Plant carbon metabolism and climate change Dusenge, Mirindi Eric; Duarte, André Galvao; Way, Danielle A.
New phytologist,
January 2019, Letnik:
221, Številka:
1
Journal Article
Recenzirano
Odprti dostop
Plant carbon metabolism is impacted by rising CO2 concentrations and temperatures, but also feeds back onto the climate system to help determine the trajectory of future climate change. Here we ...review how photosynthesis, photorespiration and respiration are affected by increasing atmospheric CO2 concentrations and climate warming, both separately and in combination. We also compile data from the literature on plants grown at multiple temperatures, focusing on net CO2 assimilation rates and leaf dark respiration rates measured at the growth temperature (A
growth and R
growth, respectively). Our analyses show that the ratio of A
growth to R
growth is generally homeostatic across a wide range of species and growth temperatures, and that species that have reduced A
growth at higher growth temperatures also tend to have reduced R
growth, while species that show stimulations in A
growth under warming tend to have higher R
growth in the hotter environment. These results highlight the need to study these physiological processes together to better predict how vegetation carbon metabolism will respond to climate change.
Increasing temperatures should facilitate the poleward movement of species distributions through a variety of processes, including increasing the growing season length. However, in temperate and ...boreal latitudes, temperature is not the only cue used by trees to determine seasonality, as changes in photoperiod provide a more consistent, reliable annual signal of seasonality than temperature. Here, we discuss how day length may limit the ability of tree species to respond to climate warming in situ, focusing on the implications of photoperiodic sensing for extending the growing season and affecting plant phenology and growth, as well as the potential role of photoperiod in controlling carbon uptake and water fluxes in forests. We also review whether there are patterns across plant functional types (based on successional strategy, xylem anatomy and leaf morphology) in their sensitivity to photoperiod that we can use to predict which species or groups might be more successful in migrating as the climate warms, or may be more successfully used for forestry and agriculture through assisted migration schemes.
Predictions of how temperate and boreal forests will respond to climate warming often rely on the assumption that temperature will extend the growing season and drive migration to higher latitudes. But in many cases, these responses are also affected by photoperiod, and day length cues may constrain the ability of high latitude forests to respond to climate change as currently predicted. Here we review how photoperiod signals interact with temperature to affect tree phenology, physiological processes, and the potential for species to migrate in a warmer climate.
Most plants show considerable capacity to adjust their photosynthetic characteristics to their growth temperatures (temperature acclimation). The most typical case is a shift in the optimum ...temperature for photosynthesis, which can maximize the photosynthetic rate at the growth temperature. These plastic adjustments can allow plants to photosynthesize more efficiently at their new growth temperatures. In this review article, we summarize the basic differences in photosynthetic reactions in C
3
, C
4
, and CAM plants. We review the current understanding of the temperature responses of C
3
, C
4
, and CAM photosynthesis, and then discuss the underlying physiological and biochemical mechanisms for temperature acclimation of photosynthesis in each photosynthetic type. Finally, we use the published data to evaluate the extent of photosynthetic temperature acclimation in higher plants, and analyze which plant groups (i.e., photosynthetic types and functional types) have a greater inherent ability for photosynthetic acclimation to temperature than others, since there have been reported interspecific variations in this ability. We found that the inherent ability for temperature acclimation of photosynthesis was different: (1) among C
3
, C
4
, and CAM species; and (2) among functional types within C
3
plants. C
3
plants generally had a greater ability for temperature acclimation of photosynthesis across a broad temperature range, CAM plants acclimated day and night photosynthetic process differentially to temperature, and C
4
plants was adapted to warm environments. Moreover, within C
3
species, evergreen woody plants and perennial herbaceous plants showed greater temperature homeostasis of photosynthesis (i.e., the photosynthetic rate at high-growth temperature divided by that at low-growth temperature was close to 1.0) than deciduous woody plants and annual herbaceous plants, indicating that photosynthetic acclimation would be particularly important in perennial, long-lived species that would experience a rise in growing season temperatures over their lifespan. Interestingly, across growth temperatures, the extent of temperature homeostasis of photosynthesis was maintained irrespective of the extent of the change in the optimum temperature for photosynthesis (
T
opt
), indicating that some plants achieve greater photosynthesis at the growth temperature by shifting
T
opt
, whereas others can also achieve greater photosynthesis at the growth temperature by changing the shape of the photosynthesis–temperature curve without shifting
T
opt
. It is considered that these differences in the inherent stability of temperature acclimation of photosynthesis would be reflected by differences in the limiting steps of photosynthetic rate.
While interest in photosynthetic thermal acclimation has been stimulated by climate warming, comparing results across studies requires consistent terminology. We identify five types of photosynthetic ...adjustments in warming experiments: photosynthesis as measured at the high growth temperature, the growth temperature, and the thermal optimum; the photosynthetic thermal optimum; and leaf-level photosynthetic capacity. Adjustments of any one of these variables need not mean a concurrent adjustment in others, which may resolve apparently contradictory results in papers using different indicators of photosynthetic acclimation. We argue that photosynthetic thermal acclimation (i.e., that benefits a plant in its new growth environment) should include adjustments of both the photosynthetic thermal optimum (T ₒₚₜ) and photosynthetic rates at the growth temperature (A gᵣₒwₜₕ), a combination termed constructive adjustment. However, many species show reduced photosynthesis when grown at elevated temperatures, despite adjustment of some photosynthetic variables, a phenomenon we term detractive adjustment. An analysis of 70 studies on 103 species shows that adjustment of T ₒₚₜ and A gᵣₒwₜₕ are more common than adjustment of other photosynthetic variables, but only half of the data demonstrate constructive adjustment. No systematic differences in these patterns were found between different plant functional groups. We also discuss the importance of thermal acclimation of respiration for net photosynthesis measurements, as respiratory temperature acclimation can generate apparent acclimation of photosynthetic processes, even if photosynthesis is unaltered. We show that while dark respiration is often used to estimate light respiration, the ratio of light to dark respiration shifts in a non-predictable manner with a change in leaf temperature.
Plant heat stress: Concepts directing future research Jagadish, S.V. Krishna; Way, Danielle A.; Sharkey, Thomas D.
Plant, cell & environment/Plant, cell and environment,
July 2021, Letnik:
44, Številka:
7
Journal Article
Recenzirano
Odprti dostop
Predicted increases in future global temperatures require us to better understand the dimensions of heat stress experienced by plants. Here we highlight four key areas for improving our approach ...towards understanding plant heat stress responses. First, although the term ‘heat stress’ is broadly used, that term encompasses heat shock, heat wave and warming experiments, which vary in the duration and magnitude of temperature increase imposed. A greater integration of results and tools across these approaches is needed to better understand how heat stress associated with global warming will affect plants. Secondly, there is a growing need to associate plant responses to tissue temperatures. We review how plant energy budgets determine tissue temperature and discuss the implications of using leaf versus air temperature for heat stress studies. Third, we need to better understand how heat stress affects reproduction, particularly understudied stages such as floral meristem initiation and development. Fourth, we emphasise the need to integrate heat stress recovery into breeding programs to complement recent progress in improving plant heat stress tolerance. Taken together, we provide insights into key research gaps in plant heat stress and provide suggestions on addressing these gaps to enhance heat stress resilience in plants.
Predicted increases in future global temperatures require us to better understand the dimensions of heat stress experienced by plants. Here we highlight four key areas for improving our approach towards understanding plant heat stress responses.
Earth is currently undergoing a global increase in atmospheric vapor pressure deficit (VPD), a trend which is expected to continue as climate warms. This phenomenon has been associated with ...productivity decreases in ecosystems and yield penalties in crops, with these losses attributed to photosynthetic limitations arising from decreased stomatal conductance. Such VPD increases, however, have occurred over decades, which raises the possibility that stomatal acclimation to VPD plays an important role in determining plant productivity under high VPD. Furthermore, evidence points to more far‐ranging and complex effects of elevated VPD on plant physiology, extending to the anatomical, biochemical, and developmental levels, which could vary substantially across species. Because these complex effects are typically not considered in modeling frameworks, we conducted a quantitative literature review documenting temperature‐independent VPD effects on 112 species and 59 traits and physiological variables, in order to develop an integrated and mechanistic physiological framework. We found that VPD increase reduced yield and primary productivity, an effect that was partially mediated by stomatal acclimation, and also linked with changes in leaf anatomy, nutrient, and hormonal status. The productivity decrease was also associated with negative effects on reproductive development, and changes in architecture and growth rates that could decrease the evaporative surface or minimize embolism risk. Cross‐species quantitative relationships were found between levels of VPD increase and trait responses, and we found differences across plant groups, indicating that future VPD impacts will depend on community assembly and crop functional diversity. Our analysis confirms predictions arising from the hydraulic corollary to Darcy's law, outlines a systemic physiological framework of plant responses to rising VPD, and provides recommendations for future research to better understand and mitigate VPD‐mediated climate change effects on ecosystems and agro‐systems.
Earth is undergoing a global increase in atmospheric vapor pressure deficit (VPD) resulting from “air drying,” the effects of which on ecosystems and agro‐systems are poorly understood. Based on a meta‐analysis of data from 112 plant species across 59 traits, we find that VPD increases systematically reduce crop yields and non‐crop productivity. This reduction, observed under well‐watered conditions, arises from complex effects of VPD on various processes underlying plant physiology, several of which are not taken into account in current modeling efforts. The results point to the need for more research that takes into account this complexity to mitigate future VPD effects.
The global shortage of fresh water is one of our most severe agricultural problems, leading to dry and saline lands that reduce plant growth and crop yield. Here we review recent work highlighting ...the molecular mechanisms allowing some plant species and genotypes to maintain productivity under water stress conditions, and suggest molecular modifications to equip plants for greater production in water‐limited environments. Aquaporins (AQPs) are thought to be the main transporters of water, small and uncharged solutes, and CO2 through plant cell membranes, thus linking leaf CO2 uptake from the intercellular airspaces to the chloroplast with water loss pathways. AQPs appear to play a role in regulating dynamic changes of root, stem and leaf hydraulic conductivity, especially in response to environmental changes, opening the door to using AQP expression to regulate plant water‐use efficiency. We highlight the role of vascular AQPs in regulating leaf hydraulic conductivity and raise questions regarding their role (as well as tonoplast AQPs) in determining the plant isohydric threshold, growth rate, fruit yield production and harvest index. The tissue‐ or cell‐specific expression of AQPs is discussed as a tool to increase yield relative to control plants under both normal and water‐stressed conditions.
Here we review the role of vascular, mesophyll and tonoplast AQPs in regulating the plant isohydric threshold. The tissue specific and cell specific activity of AQPs in controlling the membrane water and/or CO2 permeability is discussed as a tool to increase yield under both normal and water‐stressed conditions.
To predict how forests will respond to rising temperatures and atmospheric CO₂concentrations, we need to understand how trees respond to both of these environmental factors. In this review, we ...discuss the importance of scaling, moving from leaf‐level responses to those of the canopy, and from short‐term to long‐term responses of vegetation to climate change. While our knowledge of leaf‐level, instantaneous responses of photosynthesis, respiration, stomatal conductance, transpiration and water‐use efficiency to elevated CO₂and temperature is quite good, our ability to scale these responses up to larger spatial and temporal scales is less developed. We highlight which physiological processes are least understood at various levels of study, and discuss how ignoring differences in the spatial or temporal scale of a physiological process impedes our ability to predict how forest carbon and water fluxes forests will be altered in the future. We also synthesize data from the literature to show that light respiration follows a generalized temperature response across studies, and that the light compensation point of photosynthesis is reduced by elevated growth CO₂. Lastly, we emphasize the need to move beyond single factorial experiments whenever possible, and to combine both CO₂and temperature treatments in studies of tree performance.
Rising atmospheric carbon dioxide (CO2) concentrations may warm northern latitudes up to 8°C by the end of the century. Boreal forests play a large role in the global carbon cycle, and the responses ...of northern trees to climate change will thus impact the trajectory of future CO2 increases. We grew two North American boreal tree species at a range of future climate conditions to assess how growth and carbon fluxes were altered by high CO2 and warming. Black spruce (Picea mariana, an evergreen conifer) and tamarack (Larix laricina, a deciduous conifer) were grown under ambient (407 ppm) or elevated CO2 (750 ppm) and either ambient temperatures, a 4°C warming, or an 8°C warming. In both species, the thermal optimum of net photosynthesis (ToptA) increased and maximum photosynthetic rates declined in warm‐grown seedlings, but the strength of these changes varied between species. Photosynthetic capacity (maximum rates of Rubisco carboxylation, Vcmax, and of electron transport, Jmax) was reduced in warm‐grown seedlings, correlating with reductions in leaf N and chlorophyll concentrations. Warming increased the activation energy for Vcmax and Jmax (EaV and EaJ, respectively) and the thermal optimum for Jmax. In both species, the ToptA was positively correlated with both EaV and EaJ, but negatively correlated with the ratio of Jmax/Vcmax. Respiration acclimated to elevated temperatures, but there were no treatment effects on the Q10 of respiration (the increase in respiration for a 10°C increase in leaf temperature). A warming of 4°C increased biomass in tamarack, while warming reduced biomass in spruce. We show that climate change is likely to negatively affect photosynthesis and growth in black spruce more than in tamarack, and that parameters used to model photosynthesis in dynamic global vegetation models (EaV and EaJ) show no response to elevated CO2.
We grew two North American boreal tree species, tamarack and black spruce, at a range of future climate conditions to assess how high carbon dioxide (CO2) and warming alter growth and physiology. Climate change negatively affected photosynthesis and growth in black spruce more than in tamarack. Photosynthetic capacity (maximum rates of Rubisco carboxylation, Vcmax, and of electron transport, Jmax) and respiration were reduced in warm‐grown seedlings, correlating with reductions in leaf N and chlorophyll concentrations. We also show that parameters used to model photosynthesis in dynamic global vegetation models (the activation energies of Vcmax and Jmax) showed no response to elevated CO2.
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