Effects of stomatal delays on the economics of leaf gas exchange under intermittent light regimes

Abstract

Summary• Understory plants are subjected to highly intermittent light availability and their leaf gas exchanges are mediated by delayed responses of stomata and leaf biochemistry to light fluctuations. In this article, the patterns in stomatal delays across biomes and plant functional types were studied and their effects on leaf carbon gains and water losses were quantified.• A database of more than 60 published datasets on stomatal responses to light fluctuations was assembled. To interpret these experimental observations, a leaf gas exchange model was developed and coupled to a novel formulation of stomatal movement energetics. The model was used to test whether stomatal delays optimize light capture for photosynthesis, whilst limiting transpiration and carbon costs for stomatal movement.• The data analysis showed that stomatal opening and closing delays occurred over a limited range of values and were strongly correlated. Plant functional type and climate were the most important drivers of stomatal delays, with faster responses in graminoids and species from dry climates.• Although perfectly tracking stomata would maximize photosynthesis and minimize transpiration at the expense of large opening costs, the observed combinations of opening and closure times appeared to be consistent with a nearoptimal balance of carbon gain, water loss and movement costs.

Fluctuating Light Takes Crop Photosynthesis on a Rollercoaster Ride

“…For more details on both phenomena, see Kaiser et al (2015). opening after irradiance increases (τ = 4-29 minutes) and for rates of stomatal closure 320 after irradiance decreases (τ = 6-18 minutes; Vico et al, 2011). Often, initial g s after a 321 switch from low to high irradiance is small enough, and stomatal opening is slow 322 enough (Fig.…”

Stomatal Size, Speed, and Responsiveness Impact on Photosynthesis and Water Use Efficiency

“…Vico et al (2011) used 60 published gas-exchange data sets of the stomatal response to light variations to determine the impact of stomatal delays on photosynthesis and transpiration and its relationship to the energetic costs of stomatal movement. Unfortunately, the latter are compromised by the use of incorrect stoichiometries for the coupling of ATP to transport and by the assumption that stomatal closure is entirely passive, which it is not.…”

Diurnal Variation in Gas Exchange: The Balance between Carbon Fixation and Water Loss

“…However, observations of g s in response to variations in light intensity revealed that, in general, stomatal responses do not mimic these simulations. Instead, g s responses are 1 order of magnitude slower than A and can continue to increase even when A reaches steady state, resulting in a limitation of A during the initial part of the response followed by an unnecessary increase in E (Vico et al, 2011;Lawson et al, 2012;Vialet-Chabrand et al, 2013;Lawson and Blatt, 2014;McAusland et al, 2016), which results in more water loss than is necessary for the gain in CO 2 (Lawson and Blatt, 2014). In general, the diversity of coordination between A and g s observed in steady state across species suggests that there is no strong selective pressure for this trait in the field, which highlights the room for potential improvement in plant performance (McAusland et al, 2016).…”