Journal
ENVIRONMENTAL AND EXPERIMENTAL BOTANY
Volume 72, Issue 3, Pages 409-414Publisher
PERGAMON-ELSEVIER SCIENCE LTD
DOI: 10.1016/j.envexpbot.2011.02.012
Keywords
Annual plants; Climate change; Germination; Parental effects; Photosynthesis; Winter
Categories
Funding
- Helsinki University Environmental Research Centre
- Academy of Finland [122194]
- University of Helsinki
- Academy of Finland (AKA) [122194, 122194] Funding Source: Academy of Finland (AKA)
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The overwintering conditions of northern plants are expected to change substantially due to global warming. For perennial plants, winter warming may increase the risk of frost damage if the plants start dehardening prematurely. On the other hand, evergreen plants may remain photosynthetically active and thereby benefit from milder winters. The positive and negative effects of mild winters on annual plants remain, however, largely unknown. We postulated that summer annuals may be susceptible to frost damage if the seeds germinate during a mild spell in winter. Winter annuals may utilize a warm period for photosynthesis. These questions were addressed in two consecutive experiments in which pot-grown individuals of Thlaspi arvense that overwintered in the field were exposed to an elevated temperature for 8 clays in growth chambers in mid-winter. No premature germination was observed in summer annuals. However, in accordance with our hypothesis, winter annuals started photosynthesising very rapidly upon exposure to elevated temperature. The winter warming treatment affected neither the total number of seeds produced nor the mean seed weight. These seeds, possessing divergent parental overwintering histories, were used as starting material for the second experiment. Seeds originating from both summer and winter annual plants germinated both in the autumn and in the following spring. We observed a major parental effect associated with the winter warming treatment. The warm spell experienced by the mother plant (either as a winter annual rosette or as a summer annual seed) reduced the proportion of autumn germination in the next generation. Only 43% of the seeds of summer annuals possessing a parental warming history germinated before the winter, whereas the germination percentage of seeds with no previous winter warming history was 71%. In the case of seeds collected from winter annual plants, 4% of the seeds germinated in autumn if the mother plants experienced the warming treatment during the previous winter, whereas the corresponding value was 37% if the mother plants did not experience warming. Our results show that summer and winter annual individuals show diverse responses to warm spells in winter. Since the responses are not limited only to the generation that actually experiences the warm spell, but also appear in their offspring, long-term studies consisting of several generations are called for. (C) 2011 Elsevier B.V. All rights reserved.
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