umbels produced approximately 80 percent of the total seed yield while the primary and quaternary umbels produced approximately 20 percent. Seed maturity was determined by measuring the germination rate. Immature seed germinate at a slower rate than mature seed. The implications of these results for obtaining high quality carrot seed will be discussed.

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Jean-Pierre Privé, J.A. Sullivan, J.T.A. Proctor, and O.B. Allen

Abbreviations: CHU, corn heat units; GDD, growing degree days; PF, primocane fruiting. 2 Dept. of Mathematics and Statistics. Financial assistance from Agriculture Canada to J-P.P. while on educational leave is gratefully acknowledged. This study

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Arthur Villordon, Christopher Clark, Tara Smith, Don Ferrin, and Don LaBonte

radiation, relative humidity, wind (direction and speed), and rainfall. Means (total for rainfall) for all variables were calculated for 5 d before and after transplanting (DAT). Accumulated heat units, expressed as growing degree-days (base = 15.5 °C

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Uttara C. Samarakoon, Keith A. Funnell, David J. Woolley, and Edward R. Morgan

, for cultivars of gentian (Showtime Spotlight, Showtime Diva, and Showtime Starlet), as calendar days and growing degree-days [GDD base temperature 0 °C (32.0 °F)]. The standard deviation of time (days) from the emergence of first shoots to harvest

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Suzanne O’Connell and Robert Tate

yield compared with ‘Snowball Y’ across both growing seasons, and ‘Denali’ was also greater than ‘Amazing’ in 2014–15 ( Table 3 ). Table 3. Monthly growing degree days under high tunnels by season. In addition to weight, the diameter of each cauliflower

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Oussama H. Mounzer, Wenceslao Conejero, Emilio Nicolás, Isabel Abrisqueta, Yelitza V. García-Orellana, Luis M. Tapia, Juan Vera, Jose M. Abrisqueta, and Maria del Carmen Ruiz-Sánchez

( Baggiolini, 1980 ). Accumulated heat requirement was considered as the number of growing degree hours (GDH) or growing degree days (GDD) between the date of dormancy breaking and the date when 50% of flowers were in a particular phenological stage. The

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Thomas Björkman and Joseph W. Shail Jr.

were determined. Growing degree days (GDD 50 ) were calculated based on daily temperatures measured at a weather station at the field site on the Cornell University New York State Agricultural Experiment Station Vegetable Research Farm, Geneva, NY. The

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Richard P. Marini, James R. Schupp, Tara Auxt Baugher, and Robert Crassweller

. The year × orchard interaction was always significant at the 5% level. Cumulative growing degree days, 10 °C base temperature for the 60 d (CGDD60) before early-season fruit diameter was measured were obtained from nearby weather stations. Fig. 2

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Keith A. Funnell

. In other crop species, a common method of production scheduling uses the accumulation of heat units or sum of growing degree-days (GDD) to estimate the expected time to anthesis ( Huang et al., 1999 ; Whitman et al., 1997 ). Production scheduling