Dynamics of photosynthetic induction and relaxation within the canopy of rice and two wild relatives

Abstract

Wild rice species are a source of genetic material for improving cultivated rice (Oryza sativa) and a means to understand its evolutionary history. Renewed interest in non‐steady‐state photosynthesis in crops has taken place due its potential in improving sustainable productivity. Variation was characterized for photosynthetic induction and relaxation at two leaf canopy levels in three rice species. The wild rice accessions had 16%–40% higher rates of leaf CO2 uptake (A) during photosynthetic induction relative to the O. sativa accession. However, O. sativa had an overall higher photosynthetic capacity when compared to accessions of its wild progenitors. Additionally, O. sativa had a faster stomatal closing response, resulting in higher intrinsic water‐use efficiency during high‐to‐low light transitions. Leaf position in the canopy had a significant effect on non‐steady‐state photosynthesis, but not steady‐state photosynthesis. The results show potential to utilize wild material to refine plant models and improve non‐steady‐state photosynthesis in cultivated rice for increased productivity.

Natural variation in stomatal dynamics drives divergence in heat stress tolerance and contributes to seasonal intrinsic water-use efficiency in Vitis vinifera (subsp. sativa and sylvestris)

“…Speed of stomatal responses to fluctuating environmental conditions is an underrated physiological trait with potential for contribution to future crop improvement. However, while variation has been shown in a few crop species (McAusland et al, 2016;Eyland et al, 2021;Acevedo-Siaca et al, 2021, Faralli et al, 2019, to our knowledge, this is the first report presenting phenotypic variation in g s for rapid variation in VPD and light levels in grapevine.…”

Sunflecks in the upper canopy: dynamics of light‐use efficiency in sun and shade leaves of Fagus sylvatica

“…A study of photosynthesis in rice canopies by Acevedo‐Siaca et al . (2021) found no difference in stomatal response speed between two canopy levels in three closely related species, and likewise between upper and lower canopy leaves in two shade‐intolerant poplar species (Roden & Pearcy, 1993b). Although, it should be noted that both studies also reported a lack of those physiological and morphological differences between leaves or canopy levels that typically allow for a distinction between sun and shade leaves.…”

Genetics as a key to improving crop photosynthesis

“…Photosynthesis is not an easy trait to study: it is highly polygenic and phenotypically highly responsive to environmental conditions ( Zargar et al , 2017 ; Kaiser et al , 2018 ; Vico et al , 2019 ). In crop production, environments are rarely constant, but typically highly dynamic, and inevitably, it will be challenging to reliably phenotype photosynthesis in dynamic conditions to support analysis of genetic variation ( Soleh et al ., 2016 , 2017 ; Flood et al , 2020 ; McAusland et al , 2020 ; Acevedo-Siaca et al , 2021 b ). It will be more the rule than the exception that apparently similar phenotypes are caused by different QTLs.…”

“…In addition, there is likely to be a strong genotype by environment interaction, meaning that alleles that improve photosynthesis in one condition may be unfavourable in another. Adding to the challenge is that there is poor correlation between photosynthesis in constant and dynamic conditions ( Acevedo-Siaca et al , 2021 b ). Therefore, to allow the screening of functional variation for photosynthesis in dynamic conditions, it is essential to reproducibly mimic such conditions in controlled environmental facilities (as described by Murchie et al , 2018 ) and to be able to phenotype photosynthesis at high throughput in such facilities, to reliably identify genetic variation amenable to breeding ( van Bezouw et al , 2019 ).…”