Changes In Photosynthetic Traits Research Articles

Anthocyanins act as a sugar-buffer and an alternative electron sink in response to starch depletion during leaf senescence: a case study on a typical anthocyanic tree species, Acer japonicum.

We hypothesized that anthocyanins act as a sugar-buffer and an alternative electron sink during leaf senescence to prevent sugar-mediated early senescence and photoinhibition. To elucidate the anthocyanin role, we monitored seasonal changes in photosynthetic traits, sugar, starch and N contents, pigment composition, and gene expression profiles in leaves exposed to substantially different light conditions within a canopy of an adult tree of fullmoon maple (Acer japonicum). Enhancement of starch amylolysis accompanied with cessation of starch synthesis occurred in the same manner independent of light conditions. Leaf sugar contents increased, but reached upper limits in the late stage of leaf senescence, even though leaf anthocyanins further increased after complete depletion of starch. Sun-exposed leaves maintained higher energy consumption via electron flow than shade-grown leaves during leaf N resorption. Thus, anthocyanins accumulated in sun-exposed leaves might have a regulative role as a sugar buffer, retarding leaf senescence, and an indirect photoprotective role as an alternative sink for electron consumption to compensate declines in other metabolic processes such as starch and protein synthesis. In this context, anthocyanins might be key substrates protecting both outer-canopy leaves (against photoinhibition) and inner-canopy leaves (via shading by outer-canopy leaves) from high light stress during N resorption.

Implications of seasonal changes in photosynthetic traits and leaf area index for canopy CO2 and H2O fluxes in a Japanese cedar (Cryptomeria japonica D. Don) plantation

Recently, requests for forest management to conserve water resources and sequester carbon have increased in Japan, where approximately 27% and 12% of the total land area are covered by forest plantations and Japanese cedar (Cryptomeria japonica D. Don). To formulate better forest management practices that maximize forest functions by maintaining water and carbon cycles, an understanding of how leaf-level ecophysiological traits influence canopy-level CO2 and H2O exchanges in Japanese cedar plantations is required. In this study, observations of eddy covariance flux and leaf ecophysiology in a Japanese cedar plantation in southern Japan indicate that significantly greater productivity and seasonal variations tend to occur in canopy CO2 and H2O fluxes, with seasonal patterns of photosynthetic traits (maximum carboxylation rate normalized at 25 °C, Vcmax,25) and leaf area index (LAI). We also examined how biotic (e.g., Vcmax,25 and LAI) and abiotic (e.g., meteorological variables) factors govern canopy fluxes using a multi-layer soil–vegetation–atmosphere transfer (SVAT) model. The model validation suggests that seasonal variations in Vcmax,25 and LAI must be included to reproduce the fluxes observed in the plantation. Quantitative experiments using the validated SVAT model indicate that considering cold acclimation during the winter improved the reproducibility of the model with regard to the measured fluxes, constant high intra-annual LAI had the least impact on forest productivity, and a consistently high Vcmax,25 value increased forest productivity but considerably decreased the nitrogen use efficiency and required a larger nitrogen supply from the ecosystem during the winter. These findings highlight the necessity of decreasing photosynthetic ability during the winter, which safeguards the ecosystem's nitrogen resources to sustain the productivity of the Japanese cedar plantation throughout the year.

The interspecific interactions in agroforestry systems enhance leaf water use efficiency and carbon storage in cocoa

Global climate changes include more intense and concentrated rainy seasons and severe and longer-lasting dry seasons. In this context, the benefits carried out within agroforestry systems (AFS) have played a significant role, especially for tropical crops such as cocoa. The present study evaluated the changes in photosynthetic traits and the physical, chemical, and microbiological soil properties in response to variations in the shading tree species. Three cocoa genotypes (CCN51, TCS01, and TCS19) were cultivated under three AFS designs, differing in the accompanying shade tree species ( Cariniana pyriformis , Tabebuia rosea, and Terminalia superba ). No significant differences in CO 2 assimilation rates among the different cocoa genotypes were observed. However, TCS01 exhibited a 20% higher leaf water use efficiency (WUEl) than the TCS19 genotype, associated with decreased stomatal conductance. The designs combining C. pyriformis with CCN51 and TCS01, as well as the design associating CCN51 with T. rosea, exhibited significantly higher WUEl for cocoa plants as compared to the systems involving T. superba combined with TCS19. In addition, the cocoa genotype TCS01 exhibited the highest potential for carbon storage when combined with C. pyriformis , whereas TCS19 exhibited the lowest potential for this feature under the T. superba association. The chemical, physical and biological properties of soils were evaluated, and an orthoPLS-DA multivariate analysis was performed to contrast the differences between TCS01 associated with C. pyriformis (higher WUEl and C sequestration) with the combination of TCS19 with T. superba (lower WUEl and carbon sequestration). The results highlight the importance of soil pH, [Al], [Mn], and [Mg] for a better physiological performance exhibited by TCS01 under C. pyriformis AFS as compared to TCS19 under T. superba . Thus, taken together the data obtained here suggest that species-genotype-dependent interactions in AFS-cocoa may determine soil characteristics, which may indirectly affect important physiological traits, such as leaf water use efficiency and long-term carbon storage of cocoa plants. • Advantageous interspecific interactions can generate improve leaf-level water use efficiency and carbon storage in cocoa. • Cocoa TCS01 associated with C pyriformis shows better leaf-level water use efficiency and carbon storage as compared with TCS19 associated with T. superba . • The evaluated shade tree species contrasted regarding their effects on the chemical features of adjacent soils. • Soil acidity, aluminium, manganese and magnesium concentrations were the soil features most correlated with the contrasts observed in the cocoa genotypes.

Changes in photosynthetic traits and their responses to increasing fertilization rates in soybean (Glycine max (L.) Merr.) during decades of genetic improvement

Changes in photosynthetic traits (PTs) during the long-term genetic improvement of soybean (Glycine max (L.) Merr.) yield have been studied, but detailed information on whether PT responses to environmental stress have improved, and their correlations with seed yield, are still unknown. Our objectives were to describe the changes in soybean PTs - leaf area index (LAI), leaf chlorophyll content (Chl), net photosynthetic rate (PN ), stomatal conductance (gs ), and transpiration rate (E) - during decades of genetic improvement, and to detect whether the responses to increasing fertilizer application rates (FRs) of the PTs of 13 different soybean cultivars released in various decades differed. All of the soybean PTs increased significantly along with the year in which each cultivar was released, under different FR treatments, indicating that PTs have improved during decades of genetic breeding. Medium FR (nitrogen) treatment (150 kg ha -1 ) increased PT values, to different extents, at all the investigated growth stages. Leaf area index, Chl, and PN of the old and middle cultivar groups at the full bloom (R2), full seed (R6), and beginning maturity (R7) stages decreased significantly under high FR treatment (300 kg ha-1 ) compared with the medium FR treatment. The former had no effect on any of the PTs of new cultivar group, or had promotive effects. Thus, the photosynthetic capacities of the new cultivars are more tolerant to high FR-related stress than older cultivars. The photosynthetic capacities, and tolerance to high FR-related stress, of soybean cultivars that were released in different years improved after long-term genetic breeding. © 2021 Society of Chemical Industry.

Seasonal changes in photosynthesis and starch content in Japanese fir (Abies firma Sieb. et Zucc.) saplings under different levels of irradiance

In response to irradiance seasonality, saplings under brighter conditions increased leaf biomass with high photosynthesis to realize high growth, whereas understory saplings depend on photosynthesis during canopy leaf fall, and larger root biomass contributed to storage. We studied the changes in photosynthesis, biomass partitioning, and starch content in Abies firma saplings in a mixed deciduous forest in southwest Japan. Saplings were examined under high, intermediate, and low irradiance levels. The relative irradiance at intermediate and low irradiance levels increased significantly during winter and spring due to leaf fall in the deciduous canopy trees. The maximum photosynthetic rates (P max) under low irradiance were lower than those under high irradiance throughout the year. The needle daily carbon balance in summer was negative under low irradiance, whereas the balance became positive in winter and spring due to increases in irradiance. The needle daily carbon balance in intermediate- and high-irradiance saplings remained positive year-round, although the midday photosynthetic depression suppressed the daily needle carbon gain under high irradiance. The starch content in needles, branches, and roots was higher in spring due to high photosynthetic production, and then decreased in summer under all irradiance levels. Root starch under low irradiance levels may be used to maintain carbon balance during summer, thereby contributing to survival. High needle biomass coupled with a high P max facilitated carbon gain under high and intermediate irradiance, whereas high relative root biomass under low irradiance may enhance storage ability. Overall, A. firma saplings seemed to acclimate to different irradiance levels with seasonal changes through changes in photosynthetic traits, starch storage, and biomass partitioning.

Responses of leafing phenology and photosynthesis to soil warming in forest-floor plants

Phenological and physiological responses of plants to climate change are key issues to understand the global change impact on ecosystems. To evaluate the species-specific responses, a soil-warming experiment was conducted for seven understory species having various leaf habits in a deciduous forest, northern Japan; one evergreen shrub, one semi-evergreen fern, one summer-deciduous shrub, and four summer-green herbs. Soil temperature in the warming plots was electrically maintained 5 °C higher than control plots. Responses of leafing phenology highly varied among species: new leaf emergence of the evergreen shrub was delayed; senescence of overwintering leaves of the semi-evergreen fern was accelerated resulting in the shift to deciduousness; leaf shedding of the summer-deciduous shrub was accelerated. Among four summer-green species, only an earliest leaf-out species advanced growth initiation, but the period of growth season was not changed. Physiological responses to soil warming were also highly species-specific: the warming treatment increased the photosynthetic activity of the summer-deciduous shrub and one summer-green species, decreased that of the semi-evergreen fern, while other species did not show any changes in photosynthetic traits. Totally, the soil warming impacts on understory plants was apparent in spring. It was suggested that modification of snow conditions is important issue especially for plants with overwintering leaves. Responses of understory vegetation to climate change may highly vary depending on the composition of leaf habits in the cool-temperate forests.

Population‐specific responses to light influence herbivory in the understory shrub Lindera benzoin

Plants display photosynthetic plasticity in response to variation in light environment, and the extent of this plasticity often varies with genotype, i.e., genotype x environment interaction. Herbivory may also covary with light environment as a result of light-induced changes in photosynthetic traits. For example, greater levels of photoprotective phenolic compounds in high-light environments may reduce host quality to herbivores. We investigated intraspecific variation in photosynthetic responses to light and its consequences for herbivory in the understory shrub, Lindera benzoin (Lauraceae). We transplanted five plants from eight populations (N = 240) into three replicate sun and shade common gardens. Two years after transplantation, we tested for population x light environment interactions in six photosynthesis-related responses: specific leaf area, water content, chlorophyll content, chlorophyll fluorescence (F(0)), maximum quantum yield (F(v)/F(m)), and total phenolics. We assessed seasonal herbivory and consumption by a specialist lepidopteran herbivore (Epimecis hortaria). This allowed us to test for (1) population-specific patterns of photosynthetic acclimation and photoinhibition, (2) population-specific production of phenolics in response to photoinhibition, and (3) population-specific photosynthetic responses that contribute to population x light environment interactions in herbivory. Population X light environment interactions were insignificant in leaf variables but statistically significant for herbivory measured as consumption by E. hortaria. We found similar trends for population x light environment interactions in seasonal herbivory. Total phenolics and minimum chlorophyll fluorescence (F(0)) were significant covariates with herbivory, but their effects depended on light environment and population of origin. High-light environments eliminated differences among populations in how these leaf variables affected herbivory, while population-specific relationships were apparent in the shade. Analysis of total phenolics revealed that they were likely induced by photoinhibition, but that this response varied among the populations we assessed. However, phenolics increased herbivory in L. benzoin, which would limit the fitness value of this protective response to light-induced photoinhibition. Our results suggest that herbivores could affect evolution of photosynthetic plasticity in L. benzoin.

Comparison of sapling-level daily light capture and carbon gain between a temperate deciduous and a co-occurring evergreen tree species in the growing season and in winter

Light capture efficiency (Ea) and mass-based daily carbon gain (Amass) were compared between saplings of a deciduous tree species, Ficus erecta Thunb. and the co-occurring evergreen broadleaved tree species, Neolitsea aciculata (Bl.) Koidzumi, in a temperate forest in Japan. Using obtained data and an ecophysiological–architectural model, we calculated the Ea and Amass of each study sapling. We also analysed the response of Amass to changes in photosynthetic traits and Ea. Saplings of F. erecta had a higher Amass than N. aciculata, due to the high leaf area : aboveground mass ratio (LAR). The model calculation suggested that changes in photosynthetic traits and Ea changed Amass but did not modify the interspecific difference of Amass. In winter Amass was lower than that in the growing season due to low light availability during the short day lenght, suggesting modest importance of winter carbon gain for the evergreen saplings of N. aciculata. In conclusion, the advantage of this deciduous species for carbon gain over the co-occurring evergreen broadleaved saplings is not modified by acclimative changes in leaf physiology, crown architecture or prolonged photosynthesis period by evergreen broadleaved trees.

Seasonal time-course of gradients of photosynthetic capacity and mesophyll conductance to CO2 across a beech (Fagus sylvatica L.) canopy

Leaf photosynthesis is known to acclimate to the actual irradiance received by the different layers of a canopy. This acclimation is usually described in terms of changes in leaf structure, and in photosynthetic capacity. Photosynthetic capacity is likely to be affected by mesophyll conductance to CO(2) which has seldom been assessed in tree species, and whose plasticity in response to local irradiance is still poorly known. Structural [N and chlorophyll content, leaf mass to area ratio (LMA)] and functional leaf traits [maximum carboxylation rate (V(cmax)), maximum light-driven electron flux (J(max)), and mesophyll conductance (g(i))] were assessed by measuring leaf response curves of net CO(2) assimilation versus intercellular CO(2) partial pressure, along a vertical profile across a beech canopy, and by fitting a version of the Farquhar model including g(i). The measurements were repeated five times during a growth season to catch potential seasonal variation. Irradiance gradients resulted in large decreasing gradients of LMA, g(i), V(cmax), and J(max). Relative allocation of leaf N to the different photosynthetic processes was only slightly affected by local irradiance. Seasonal changes after leaf expansion and before induction of leaf senescence were only minor. Structural equation modelling confirmed that LMA was the main driving force for changes in photosynthetic traits, with only a minor contribution of leaf Nitrogen content. In conclusion, mesophyll conductance to CO(2) displays a large plasticity that scales with photosynthetic capacity across a tree canopy, and that it is only moderately (if at all) affected by seasonal changes in the absence of significant soil water depletion.

Post-anthesis changes in photosynthetic traits of maize hybrids released in different years

Changes in post-anthesis physiological attributes related to genetic improvement for grain-yield were studied for six Chinese maize ( Zea mays L.) hybrids widely grown in North China during the past 50 years. The characteristics assessed included light-saturated photosynthetic rate ( P sat), chlorophyll content, soluble protein content, maximal efficiency of PS2 photochemistry ( F v/ F m), PS2 efficiency ( Φ PS2), ribulose-1,5-bisphosphate carboxylase (RuBPCase) activity and phosphoenolpyruvate carboxylase (PEPCase) activity. We found that P sat of the newer hybrids was not always higher than the older ones. However, P sat of the 1950s hybrids was the highest among all at flowering stage, which was associated with their high PEPCase activity and soluble protein content. Post-anthesis changes in P sat of the older hybrids can be divided into two phases. During the first phase, which was the decisive phase of grain filling, P sat of the older hybrids declined gradually whereas the new hybrids remained relatively constant. P sat of 1950s hybrids was not the highest among all maize hybrids any longer although their PEPCase activities were also the highest. The reduction in P sat of the older hybrids during this phase was associated with a reduction in the chlorophyll content and the soluble protein content but was not influenced by the specific activity of RuBPCase and PEPCase. Adapting to the lowered CO 2 assimilation capacity, a down-regulation of Φ PS2 occurred in the older hybrids to protect the photosynthetic apparatus from photo-damage by strong light, while F v/ F m only decreased slightly during this phase, suggesting a functional PS2 apparatus in senescent flag leaves. During the second phase, the older hybrids underwent an irreversible leaf senescence that certain photosynthetic traits declined substantially with P sat, whereas the photosynthetic components of the newer hybrids remained functional. Newer maize hybrids produced higher grain yield compared to the old ones mainly because they could remain photosynthetically active when the older hybrids aged during the grain-filling period. The decline in photosynthetic rate of older hybrids during senescence is generally attributed to the degradation of both structural and functional components of chloroplasts.