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Title: SEPARATING TEMPERATURE AND PHOTOPERIOD EFFECTS ON GROWING DEGREE DAYS FROM EMERGENCE (VE) TO FLORAL BUD INITIATION (R0) AND FLOWERING (R1) IN SOYBEAN

Author
item ZHANG, L - U OF ILLINOIS, URBANA
item WANG, R - U OF ILLINOIS, URBANA
item Hesketh, John

Submitted to: Crop Simulation Workshop Proceedings
Publication Type: Proceedings
Publication Acceptance Date: 3/16/1995
Publication Date: N/A
Citation: N/A

Interpretive Summary:

Technical Abstract: The date-of-planting data set reported last year was reanalyzed to separate out a temperature effect from photoperiod effects on Growing Degree Days (GDD) to floral bud initiation and flowering among genotypes adapted to Urbana IL. A second order equation was fitted to GDD between VE, R0 and R1 events for early genotypes (ACME - MG 00, L71-920 - MG I and L65-778 - MG I+) plotted against temperature, accounting for 70 to 85% of the variation. A GDD value was then estimated for the same growth period of other genotypes varying in MG II to IV, based upon the average temperature between events and the GDD temperature function for the very early maturing genotypes. Such 'temperature adjusted' GDD values were then subtracted from measured ones of later-maturing genotypes, and remainders were plotted vs. photoperiod, resulting in much better fits of equation to the adjusted VE-R0 GDD data vs. photoperiod. The photoperiod used was either the average for the growth period or that at R0. The photoperiod at R0 resulted in better-shaped adjusted GDD response curves for MG II-IV (as well as for MG V-VIII). Changing the base temperature from 10 to 7 C did not help much in improving equation fits to data. We are still searching for how to calculate photoperiod to give the best fit of equations to data and the most biologically meaningful shape of the response curve.