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Climate change induces shifts in suitable areas for cultivation and phenology of grapevines, which regulate complex sunlight patterns within hedge rows and canopy photosynthetic gain. However, suitability assessments have focused on climate indices, such as growing season temperature, but have ignored canopy photosynthesis, despite its close connection to berry yield and wine quality. Here, we visualized global maps of the theoretical maxima of grapevine canopy photosynthetic gain during berry development under present and future climates scenarios using an integrated model of canopy light interception, leaf thermal balance, and photosynthetic processes. The high-latitude zone accommodated high-gain sites under future scenarios, characterized by shifted suitable areas and elevated atmospheric CO2 concentrations. By contrast, at some prestigious sites located at low latitudes, the projected leaf temperatures exceeded the optimal range for photosynthesis, resulting in reduced gain. Our results highlight a north-south gradient in canopy photosynthesis and support the decision-making of winemaking stakeholders.

sion="1.0" encoding="utf-8"?FP Functional Plant Biology Funct. Plant Biol. 1445-4408 1445-4416 CSIRO Publishing 36 Gardiner Road Clayton VIC 3168 Australia FP22050 10.1071/FP22050 Foreword Advanced technologies in studying plant photosynthesis: principles and applications A. Zavafer et al . https://orcid.org/0000-0002-8905-1618 Zavafer Alonso A Fan Dayong B * https://orcid.org/0000-0001-8150-9535 Murakami Keach C Handling Editor Shabala Sergey Plant Science Division, Research School of Biology, The Australian National University, Canberra, ACT 2001, Australia. Hokkaido Agricultural Research Center (HARC), National Agriculture and Food Research Organization (NARO), 1 Hitsujigaoka, Toyohira, Sapporo 062-8555, Japan. College of Forestry, Beijing Forestry, University, Beijing 100083, China. * Correspondence to: Dayong Fan Hokkaido Agricultural Research Center (HARC), National Agriculture and Food Research Organization (NARO), 1 Hitsujigaoka, Toyohira, Sapporo 062-8555, Japan Email: dayong73fan@163.com 9 May 2022 49 6 Special Issue i iii 9 May 2022 Published: 9 May 2022 © 2022 The Author(s) (or their employer(s)). Published by CSIRO Publishing 2022 The Authors The foreword to this special issue on the advanced technologies in studying photosynthesis focuses on the main contributions of Fred Chow, one of the key Australian scientists studying light reactions in plants.

A negative correlation between grain yield and protein concentration hinders an efficient nutrient supply. To analyze the causation of this inverse relationship, we compared the leaf and canopy photosynthesis of two Japanese wheat cultivars. Gas exchange measurements of leaves revealed that ‘Kitahonami’ (a high-yielding and low-protein cultivar) maintained high stomatal conductance from pre-anthesis to late grain-filling stage while stomata of ‘Yumechikara’ (a low-yielding and high-protein cultivar) were closed during the daytime, leading to decreased photosynthesis. We simulated canopy photosynthesis using a model and quantified the contribution of distinct stomatal behavior to canopy carbon gain. Although daily canopy photosynthetic gain was comparable or slightly low in ‘Yumechikara’ when model parameters obtained in the morning were used, the gain was substantially lower in ‘Yumechikara’ than in ‘Kitahonami’ when midday parameters were used. Canopy respiratory loss in ‘Yumechikara’ was greater than that in ‘Kitahonami’ during the middle of the grain-filling period because of its high canopy nitrogen content, leading to a considerable difference in net canopy carbon gain between the cultivars. Our study suggests one of the pathways for a lower carbon gain of a high protein cultivar and the greater nitrogen content does not necessarily result in a greater carbon gain.

The use of agricultural machines for field operations is often restricted by soil status determined by meteorological conditions several days before the operation. While a projected increase in air temperature caused by climate change may promote evapotranspiration and have positive impacts on the use of agricultural machines, intensified rainfall may have negative effects at the same time. This study aimed to provide probabilistic estimates of climate change impacts the meteorological constraints on field workability of agricultural machines in Hokkaido, Japan. Analyses based on historical meteorological data and machinery operation logs recorded at two agricultural research stations revealed that operations concentrated on days with smaller antecedent precipitation index (API). A simple derivative of API that reflects a practically maximum API value to carry out a certain field operation, termed threshold API, was proposed to evaluate the meteorological constraints on field operations. Because threshold API values for operations that are vulnerable to soil conditions (e.g., sowing and soil preparation) and/or at fields with poor drainage soil were small, this threshold should be a reasonable and quantitative measure of the meteorological constraint on field workability. Using 1-km gridded API values under historical and future climates calculated from a large ensemble dataset of daily mean air temperature and precipitation, we separated workable and unworkable days from June to October based on a threshold value of 5 mm and calculated projected changes in monthly numbers of the total workable day and consecutive unworkable day. While there were slight negative effects in several regions in the Southern and Central regions under future climate with a 4-K higher global mean temperature, preferable changes prevailed in both metrics in the other regions and months. The present results facilitate probabilistic discussion of changes in agricultural calendars and suggest that climate change may extend the agricultural season in Hokkaido.

Photosynthetic induction, a gradual increase in photosynthetic rate on a transition from darkness or low light to high light, has ecological significance, impact on biomass accumulation in fluctuating light and relevance to photoprotection in strong light. However, the experimental quantification of the component electron fluxes in and around both photosystems during induction has been rare. Combining optimized chlorophyll fluorescence, the redox kinetics of P700 [primary electron donor in Photosystem I (PSI)] and membrane inlet mass spectrometry in the absence/presence of inhibitors/mediator, we partially estimated the components of electron fluxes in spinach leaf disks on transition from darkness to 1,000 �mol photons�m−2�s−1 for up to 10 min, obtaining the following findings: (i) the partitioning of energy between both photosystems did not change noticeably; (ii) in Photosystem II (PSII), the combined cyclic electron flow (CEF2) and charge recombination (CR2) to the ground state decreased gradually toward 0 in steady state; (iii) oxygen reduction by electrons from PSII, partly bypassing PSI, was small but measurable; (iv) cyclic electron flow around PSI (CEF1) peaked before becoming somewhat steady; (v) peak magnitudes of some of the electron fluxes, all probably photoprotective, were in the descending order: CEF1 > CEF2 + CR2 > chloroplast O2 uptake; and (vi) the chloroplast NADH dehydrogenase-like complex appeared to aid the antimycin A-sensitive CEF1. The results are important for fine-tuning in silico simulation of in vivo photosynthetic electron transport processes; such simulation is, in turn, necessary to probe partial processes in a complex network of interactions in response to environmental changes.

Photosynthetic models sometimes incorporate meteorological elements typically recorded at a time interval of 10 min or 1 h. Because these data are calculated by averaging instantaneous values over time, short-term environmental fluctuations are concealed, which may affect outputs of the model. To assess an appropriate time interval of photosynthetic photon flux density (PPFD) measurement for accurate estimation of photosynthetic gain under open field conditions, we simulated the daily integral net photosynthetic gain using photosynthetic models with or without considering induction kinetics in response to changes in PPFD. Compared with the daily gain calculated from 60-min-interval PPFD data using a steady-state model that ignored the induction kinetics (i.e. a baseline gain), the gains simulated using higher-resolution PPFD data (10-s, 1-min, and 10-min intervals) and using a dynamic model that considered slow induction kinetics were both smaller by ~2%. The gain estimated by the slow dynamic model with 10-s-interval PPFD data was smaller than the baseline gain by more than 5% with a probability of 66%. Thus, the use of low-resolution PPFD data causes overestimation of daily photosynthetic gain in open fields. An appropriate time interval for PPFD measurement is 1 min or shorter to ensure accuracy of the estimates.

To enable us to analyze more systematically the effects of the spectral distribution of light (i.e. light quality) on photosynthetic electron transport, we propose a simple mathematical model which describes electron transport reactions under light-limited conditions based on the excitation energy distributed to the photosystems. The model assumes that the rate-limiting photosystem performs the photochemical reaction at its maximum yield, while the yield in the other photosystem is passively down-regulated to equalize the rates of linear electron transport through the photosystems. Using intact cucumber leaves, we tested the model by comparing actual and estimated photosynthetic parameters under several combinations of photon flux densities of red and far-red lights (R and FR, respectively). Simultaneously provided R and FR yielded greater gross photosynthetic rates than the sums of the rates under only R and only FR, which is known as the 'enhancement effect'. The present model reproduced these non-additive increases in the gross photosynthetic rates in response to supplemental FR to R and provided more accurate estimates than an existing method that did not take the enhancement effect into account (root mean square errors: 0.11 and 0.21 μmol m-2 s-1, respectively). Using the present model, the photon flux density of the supplemental FR which gives the changing point of rate-limiting photosystem and the photochemical yields of the non-rate-limiting photosystems were estimated reasonably well. The present study has therefore formulated a simplified quantitative electron transport model in response to the light spectrum based on generally accepted concepts and demonstrated its validity experimentally.

Absorbed light energy is converted into excitation energy. The excitation energy is distributed to photosystems depending on the wavelength and drives photochemical reactions. A non-destructive, mechanistic, and quantitative method for estimating the fraction of the excitation energy distributed to photosystem II (f) was developed. To estimate the f values for two simultaneously provided actinic lights (ALs) with different spectral distributions, photochemical yields of the photosystems were measured under the ALs and were then fitted to an electron transport model assuming the balance between the electron transport rates through the photosystems. To test the method using leaves with different properties in terms of the long- and short-term acclimation (adjustment of photosystem stoichiometry and state transition, respectively), the f values for red and far-red light (R and FR) were estimated in leaves grown (~1 week) under white light without and with supplemental FR and adapted (~10 min) to R without and with supplemental FR. The f values for R were clearly greater than those for FR and those of leaves grown with and adapted to supplemental FR tended to be higher than the controls. These results are consistent with previous studies and therefore support the validity of the proposed method.

We investigated the effects of spectral distribution and photosynthetic photon flux density (PPFD) for overnight light irradiation supplied by light-emitting diodes (LEDs) on the growth and degree of continuous light (CL)-induced leaf injury of tomato seedlings in a growth-chamber experiment. Over a 14-day treatment period, all plants were irradiated daily for 12 h with white LED light at 300 μmol m−2 s−1 PPFD. During each 12-h nighttime interval, all plants except for the controls were irradiated with white LED light at 150 or 300 μmol m−2 s−1, or alternatively with blue, orange, or red LED light at 150 μmol m−2 s−1. Plants irradiated overnight exhibited injuries, with their visually rated severity of injury increased as the PPFD of nighttime white light was increased. In plants irradiated overnight at 150 μmol m−2 s−1, a higher degree of injury was experienced under blue light than under orange and red light. Overnight white-light irradiation at 150 μmol m−2 s−1 PPFD promoted dry matter production compared with the no-irradiation control, but no further increase was observed at a PPFD of 300 μmol m−2 s−1. Among different spectra, blue light was less effective than orange light at promoting dry matter production when white light was supplied during the day. Thus, both spectral distribution and PPFD of overnight LED light irradiation were demonstrated to affect tomato seedling growth and degree of injury.

Time courses of photochemical reflectance index (PRI) of an attached cucumber leaf during a dark-light transition were compared with those of photochemical yields of photosystem II (YII ) to discuss the feasibility of PRI imaging for estimating the efficiency of photosynthetic light use. YII and PRI were simultaneously evaluated with a pulse-amplitude modulation chlorophyll fluorometer and a low-cost imaging system consisting of digital cameras and band-pass filters, respectively. YII decreased immediately after the transition and then increased under various photon flux densities. Although PRI exhibited delayed time courses with respect to YII under low light conditions, PRI decreased monotonically under high light conditions. There was no correlation between YII and the changes in PRI (ΔPRI) immediately after the transition but YII was correlated with ΔPRI under the steady-state photosynthesis. These results indicate that the use of PRI to estimate YII under fluctuating light based on the regression obtained at steady state can overestimate YII . The imaging system was also applied to evaluate the spatial PRI distribution within a leaf. While PRI of leaf areas that remained untreated, or had been treated with H2 O again, first dropped and then rose under low light and monotonically decreased under high light conditions, leaf areas treated with inhibitor (dichlorophenyl dimethylurea) did not exhibit any changes. It is likely that the inhibitor suppressed lumen acidification, which triggers a decrease in PRI. It was suggested that YII of leaves with malfunctions in the photosynthetic electron transport can be overestimated by the PRI-based estimation.

Plant leaves do not only sense and respond to their local environment but also the environment experienced by the other leaves within the same plant. This long-distance signaling is involved in the systemic regulation of various photosynthesis-related phenotypic features of leaves. Here, we summarize the recent research on light- and CO2-dependent, leaf-to-leaf systemic regulation. In the short term, leaves can pre-acclimate to excess light at the transcriptional level, in response to systemic signals from other leaves. Several substances, including reactive oxygen species and phytohormones, have been suggested to play key roles in the signaling pathway. In the long term, the light and CO2 environment around mature leaves systemically regulates stomatal development, anatomical structure, and photosynthetic characteristics of young leaves. Possible mechanisms underlying the systemic regulation and the potential importance of systemic regulation in horticultural crop production are discussed.

The most important role of a leaf is capturing light energy and fixing CO2 into carbohydrates (i.e., photosynthesis). Fundamental knowledge on the optical and physiological properties of an individual leaf of a C3 plant is summarized below. A leaf adjusts light absorption, at the scales of both whole-leaf and intra-leaf, in order to efficiently capture light energy and to avoid photodamage caused by excessive light energy. Several interacting factors involved in orchestrating these optical properties, such as leaf orientation, mesophyll structure, chloroplast movement, and the absorption properties of phytopigments, are outlined. Photosynthesis consists of two reactions that are spatially separated within the chloroplast. Light energy is converted into reducing power and chemical energy via the electron transport chain. These are then consumed during CO2 fixation in the carbon assimilation process. The electron transport reaction is affected significantly by the spectral distribution of light due to the optical properties of the leaf. Photosynthesis is closely related to other physiological processes. CO2 uptake accompanies water vapor release (transpiration). Produced photosynthates are transported to the other plant organs (translocation). Brief information about the significance and the machinery of these photosynthesis-related processes is provided.

The net photosynthetic rate of a leaf becomes acclimated to the plant's environment during growth. These rates are often measured, evaluated and compared among leaves of plants grown under different light conditions. In this study, we compared net photosynthetic rates of cucumber leaves grown under white light-emitting diode (LED) light without and with supplemental far-red (FR) LED light (W- and WFR-leaves, respectively) under three different measuring light (ML) conditions: their respective growth light (GL), artificial sunlight (AS) and blue and red (BR) light. The difference in the measured photosynthetic rates between W- and WFR-leaves was greater under BR than under GL and AS. In other words, an interaction between supplemental FR light during growth and the spectral photon flux density distribution (SPD) of ML affected the measured net photosynthetic rates. We showed that the comparison and evaluation of leaf photosynthetic rates and characteristics can be biased depending on the SPD of ML, especially for plants grown under different photon flux densities in the FR waveband. We also investigated the mechanism of the interaction. We confirmed that the distribution of excitation energy between the two photosystems (PSs) changed in response to the SPD of GL, and that this change resulted in the interaction, as suggested in previous reports. However, changes in PS stoichiometry could not completely explain the adjustment in excitation energy distribution observed in this study, suggesting that other mechanisms may be involved in the interaction.

The objectives of this work using Phaseolus vulgaris were to examine whether the light spectrum incident on mature primary leaves (PLs) is related to leaf-to-leaf systemic regulation of developing trifoliate leaves (TLs) in photosynthetic characteristics, and to investigate the relative importance of spectrum and photosynthetic photon flux density (PPFD) in light-induced systemic regulation. Systemic regulation was induced by altering PPFD and the spectrum of light incident on PLs using a shading treatment and lighting treatments including either white, blue, green or red light-emitting diodes (LEDs). Photosynthetic characteristics were evaluated by measuring the light-limited and light-saturated net photosynthetic rates and the amounts of nitrogen (N), chlorophyll (Chl) and ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco; EC 4.1.1.39). Shading treatment on PLs decreased the amounts of N, Chl and Rubisco of TLs and tended to decrease the photosynthetic rates. However, we observed no systemic effects induced by the light spectrum on PLs in this study, except that a higher amount of Rubisco of TLs was observed when the PLs were irradiated with blue LEDs. Our results imply that photoreceptors in mature leaves have little influence on photosynthetic rates and amounts of N and Chl of developing leaves through systemic regulation, although the possibility of the action of blue light irradiation on the amount of Rubisco cannot be ruled out. Based on these results, we concluded that the light spectrum incident on mature leaves has little systemic effect on developing leaves in terms of photosynthetic characteristics and that the light-induced systemic regulation was largely accounted for by PPFD.