Abstract
Strong solar irradiation in combination with still air and dry soil can cause prostrate high-mountain plants to heat up considerably and ultimately suffer heat damage. Such heat damage has been repeatedly shown for vegetative structures, but not for reproductive structures, which we expected to be particularly vulnerable to heat. Heat effects on cold-adapted plants may increase with rising global temperatures and the predicted increase in heat waves. We have tested the heat tolerance of reproductive versus vegetative shoots at different reproductive stages, comparing ten common plant species from different elevation belts in the European Alps. Plant samples were exposed to temperatures in 2-K steps of 30 min each between 42 and 56 °C. Heat damage was assessed by visual rating and vital staining. Reproductive shoots were on average 2.5 K less heat tolerant (LT50, i.e. the mean temperature causing 50 % heat damage, 47.2 °C) than vegetative shoots (mean LT50 49.7 °C). Initial heat injuries (mean LT10) were observed at 43–45 °C in heat-susceptible species and at 45–47 °C in more heat-tolerant species, in at least one reproductive stage. Generally, heat tolerance was significantly higher during fruiting than during the bud stages and anthesis. Prostrate species with acaulescent buds and flowers tolerated heat better than those with caulescent buds and flowers. Petals were the most heat-susceptible plant structure and mature pollen the most heat tolerant. Based on these data, heat tolerance of reproductive structures appears to be adapted to the prevailing maximum temperatures which the plants experience during different reproductive stages in their environment. During hot spells, however, heat tolerance thresholds may be exceeded. More frequent heat waves would decrease the reproductive output and, consequently, the competitiveness of heat-susceptible species.Electronic supplementary materialThe online version of this article (doi:10.1007/s00442-015-3247-0) contains supplementary material, which is available to authorized users.
Highlights
High mountains are generally associated with a cold environment
We addressed the following questions: (1) Are there differences in heat tolerance between vegetative and reproductive structures within a species? (2) Are there differences in heat susceptibility among the main reproductive stages? (3) Is there a relationship between growth form, habit and elevational distribution and heat tolerance? (4) On the basis of in situ temperature maxima, what is the potential risk of suffering heat damage during reproductive development in the respective environment?
Mean heat tolerance of vegetative shoots (LT50) over all reproductive stages was highest in S. oppositifolia (>52 °C), followed by the dwarf shrubs C. vulgaris and L. procumbens and the cushion plant S. acaulis
Summary
High mountains are generally associated with a cold environment. due to strong solar irradiation, the surface temperatures of the short vegetation can considerably exceed free air temperatures (Cernusca 1976; Wilson et al 1987). Conditions of still air and dry soil increase this effect (Körner and De Moraes 1979; Neuner et al 1999; Buchner and Neuner 2003; Körner 2003). Species with prostrate shoots, including rosette plants and cushion plants, may heat up to 30–40 K above air temperature, and erect plants up to 20 K (Salisbury and Spomer 1964; Körner and Cochrane 1983; Gauslaa 1984; Körner 2003; Larcher and Wagner 2009, 2010; Neuner and Buchner 2012). Different plant statures within a stand and a variable micro-topography lead to considerable differences in plant temperatures at a small scale (Scherrer and Körner 2010; Neuner and Buchner 2012)
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
