Effect of Temperatures on Dormancy and Germination in Three Species in the Lamiaceae Occurring in Northern Wetlands |
| |
Authors: | Markus Brändel |
| |
Institution: | (1) Biocenter Klein Flottbek, University of Hamburg, Ohnhorststr. 18, 22609 Hamburg, Germany |
| |
Abstract: | In the temperate region temperature is the main factor influencing the germination period of plant species. The purpose of
this study was to examine effects of constant and fluctuating temperatures on dormancy and germination under laboratory and
field conditions in the three wetland species Lycopus europaeus, Mentha aquatica and Stachys palustris. The results should give indications if the temperature-dependent regulation of dormancy and germination is phylogenetically
constrained. Tests for germination requirements showed a minimum temperature for germination of 9 °C in Mentha and 12 °C in Lycopus and Stachys, and a maximum temperature of 33 °C for Lycopus and 36 °C for Mentha and Stachys. Fluctuating temperatures promoted germination in all three species but the amplitude required for high germination (>50%)
differed: it was 8 °C in Mentha, 10 °C in Stachys and 14 °C in Lycopus (mean temperature 22 °C). The effect of temperatures on the level of dormancy was examined in the laboratory by imbibing
seeds at temperatures between 3 °C and 18 °C for periods between 2 and 28 weeks, as well as by a 30-month burial period, followed
by germination tests at various temperatures, in light and darkness. In the laboratory only low temperatures
(≤12 °C) relieved primary dormancy in seeds of Lycopus, while in Mentha and Stachys also higher temperatures lead to an increase of germination. Dormancy was only induced in Lycopus seeds after prolonged imbibition at 12 °C in the laboratory. Buried seeds of all species exhibited annual dormancy cycles
with lower germination in summer and higher germination from autumn to spring. Exhumed seeds, however, showed considerable
differences in periods of germination success. Dormancy was relieved when ambient temperatures were below 12 °C. Ambient temperatures
that caused an induction of dormancy varied depending on species and test condition, but even low temperatures (8 °C) were
effective. At high test temperatures (25 °C) in light, exhumed seeds of all three species showed high germination throughout
the year. The three species showed various differences in the effects of temperatures on dormancy and germination. Similarities
in dormancy and germination found among the species are in common with other spring-germinating species occurring in wetlands,
so it seems that the temperature dependent regulation of dormancy and germination are related to habitat and not to phylogenetic
relatedness. |
| |
Keywords: | Dormancy-cycle Germination Lamiaceae Lycopus Mentha Stachys Stratification Temperature Wetland |
本文献已被 SpringerLink 等数据库收录! |
|