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Is sexual reproduction of high-mountain plants endangered by heat?

Ladinig U, Pramsohler M, Bauer I, Zimmermann S, Neuner G, Wagner J - Oecologia (2015)

Bottom Line: Heat effects on cold-adapted plants may increase with rising global temperatures and the predicted increase in heat waves.Plant samples were exposed to temperatures in 2-K steps of 30 min each between 42 and 56 °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.

View Article: PubMed Central - PubMed

Affiliation: Institute of Botany, Faculty of Biology, University of Innsbruck, Sternwartestraße 15, 6020, Innsbruck, Austria.

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.

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Safety margin (in Kelvin) between the temperature threshold causing LT10 and maximum temperatures of reproductive shoots recorded at the growing site during early bud stage b1 (diamond), late bud stage b2 (triangle), anthesis a (gray circle) and early fruit development f (black square) in the different species (for species names, see Table 1). Vertical lines mark the range between the lowest and highest safety margin during reproductive development
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Fig9: Safety margin (in Kelvin) between the temperature threshold causing LT10 and maximum temperatures of reproductive shoots recorded at the growing site during early bud stage b1 (diamond), late bud stage b2 (triangle), anthesis a (gray circle) and early fruit development f (black square) in the different species (for species names, see Table 1). Vertical lines mark the range between the lowest and highest safety margin during reproductive development

Mentions: Absolute 2 m air temperature maxima between 2002 and 2012 in the summer months June–August were 25.9 °C at the treeline, 22.9 °C at the alpine site and 17.7 °C at the subnival site. Maximum plant temperatures were considerably higher and depended mainly on plant habit. Leaves of R. ferrugineum shrubs situated about 70 cm aboveground heated up to a maximum of 36 °C (30-min means), which did not pose any risk for vegetative shoots (lowest mean LT10 45.4 °C) or reproductive structures at the same height (lowest mean LT10 42.7 °C for petals) (Fig. 9). In contrast, the leaf canopy of the prostrate L. procumbens (PAA habit) reached 44 °C, which is near the temperature threshold causing first heat damage in reproductive tissues (lowest mean LT10 45.7 °C for ovaries). Canopy temperatures measured in cushion plants usually remained <40 °C, and temperatures in flowers usually remained <35 °C. During hot and dry periods, however, canopy temperatures of cushion plants could reach up to 48 °C (S. oppositifolia, PAA habit), which is in the range of temperatures causing the first heat damage in acaulescent flower buds and flowers (compare Fig. 1). Leaves of the herbs C. uniflorum and R. glacialis reached maximum temperatures of 38 and 35 °C, respectively; their flowers and inflorescences, 30–33 °C. This results in a broad safety margin of about 8 K between maximum plant temperatures and LT10 for heat damage (Fig. 9) at the subnival growing sites.Fig. 9


Is sexual reproduction of high-mountain plants endangered by heat?

Ladinig U, Pramsohler M, Bauer I, Zimmermann S, Neuner G, Wagner J - Oecologia (2015)

Safety margin (in Kelvin) between the temperature threshold causing LT10 and maximum temperatures of reproductive shoots recorded at the growing site during early bud stage b1 (diamond), late bud stage b2 (triangle), anthesis a (gray circle) and early fruit development f (black square) in the different species (for species names, see Table 1). Vertical lines mark the range between the lowest and highest safety margin during reproductive development
© Copyright Policy - OpenAccess
Related In: Results  -  Collection

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getmorefigures.php?uid=PMC4363489&req=5

Fig9: Safety margin (in Kelvin) between the temperature threshold causing LT10 and maximum temperatures of reproductive shoots recorded at the growing site during early bud stage b1 (diamond), late bud stage b2 (triangle), anthesis a (gray circle) and early fruit development f (black square) in the different species (for species names, see Table 1). Vertical lines mark the range between the lowest and highest safety margin during reproductive development
Mentions: Absolute 2 m air temperature maxima between 2002 and 2012 in the summer months June–August were 25.9 °C at the treeline, 22.9 °C at the alpine site and 17.7 °C at the subnival site. Maximum plant temperatures were considerably higher and depended mainly on plant habit. Leaves of R. ferrugineum shrubs situated about 70 cm aboveground heated up to a maximum of 36 °C (30-min means), which did not pose any risk for vegetative shoots (lowest mean LT10 45.4 °C) or reproductive structures at the same height (lowest mean LT10 42.7 °C for petals) (Fig. 9). In contrast, the leaf canopy of the prostrate L. procumbens (PAA habit) reached 44 °C, which is near the temperature threshold causing first heat damage in reproductive tissues (lowest mean LT10 45.7 °C for ovaries). Canopy temperatures measured in cushion plants usually remained <40 °C, and temperatures in flowers usually remained <35 °C. During hot and dry periods, however, canopy temperatures of cushion plants could reach up to 48 °C (S. oppositifolia, PAA habit), which is in the range of temperatures causing the first heat damage in acaulescent flower buds and flowers (compare Fig. 1). Leaves of the herbs C. uniflorum and R. glacialis reached maximum temperatures of 38 and 35 °C, respectively; their flowers and inflorescences, 30–33 °C. This results in a broad safety margin of about 8 K between maximum plant temperatures and LT10 for heat damage (Fig. 9) at the subnival growing sites.Fig. 9

Bottom Line: Heat effects on cold-adapted plants may increase with rising global temperatures and the predicted increase in heat waves.Plant samples were exposed to temperatures in 2-K steps of 30 min each between 42 and 56 °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.

View Article: PubMed Central - PubMed

Affiliation: Institute of Botany, Faculty of Biology, University of Innsbruck, Sternwartestraße 15, 6020, Innsbruck, Austria.

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.

Show MeSH
Related in: MedlinePlus