High photosynthesis rates in Brassiceae species are mediated by leaf anatomy enabling high biochemical capacity, rapid CO diffusion and efficient light use.

Certain species in the Brassicaceae family exhibit high photosynthesis rates, potentially providing a valuable route toward improving agricultural productivity. However, factors contributing to their high photosynthesis rates are still unknown. We compared Hirschfeldia incana, Brassica nigra, Brassica rapa and Arabidopsis thaliana, grown under two contrasting light intensities.

Source-sink relationships during grain filling in wheat in response to various temperature, water deficit, and nitrogen deficit regimes.

Grain filling is a critical process for improving crop production under adverse conditions caused by climate change. Here, using a quantitative method, we quantified post-anthesis source-sink relationships of a large dataset to assess the contribution of remobilized pre-anthesis assimilates to grain growth for both biomass and nitrogen. The dataset came from 13 years of semi-controlled field experimentation, in which six bread wheat genotypes were grown at plot scale under contrasting temperature, water, and nitrogen regimes.

Roles for leakiness and O evolution in explaining lower-than-theoretical quantum yields of photosynthesis in the PEP-CK subtype of C plants.

Theoretically, the PEP-CK C subtype has a higher quantum yield of CO assimilation ( ) than NADP-ME or NAD-ME subtypes because ATP required for operating the CO-concentrating mechanism is believed to mostly come from the mitochondrial electron transport chain (mETC). However, reported is not higher in PEP-CK than in the other subtypes. We hypothesise, more photorespiration, associated with higher leakiness and O evolution in bundle-sheath (BS) cells, cancels out energetic advantages in PEP-CK species.

Phenotyping and metabolome analysis reveal the role of AdoMetDC and Di19 genes in determining acquired tolerance to drought in rice.

Water-saving attempts for rice cultivation often reduce yields. Maintaining productivity under drought is possible when rice genotypes are bred with improved metabolism and spikelet fertility. Although attempts have been made to introgress water mining and water use efficiency traits, combining acquired tolerance traits (ATTs), that is, specific traits induced or upregulated to better tolerate severe stress, appears equally important.

Estimating leaf day respiration from conventional gas exchange measurements.

Leaf day respiration (R ) strongly influences carbon-use efficiencies of whole plants and the global terrestrial biosphere. It has long been thought that R is slower than respiration in the dark at a given temperature, but measuring R by gas exchange remains a challenge because leaves in the light are also photosynthesizing. The Kok method and the Laisk method are widely used to estimate R .

Triose phosphate utilization in leaves is modulated by whole-plant sink-source ratios and nitrogen budgets in rice.

Triose phosphate utilization (TPU) is a biochemical process indicating carbon sink-source (im)balance within leaves. When TPU limits leaf photosynthesis, photorespiration-associated amino acid exports probably provide an additional carbon outlet and increase leaf CO2 uptake. However, whether TPU is modulated by whole-plant sink-source relations and nitrogen (N) budgets remains unclear.

The role of chloroplast movement in C4 photosynthesis: a theoretical analysis using a three-dimensional reaction-diffusion model for maize.

Chloroplasts movement within mesophyll cells in C4 plants is hypothesized to enhance the CO2 concentrating mechanism, but this is difficult to verify experimentally. A three-dimensional (3D) leaf model can help analyse how chloroplast movement influences the operation of the CO2 concentrating mechanism. The first volumetric reaction-diffusion model of C4 photosynthesis that incorporates detailed 3D leaf anatomy, light propagation, ATP and NADPH production, and CO2, O2 and bicarbonate concentration driven by diffusional and assimilation/emission processes was developed.

Improving crop yield potential: Underlying biological processes and future prospects.

The growing world population and global increases in the standard of living both result in an increasing demand for food, feed and other plant-derived products. In the coming years, plant-based research will be among the major drivers ensuring food security and the expansion of the bio-based economy. Crop productivity is determined by several factors, including the available physical and agricultural resources, crop management, and the resource use efficiency, quality and intrinsic yield potential of the chosen crop.

Neglecting acclimation of photosynthesis under drought can cause significant errors in predicting leaf photosynthesis in wheat.

Extreme climatic events, such as heat waves, cold snaps and drought spells, related to global climate change, have become more frequent and intense in recent years. Acclimation of plant physiological processes to changes in environmental conditions is a key component of plant adaptation to climate change. We assessed the temperature response of leaf photosynthetic parameters in wheat grown under contrasting water regimes and growth temperatures (T ).

Effects of sublethal single, simultaneous and sequential abiotic stresses on phenotypic traits of .

Plant responses to abiotic stresses are complex and dynamic, and involve changes in different traits, either as the direct consequence of the stress, or as an active acclimatory response. Abiotic stresses frequently occur simultaneously or in succession, rather than in isolation. Despite this, most studies have focused on a single stress and single or few plant traits.

Drought exerts a greater influence than growth temperature on the temperature response of leaf day respiration in wheat (Triticum aestivum).

We assessed how the temperature response of leaf day respiration (R ) in wheat responded to contrasting water regimes and growth temperatures. In Experiment 1, well-watered and drought-stressed conditions were imposed on two genotypes; in Experiment 2, the two water regimes combined with high (HT), medium (MT) and low (LT) growth temperatures were imposed on one of the genotypes. R was estimated from simultaneous gas exchange and chlorophyll fluorescence measurements at six leaf temperatures (T ) for each treatment, using the Yin method for nonphotorespiratory conditions and the nonrectangular hyperbolic fitting method for photorespiratory conditions.

A model-guided holistic review of exploiting natural variation of photosynthesis traits in crop improvement.

Breeding for improved leaf photosynthesis is considered as a viable approach to increase crop yield. Whether it should be improved in combination with other traits has not been assessed critically. Based on the quantitative crop model GECROS that interconnects various traits to crop productivity, we review natural variation in relevant traits, from biochemical aspects of leaf photosynthesis to morpho-physiological crop characteristics.

Role of bundle sheath conductance in sustaining photosynthesis competence in sugarcane plants under nitrogen deficiency.

The role of bundle sheath conductance (g) in sustaining sugarcane photosynthesis under nitrogen deficiency was investigated. Sugarcane was grown under different levels of nitrogen supply and g was estimated using simultaneous measurements of leaf gas exchange and chlorophyll fluorescence at 21% or 2% [O] and varying air [CO] and light intensity. Maximum rates of PEPC carboxylation, Rubisco carboxylation, and ATP production increased with an increase in leaf nitrogen concentration (LNC) from 1 to 3 g m.

Evolution of a biochemical model of steady-state photosynthesis.

On the occasion of the 40th anniversary of the publication of the landmark model by Farquhar, von Caemmerer & Berry on steady-state C photosynthesis (known as the "FvCB model"), we review three major further developments of the model. These include: (1) limitation by triose phosphate utilization, (2) alternative electron transport pathways, and (3) photorespiration-associated nitrogen and C metabolisms. We discussed the relation of the third extension with the two other extensions, and some equivalent extensions to model C photosynthesis.

Metabolome profiling reveals impact of water limitation on grain filling in contrasting rice genotypes.

Drought significantly decreases crop productivity, especially in high water consuming crops like rice. Grain filling is one of the important critical growth phases in rice and drought during this phase leads to significant reduction in yield. In this study, a comparison was made between IR64 (drought susceptible) and Apo (drought tolerant) rice genotypes to capture the response to water limitation (50% field capacity (FC)) compared with the control (100%FC) during grain filling.

Acquired Traits Contribute More to Drought Tolerance in Wheat Than in Rice.

Drought tolerance is governed by constitutive and acquired traits. Combining them has relevance for sustaining crop productivity under drought. Mild levels of stress induce specific mechanisms that protect metabolism when stress becomes severe.

The impact of global dimming on crop yields is determined by the source-sink imbalance of carbon during grain filling.

Global dimming reduces incident global radiation but increases the fraction of diffuse radiation, and thus affects crop yields; however, the underlying mechanisms of such an effect have not been revealed. We hypothesized that crop source-sink imbalance of either carbon (C) or nitrogen (N) during grain filling is a key factor underlying the effect of global dimming on yields. We presented a practical framework to assess both C and N source-sink relationships, using data of biomass and N accumulation from periodical sampling conducted in field experiments for wheat and rice from 2013 to 2016.

Exploiting differences in the energy budget among C subtypes to improve crop productivity.

C crops of agricultural importance all belong to the NADP-malic enzyme (ME) subtype, and this subtype has been the template for C introductions into C crops, like rice, to improve their productivity. However, the ATP cost for the C cycle in both NADP-ME and NAD-ME subtypes accounts for > 40% of the total ATP requirement for CO assimilation. These high ATP costs, and the associated need for intense cyclic electron transport and low intrinsic quantum yield , are major constraints in realizing strong improvements of canopy photosynthesis and crop productivity.

The case for improving crop carbon sink strength or plasticity for a CO-rich future.

Atmospheric CO concentration [CO] has increased from 260 to 280μmolmol (level during crop domestication up to the industrial revolution) to currently 400 and will reach 550μmolmol by 2050. C3 crops are expected to benefit from elevated [CO] (e-CO) thanks to photosynthesis responsiveness to [CO] but this may require greater sink capacity. We review recent literature on crop e-CO responses, related source-sink interactions, how abiotic stresses potentially interact, and prospects to improve e-CO response via breeding or genetic engineering.

The Kok effect revisited.

The Kok effect refers to the abrupt decrease around the light compensation point in the slope of net photosynthetic rate vs irradiance. Arguably, this switch arises from light inhibition of respiration, allowing the Kok method to estimate day respiration (R ). Recent analysis suggests that increasing proportions of photorespiration (quantified as Γ*/C , the ratio of CO compensation point Γ* to chloroplast CO concentration, C ) with irradiance explain much of the Kok effect.

Towards a multiscale crop modelling framework for climate change adaptation assessment.

Predicting the consequences of manipulating genotype (G) and agronomic management (M) on agricultural ecosystem performances under future environmental (E) conditions remains a challenge. Crop modelling has the potential to enable society to assess the efficacy of G × M technologies to mitigate and adapt crop production systems to climate change. Despite recent achievements, dedicated research to develop and improve modelling capabilities from gene to global scales is needed to provide guidance on designing G × M adaptation strategies with full consideration of their impacts on both crop productivity and ecosystem sustainability under varying climatic conditions.

Using photorespiratory oxygen response to analyse leaf mesophyll resistance.

Classical approaches to estimate mesophyll conductance ignore differences in resistance components for CO from intercellular air spaces (IAS) and CO from photorespiration (F) and respiration (R). Consequently, mesophyll conductance apparently becomes sensitive to (photo)respiration relative to net photosynthesis, (F + R)/A. This sensitivity depends on several hard-to-measure anatomical properties of mesophyll cells.