scholarly journals The Optical Properties of Leaf Structural Elements and Their Contribution to Photosynthetic Performance and Photoprotection

Plants ◽  
2021 ◽  
Vol 10 (7) ◽  
pp. 1455
Author(s):  
George Karabourniotis ◽  
Georgios Liakopoulos ◽  
Panagiota Bresta ◽  
Dimosthenis Nikolopoulos
Keyword(s):  
Glandular Trichomes ◽  
Spectral Band ◽  
Co2 Assimilation ◽  
Photosynthetic Performance ◽  
Structural Elements ◽  
Internal Layers ◽  
Water Losses ◽  
Light Gradient ◽  
Propagation Of Light ◽  
Light Capture

Leaves have evolved to effectively harvest light, and, in parallel, to balance photosynthetic CO2 assimilation with water losses. At times, leaves must operate under light limiting conditions while at other instances (temporally distant or even within seconds), the same leaves must modulate light capture to avoid photoinhibition and achieve a uniform internal light gradient. The light-harvesting capacity and the photosynthetic performance of a given leaf are both determined by the organization and the properties of its structural elements, with some of these having evolved as adaptations to stressful environments. In this respect, the present review focuses on the optical roles of particular leaf structural elements (the light capture module) while integrating their involvement in other important functional modules. Superficial leaf tissues (epidermis including cuticle) and structures (epidermal appendages such as trichomes) play a crucial role against light interception. The epidermis, together with the cuticle, behaves as a reflector, as a selective UV filter and, in some cases, each epidermal cell acts as a lens focusing light to the interior. Non glandular trichomes reflect a considerable part of the solar radiation and absorb mainly in the UV spectral band. Mesophyll photosynthetic tissues and biominerals are involved in the efficient propagation of light within the mesophyll. Bundle sheath extensions and sclereids transfer light to internal layers of the mesophyll, particularly important in thick and compact leaves or in leaves with a flutter habit. All of the aforementioned structural elements have been typically optimized during evolution for multiple functions, thus offering adaptive advantages in challenging environments. Hence, each particular leaf design incorporates suitable optical traits advantageously and cost-effectively with the other fundamental functions of the leaf.

scholarly journals Photorespiration Alleviates Photoinhibition of Photosystem I under Fluctuating Light in Tomato

Plants ◽  
2022 ◽  
Vol 11 (2) ◽  
pp. 195
Author(s):  
Qi Shi ◽  
Hu Sun ◽  
Stefan Timm ◽  
Shibao Zhang ◽  
Wei Huang
Keyword(s):  
Electron Transport ◽  
Photosystem I ◽  
Light Stress ◽  
Co2 Assimilation ◽  
Photosynthetic Performance ◽  
High Light ◽  
Sudden Increase ◽  
Fluctuating Light ◽  
Significant Difference ◽  
The Difference

Fluctuating light (FL) is a typical natural light stress that can cause photodamage to photosystem I (PSI). However, the effect of growth light on FL-induced PSI photoinhibition remains controversial. Plants grown under high light enhance photorespiration to sustain photosynthesis, but the contribution of photorespiration to PSI photoprotection under FL is largely unknown. In this study, we examined the photosynthetic performance under FL in tomato (Lycopersicon esculentum) plants grown under high light (HL-plants) and moderate light (ML-plants). After an abrupt increase in illumination, the over-reduction of PSI was lowered in HL-plants, resulting in a lower FL-induced PSI photoinhibition. HL-plants displayed higher capacities for CO2 fixation and photorespiration than ML-plants. Within the first 60 s after transition from low to high light, PSII electron transport was much higher in HL-plants, but the gross CO2 assimilation rate showed no significant difference between them. Therefore, upon a sudden increase in illumination, the difference in PSII electron transport between HL- and ML-plants was not attributed to the Calvin–Benson cycle but was caused by the change in photorespiration. These results indicated that the higher photorespiration in HL-plants enhanced the PSI electron sink downstream under FL, which mitigated the over-reduction of PSI and thus alleviated PSI photoinhibition under FL. Taking together, we here for the first time propose that photorespiration acts as a safety valve for PSI photoprotection under FL.

scholarly journals PYRACLOSTROBIN PRESERVES PHOTOSYNTHESIS IN ARABICA COFFEE PLANTS SUBJECTED TO WATER DEFICIT

2020 ◽  
Vol 28 ◽  
pp. 109-119
Author(s):  
Anelisa Figueiredo Peloso ◽  
Sandro Dan Tatagiba ◽  
Francisco José Teixeira Amaral ◽  
Paulo César Cavatte ◽  
José Eduardo Macedo Pezzopane
Keyword(s):  
Quantum Yield ◽  
Water Deficit ◽  
Chlorophyll A ◽  
Co2 Concentration ◽  
Co2 Assimilation ◽  
Photosynthetic Performance ◽  
Effective Quantum Yield ◽  
Fluorescence Maximum ◽  
Common Strategy ◽  
Coffee Plants

The objective of this study was to investigate the effect of pyraclostrobin on the photosynthetic performance of rabica coffee plants subjected or not to a water deficit, using the parameter of gas exchange (net CO2 assimilation, stomatal conductance, transpiration rate, and internal CO2 concentration and nocturnal respiration), chlorophyll fluorescence a parameters (minimum fluorescence, maximum fluorescence, maximum quantum yield of photosystem II, effective quantum yield of PSII, quantum yield of regulated energy dissipation and quantum yield dissipation non-regulated) as well as the concentrations of chloroplast pigments. In the plants maintained without water deficit, pyraclostrobin did not cause any alteration on the parameters of chlorophyll a fluorescence; however, it contributed to an increase in the level of chlorophyll a + b, CO2 assimilation and CO2 influx for the carboxylation sites of the stroma. Decreases in nocturnal respiration in plants treated with pyraclostrobin, submitted or not to water deficit seems to be a common strategy in reducing energy waste in the maintenance metabolism. Under water deficit, pyraclostrobin contributed to increase the photochemical yield, enabling plants to effectively prevent the capture, use and dissipation of light energy.

scholarly journals Far-Red Light Accelerates Photosynthesis in the Low-Light Phases of Fluctuating Light

2019 ◽  
Vol 61 (1) ◽  
pp. 192-202 ◽  
Author(s):  
Masaru Kono ◽  
Hikaru Kawaguchi ◽  
Naoki Mizusawa ◽  
Wataru Yamori ◽  
Yoshihiro Suzuki ◽  
...  
Keyword(s):  
Red Light ◽  
Atp Synthesis ◽  
Co2 Assimilation ◽  
Photosynthetic Performance ◽  
Antenna System ◽  
Photochemical Quenching ◽  
Low Light ◽  
Yield Increase ◽  
Fluctuating Light ◽  
Psii Photochemistry

Abstract It is well known that far-red light (FR; >700 nm) drives PSI photochemistry, but its effect on photosynthetic performance has received little attention. In this study, the effects of the addition of FR to red fluctuating light (FL) have on photosynthesis were examined in the leaves of Arabidopsis thaliana. Light-activated leaves were illuminated with FL [alternating high light/low light (HL/LL) at 800/30 μmol m−2 s−1] for 10–15 min without or with FR at intensities that reflected natural conditions. The CO2 assimilation rates upon the transition from HL to LL were significantly greater with FR than without FR. The enhancement of photosynthesis by FR was small under the steady-state conditions and in the HL phases of FL. Proton conductivity through the thylakoid membrane (gH+) in the LL phases of FL, estimated from the dark relaxation kinetics of the electrochromic absorbance shift, was greater with FR than without FR. The relaxation of non-photochemical quenching (NPQ) in the PSII antenna system and the increase in PSII photochemistry in the LL phases accelerated in the presence of FR. Similar FR-effects in FL were confirmed in typical sun and shade plants. On the basis of these results, we concluded that FR exerted beneficial effects on photosynthesis in FL by exciting PSI and accelerating NPQ relaxation and PSII-yield increase. This was probably because of the increased gH+, which would reflect faster ΔpH dissipation and ATP synthesis.

scholarly journals Photosynthesis and Growth of Pennisetum centrasiaticum (C4) is Superior to Calamagrostis pseudophragmites (C3) during Drought and Recovery

Plants ◽  
2020 ◽  
Vol 9 (8) ◽  
pp. 991
Author(s):  
Yayong Luo ◽  
Xueyong Zhao ◽  
Ginger R. H. Allington ◽  
Lilong Wang ◽  
Wenda Huang ◽  
...  
Keyword(s):  
Drought Stress ◽  
Water Status ◽  
Regional Climate ◽  
Co2 Assimilation ◽  
Photosynthetic Performance ◽  
Thermal Dissipation ◽  
Plant Responses ◽  
C4 Plant ◽  
C3 Plant ◽  
Ecosystem Level

Global warming and changes in rainfall patterns may put many ecosystems at risk of drought. These stressors could be particularly destructive in arid systems where species are already water-limited. Understanding plant responses in terms of photosynthesis and growth to drought and rewatering is essential for predicting ecosystem-level responses to climate change. Different drought responses of C3 and C4 species could have important ecological implications affecting interspecific competition and distribution of plant communities in the future. For this study, C4 plant Pennisetum centrasiaticum and C3 plant Calamagrostis pseudophragmites were subjected to progressive drought and subsequent rewatering in order to better understand their differential responses to regional climate changes. We tracked responses in gas exchange, chlorophyll fluorescence, biomass as well as soil water status in order to investigate the ecophysiological responses of these two plant functional types. Similar patterns of photosynthetic regulations were observed during drought and rewatering for both psammophytes. They experienced stomatal restriction and nonstomatal restriction successively during drought. Photosynthetic performance recovered to the levels in well-watered plants after rewatering for 6–8 days. The C4 plant, P. centrasiaticum, exhibited the classic CO2-concentrating mechanism and more efficient thermal dissipation in the leaves, which confers more efficient CO2 assimilation and water use efficiency, alleviating drought stress, maintaining their photosynthetic advantage until water deficits became severe and quicker recovery after rewatering. In addition, P. centrasiaticum can allocate a greater proportion of root biomass in case of adequate water supply and a greater proportion of above-ground biomass in case of drought stress. This physiological adaptability and morphological adjustment underline the capacity of C4 plant P. centrasiaticum to withstand drought more efficiently and recover upon rewatering more quickly than C. pseudophragmites and dominate in the Horqin Sandy Land.

scholarly journals Photosynthetic responses of young cashew plants to varying environmental conditions

2005 ◽  
Vol 40 (8) ◽  
pp. 735-744 ◽  
Author(s):  
Rogéria Pereira de Souza ◽  
Rafael Vasconcelos Ribeiro ◽  
Eduardo Caruso Machado ◽  
Ricardo Ferraz de Oliveira ◽  
Joaquim Albenísio Gomes da Silveira
Keyword(s):  
Gas Exchange ◽  
Intercellular Co2 Concentration ◽  
Co2 Concentration ◽  
Co2 Assimilation ◽  
Photon Flux ◽  
Photochemical Quenching ◽  
Photon Flux Density ◽  
Effective Quantum Yield ◽  
Water Losses ◽  
Controlled Conditions

The aim of this study was to characterize gas exchange responses of young cashew plants to varying photosynthetic photon flux density (PPFD), temperature, vapor-pressure deficit (VPD), and intercellular CO2 concentration (Ci), under controlled conditions. Daily courses of gas exchange and chlorophyll a fluorescence parameters were measured under natural conditions. Maximum CO2 assimilation rates, under optimal controlled conditions, were about 13 mmol m-2 s-1 , with light saturation around 1,000 mmol m-2 s-1. Leaf temperatures between 25ºC and 35ºC were optimal for photosynthesis. Stomata showed sensitivity to CO2, and a closing response with increasing Ci. Increasing VPD had a small effect on CO2 assimilation rates, with a small decrease above 2.5 kPa. Stomata, however, were strongly affected by VPD, exhibiting gradual closure above 1.5 kPa. The reduced stomatal conductances at high VPD were efficient in restricting water losses by transpiration, demonstrating the species adaptability to dry environments. Under natural irradiance, CO2 assimilation rates were saturated in early morning, following thereafter the PPFD changes. Transient Fv/Fm decreases were registered around 11h, indicating the occurrence of photoinhibition. Decreases of excitation capture efficiency, decreases of effective quantum yield of photosystem II, and increases in non-photochemical quenching were consistent with the occurrence of photoprotection under excessive irradiance levels.

Seasonal photosynthesis and anthocyanin production in 10 broadleaf evergreen species

2007 ◽  
Vol 34 (12) ◽  
pp. 1072 ◽  
Author(s):  
Nicole M. Hughes ◽  
William K. Smith
Keyword(s):  
Gas Exchange ◽  
Chlorophyll Content ◽  
Chlorophyll A ◽  
Photosynthetic Capacity ◽  
Photosynthetic Performance ◽  
Evergreen Species ◽  
Maximum Light ◽  
Anthocyanin Pigments ◽  
Anthocyanin Production ◽  
Light Capture

Leaves of many evergreen species turn red when exposed to high sunlight during winter due to production of photoprotective anthocyanin pigments, while leaves of other species, lacking anthocyanin, remain green. Why some evergreen species synthesise anthocyanin pigments while others do not is currently unknown. Furthermore, the relative photosynthetic performance of anthocyanic (red) and acyanic (green) evergreens has yet to be described. Here we present seasonal ecophysiological data for five red and green broadleaf evergreen species. We hypothesise that species which synthesise anthocyanins in winter leaves correspond to those with the most drastic seasonal photosynthetic declines, as reduced energy sinks increase vulnerability to photoinhibition and need for photoprotection. Our results did not support this hypothesis, as gas exchange measurements showed no difference in mean seasonal photosynthetic capacity between red- and green-leafed species. Consistent with anthocyanin’s shading effect, red-leafed species had significantly higher chlorophyll content, lower chlorophyll a/b ratios, and higher maximum light capture efficiency of PSII (Fv/Fm) than green-leafed species during the winter, but not during the summer (when all leaves were green). We conclude that anthocyanin production during winter is likely not associated with diminished photosynthetic capacity, and may simply represent an alternative photoprotective strategy utilised by some species during winter.

scholarly journals Efficient Regulation of CO2 Assimilation Enables Greater Resilience to High Temperature and Drought in Maize

2021 ◽  
Vol 12 ◽  
Author(s):  
Pedro M. P. Correia ◽  
Anabela Bernardes da Silva ◽  
Margarida Vaz ◽  
Elizabete Carmo-Silva ◽  
Jorge Marques da Silva
Keyword(s):  
High Temperature ◽  
Drought Stress ◽  
Heat Tolerance ◽  
Food Production ◽  
Carbon Fixation ◽  
Electron Transport Rate ◽  
Carbon Assimilation ◽  
Co2 Assimilation ◽  
Photosynthetic Performance

Increasing temperatures and extended drought episodes are among the major constraints affecting food production. Maize has a relatively high temperature optimum for photosynthesis compared to C3 crops, however, the response of this important C4 crop to the combination of heat and drought stress is poorly understood. Here, we hypothesized that resilience to high temperature combined with water deficit (WD) would require efficient regulation of the photosynthetic traits of maize, including the C4–CO2 concentrating mechanism (CCM). Two genotypes of maize with contrasting levels of drought and heat tolerance, B73 and P0023, were acclimatized at high temperature (38°C versus 25°C) under well-watered (WW) or WD conditions. The photosynthetic performance was evaluated by gas exchange and chlorophyll a fluorescence, and in vitro activities of key enzymes for carboxylation (phosphoenolpyruvate carboxylase), decarboxylation (NADP-malic enzyme), and carbon fixation (Rubisco). Both genotypes successfully acclimatized to the high temperature, although with different mechanisms: while B73 maintained the photosynthetic rates by increasing stomatal conductance (gs), P0023 maintained gs and showed limited transpiration. When WD was experienced in combination with high temperatures, limited transpiration allowed water-savings and acted as a drought stress avoidance mechanism. The photosynthetic efficiency in P0023 was sustained by higher phosphorylated PEPC and electron transport rate (ETR) near vascular tissues, supplying chemical energy for an effective CCM. These results suggest that the key traits for drought and heat tolerance in maize are limited transpiration rate, allied with a synchronized regulation of the carbon assimilation metabolism. These findings can be exploited in future breeding efforts aimed at improving maize resilience to climate change.

scholarly journals Photosynthetic performance of contrasting Jatropha curcas genotypes during the flowering and fruiting stages

2018 ◽  
Vol 53 (1) ◽  
pp. 10-21
Author(s):  
Gisele Pereira Domiciano ◽  
Adilson Kenji Kobayashi ◽  
Hugo Bruno Correa Molinari ◽  
Bruno Galveas Laviola ◽  
Alexandre Alonso Alves
Keyword(s):  
Jatropha Curcas ◽  
Block Design ◽  
Co2 Assimilation ◽  
Photosynthetic Performance ◽  
Sink Strength ◽  
Gas Exchange Parameters ◽  
Physiological Processes ◽  
Net Co2 Assimilation ◽  
Genetically Determined ◽  
Positive Effect

Abstract: The objective of this work was to evaluate physiological processes in contrasting physic nut (Jatropha curcas) genotypes during the flowering and fruiting stages. Gas exchange parameters were measured using an infrared gas analyzer, and morphological traits were evaluated during each stage under natural conditions, in a randomized complete block design with five replicates. Differences in yield between J. curcas accessions were not related to photosynthetic performance, but rather to the number of inflorescences and female flowers, which are genetically determined. Moreover, the net CO2 assimilation was equivalent in both genotypes, although they produced different amount of fruit. The genotypes differed consistently in terms of carboxylation efficiency and ribulose bisphosphate regeneration. Finally, J. curcas branch growth is not impaired by the increased sink strength during fruiting, and fruit may have been actually exerting a positive effect on the net CO2 assimilation, which may have enabled plants to maintain growth while producing flowers and fruits.

Fluxes of carbon dioxide and water vapour over a C4 pasture in southwestern Amazonia (Brazil)

1998 ◽  
Vol 25 (5) ◽  
pp. 519 ◽  
Author(s):  
John Grace ◽  
Jon Lloyd ◽  
Antonio Carlos Miranda ◽  
Heloisa Miranda ◽  
J.H.C. Gash
Keyword(s):  
Water Vapour ◽  
Intercellular Co2 Concentration ◽  
Nutrient Status ◽  
Co2 Concentration ◽  
Co2 Assimilation ◽  
Daily Basis ◽  
Photosynthetic Performance ◽  
Wet Season ◽  
Area Index ◽  
C4 Grass

In Brazil, pastures for cattle ranching are being established in areas that were previously forested. To investigate some consequences of this change in land use we measured fluxes of CO2 and water vapour over a typical pasture, dominated by the introduced C4 grass Brachiaria brizantha. In addition, we compared the CO2, water vapour fluxes and canopy stomatal conductances observed with those obtained simultaneously over a nearby undisturbed rain forest. Measurements were made near the end of the wet season under conditions of ample soil moisture. Leaf area index of the pasture was 3.9. The pasture had a lower canopy stomatal conductance than the forest (typically 0.2–0.3 mol m-2 s-1 versus 0.4–0.9 mol m-2 s-1 at high photon irradiance) and was less responsive to the canopy-to-air vapour pressure difference. As a consequence of these lower canopy stomatal conductances, the pasture used much less water than the forest with average values over the period examined being 153 mol H2O m-2 d-1 and 249 mol H2O m-2 d-1 for pasture and forest respectively (2.74 and 4.48 mm d-1 respectively). This was also reflected by differing fractions of the absorbed energy being dissipated as evaporation. This proportion was typically 0.56 for the pasture and 0.74 for the forest. After allowing for soil and plant respiration, average daily photosynthetic rates were 0.67 mol C m-2 d-1 for the pasture and 0.57 mol C m-2 d-1for the forest (8.0 and 6.8 g C m-2 d-1, respectively). Thus, despite an appreciably lower rate of water use the pasture assimilated more carbon on a daily basis. Nevertheless, Brachiaria displayed a somewhat lower rate of photosynthesis than expected for a C4 grass, perhaps because of a low nutrient status. Indeed, at low and medium photon irradiance the pasture and forest showed remarkably similar photosynthetic performance. There was, however, less tendency for CO2 assimilation rates of the pasture canopy to saturate at high photon irradiance. The respiratory fluxes from the two ecosystems at night were quite similar, 6–8 µmol m-2 s-1. The ratio of intercellular CO2 concentration to ambient CO2 concentration was usually 0.4 to 0.6 for the pasture, a range which is higher than that often reported for C4 plants but possibly not unusual for tropical grasses in their natural environment.

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