Stomatal versus biochemical limitations to dynamic photosynthetic performance in four tropical rainforest shrub species

Abstract

Photosynthetic performance under dynamic light regimes was assessed in four different species of tropical shrubs from the family Rubiaceae via field gas exchange measurements conducted on Barro Colorado Island, Panamá. Rates of photosynthetic induction and induction loss were assessed throughout the day in both the wet and dry seasons in order to determine the relative roles of stomata and biochemistry in limiting photosynthetic performance under transient light conditions. A high degree of coordination was observed between stomatal conductance and biochemical capacity for CO assimilation during induction. Rates of biochemical and overall photosynthetic induction sharply decreased when initial stomatal conductance fell below a narrow range of critical values. Time of day or season did not affect rates of biochemical deactivation upon shading, but did influence stomatal closure, which often exerted a significant influence over induction loss in the darkness. In measurements of total assimilation due to a 60-s light pulse, both biochemical activity and stomatal conductance were linearly related to total CO uptake. Only during the mornings of the wet season was stomatal conductance consistently high enough to be non-limiting to dynamic photosynthetic performance. At all other times, stomatal behavior exercised significant influence over induction times, photosynthetic induction loss, and total CO uptake from 60-s light pulses.

Dynamic light use and protection from excess light in upper canopy and coppice leaves of Nothofagus cunninghamii in an old growth, cool temperate rainforest in Victoria, Australia

“…6) -by contrast to results reported for many other species (Pepin & Livingston, 1997;Allen & Pearcy, 2000a;Naumberg & Ellsworth, 2000). Large variation in stomatal response times have, however, been reported (Allen & Pearcy, 2000a;Naumberg & Ellsworth, 2000) Estimated daily C gain was calculated assuming a clear spring day using irradiance curves from 20 October (as in Fig. 1) from four positions at both canopy levels and steady-state photosynthesis characteristics (eqn 1).…”

“…In a tropical ecosystem, stomatal response times determined the photosynthetic response times to sunflecks when water was limiting, but stomata exhibited little or no control when water was not limiting (Allen & Pearcy, 2000a). In a temperate pine plantation, stomatal responses generally limited sunfleck responses, but to different extents in different species (Naumberg & Ellsworth, 2000).…”

Dynamic photosynthesis under a fluctuating environment: a modelling-based analysis

“…Measurements of photosynthetic induction have played an important role in elucidating the mechanisms of photosynthesis, and in the development of dynamic models (Walker, 1973;Govindjee, 1995;. It is now generally accepted that induction of photosynthesis (at the scale of minutes) is, at least, limited by activation of Rubisco and opening of the stomata (Allen and Pearcy, 2000a;Vialet-Chabrand et al, 2016). Other potential effects may be associated with activation of other enzymes in the Calvin cycle (Sassenrath-Cole et al, 1994), build-up of metabolites in the Calvin cycle (Walker, 1973), and activation of sucrose phosphate synthase (Stitt and Grosse, 1988).…”

A interação ecofisiológica planta-ambiente

“…Furthermore, several authors have reported that non-uniform stomata opening (i.e. stomata patchiness) in response to a sudden increase in irradiance might cause differences in biochemical activation throughout the leaf (KIRSCHBAUM & PEARCY, 1988b; TINOCO-OJANGUREN & PEARCY, 1993a;KÜPPERS et al, 1999;ALLEN & PEARCY, 2000).In order to grow in low irradiance environments such as the forest understorey, where plants have low carbon gain (CHAZDON et al, 1996; STRAUSS-DEBENEDETTI & BAZZAZ, 1996), plants must minimize carbon loss trough reduction of both respiration and tissue construction costs (GIVNISH, 1988), attaining 101 a positive leaf carbon balance. Our data are in accordance with those previously reported since all species studied showed significant higher R D in the forest gap than in the understorey (Figures 2, 4).…”

“…Furthermore, several authors have reported that non-uniform stomata opening (i.e. stomata patchiness) in response to a sudden increase in irradiance might cause differences in biochemical activation throughout the leaf (KIRSCHBAUM & PEARCY, 1988b; TINOCO-OJANGUREN & PEARCY, 1993a;KÜPPERS et al, 1999;ALLEN & PEARCY, 2000).…”