Response Of Photosynthesis Research Articles

Short-Term Evaluation of Woodland Strawberry in Response to Melatonin Treatment under Low Light Environment

The cultivation of strawberries in controlled environments presents challenges related to environmental stressors, especially insufficient light. Melatonin, as a widely investigated plant growth regulator, was considered as a potential candidate to mitigate damage, and enhance photosynthesis stability. However, whether melatonin can improve photosynthesis under light deficiency in woodland strawberry (Fragaria vesca) remains elusive. In this study, we evaluated gas exchange parameters, Chlorophyll fluorescence parameters, photochemical efficiency, and the related genes’ expression levels to decipher the multifaceted impact of melatonin on photosynthesis. We found concentration-dependent effects of melatonin on photosynthetic parameters, with potential benefits at lower concentration and inhibitory effects at higher concentration. Notably, melatonin increased non-photochemical quenching (NPQ), a mechanism for dissipating excess light energy, while leaving photochemical quenching (qP) relatively stable. Further analysis showed that melatonin up-regulated key xanthophyll cycle-related genes (DHAR, VDE, and PsbS), indicating its involvement in energy dissipation processes. In conclusion, our study uncovered the dual and complex role of melatonin in the short-term response of photosynthesis in woodland strawberries under low-light conditions.

Salt-Induced Early Changes in Photosynthesis Activity Caused by Root-to-Shoot Signaling in Potato.

Salinity is one of the most dangerous types of stress in agriculture. Acting on the root, salinity causes changes in physiological processes in the shoot, especially photosynthesis, which is crucial for plant productivity. In our study, we used potato plants, the most important crop, to investigate the role of salt-induced signals in changes in photosynthesis activity. We found a salt-induced polyphasic decrease in photosynthesis activity, and the earliest phase started several minutes after salt addition. We found that salt addition triggered rapid hydraulic and calcium waves from root to shoot, which occurred earlier than the first phase of the photosynthesis response. The inhibition of calcium signals by lanthanum decreased with the formation of rapid changes in photosynthesis. In addition to this, a comparison of the characteristic times of signal propagation and the formation of a response revealed the role of calcium waves in the modulation of rapid changes in photosynthesis. Calcium waves are activated by the ionic component of salinity. The salt-induced decrease in transpiration corresponds in time to the second phase of the photosynthetic response, and it can be the cause of this change. The accumulation of sodium in the leaves occurs a few hours after salt addition, and it can be the cause of the long-term suppression of photosynthesis. Thus, salinity modulates photosynthetic activity in plants in different ways: both through the activation of rapid distant signals and by reducing the water input and sodium accumulation.

Impacts of Sea Surface Temperature Variability in the Indian Ocean on Drought Conditions over India during ENSO and IOD Events

The characteristics of terrestrial droughts are closely linked to simultaneous fluctuations in climatic factors, notably influenced by sea surface temperature (SST). This study explores the response of vegetation photosynthesis, indicated by solar-induced chlorophyll fluorescence (SIF), in India during the summer monsoon period (JJAS) under drought conditions. Notably, statistically significant associations between SST variations in the tropical Indian Ocean and land-based drought responses (precipitation, temperature, soil moisture, and SIF) were observed, which were attributed to atmospheric teleconnections. The positive phases of El Niño and the Indian Ocean Dipole (IOD) significantly impacted SST, triggering severe droughts in India in 2009 and 2015. The results revealed that positive SST anomalies weaken monsoon flow during the onset period, reducing moisture transmission to the Indian subcontinent. In 2009, the precipitation anomaly showed severe drought conditions (<−1.5) primarily in the northwest, central northeast, and west-central subregions, respectively, with soil moisture deficit and reduced photosynthetic activity (indicated by negative SIF anomalies) mirroring precipitation anomalies. In 2015, moderate to severe drought conditions affected regions primarily in the west-central and peninsular areas, with corresponding consistency in SIF anomalies and soil moisture deficits. These conditions led to decreased photosynthetic rates and negative SIF anomalies observed across India. The findings provide insights for predicting droughts and understanding ecosystem impacts across India amidst rapidly changing climate conditions in the Indian Ocean region.

Heterocapsa cf. bohaiensis (dinoflagellate): identification and response to nickel and iron stress revealed through chlorophyll a fluorescence.

Metal toxicity in marine ecosystems is a growing issue owing to terrestrial runoff and anthropogenic pollution. Heterocapsa cf. bohaiensis, a newly isolated dinoflagellate from New Caledonia, was cultivated in photobioreactors operating continuously with high concentrations of nickel (1.70 10-5M) (Ni2+) and/or iron (1.79 10-5M) (Fe2+) and their photosynthetic efficiency was assessed. The photosynthetic measurements indicated that H. cf. bohaiensis was tolerant to Ni2+ but sensitive to Fe2+ high concentrations. In the presence of Fe2+, maximum quantum efficiency and maximal relative electron transport rate decreased from 0.62 to 0.47 and from 156 to 102, respectively. The JIP-tests suggested a reduction of the photosynthesis in response to Fe2+ due to a disruption in the electron transport chain rather than a defect in the light absorption and trapping capacity which were on the contrary enhanced by Fe2+. These results bring new knowledge on the impact of nickel and iron on microalgae photosynthetic pathways.

Response of photosynthesis, population physiological indexes, and yield of cotton in dry areas to the new technology of "dry sowing and wet emergence".

In arid areas, exploring new "dry sowing wet emergence (DSWE)" water-saving irrigation techniques may become one of the most important ways to reduce agricultural irrigation water use and improve economic efficiency. The study was conducted in a two-year field trial in 2021 and 2022, setting up three seedling emergence rates (W1: 6 mm, W2: 10.5 mm, W3: 15 mm) and two drip frequencies (D1: 2 times, D2: 4 times) for a total of six irrigation combinations. The results indicate that under the "DSWE" irrigation pattern, in contrast to the low frequency treatment, the photosynthetic efficiency of cotton leaves in the high-frequency treatment is significantly higher. The stomatal conductance of cotton leaves has increased by 6.67% within two years, and the net photosynthetic rate has risen by 12.22%. Compared with the CK treatment, there is no remarkable difference in the photosynthetic indicators of the W3D2 treatment, while the net photosynthetic rate has increased by 1.68%. The population physiological indicators of each treatment group exhibit a trend of initially increasing and then decreasing as the growth period prolongs. The differences in the group population physiological indicators of cotton at the seedling stage among different seedling water treatments are relatively minor. The high frequency treatment maintains a relatively high level throughout the growth period. Compared with the low-frequency treatment, the yields of lint cotton and seed cotton in the high-frequency treatment have increased by 14.77% and 20.89%, respectively. Compared with the winter irrigation technology, there are no significant differences in the cotton yield and quality indicators of the "DSWE" high-frequency and high-seedling water treatment (W3D2). Over two years, the average unit yields of lint and seed cotton have decreased by 1.95% and 3.01%, respectively. Nevertheless, irrigation water during the growth period declined by 38.46%. The appropriate "DSWE" irrigation technology (W3D2) can significantly enhance the physiological indicators of cotton, ensuring crop yield and quality while significantly reducing the amount of agricultural irrigation water.

Response of stomatal conductance, transpiration, and photosynthesis to light and CO2 for rice leaves with different appearance days.

To investigate the dynamics of stomata, transpiration, and photosynthesis under varying light intensities and CO2 conditions during leaf development, the light response and CO2 response of stomatal conductance (g sw), transpiration rate (T r), and net photosynthetic rate (P n) were observed for rice leaves at different days after leaf emergence (DAE). The results showed that (1) as photosynthetically active radiation (PAR) increased, leaf g sw, T r, and P n initially increased rapidly and linearly, followed by a more gradual rise to maximum values, and then either stabilized or showed a declining trend. The maximum g sw, T r, and P n were smaller and occurred earlier for old leaves than for young leaves. The g sw, T r, and P n all exhibited a linear decreasing trend with increasing DAE, and the rate of decrease slowed down with the reduction in PAR; (2) as the CO2 concentration (C a) increased, g sw and T r decreased gradually to a stable minimum value, while P n increased linearly and slowly up to the maximum and then kept stable or decreased. The g sw, T r, and P n values initially kept high and then decreased with the increase of DAE. These results contribute to understanding the dynamics in g sw, T r, and P n during rice leaf growth and their response to varied light and CO2 concentration conditions and provide mechanistic support to estimate dynamic evapotranspiration and net ecosystem productivity at field-scale and a larger scale in paddy field ecosystems through the upscaling of leaf-level stomatal conductance, transpiration, and photosynthesis.

Seasonal dynamics in photosynthetic characteristics and growth of Cunninghamia lanceolata saplings and their response to soil warming

In order to understand the response and adaptation mechanisms of photosynthetic characteristics and growth for Cunninghamia lanceolata saplings in the subtropical region to global warming, we conducted the root-box warming experiment (ambient, ambient+4 ℃) at the Sanming Forest Ecosystem National Observation and Research Station in Fujian Province to investigate the effects of soil warming on the photosynthetic characteristics and growth of C. lanceolata saplings in different seasons. The results showed that the net photosynthetic rate (Pn) and stomatal conductance (gs) of C. lanceolata significantly decreased in summer compared with in spring and autumn. Soil warming had no effect on the Pn and gs of C. lanceolata. However, the interaction between warming and season significantly impacted the leaf water use efficiency (WUE). The tree height and ground diameter growth of C. lanceolata significantly increased in spring compared with in summer and autumn. Warming significantly reduced ground diameter growth, and it diminished the net diameter growth by 48.1% in autumn. However, warming had no impact on the tree height growth of C. lanceolata in each season. The specific leaf area, soluble sugar, and non-structural carbohydrates contents of C. lanceolata significantly improved in summer and autumn compared with in spring. Warming had rarely influence on leaf functional traits in each season. In conclusion, the response of photosynthesis for C. lanceolata to soil warming was insignificant. The photosynthesis of C. lanceolata exhibited significant seasonal dynamics, primarily controlled by gs. C. lanceolata adapted to soil warming by adjusting WUE, and it adjusted to high temperatures and drought stress in summer by increasing soluble sugar content and specific leaf area. The effect of warming on ground diameter growth of C. lanceolata was primarily driven by soil moisture. The seasonal difference in the growth of C. lanceolata was influenced by the photosynthesis of C. lanceolata and the trade-off between the utilization and storage of photosynthetic products.

Genotypic Differences in Photosynthetic Limitations to Carbon Assimilation in Peanut under Drought at the Onset of Flowering

Drought can greatly limit carbon assimilation in plants. However, different species have distinct photosynthetic components governing limitations to photosynthesis exposed to drought conditions. Furthermore, intra-species variations in photosynthetic response to drought is also expected. Information on underlying limitations to carbon assimilation in peanut (Arachis hypogaea L.) has been controversial. Therefore, this study aimed to verify potential drought tolerance associated with the photosynthetic process within ten diverse peanut genotypes grown under drought as well as to determine the limitation to carbon assimilation in these genotypes and identify parameter(s) that can be used as a reference indicator of photosynthesis response to drought intensity. Experiments were conducted in 2017 and 2018 using rainout shelters to impose drought for 40 days starting 34 days after planting. Ten peanut genotypes were planted in two blocks, one fully irrigated and one under drought stress during reproductive development. Photosynthetic measurements were taken at 25 and 40 days after onset of stress. C76-16 was identified as the most tolerant genotype due to improved plasticity by downregulating photosynthesis under mild drought stress (25 progressive days under drought) and upregulating multiple photosynthetic component processes under more severe drought (40 days under drought) to sustain photosynthesis. The primary limitation to photosynthesis across all peanut genotypes was stomatal conductance, whereas non-stomatal factors (photochemical reactions) were nearly unaffected by mild drought. In addition, stomatal conductance and electron flux to CO2 assimilation contributed most to drought tolerance in peanut genotypes. Moreover, these two photosynthetic component processes can be jointly used as reference indicators of photosynthetic status of peanut under varying drought intensities.

Measurement of the Kinetics of Chlorophyll a Fluorescence by an LED-Light Source Fluorimeter, Handy PEA.

The chlorophyll a fluorescence measurement method is used to determine the efficiency of the photosynthetic apparatus and to assess the physiological state of photosynthetic organisms. The measurement is simple, fast, and noninvasive. It is a precise tool to study photosynthesis response under stress conditions or to assess the impact of specific environmental factors on plants. Here we describe the usage of this method in environmental-controlled plant production systems differing in temperature or light source on the growth and development of common buckwheat.

Responses in growth, photosynthesis, and water uptake of a halophyte (Tetragonia tetragonoides) under halophilism condition

Halophytes not only tolerate to salinity, but also promote their growth under a suitable saline condition (referred to as halophilism). Tetagonia tetragonioides is a halophyte that its growth is promoted by NaCl salinity up to 100 mM, but the mechanism of halophilism has not been elucidated. The present study examined responses in the plant’s growth, photosynthesis, and water uptake under the halophilism condition. The results the fresh and dry biomass were increased by 35.86 and 37.04% compared to the plant grown without salt, respectively. The growth enhancement of plant was contributed by the growth of both shoots and roots. Leaf chlorophyll content was also increased 1.10 times under the halophilism condition. Relative water content was not significantly increased, but proline content was increased 15.93 – 52.31 times with increasing salinity levels. These results suggest mechanisms that regulated photosynthesis and water uptake for the halophilism.

Nitrogen enrichment delays the drought threshold responses of leaf photosynthesis in alpine grassland plants

Extreme drought is found to cause a threshold response in photosynthesis in ecosystem level. However, the mechanisms behind this phenomenon are not well understood, highlighting the importance of revealing the drought thresholds for multiple leaf-level photosynthetic processes.Thus, we conducted a long-term experiment involving precipitation reduction and nitrogen (N) addition. Moreover, an extreme drought event occurred within the experimental period.We found the presence of drought thresholds for multiple leaf-level photosynthetic processes, with the leaf light-saturated carbon assimilation rate (Asat) displaying the highest threshold (10.76 v/v%) and the maximum rate of carboxylation by Rubisco (Vcmax) showing the lowest threshold (5.38 v/v%). Beyond the drought thresholds, the sensitivities of leaf-level photosynthetic processes to soil water content could be greater. Moreover, N addition lowered the drought thresholds of Asat and stomatal conductance (gs), but had no effect on that of Vcmax. Among species, plants with higher leaf K concentration traits had a lower drought threshold of Asat.Overall, this study highlights that leaf photosynthesis may be suppressed abruptly as soil water content surpasses the drought threshold. However, N enrichment helps to improve the resistance via delaying drought threshold response. These new findings have important implications for understanding the nonlinearity of ecosystem productivity response and early warning management in the scenario of combined extreme drought events and continuous N deposition.

Stem Hydraulic Conductance, Leaf Photosynthesis, and Carbon Metabolism Responses of Cotton to Short-Term Drought and Rewatering

Water stress can trigger acclimation responses and damage plants. The aim of this study was to evaluate the integrative responses of cotton hydraulic conductance, leaf photosynthesis, and carbon metabolism to short-term drought and subsequent rewatering. A water-controlled pot experiment was conducted in 2020, with soil water drying continuing for one day (D1), two days (D2), and three days (D3) after it reached 40% ± 5% of the soil water holding capacity at the blooming stage of cotton, and the soil was then rewatered to the soil water holding capacity. We investigated how the stem hydraulic conductance, gas exchange, and biochemical traits of cotton were affected by imposed drought stress and subsequent rewatering. The hydraulic characteristics of cotton in the D2 and D3 treatments evolved with damage, complete closure of stomatal conductance, and complete deterioration of photosynthesis, in addition to severe floating changes in the carbon metabolism affected by drought. The leaves’ functional characteristics after rewatering cannot be completely recovered to full-irrigation levels, and the recovery extent was strongly linked to the duration. Consequently, it is considered desirable to maintain normal physiological activity during the cotton reproductive period, and the drought episode can be sustained for 1 day in a long-term perspective when the soil water content is depleted to 40% ± 5% of the soil water holding capacity. These results can provide in-depth ideas for better understanding the hydraulic and physiological responses of cotton to drought episodes and rewatering, and they can help drought-affected cotton to cope with future climate change.

Response of photosynthesis and electrical reactions of wheat plants upon the action of magnetic fields in the Schumann resonance frequency band

ABSTRACT Alternating magnetic fields (MF) with Schumann resonance frequencies accompanied the development of living organisms throughout evolution, but today it remains unclear whether they can have a special biological effect in comparison with surrounding non-resonant frequencies. This work shows some stimulating effect of extremely low-frequency MFs on morphometric parameters and the activity of physiological processes in wheat (Triticum aestivum L.). It is shown that the MF effect is more pronounced for transient processes – photosynthesis reactions and changes in electrical potential caused by turning on light. For light-induced electrical reactions, the dependence of the severity of the effect on the frequency of the applied MF was demonstrated. It is shown that the most pronounced effect occurs in the 14.3 Hz field, which corresponds to the second harmonic of the Schumann resonance. The predominant sensitivity of signal-regulatory systems gives reason to assume the influence of MFs with Schumann resonance frequencies on the interaction of plants with environmental factors under conditions of a changed electromagnetic environment. Such conditions can occur, for example, with an increase in lightning activity caused by climate change, which serves as the basis for the generation of Schumann resonances, and with the development of artificial ecosystems outside the Earth’s atmosphere.

A singular PpaA/AerR-like protein in Rhodospirillum rubrum rules beyond the boundaries of photosynthesis in response to the intracellular redox state.

Rhodospirillum rubrum vast metabolic versatility places it as a remarkable model bacterium and an excellent biotechnological chassis. The key component of photosynthesis (PS) studied in this work (HP1) stands out among the other members of PpaA/AerR anti-repressor family since it lacks the motif they all share: the cobalamin B-12 binding motif. Despite being reduced and poorly conserved, HP1 stills controls PS as the other members of the family, allowing a fast response to changes in the redox state of the cell. This work also shows that HP1 absence affects genes from relevant biological processes other than PS, including nitrogen fixation and stress response. From a biotechnological perspective, HP1 could be manipulated in approaches where PS is not necessary, such as hydrogen or polyhydroxyalkanoates production, to save energy.

The response of LncRNAs associated with photosynthesis-and pigment synthesis-related genes to green light in Chlamydomonas reinhardtii.

The quality of light is an important abiotic factor that affects the growth and development of green plants. Ultraviolet, red, blue, and far-red light all have demonstrated roles in regulating green plant growth and development, as well as light morphogenesis. However, the mechanism underlying photosynthetic organism responses to green light throughout the life of them are not clear. In this study, we exposed the unicellular green alga Chlamydomonas reinhardtii to green light and analyzed the dynamics of transcriptome changes. Based on the whole transcriptome data from C. reinhardtii, a total of 9974 differentially expressed genes (DEGs) were identified under green light. The Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment analyses indicated that these DEGs were mainly related to "carboxylic acid metabolic process," "enzyme activity," "carbon metabolism," and "photosynthesis and other processes." At the same time, 253 differentially expressed long non-coding RNAs (DELs) were characterized as green light responsive. We also made a detailed analysis of the responses of photosynthesis- and pigment synthesis-related genes in C. reinhardtii to green light and found that these genes exhibited obvious dynamic expression. Lastly, we constructed a co-expression regulatory network, comprising 49 long non-coding RNAs (lncRNAs) and 20 photosynthesis and pigment related genes, of which 9 mRNAs were also the predicted trans/cis-targets of 8 lncRNAs, these results suggested that lncRNAs may affect the expression of mRNAs related to photosynthesis and pigment synthesis. Our findings give a preliminary explanation of the response mechanism of C. reinhardtii to green light at the transcriptional level.

Study of the Photosynthesis Response during the Gradual Lack of Water for 14 Olea europaea L. subsp europaea Cultivars and Their Adaptation to Climate Change.

Understanding the tolerance of plants to drought and their gradual response to lack of water is a multifaceted challenge that requires a combination of scientific research and technological innovation. Selecting naturally drought-tolerant plants and knowing their response to photosynthesis in a wide range of water availability opens a door to making decisions about the suitability of different cultivars to be implanted in specific geographical areas, based on their tolerance to drought and light absorption capacity. In this work, photosynthesis-light curves were carried out using a LiCor LI-6800 IRGA device, applying increasing light intensities to plants of 14 olive cultivars, either under control conditions (no water stress) or subject to moderate and severe water deficits. The plants were grown in a culture chamber under controlled conditions for photoperiod, air humidity, temperature, and carbon dioxide concentration. For each cultivar, the electronic transference ratio (ETR) in response to light was also obtained. Different equations were used to fit experimental data allowing us to calculate, with a regression coefficient above 0.95, different photosynthetic parameters such as the maximum photosynthetic capacity, the photosynthetic efficiency, the number of electrons or the number of photons to assimilate a molecule of CO2, and the effect of the lack of water on these parameters. This work represents the first contribution of the response to photosynthesis of many olive cultivars subjected to moderate and severe drought conditions. The parameters described, and the results provided, pave the road for subsequent work related to plant physiology and other areas of science and technology, and allow us to objectively compare the tolerance to water stress in these fourteen olive cultivars.

Light and temperature controls of aquatic plant photosynthesis downstream of a hydropower plant and the effect of plant removal

Many rivers worldwide are regulated, and the altered hydrology can lead to mass development of aquatic plants. Plant invasions are often seen as a nuisance for human activities leading to costly remedial actions with uncertain implications for aquatic biodiversity and ecosystem functioning. Mechanical harvesting is often used to remove aquatic plants and knowledge of plant growth rate could improve management decisions. Here, we used a simple light-temperature theoretical model to make a priori prediction of aquatic plant photosynthesis. These predictions were assessed through an open-channel diel change in O2 mass balance approach. A Michaelis-Menten type model was fitted to observed gross primary production (GPP) standardised at 10 °C using a temperature dependence from thermodynamic theory of enzyme kinetics. The model explained 87 % of the variability in GPP of a submerged aquatic plant (Juncus bulbosus L.) throughout an annual cycle in the River Otra, Norway. The annual net plant production was about 2.4 (1.0–3.8) times the standing biomass of J. bulbosus. This suggests a high continuous mass loss due to hydraulic stress and natural mechanical breakage of stems, as the biomass of J. bulbosus remained relatively constant throughout the year. J. bulbosus was predicted to be resilient to mechanical harvesting with photosynthetic capacity recovered within two years following 50–85 % plant removal. The predicted recovery was confirmed through a field experiment where 72 % of J. bulbosus biomass was mechanically removed. We emphasise the value of using a theoretical approach, like metabolic theory, over statistical models where a posteriori results are not always easy to interpret. Finally, the ability to predict ecosystem resilience of aquatic photosynthesis in response to varying management scenarios offers a valuable tool for estimating aquatic ecosystem services, such as carbon regulation. This tool can benefit the EU Biodiversity Strategy and UN Sustainable Development Goals.

Exploring the responses of crop photosynthesis to CO2 elevation at the molecular, physiological, and morphological levels toward increasing crop production

Exploring the impact of elevated CO2 on photosynthesis is vital for understanding plant responses to climate change. In C3 plants, elevated CO2 concentrations generally enhance CO2 assimilation by increasing chloroplast CO2 concentration. However, the underlying mechanisms are complex since photosynthesis involves multiple physiological processes operating at different time scales and varying among plant species. In this review, we focused on the responses of key photosynthetic processes in crop, including CO2 diffusion conductances such as stomatal conductance (gs), mesophyll conductance (gm), photochemical reactions, the Calvin-Benson cycle, and related metabolic pathways. Short-term exposure to elevated CO2 often decreases gs and gm while increasing the electron transport rate. However, long-term exposure to elevated CO2 can decrease photosynthetic capacity due to coordinated downregulation of multiple processes, particularly when the sink‒source ratio declines. To enhance plant productivity under elevated CO2, it is crucial to maintain or enhance sink activity and understand the CO2 response mechanisms at the molecular, physiological, and morphological levels. This review provides an update on the short- and long-term responses of gs, gm, electron transport system, and carbon assimilation metabolism to elevated CO2. Furthermore, it offers a perspective on improving crop production in the future with elevated CO2 levels.

Phytoplankton primary production in Chascomus pond (Provincia de Buenos Aires, Argentina)

In situ phytoplankton primary production in Chascomús pond (eutrophic Pampasic “laguna”) was studied by the oxygen method (light and dark bottle) between.January 1984-January 1985. Valúes obtained ranged from37,9 to 981,6 mg C • m-1 • d-1. Factors influencing it, as suspended particulate matter and hydrological changes, are discussed. Parallel determinations of the artificial light photosynthesis response proved to be useful,almostqualitatively under the experimental conditions applied, to follow the behaviour obtained by incubations in natural environment.

Increased photosynthesis during spring drought in energy-limited ecosystems

Drought is often thought to reduce ecosystem photosynthesis. However, theory suggests there is potential for increased photosynthesis during meteorological drought, especially in energy-limited ecosystems. Here, we examine the response of photosynthesis (gross primary productivity, GPP) to meteorological drought across the water-energy limitation spectrum. We find a consistent increase in eddy covariance GPP during spring drought in energy-limited ecosystems (83% of the energy-limited sites). Half of spring GPP sensitivity to precipitation was predicted solely from the wetness index (R2 = 0.47, p < 0.001), with weaker relationships in summer and fall. Our results suggest GPP increases during spring drought for 55% of vegetated Northern Hemisphere lands ( >30° N). We then compare these results to terrestrial biosphere model outputs and remote sensing products. In contrast to trends detected in eddy covariance data, model mean GPP always declined under spring precipitation deficits after controlling for air temperature and light availability. While remote sensing products captured the observed negative spring GPP sensitivity in energy-limited ecosystems, terrestrial biosphere models proved insufficiently sensitive to spring precipitation deficits.