Genotypic variation in source and sink traits affects the response of photosynthesis and growth to elevated atmospheric CO₂

Abstract

This study aimed to understand the response of photosynthesis and growth to e‐CO2 conditions (800 vs. 400 μmol mol−1) of rice genotypes differing in source–sink relationships. A proxy trait called local C source–sink ratio was defined as the ratio of flag leaf area to the number of spikelets on the corresponding panicle, and five genotypes differing in this ratio were grown in a controlled greenhouse. Differential CO2 resources were applied either during the 2 weeks following heading (EXP1) or during the whole growth cycle (EXP2). Under e‐CO2, low source–sink ratio cultivars (LSS) had greater gains in photosynthesis, and they accumulated less nonstructural carbohydrate in the flag leaf than high source–sink ratio cultivars (HSS). In EXP2, grain yield and biomass gain was also greater in LSS probably caused by their strong sink. Photosynthetic capacity response to e‐CO2 was negatively correlated across genotypes with local C source–sink ratio, a trait highly conserved across environments. HSS were sink‐limited under e‐CO2, probably associated with low triose phosphate utilization (TPU) capacity. We suggest that the local C source–sink ratio is a potential target for selecting more CO2‐responsive cultivars, pending validation for a broader genotypic spectrum and for field conditions.

WITHDRAWN: Effect of Elevated CO2 on Photosynthetic Accumulation and Sucrose Metabolism-related Enzyme Activity and Gene Expression Patterns in Goji Berry (Lycium Barbarum L.)

“…Several studies showed similar results-e.g., a synchronous increase in Pn, C i , and WUE was observed in the Paris polyphylla cultivars under eCO 2 concentrations (800 µmol mol − 1 ), while g s and Tr remained unchanged [30]. Consistently, different Indica rice cultivars showed an increase in Pn under eCO 2 but no signi cant variations in leaf chlorophyll content during short-term eCO 2 treatment [31].…”

Alterations in Source-Sink Relations Affect Rice Yield Response to Elevated CO2: A Free-Air CO2 Enrichment Study

“…The mitigation of the photosynthesis level for the SR treatment under eCO 2 was due to the increase in NSC in the leaves (Supplementary Figure 5 and Supplementary Table 1). Fabre et al (2020) also pointed out that low sourcesink ratio cultivars had greater gains in photosynthesis because they accumulated less NSCs in the flag leaf than high sourcesink ratio cultivars. Conversely, leaf-cutting treatments (LCs) enhanced the Pn response of the remaining leaves to eCO 2 (i.e., LC1 enhanced Pn of the second leaf and LC3 enhanced Pn of the fourth leaf).…”

“…As we cannot really decide on the role of sugars in the present study, more research is needed on the regulation of carbohydrate accumulation and remobilization in the context of source-sink relationships. Fabre et al (2020), using five naturally contrasting cultivars in terms of their source-sink ratio to investigate the response of photosynthetic capacity to eCO 2 , found a negative correlation between source-sink ratio and the response of Pn. Therefore, compared with a high source-sink ratio, a low source-sink ratio may be more conducive to improve photosynthetic capacity and maximize the 'fertilizer effect' of eCO 2 .…”

“…Stems are sites of temporary carbon storage that can be remobilized to reproductive tissues, significantly contributing to grain filling in later developmental stages (Hirose et al, 2006). However, for crops with high SSTs (spikelet removal), the carbon may not be remobilized to compensate for a lack of photosynthesis during the grain filling phase under eCO 2 (MacNeill et al, 2017;Fabre et al, 2020), potentially causing a feedback inhibition effect on the net photosynthetic rate of rice (Ding et al, 2005).…”

“…and yield potential [the product of spikelet number per unit area (SNA) and single grain weight] when the CO 2 concentration was increased by 200 ppm. Similarly, by conducting a pot experiment with five naturally contrasting cultivars in the source-sink ratio and grown in a greenhouse under controlled conditions, Fabre et al (2020) found that the response of Pn of cultivars with a low source-sink ratio to eCO 2 was greater than that with a high source-sink ratio. Yield, biomass, and seed setting traits showed a similar trend, but these parameters were not statistically significant.…”