HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS		QUICK SEARCH:   [advanced] Author: Keyword(s): Year:  Vol:  Page:

This Article Abstract Full Text Free Full Text (PDF) Free Alert me when this article is cited Alert me if a correction is posted Services Similar articles in this journal Similar articles in ISI Web of Science Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via ISI Web of Science (2) Citing Articles via Google Scholar Google Scholar Articles by Aiken, R. M. Search for Related Content PubMed Articles by Aiken, R. M. Agricola Articles by Aiken, R. M. Related Collections Crop Growth and Development Inverse Procedures/Parameter Estimation Sunflower

Applying Thermal Time Scales to Sunflower Development

Kansas State Univ., NWREC, Colby, KS 67701

View larger version (26K): [in a new window]   Fig. 1. Computation of 3-h thermal time interval (TTi), used on the optimized developmental response to temperature (OR) algorithm (Eq. [2]), is depicted for conditions where daily temperature minimum (Tmn) is less than base temperature (Tb = 4°C) or daily maximum temperature (Tmx) exceeds the optimum temperature (Topt = 28°C). Eight provisional values (TTi') are computed from daily thermal extremes and a temperature factor (TFi). The effective value for each of the eight TTi is computed according to its relation to Tb, Topt, and the upper temperature limit (Tul = 40°C).

View larger version (22K): [in a new window]   Fig. 2. Daylength, computed from latitude and day of year, is depicted for Colby, KS (39°24'), the northern border of Colorado (41°), Carrington, ND (47° 30'), and Watrous, SK, Canada (51°30'). Photoperiod effects have been demonstrated for daylengths less than 15 h (also depicted).

View larger version (29K): [in a new window]   Fig. 3. Monthly means of daily temperature [average (•), maximum, and minimum] are depicted for April–September from 1999 through 2003 at Colby, KS. Base temperature (Tb = 4°C), optimum temperature (Topt = 28°C), and upper temperature limits [Tul, linear developmental response to temperature (LR) = 34°C; Tul, optimized developmental response to temperature (OR) = 40°C] also are indicated.

View larger version (29K): [in a new window]   Fig. 4. (a) Cumulative precipitation and (b) cumulative pan evaporation are shown for April–September from 1999 through 2003 at Colby, KS. Normal values (1971–2000) are provided for reference.

View larger version (25K): [in a new window]   Fig. 5. Cumulative growing degree days required for hybrid SF 187 to develop from emergence to visual appearance of the floral bud (R1) and to physiological maturity (R9) are shown in relation to daylength. Daylength corresponds to the date of floral bud appearance (R1) for cumulative growing degree days from emergence to R1 and for the presumed date of floral initiation (assumed 295 oCd following emergence) for cumulative growing degree days from emergence to R9. Degree days were calculated by assuming an optimized developmental response to temperature (Eq. [2], Fig. 1). Coefficients for linear regression models depicted here are presented in Table 4.

View larger version (41K): [in a new window]   Fig. 6. Sunflower development [vegetative (PSV) and reproductive (PSR) phenostages] from three to five planting periods are shown, with respect to cumulative growing degree days after emergence (PSV) or to scaled thermal time (PSR), which accounts for photoperiod effects on the duration of reproductive phenostages. Linear and logistic relationships fitted to PSV and PSR, respectively, for the hybrid SF 187 are reproduced for all three cultivars observed. Growing degree days and scaled thermal time (Eq. [5]) were calculated by assuming an optimized developmental response to temperature (Eq. [2], Fig. 1).