Abstract
An experiment was performed to elucidate interspecific differences in survival time of grass species subjected to an extreme climatic event. We exposed eight grass species to a simulated heat wave in the field (‘free air’ temperature increase at 11°C above ambient) combined with drought. We determined whether interspecific differences in survival time were related to the responses of the species to the imposed stress or could be explained by their ecophysiological or morphological characteristics in unstressed conditions. Surprisingly, there was no effect of specific leaf area, but species with a higher total leaf area survived longer. This may arise from a greater water reserve in the plant as a whole, which could delay the desiccation of the meristem, or from reduced evaporation due to a higher leaf area index. Species in which the decrease in light‐saturated stomatal conductance ( g s ) and photosynthetic CO 2 uptake rate ( A max ) was strongly related to the decrease in soil water availability (measured as soil relative water content and stress duration) survived longer than species in which g s and A max likewise declined but responded more to daily fluctuations in irradiance, temperature, and vapor pressure deficit during the heat wave. We, therefore, hypothesize that interspecific differences in stress survival time might be related to the extent to which stomata react to changes in soil water conditions relatively to changes in other environmental and physiological factors. The results suggest that resistance to extremes is governed by other mechanisms than resistance to moderate drought.
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Claims 4
Claim · model-written summary
Specific leaf area had no effect on grass survival time.
Not reportedSetting
Verbatim
e0“there was no effect of specific leaf area”
t0“grass species”
Claim · model-written summary
Grass species with higher total leaf area survived longer.
Verbatim
e0“species with a higher total leaf area survived longer”
t0“grass species”
Claim · model-written summary
Species whose stomatal conductance and photosynthetic uptake tracked declining soil water survived longer than species responding more to daily atmospheric variation.
Verbatim
e0“Species in which the decrease in light‐saturated stomatal conductance ( g s ) and photosynthetic CO 2 uptake rate ( A max ) was strongly related to the decrease in soil water availability (measured as soil relative water content and stress duration) survived longer than species in which g s and A max likewise declined but responded more to daily fluctuations in irradiance, temperature, and vapor pressure deficit during the heat wave.”
Claim · model-written summary
The authors hypothesize that survival differences depend on relative stomatal responsiveness to soil water versus other environmental factors.
Verbatim
e0“interspecific differences in stress survival time might be related to the extent to which stomata react to changes in soil water conditions relatively to changes in other environmental and physiological factors”
t0“grass species”