A quantitative analysis of dormancy loss dynamics in Polygonum aviculare L. seeds. Development of a thermal time model based on changes in seed population thermal parameters

DIEGO BATLLA; ROBERTO LUIS BENECH-ARNOLD

SEED SCIENCE RESEARCH

Año: 2003 p. 55 - 68

0960-2585

A model for simulating Polygonum aviculare L. seed dormancy loss in relation to stratification temperature was developed. The model employs the lower limit temperature for germination (Tl) as an index of seed population dormancy status. While population mean Tl (Tl (50)) and Tl distribution within the population (sTl) are allowed to vary as seeds are released from dormancy, other thermal parameters characterising the germination thermal responses (base, optimal and maximal temperatures, and thermal time required for germination) and the higher limit temperature for germination (Th) are held constant. In order to relate changes in Tl (50) and sTl to variable time and temperature, a stratification thermal time index (Stt) was developed, which consists of the accumulation of thermal time units under a threshold temperature for dormancy loss to occur. Therefore, Tl (50) and sTl varied in relation to the accumulation of Stt according to time and temperature. To derive model equations, changes in seed population thermal parameters were estimated for buried seeds stored at 1.6, 7 and 12 °C for 110 d. Seeds were exhumed at regular intervals, and were incubated at 15 °C and at a gradually increasing temperature regime in the range 6-25 °C. The germination time-course curves obtained were reproduced using a mathematical model. Thermal parameters that best fit simulated and experimentally obtained germination time-course curves were determined. Model performance was evaluated against data of two unrelated experiments, showing acceptable prediction of timing and percentage of germination of seeds exhumed from field and controlled temperature conditions.