Variation in photosynthetic induction between rice accessions and its potential for improving productivity

Abstract

Photosynthetic induction describes the transient increase in leaf CO 2 uptake with an increase in light. During induction, efficiency is lower than at steady state. Under field conditions of fluctuating light, this lower efficiency during induction may cost > 20% of potential crop assimilation. Accelerating induction would boost photosynthetic and resource-use efficiencies.Variation between rice accessions and potential for accelerating induction was analysed by gas exchange. Induction during shade to sun transitions of 14 accessions representing five subpopulations from the 3000 Rice Genome Project Panel (3K RGP) was analysed.Differences of 109% occurred in the CO 2 fixed during the first 300 s of induction, 117% in the half-time to completion of induction, and 65% in intrinsic water-use efficiency during induction, between the highest and lowest performing accessions. Induction in three accessions with contrasting responses (AUS 278, NCS 771 A and IR64-21) was compared for a range of [CO 2 ] to analyse limitations. This showed in vivo capacity for carboxylation at Rubisco (V c,max ), and not stomata, as the primary limitation to induction, with significant differences between accessions.Variation in nonsteady-state efficiency greatly exceeded that at steady state, suggesting a new and more promising opportunity for selection of greater crop photosynthetic efficiency in this key food crop.

Photosynthesis in the fleeting shadows: an overlooked opportunity for increasing crop productivity?

“…Sufficient accumulation of ribulose 1,5-bisphoshate is assumed to require approximately 60 sec, whereas the activation of Rubisco may require more than 10 min (Mott and Woodrow, 2000;Taylor and Long, 2017). At the leaf level, induction can be limited by slow stomatal opening, where full opening can require many minutes (McAusland et al, 2016;De Souza et al, 2019;Faralli et al, 2019;Acevedo-Siaca et al, 2020), and by mesophyll conductance, which generally increases with incident light. The rate of increase in mesophyll conductance upon induction is generally considered faster than both stomatal opening and Rubisco activation (Deans et al, 2019), but the variability between species and environmental conditions is not well defined.…”

“…Again, it is unlikely that there has been sufficient time for any adaptation to this change. This may be reflected in the large variation in speeds of induction on shade–sun transitions within the germplasm of Manihot esculenta (cassava), Oryza sativa (rice), soybean and wheat (Soleh et al , ; De Souza et al , ; Salter et al , ; Acevedo‐Siaca et al , ). For example, the between‐accession variation in CO 2 assimilated during the induction was three times that of the steady‐state assimilation in cassava (De Souza et al , ), suggesting that optimization of photosynthesis in fluctuating light has not occurred.…”

During photosynthetic induction, biochemical and stomatal limitations differ between Brassica crops

“…To characterise changes in factors limiting photosynthesis during shade-sun transitions, a dynamic A/c i method was implemented that improved on previously published versions (Acevedo-Siaca et al, 2020;Chazdon & Pearcy, 1986;De Souza et al, 2020;Salter et al, 2019;Soleh et al, 2016;Taylor & Long, 2017) For each leaf to be measured, an independent sequence of reference [CO 2 ]s was drawn from the following set: 50, 100, 200, 300, 400, 500, 600, 700, 800 and 1000 μmol mol −1 . The [CO 2 ]s were ordered so that concentrations from the ≤400 and ≥500 μmol mol −1 ranges were interspersed randomly (e.g., 800, 200, 600, 100, 500, 400, 700, 300, 1000 and 50 μmol mol −1 ), and were rotated over 10 separate inductions so that every [CO 2 ] was measured at every interval between 2 and 20 min following shade (Supplementary Figure 2).…”

“…(Deans, Brodribb, et al, 2019;McAusland et al, 2016). Intraspecific studies addressing crops have also confirmed that the importance of stomatal limitations during induction can differ between species: stomata have little apparent importance in determining genetic variation for induction in soybean or rice (Acevedo-Siaca et al, 2020;Soleh et al, 2016), but are a dominant factor in cassava (De Souza et al, 2020).…”

Rice Cultivar Takanari Has Higher Photosynthetic Performance Under Fluctuating Light Than Koshihikari, Especially Under Limited Nitrogen Supply and Elevated CO2

“…Quantitative trait locus analysis and genome-wide association studies were conducted to use these variations in crop breeding ( Adachi et al., 2011 ; Adachi et al., 2019b ; Wang et al., 2020 ). Very recently, Acevedo-Siaca et al. (2020) reported a difference of 109% in the total amount of CO 2 fixed during the first 5 min of induction after a sudden increase in irradiance (CCF 5 ) among 14 rice accessions.…”