Abstract
Global warming events have coincided with turnover of plant species at intervals in Earth history. As mean global temperatures rise, the number, frequency and duration of heat-waves will increase. Ginkgo biloba was grown under controlled climatic conditions at two different day/night temperature regimes (25/20 °C and 35/30 °C) to investigate the impact of heat stress. Photosynthetic CO2-uptake and electron transport were reduced at the higher temperature, while rates of respiration were greater; suggesting that the carbon balance of the leaves was adversely affected. Stomatal conductance and the potential for evaporative cooling of the leaves was reduced at the higher temperature. Furthermore, the capacity of the leaves to dissipate excess energy was also reduced at 35/30 °C, indicating that photo-protective mechanisms were no longer functioning effectively. Leaf economics were adversely affected by heat stress, exhibiting an increase in leaf mass per area and leaf construction costs. This may be consistent with the selective pressures experienced by fossil Ginkgoales during intervals of global warming such as the Triassic – Jurassic boundary or Early Eocene Climatic Optimum. The physiological and morphological responses of the G. biloba leaves were closely interrelated; these relationships may be used to infer the leaf economics and photosynthetic/stress physiology of fossil plants.
Highlights
Global warming events have coincided with turnover of plant species at intervals in Earth history
This study has shown that heat stress impaired PN and affected leaf morphology in greater stomatal conductance (Gs). biloba
The female tree which was the source of the seeds and the nursery where the seedlings grew were located in a region with a warm sub-Mediterranean climate, suggesting that adaptation to cooler temperatures was not associated with the pronounced response to heat stress observed in the study.- Exposure to 35 °C for 14 hours each day may have exceeded the tolerance of G. biloba by progressively degrading the protective physiology
Summary
Global warming events have coincided with turnover of plant species at intervals in Earth history. Leaf economics were adversely affected by heat stress, exhibiting an increase in leaf mass per area and leaf construction costs This may be consistent with the selective pressures experienced by fossil Ginkgoales during intervals of global warming such as the Triassic – Jurassic boundary or Early Eocene Climatic Optimum. The physiological and morphological responses of the G. biloba leaves were closely interrelated; these relationships may be used to infer the leaf economics and photosynthetic/stress physiology of fossil plants. We grew the relict gymnosperm Ginkgo biloba[13] under controlled environment conditions to examine the impact of heat stress on photosynthetic physiology and leaf morphology. One possible explanation may be that the lack of experimental studies quantifying relationships between the energy balance of leaves and the associated physiological and morphological characteristics has limited their application in the reconstruction of the palaeo-physiology of fossil plants
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