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Abstract Background and AimsAs winter and spring temperatures continue to increase, the timing of flowering and leaf-out is advancing in many seasonally cold regions. This advancement could put plants that flower early in the spring at risk of decreased reproduction in years when there are late freeze events. Unfortunately, relatively little is known about floral freezing tolerance in forest communities. In this study, we examined the impact of freezing temperatures on the flowers of woody plants in a region where there is rapid winter warming in North America. MethodsWe subjected the flowers of 25 woody species to a hard (−5 °C) and a light freeze (0 °C). We assessed tissue damage using electrolyte leakage. In a subset of species, we also examined the impact of a hard freeze on pollen tube growth. To determine if the vulnerability of flowers to freezing damage relates to flowering time and to examine the responsiveness of flowering time to spring temperature, we recorded the date of first flower for our study species for 3 years. Key Results and ConclusionsAcross species, we found that floral freezing tolerance was strongly tied to flowering time, with the highest freezing tolerance occurring in plants that bloomed earlier in the year. We hypothesize that these early blooming species are unlikely to be impacted by a false spring. Instead, the most vulnerable species to a false spring should be those that bloom later in the season. The flowering time in these species is also more sensitive to temperature, putting them at a great risk of experiencing a false spring. Ultimately, floral damage in one year will not have a large impact on species fitness, but if false springs become more frequent, there could be long-term impacts on reproduction of vulnerable species.
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Weighing the risks and benefits of flowering early in the spring for the woody perennial Prunus pumila
Abstract PremiseThere are advantages to flowering early in the spring, including greater pollinator fidelity and longer fruit maturation time. But plant phenology has advanced in recent years, making many plants vulnerable to freezing damage from late frosts. MethodsTo determine the costs and benefits of flowering early in the growing season, we exposedPrunus pumilaplants to two freezing treatments and a delayed flowering treatment in subsequent years. Data were collected on ovary swelling, fruit production, and pollinator visitation on hand‐ and open‐pollinated plants in all treatments. We also measured tissue damage after freeze events. ResultsOur results suggest that flowering time and temperature affect reproductive success, with fewer fruits produced after hard freezes. The same was not true for light freezes, which had minimal impact on reproduction. Freezing damage to plants after a hard freeze did affect the number of dipteran pollinators but not the overall pollinator visitation rate. Despite the clear impact of freezing temperatures on plant reproduction, flowering early provided an advantage in that reproductive output decreased with delayed flowering. ConclusionsOur findings suggest thatPrunus pumilawill retain the ability to attract pollinators and produce viable seeds if exposed to false spring conditions that involve a light freeze, but hard freezes may reduce yield by an order of magnitude. Although the advantages to flowering early may outweigh the risk of freezing damage under current conditions, it is possible that flower viability may be constrained under continued climate warming.
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- Award ID(s):
- 1656318
- PAR ID:
- 10695412
- Publisher / Repository:
- Annals of Botany
- Date Published:
- Journal Name:
- American Journal of Botany
- Volume:
- 111
- Issue:
- 11
- ISSN:
- 0002-9122
- Subject(s) / Keyword(s):
- Flowers, false spring, woody plants, trees, angiosperms, freezing tolerance, cold tolerance, freezing damage, flowering phenology, flowering time, pollen tube growth, electrolyte leakage
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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- Free Publicly Accessible Full Text
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Accepted Manuscript
- Journal Article:
- https://doi.org/10.1002/ajb2.16417
