A quantitative analysis of the dependency on temperature of the entrance of Polygonum aviculare (L.) seeds into secondary dormancy

CRISTIAN MALAVERT; DIEGO BATLLA; ROBERTO LUIS BENECH-ARNOLD

Caeté, Minas Gerais

Congreso; Seed Ecology V; 2016

International Society for Seed Science (ISSS)

In seeds of many summer annuals low temperatures under moist conditions provoke dormancy release while high temperatures induce secondary dormancy. These temperature-dependent changes in seed dormancy level are related to changes in the thermal range permissive for seed germination through variations in the minimum or lower-limit temperature (Tl) allowing germination. Although numerous studies have been conducted to characterize the effect of temperature on dormancy release, there is less information on how temperature regulates induction into secondary dormancy. The aim of this work was to: (1) characterize the role of temperature on dormancy induction in P. aviculare seeds and (2) evaluate the effect of previous stratification temperature on the subsequent dynamics of induction into secondary dormancy. To achieve these objectives seeds of P. aviculare were stratified at 1.6, 5 and 10°C until achieving a minimum dormancy, and then were induced into secondary dormancy by further storage at 10, 15, 20, 25 and 30°C. At different times during storage seeds were exhumed and germinated at 10 and 15°C. Based on obtained germination time course-curves we quantified changes in the thermal range permissive for seed germination through variations in the mean lower limit temperature for seed germination (Tl(50)) using a mathematical simulation germination model. We found that induction into secondary dormancy in P. aviculare seeds can be assessed quantitatively through changes in Tl(50). The dependency on temperature of the induction into secondary dormancy could be described formally through: i) the identification of a threshold temperature for secondary dormancy to be induced (7.9°C); ii) the development of a Dormancy Induction Thermal Time Index (DItt); iii) the establishment of a bi-linear and positive relationship between Tl(50) and the accumulation of DItt. Additionally, we found that the induction rate into secondary dormancy was affected by the stratification temperature at which the seeds were exposed during dormancy loss.