Dynamic changes in base water potential during incubation explain the mixed effects of temperature on germination and dormancy during germination tests

DIEGO BATLLA; ROBERTO LUIS BENECH-ARNOLD

Salvador de Bahia

Congreso; 10 Conference of the International Society for Seed Science-Seed Science in the 21 Century; 2011

International Seed Science Society

In many non-domesticated seed populations germination test results can be altered by changes in seed dormancy status occurring during incubation time, often leading to misinterpretation of obtained results. In the present work we propose an interpretation of the mixed effects of temperature on germination per se and dormancy during incubation based on a hydrothermal time modeling approach. To achieve this objective we analyzed a germination data set corresponding to Polygonum aviculare seeds stratified for different time periods at 5ºC, and afterwards germinated in water (0 MPa) and PEG solutions (-0.25, -0.5, -0.75 and -1 MPa) at 5, 10, 15, 20 and 25ºC. Obtained results showed a clear dormancy release pattern through stratification, in which a gradual increase in germination percentage at the different germination temperatures with stratification time can be observed. However, when germination data at the different temperatures for each stratification time was analyzed using a hydrothermal time model the fit was poor. This was mainly because obtained germination patterns at certain temperatures do not match those excepted for germination of non-dormant seeds. For example, at relatively high incubation temperatures (25 ºC) seeds presented the highest germination rate, but low germination percentage due a fast induction into secondary dormancy, while at low temperatures (5ºC) seeds showed the lowest germination rate but a sharp increase in germination percentage a the end of the incubation period due to dormancy release. To account for these dormancy effects on germination test dynamics, base water potential was allowed to vary together with progress of incubation time at the different temperatures. A progressive increase in the value of base water potential during incubation stopped germination due to dormancy induction at high temperatures, while a lowering of base water potential increased germination due to dormancy release at lower temperature. These dynamic changes in seed population base water potential during incubation at the different temperatures allowed a good fit of predicted to observed germination dynamics and a correct interpretation of temperature effects on germination per se and dormancy occurring during the germination test. Moreover, obtained results suggest that widening of the thermal range for seed germination as a consequence of dormancy release can be explained through dynamic changes in seed population base water potential.