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Although our observing capabilities of solar‐induced chlorophyll fluorescence (SIF) have been growing rapidly, the quality and consistency of SIF datasets are still in an active stage of research and development. As a result, there are considerable inconsistencies among diverse SIF datasets at all scales and the widespread applications of them have led to contradictory findings. The present review is the second of the two companion reviews, and data oriented. It aims to (1) synthesize the variety, scale, and uncertainty of existing SIF datasets, (2) synthesize the diverse applications in the sector of ecology, agriculture, hydrology, climate, and socioeconomics, and (3) clarify how such data inconsistency superimposed with the theoretical complexities laid out in (Sun et al., 2023) may impact process interpretation of various applications and contribute to inconsistent findings. We emphasize that accurate interpretation of the functional relationships between SIF and other ecological indicators is contingent upon complete understanding of SIF data quality and uncertainty. Biases and uncertainties in SIF observations can significantly confound interpretation of their relationships and how such relationships respond to environmental variations. Built upon our syntheses, we summarize existing gaps and uncertainties in current SIF observations. Further, we offer our perspectives on innovations needed to help improve informing ecosystem structure, function, and service under climate change, including enhancing in‐situ SIF observing capability especially in "data desert" regions, improving cross‐instrument data standardization and network coordination, and advancing applications by fully harnessing theory and data. [ABSTRACT FROM AUTHOR]

Solar‐induced chlorophyll fluorescence (SIF) is a remotely sensed optical signal emitted during the light reactions of photosynthesis. The past two decades have witnessed an explosion in availability of SIF data at increasingly higher spatial and temporal resolutions, sparking applications in diverse research sectors (e.g., ecology, agriculture, hydrology, climate, and socioeconomics). These applications must deal with complexities caused by tremendous variations in scale and the impacts of interacting and superimposing plant physiology and three‐dimensional vegetation structure on the emission and scattering of SIF. At present, these complexities have not been overcome. To advance future research, the two companion reviews aim to (1) develop an analytical framework for inferring terrestrial vegetation structures and function that are tied to SIF emission, (2) synthesize progress and identify challenges in SIF research via the lens of multi‐sector applications, and (3) map out actionable solutions to tackle these challenges and offer our vision for research priorities over the next 5–10 years based on the proposed analytical framework. This paper is the first of the two companion reviews, and theory oriented. It introduces a theoretically rigorous yet practically applicable analytical framework. Guided by this framework, we offer theoretical perspectives on three overarching questions: (1) The forward (mechanism) question—How are the dynamics of SIF affected by terrestrial ecosystem structure and function? (2) The inference question: What aspects of terrestrial ecosystem structure, function, and service can be reliably inferred from remotely sensed SIF and how? (3) The innovation question: What innovations are needed to realize the full potential of SIF remote sensing for real‐world applications under climate change? The analytical framework elucidates that process complexity must be appreciated in inferring ecosystem structure and function from the observed SIF; this framework can serve as a diagnosis and inference tool for versatile applications across diverse spatial and temporal scales. [ABSTRACT FROM AUTHOR]

In this paper, we present GrowliFlower, a georeferenced, image‐based unmanned aerial vehicle time‐series dataset of two monitored cauliflower fields (0.39 and 0.60 ha) acquired in 2 years, 2020 and 2021. The proposed dataset contains RGB and multispectral orthophotos with coordinates of approximately 14,000 individual cauliflower plants. The coordinates enable the extraction of complete and incomplete time‐series of image patches showing individual plants. The dataset contains the collected phenotypic traits of 740 plants, including the developmental stage and plant and cauliflower size. The harvestable product is completely covered by leaves, thus, plant IDs and coordinates are provided to extract image pairs of plants pre‐ and post‐defoliation. In addition, to facilitate classification, detection, segmentation, instance segmentation, and other similar computer vision tasks, the proposed dataset contains pixel‐accurate leaf and plant instance segmentations, as well as stem annotations. The proposed dataset was created to facilitate the development and evaluation of various machine‐learning approaches. It focuses on the analysis of growth and development of cauliflower and the derivation of phenotypic traits to advance automation in agriculture. Two baseline results of instance segmentation tasks at the plant and leaf level based on labeled instance segmentation data are presented. The complete GrowliFlower dataset is publicly available (http://rs.ipb.uni-bonn.de/data/growliflower/). [ABSTRACT FROM AUTHOR]

Water deficit is the most severe stress factor in crop production threatening global food security. In this study, we evaluated the genetic variation in photosynthetic traits among 200 wheat cultivars evaluated under drought and rainfed conditions. Significant genotypic, treatments, and their interaction effects were detected for chlorophyll content and chlorophyll fluorescence parameters. Drought stress reduced the effective quantum yield of photosystem II (YII) from the anthesis growth stage on. Leaf chlorophyll content measured at anthesis growth stages was significantly correlated with YII and non‐photochemical quenching under drought conditions, suggesting that high throughput chlorophyll content screening can serve as a good indicator of plant drought tolerance status in wheat. Breeding significantly increased the photosynthetic efficiency as newer released genotypes had higher YII and chlorophyll content than the older ones. GWAS identified a stable drought‐responsive QTL on chromosome 3A for YII, while under rainfed conditions, it detected another QTL on chromosome 7A for chlorophyll content across both growing seasons. Molecular analysis revealed that the associated alleles of AX‐158576783 (515.889 Mbp) on 3A co‐segregates with the NADH‐ubiquinone oxidoreductase (TraesCS3A02G287600) gene involved in ATP synthesis coupled electron transport and is proximal to WKRY transcription factor locus. This allele on 3A has been positively selected through breeding and has contributed to increasing the grain yield. Highlight: Breeding has aided the selection of multiple pleiotropic and stable drought‐responsive alleles on chromosome 3A associated with improved photosynthetic activity and grain yield under drought stress in winter wheat. [ABSTRACT FROM AUTHOR]

Summary: Sun‐induced fluorescence in the far‐red region (SIF) is increasingly used as a remote and proximal‐sensing tool capable of tracking vegetation gross primary production (GPP). However, the use of SIF to probe changes in GPP is challenged during extreme climatic events, such as heatwaves.Here, we examined how the 2018 European heatwave (HW) affected the GPP–SIF relationship in evergreen broadleaved trees with a relatively invariant canopy structure. To do so, we combined canopy‐scale SIF measurements, GPP estimated from an eddy covariance tower, and active pulse amplitude modulation fluorescence.The HW caused an inversion of the photosynthesis–fluorescence relationship at both the canopy and leaf scales. The highly nonlinear relationship was strongly shaped by nonphotochemical quenching (NPQ), that is, a dissipation mechanism to protect from the adverse effects of high light intensity. During the extreme heat stress, plants experienced a saturation of NPQ, causing a change in the allocation of energy dissipation pathways towards SIF.Our results show the complex modulation of the NPQ–SIF–GPP relationship at an extreme level of heat stress, which is not completely represented in state‐of‐the‐art coupled radiative transfer and photosynthesis models. [ABSTRACT FROM AUTHOR]

Chlorophyll fluorescence (ChlF) is a powerful non‐invasive technique for probing photosynthesis. Although proposed as a method for drought tolerance screening, ChlF has not yet been fully adopted in physiological breeding, mainly due to limitations in high‐throughput field phenotyping capabilities. The light‐induced fluorescence transient (LIFT) sensor has recently been shown to reliably provide active ChlF data for rapid and remote characterisation of plant photosynthetic performance. We used the LIFT sensor to quantify photosynthesis traits across time in a large panel of durum wheat genotypes subjected to a progressive drought in replicated field trials over two growing seasons. The photosynthetic performance was measured at the canopy level by means of the operating efficiency of Photosystem II (Fq′/Fm′) and the kinetics of electron transport measured by reoxidation rates (Fr1′ and Fr2′). Short‐ and long‐term changes in ChlF traits were found in response to soil water availability and due to interactions with weather fluctuations. In mild drought, Fq′/Fm′ and Fr2′ were little affected, while Fr1′ was consistently accelerated in water‐limited compared to well‐watered plants, increasingly so with rising vapour pressure deficit. This high‐throughput approach allowed assessment of the native genetic diversity in ChlF traits while considering the diurnal dynamics of photosynthesis. Photosynthetic performance of a large durum wheat panel under progressive drought in the field was quantified using the light‐induced fluorescence transient (LIFT) sensor for high‐throughput phenotyping. Photosynthesis traits showed high genetic variability, aiding physiological crop breeding. [ABSTRACT FROM AUTHOR]

Summary: Solar‐induced fluorescence (SIF) is highly relevant in mapping photosynthesis from remote‐sensing platforms. This requires linking SIF to photosynthesis and understanding the role of nonphotochemical quenching (NPQ) mechanisms under field conditions. Hence, active and passive fluorescence were measured in Arabidopsis with altered NPQ in outdoor conditions.Plants with mutations in either violaxanthin de‐epoxidase (npq1) or PsbS protein (npq4) exhibited reduced NPQ capacity. Parallel measurements of NPQ, photosystem II efficiency, SIF and spectral reflectance (ρ) were conducted diurnally on one sunny summer day and two consecutive days during a simulated cold spell.Results showed that both npq mutants exhibited higher levels of SIF compared to wild‐type plants. Changes in reflectance were related to changes in the violaxanthin–antheraxanthin–zeaxanthin cycle and not to PsbS‐mediated conformational changes. When plants were exposed to cold temperatures, rapid onset of photoinhibition strongly quenched SIF in all lines.Using well‐characterized Arabidopsisnpq mutants, we showed for the first time the quantitative link between SIF, photosynthetic efficiency, NPQ components and leaf reflectance. We discuss the functional potential and limitations of SIF and reflectance measurements for estimating photosynthetic efficiency and NPQ in the field. [ABSTRACT FROM AUTHOR]

Summary: Cassava (Manihot esculenta Crantz) is one of the important staple foods in Sub‐Saharan Africa. It produces starchy storage roots that provide food and income for several hundred million people, mainly in tropical agriculture zones. Increasing cassava storage root and starch yield is one of the major breeding targets with respect to securing the future food supply for the growing population of Sub‐Saharan Africa. The Cassava Source–Sink (CASS) project aims to increase cassava storage root and starch yield by strategically integrating approaches from different disciplines. We present our perspective and progress on cassava as an applied research organism and provide insight into the CASS strategy, which can serve as a blueprint for the improvement of other root and tuber crops. Extensive profiling of different field‐grown cassava genotypes generates information for leaf, phloem, and root metabolic and physiological processes that are relevant for biotechnological improvements. A multi‐national pipeline for genetic engineering of cassava plants covers all steps from gene discovery, cloning, transformation, molecular and biochemical characterization, confined field trials, and phenotyping of the seasonal dynamics of shoot traits under field conditions. Together, the CASS project generates comprehensive data to facilitate conventional breeding strategies for high‐yielding cassava genotypes. It also builds the foundation for genome‐scale metabolic modelling aiming to predict targets and bottlenecks in metabolic pathways. This information is used to engineer cassava genotypes with improved source–sink relations and increased yield potential. Significance Statement: Cassava (Manihot esculenta) is one of the most important staple food crops in Sub‐Sahran Africa. The Cassava Source‐Sink project aims to boost cassava storage root yield by simultaneously improving the plants source, transport and sink capacity. [ABSTRACT FROM AUTHOR]

Passive measurement of sun‐induced chlorophyll fluorescence (F) represents the most promising tool to quantify changes in photosynthetic functioning on a large scale. However, the complex relationship between this signal and other photosynthesis‐related processes restricts its interpretation under stress conditions. To address this issue, we conducted a field campaign by combining daily airborne and ground‐based measurements of F (normalized to photosynthetically active radiation), reflectance and surface temperature and related the observed changes to stress‐induced variations in photosynthesis. A lawn carpet was sprayed with different doses of the herbicide Dicuran. Canopy‐level measurements of gross primary productivity indicated dosage‐dependent inhibition of photosynthesis by the herbicide. Dosage‐dependent changes in normalized F were also detected. After spraying, we first observed a rapid increase in normalized F and in the Photochemical Reflectance Index, possibly due to the blockage of electron transport by Dicuran and the resultant impairment of xanthophyll‐mediated non‐photochemical quenching. This initial increase was followed by a gradual decrease in both signals, which coincided with a decline in pigment‐related reflectance indices. In parallel, we also detected a canopy temperature increase after the treatment. These results demonstrate the potential of using F coupled with relevant reflectance indices to estimate stress‐induced changes in canopy photosynthesis. Passive measurement of sun‐induced chlorophyll fluorescence is a promising tool to quantify stress‐induced changes in photosynthetic functioning on a large scale. In this study, aerial measurements of fluorescence clearly tracked functional impairment of the rate of photosynthetic electron transport and carbon assimilation induced by a treatment with the herbicide Dicuran. Ancillary remote sensing variables such as vegetation indices and canopy temperature were used to quantify the dynamics of non‐photochemical energy dissipation mechanisms, the amount and composition of photosynthetic pigments and the stomatal activity. These results demonstrate the potential of using sun‐induced chlorophyll fluorescence coupled with relevant reflectance indices to estimate stress‐induced changes in canopy photosynthesis. [ABSTRACT FROM AUTHOR]

Abstract: For the first time, we combine depth‐specific soil information obtained from the quantitative inversion of ground‐based multicoil electromagnetic induction data with the airborne hyperspectral vegetation mapping of 1 × 1‐m pixels including Sun‐induced fluorescence (F) to understand how subsurface structures drive above‐surface plant performance. Hyperspectral data were processed to quantitative F and selected biophysical canopy maps, which are proxies for actual photosynthetic rates. These maps showed within‐field spatial patterns, which were attributed to paleo‐river channels buried at around 1‐m depth. The soil structures at specific depths were identified by quantitative electromagnetic induction data inversions and confirmed by soil samples. Whereas the upper plowing layer showed minor correlation to the plant data, the deeper subsoil carrying vital plant resources correlated substantially. Linking depth‐specific soil information with plant performance data may greatly improve our understanding and the modeling of soil‐vegetation‐atmosphere exchange processes. [ABSTRACT FROM AUTHOR]

Abstract: Leaf fluorescence can be used to track plant development and stress, and is considered the most direct measurement of photosynthetic activity available from remote sensing techniques. Red and far‐red sun‐induced chlorophyll fluorescence (SIF) maps were generated from high spatial resolution images collected with the HyPlant airborne spectrometer over even‐aged loblolly pine plantations in North Carolina (United States). Canopy fluorescence yield (i.e., the fluorescence flux normalized by the light absorbed) in the red and far‐red peaks was computed. This quantifies the fluorescence emission efficiencies that are more directly linked to canopy function compared to SIF radiances. Fluorescence fluxes and yields were investigated in relation to tree age to infer new insights on the potential of those measurements in better describing ecosystem processes. The results showed that red fluorescence yield varies with stand age. Young stands exhibited a nearly twofold higher red fluorescence yield than mature forest plantations, while the far‐red fluorescence yield remained constant. We interpreted this finding in a context of photosynthetic stomatal limitation in aging loblolly pine stands. Current and future satellite missions provide global datasets of SIF at coarse spatial resolution, resulting in intrapixel mixture effects, which could be a confounding factor for fluorescence signal interpretation. To mitigate this effect, we propose a surrogate of the fluorescence yield, namely the Canopy Cover Fluorescence Index (CCFI) that accounts for the spatial variability in canopy structure by exploiting the vegetation fractional cover. It was found that spatial aggregation tended to mask the effective relationships, while the CCFI was still able to maintain this link. This study is a first attempt in interpreting the fluorescence variability in aging forest stands and it may open new perspectives in understanding long‐term forest dynamics in response to future climatic conditions from remote sensing of SIF. [ABSTRACT FROM AUTHOR]

The photosynthetic, optical, and morphological characteristics of a chlorophyll-deficient (Chldeficient) "yellow" soybean mutant (MinnGold) were examined in comparison with 2 green varieties (MN0095 and Eiko). Despite the large difference in Chl content, similar leaf photosynthesis rates were maintained in the Chl-deficient mutant by offsetting the reduced absorption of red photons by a small increase in photochemical efficiency and lower non-photochemical quenching. When grown in the field, at full canopy cover, the mutants reflected a significantly larger proportion of incoming shortwave radiation, but the total canopy light absorption was only slightly reduced, most likely due to a deeper penetration of light into the canopy space. As a consequence, canopy-scale gross primary production and ecosystem respiration were comparable between the Chl-deficient mutant and the green variety. However, total biomass production was lower in the mutant, which indicates that processes other than steady state photosynthesis caused a reduction in biomass accumulation over time. Analysis of non-photochemical quenching relaxation and gas exchange in Chl-deficient and green leaves after transitions from high to low light conditions suggested that dynamic photosynthesis might be responsible for the reduced biomass production in the Chl-deficient mutant under field conditions. [ABSTRACT FROM AUTHOR]

Abstract: Plant species that arrive first in the system can affect assembly (priority effects). However, effects of order of arrival of different plant functional groups (PFGs) on root development have not yet been investigated under field conditions. We measured standing and fine root length density in the first and third year of a grassland field experiment. We wanted to know if manipulating PFG order of arrival would affect root development, and if priority effects are modulated by soil type. Sowing legumes first created a priority effect that was found in the first and third year, with a lower standing root length density in this treatment, even though the plant community composition was different in each of the studied years. Fine root length density was not affected by order of arrival, but changed according to the soil type. Synthesis. We found strong evidence that sowing legumes first created a priority effect below‐ground that was found in the first and third year of this field experiment, even though the functional group dominance was different in each of the studied years. [ABSTRACT FROM AUTHOR]

Sun-induced fluorescence ( SIF) in the far-red region provides a new noninvasive measurement approach that has the potential to quantify dynamic changes in light-use efficiency and gross primary production ( GPP). However, the mechanistic link between GPP and SIF is not completely understood., We analyzed the structural and functional factors controlling the emission of SIF at 760 nm (F760) in a Mediterranean grassland manipulated with nutrient addition of nitrogen (N), phosphorous (P) or nitrogen-phosphorous ( NP). Using the soil-canopy observation of photosynthesis and energy (SCOPE) model, we investigated how nutrient-induced changes in canopy structure (i.e. changes in plant forms abundance that influence leaf inclination distribution function, LIDF) and functional traits (e.g. N content in dry mass of leaves, N%, Chlorophyll a+b concentration ( Cab) and maximum carboxylation capacity ( Vcmax)) affected the observed linear relationship between F760 and GPP., We conclude that the addition of nutrients imposed a change in the abundance of different plant forms and biochemistry of the canopy that controls F760. Changes in canopy structure mainly control the GPP-F760 relationship, with a secondary effect of Cab and Vcmax., In order to exploit F760 data to model GPP at the global/regional scale, canopy structural variability, biodiversity and functional traits are important factors that have to be considered. [ABSTRACT FROM AUTHOR]

Passive detection of sun-induced chlorophyll fluorescence (SIF) using spectroscopy has been proposed as a proxy to quantify changes in photochemical efficiency at canopy level under natural light conditions. In this study, we explored the use of imaging spectroscopy to quantify spatio-temporal dynamics of SIF within crop canopies and its sensitivity to track patterns of photosynthetic activity originating from the interaction between vegetation structure and incoming radiation as well as variations in plant function. SIF was retrieved using the Fraunhofer Line Depth (FLD) principle from imaging spectroscopy data acquired at different time scales a few metres above several crop canopies growing under natural illumination. We report the first maps of canopy SIF in high spatial resolution. Changes of SIF were monitored at different time scales ranging from quick variations under induced stress conditions to seasonal dynamics. Natural changes were primarily determined by varying levels and distribution of photosynthetic active radiation (PAR). However, this relationship changed throughout the day demonstrating an additional physiological component modulating spatio-temporal patterns of SIF emission. We successfully used detailed SIF maps to track changes in the canopy's photochemical activity under field conditions, providing a new tool to evaluate complex patterns of photosynthesis within the canopy. [ABSTRACT FROM AUTHOR]

The rhizosphere of two flooding-resistant plant species ( Arundinella anomala Steud., Alternanthera philoxeroides Mart.) from Three Gorges Reservoir area (China) has been examined for reactions to waterlogging and submergence. Rhizosphere parameters were monitored in natural sediment substrate by means of a dual-access floodable rhizobox, which allows monitoring of oxygen and pH dynamics noninvasively with planar optodes in high temporal and spatial resolution, as well as simultaneous low-invasive soil-solution sampling. Analysis of samples for low-molecular-weight organic acids (LMWOA) was done by capillary electrophoresis. Roots could be observed easily in situ during growth and exposure to flooding. The floodable rhizobox is therefore considered a valuable tool for root-reaction monitoring also under flooding conditions. During waterlogging, both species exuded oxygen into their rhizosphere and showed diurnal rhythms of rhizospheric acidification. The pH of the rhizosphere of growing root tips decreased up to 0.8 units corresponding to higher LMWOA concentrations. These rhythms weakened during flooding, but gained maximum amplitude again rapidly after resurfacing. We conclude that the root system was still fully functioning during and after flooding, and that flooding poses no threat to the physiology of the root system of the study species. [ABSTRACT FROM AUTHOR]

Studying the effects of climate or weather extremes such as drought and heat waves on biodiversity and ecosystem functions is one of the most important facets of climate change research. In particular, primary production is amounting to the common currency in field experiments world-wide. Rarely, however, are multiple ecosystem functions measured in a single study in order to address general patterns across different categories of responses and to analyse effects of climate extremes on various ecosystem functions. We set up a long-term field experiment, where we applied recurrent severe drought events annually for five consecutive years to constructed grassland communities in central Europe. The 32 response parameters studied were closely related to ecosystem functions such as primary production, nutrient cycling, carbon fixation, water regulation and community stability. Surprisingly, in the face of severe drought, above- and below-ground primary production of plants remained stable across all years of the drought manipulation. Yet, severe drought significantly reduced below-ground performance of microbes in soil indicated by reduced soil respiration, microbial biomass and cellulose decomposition rates as well as mycorrhization rates. Furthermore, drought reduced leaf water potential, leaf gas exchange and leaf protein content, while increasing maximum uptake capacity, leaf carbon isotope signature and leaf carbohydrate content. With regard to community stability, drought induced complementary plant-plant interactions and shifts in flower phenology, and decreased invasibility of plant communities and primary consumer abundance. Synthesis. Our results provide the first field-based experimental evidence that climate extremes initiate plant physiological processes, which may serve to regulate ecosystem productivity. A potential reason for different dynamics in various ecosystem services facing extreme climatic events may lie in the temporal hierarchy of patterns of fast versus slow response. Such data on multiple response parameters within climate change experiments foster the understanding of mechanisms of resilience, of synergisms or decoupling of biogeochemical processes, and of fundamental response dynamics to drought at the ecosystem level including potential tipping points and thresholds of regime shift. Future work is needed to elucidate the role of biodiversity and of biotic interactions in modulating ecosystem response to climate extremes. [ABSTRACT FROM AUTHOR]

Terrestrial gross primary production (GPP) is an important parameter to explore and quantify carbon fixation by plant ecosystems at various scales. Remote sensing (RS) offers a unique possibility to investigate GPP in a spatially explicit fashion; however, budgeting of terrestrial carbon cycles based on this approach still remains uncertain. To improve calculations, spatio-temporal variability of GPP must be investigated in more detail on local and regional scales. The overarching goal of this study is to enhance our knowledge on how environmentally induced changes of photosynthetic light-use efficiency (LUE) are linked with optical RS parameters. Diurnal courses of sun-induced fluorescence yield ( FSyield) and the photochemical reflectance index of corn were derived from high-resolution spectrometric measurements and their potential as proxies for LUE was investigated. GPP was modeled using Monteith's LUE-concept and optical-based GPP and LUE values were compared with synoptically acquired eddy covariance data. It is shown that the diurnal response of complex physiological regulation of photosynthesis can be tracked reliably with the sun-induced fluorescence. Considering structural and physiological effects, this research shows for the first time that including sun-induced fluorescence into modeling approaches improves their results in predicting diurnal courses of GPP. Our results support the hypothesis that air- or spaceborne quantification of sun-induced fluorescence yield may become a powerful tool to better understand spatio-temporal variations of fluorescence yield, photosynthetic efficiency and plant stress on a global scale. [ABSTRACT FROM AUTHOR]

This study reports evidence that the timing of leaf growth responds to developmental and environmental constraints in Clusia spp. We monitored diel patterns of leaf growth in the facultative C3-crassulacean acid metabolism (CAM) species Clusia minor and in the supposedly obligate CAM species Clusia alata using imaging methods and followed diel patterns of CO2 exchange and acidification. Developing leaves of well-watered C. minor showed a C3-like diel pattern of gas exchange and growth, with maximum relative growth rate (RGR) in the early night period. Growth slowed when water was withheld, accompanied by nocturnal CO2 exchange and the diel acid change characteristic of CAM. Maximum leaf RGR shifted from early night to early in the day when water was withheld. In well-watered C. alata, similar changes in the diel pattern of leaf growth occurred with the development of CAM during leaf ontogeny. We hypothesize that the shift in leaf growth cycle that accompanies the switch from C3 photosynthesis to CAM is mainly caused by the primary demand of CAM for substrates for nocturnal CO2 fixation and acid synthesis, thus reducing the availability of carbohydrates for leaf growth at night. Although the shift to leaf growth early in the light is presumably associated with the availability of carbohydrates, source–sink relationships and sustained diurnal acid levels in young leaves of Clusia spp. need further evaluation in relation to growth processes. [ABSTRACT FROM AUTHOR]

Plants constantly adapt their leaf orientation in response to fluctuations in the environment, to maintain radiation use efficiency in the face of varying intensity and incidence direction of sunlight. Various methods exist for measuring structural canopy parameters such as leaf angle distribution. However, direct methods tend to be labour-intensive, while indirect methods usually give statistical information on stand level rather than on individual leaves. We present an area-based, binocular stereo system composed of commercially available components that allows three-dimensional reconstruction of small- to medium-sized canopies on the level of single leaves under field conditions. Spatial orientation of single leaves is computed with automated processes using modern, well-established stereo matching and segmentation techniques, which were adapted for the properties of plant canopies, providing high spatial and temporal resolution (angle measurements with an accuracy of approx. ±5° and a maximum sampling rate of three frames per second). The applicability of our approach is demonstrated in three case studies: (1) the dihedral leaflet angle of an individual soybean was tracked to monitor nocturnal and daytime leaf movement showing different frequencies and amplitudes; (2) drought stress was diagnosed in soybean by quantifying changes in the zenith leaflet angle distribution; and (3) the diurnal course of the zenith leaf angle distribution of a closed soybean canopy was measured. [ABSTRACT FROM AUTHOR]

• In tropical lowland forests, corticolous crustose green algal lichens are abundant and highly diverse. This may be related to adaptation to prevailing microenvironmental conditions including, for example, high precipitation and low light intensities. • In the understory of a tropical lowland rain forest in French Guiana, we studied the morphology of crustose green algal lichens and measured gas exchange and chlorophyll a fluorescence. • We found that (i) periods of thallus suprasaturation with water were reduced by the presence of water-repelling surface structures of mycobiont hyphae at the thallus surface and the medulla; (ii) photosynthesis was adapted to the low light intensities present in the understory; and (iii) photosynthesis was rapidly activated in fluctuating light. • The combination of these three mechanisms enables corticolous lichens to implement specific morphological and physiological strategies, which may favour growth in the limiting understory habitat of tropical lowland rain forests. [ABSTRACT FROM AUTHOR]

Determining the spatial and temporal diversity of photosynthetic processes in forest canopies presents a challenge to the evaluation of biological feedbacks needed for improvement of carbon and climate models. Limited access with portable instrumentation, especially in the outer canopy, makes remote sensing of these processes a priority in experimental ecosystem and climate change research. Here, we describe the application of a new, active, chlorophyll fluorescence measurement system for remote sensing of light use efficiency, based on analysis of laser-induced fluorescence transients (LIFT). We used mature stands of Populus grown at ambient (380 ppm) and elevated CO2 (1220 ppm) in the enclosed agriforests of the Biosphere 2 Laboratory (B2L) to compare parameters of photosynthetic efficiency, photosynthetic electron transport, and dissipation of excess light measured by LIFT and by standard on-the-leaf saturating flash methods using a commercially available pulse-modulated chlorophyll fluorescence instrument (Mini-PAM). We also used LIFT to observe the diel courses of these parameters in leaves of two tropical forest dominants, Inga and Pterocarpus, growing in the enclosed model tropical forest of B2L. Midcanopy leaves of both trees showed the expected relationships among chlorophyll fluorescence-derived photosynthetic parameters in response to sun exposure, but, unusually, both displayed an afternoon increase in nonphotochemical quenching in the shade, which was ascribed to reversible inhibition of photosynthesis at high leaf temperatures in the enclosed canopy. Inga generally showed higher rates of photosynthetic electron transport, but greater afternoon reduction in photosynthetic efficiency. The potential for estimation of the contribution of outer canopy photosynthesis to forest CO2 assimilation, and assessment of its response to environmental stress using remote sensing devices such as LIFT, is briefly discussed. [ABSTRACT FROM AUTHOR]

Image sequence processing methods were applied to study the effect of elevated CO2 on the diel leaf growth cycle for the first time in a dicot plant. Growing leaves of Populus deltoides, in stands maintained under ambient and elevated CO2 for up to 4 years, showed a high degree of heterogeneity and pronounced diel variations of their relative growth rate (RGR) with maxima at dusk. At the beginning of the season, leaf growth did not differ between treatments. At the end of the season, final individual leaf area and total leaf biomass of the canopy was increased in elevated CO2. Increased final leaf area at elevated CO2 was achieved via a prolonged phase of leaf expansion activity and not via larger leaf size upon emergence. The fraction of leaves growing at 30–40% day−1 was increased by a factor of two in the elevated CO2 treatment. A transient minimum of leaf expansion developed during the late afternoon in leaves grown under elevated CO2 as the growing season progressed. During this minimum, leaves grown under elevated CO2 decreased their RGR to 50% of the ambient value. The transient growth minimum in the afternoon was correlated with a transient depletion of glucose (less than 50%) in the growing leaf in elevated CO2, suggesting diversion of glucose to starch or other carbohydrates, making this substrate temporarily unavailable for growth. Increased leaf growth was observed at the end of the night in elevated CO2. Net CO2 exchange and starch concentration of growing leaves was higher in elevated CO2. The extent to which the transient reduction in diel leaf growth might dampen the overall growth response of these trees to elevated CO2 is discussed. [ABSTRACT FROM AUTHOR]

Scaling is a naturally iterative and bi-directional component of problem solving in ecology and in climate science. Ecosystems and climate systems are unquestionably the sum of all their parts, to the smallest imaginable scale, in genomic processes or in the laws of fluid dynamics. However, in the process of scaling-up, for practical purposes thewhole usually has to be construed as a good deal less than this. This essay demonstrates how controlled large-scale experiments can be used to deduce key mechanisms and thereby reduce much of the detail needed for the process of scaling-up. Collection of the relevant experimental evidence depends on controlling the environment and complexity of experiments, and on applications of technologies that report on, and integrate, small-scale processes. As the role of biological feedbacks in the behavior of climate systems is better appreciated, so the need grows for experimentally based understanding of ecosystem processes. We argue that we cannot continue as we are doing, simply observing the progress of the greenhouse gas-driven experiment in global change, and modeling its future outcomes. We have to change the way we think about climate system and ecosystem science, and in the process move to experimental modes at larger scales than previously thought achievable. [ABSTRACT FROM AUTHOR]

The article offers information on the European Field Phenotyping Workshop held at Copenhagen, Denmark on September 2014. Topics discussed include the development of field phenotyping toolbox, agriculture and genomic breeding as future challenges, and field phenotyping methods result use as a basis to improve and develop techniques in phenotyping platforms.

The cover image is based on the Original Article High‐throughput field phenotyping reveals genetic variation in photosynthetic traits in durum wheat under drought by Nícolas Zendonadi dos Santos et al., https://doi.org/10.1111/pce.14136. [ABSTRACT FROM AUTHOR]