Abiotic Stress/Whole Plant Bio

Abstract

CS-19-4 - Steady state water-use strategy mediates the impact of stomatal opening time on photosynthetic induction in response to an increase in irradiance.

Monday, July 16
4:18 PM - 4:38 PM

Improving dynamic photosynthesis in response to changes in irradiance has been highlighted as a possible next target in increasing plant photosynthesis and yield. Stomatal dynamics can play an important role.


In response to an increase in irradiance, slow biochemical activation and stomatal opening limits the potential photosynthesis the plant could be doing compared with the final steady-state photosynthetic rate. Following a decrease in irradiance, slow stomatal closure results in plants losing excess transpiration above the final steady-state transpiration, while there is little gain in photosynthesis from possessing over-open stomata.


This study tracked stomatal and photosynthesis dynamics in response to increases and decreases in irradiance across 16 species, including ferns, gymnosperms and angiosperms. The aim was to uncover general patterns among dynamic and steady-state photosynthesis and water loss characteristics, to better understand what are the key drivers affecting dynamic photosynthesis and water loss.


In response to an increase in irradiance, species with slow opening stomata lost more potential photosynthesis than species with rapid stomatal opening, with stomatal opening rates, not biochemical activation, providing the main driver for variation in lost potential assimilation. However, the relationship between photosynthetic induction time and stomatal opening time can be strongly modified by steady-state water-use strategy, with the photosynthetic induction time in plants with a more conservative water-use strategy more constrained by stomatal opening time than plants with a less conservative water-use strategy. In response to a decrease in irradiance, species with slow stomatal closure lost more excess transpiration. Results also hinted towards dynamic conservation of water through rapid stomatal closure in species with high steady state gas exchange. General relations between stomatal response times and sun/shade adaption also supported classic lightfleck theory.


The implications of this study will be discussed in evolutionary, crop breeding and lightfleck ecology settings.


 

Co-Authors

Graham Farquhar – The Australian National University; Florian Busch – The Australian National University; Tim Brodribb – The University of Tasmania

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Assets

CS-19-4 - Steady state water-use strategy mediates the impact of stomatal opening time on photosynthetic induction in response to an increase in irradiance.



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