Photosynthetica最新文献

A 50-year-old solitary, sun-exposed ginkgo tree had strongly been pruned in the fall of 2021. Very few buds for the formation of new leaves, twigs, and branches were left over. In spring 2022, these few remaining buds responded with the formation of a different leaf type. These leaves were 2.7 times larger and also thicker than in the years before. In addition, the mean content of total chlorophylls [Chl (a+b)] per leaf area unit of dark-green leaves was 1.45, those of green leaves two times higher as compared to the years before pruning and the two other ginkgo trees which had been investigated in parallel. A comparable increase was also found for the level of total carotenoids (x+c). The mean content for Chl (a+b) were 1,118 mg m^-2 for dark-green and 898 mg m^-2 for green leaves as compared to 435 to 770 mg m^-2 in leaves of other trees. The higher values for Chl (a+b) and total carotenoid content showed up also on a fresh and dry mass basis. Thus, with the formation of a new, larger leaf type by changes in morphology (leaf size and thickness) and the increase of photosynthetic pigments, the pruned ginkgo tree was able to compensate for the much lower number of leaves and photosynthetic units.

Color-tuning is a critical survival mechanism for photosynthetic organisms. Calcium ions are believed to enhance both spectral tuning and thermostability in obligatory calcium-containing sulfur purple bacteria. This study examined the thermo- and piezo stability of the LH1-RC complexes from two calcium-containing sulfur purple bacteria notable for their extreme red-shifted spectra. The results generally show limited reversibility of both temperature and pressure effects related to the malleability of calcium-binding sites. While the pressure-induced decomposition product closely resembles the calcium-depleted form of the chromoproteins, the thermally induced products reveal monomeric B777 and dimeric B820 forms of bacteriochlorophyll a, similar to those seen in non-sulfur purple bacteria treated with detergent. The study further found nearly unison melting of the protein tertiary and secondary structures. Overall, our findings do not support a direct link between color adjustment and thermodynamic stability in light-harvesting chromoproteins.

Woody plant areal encroachment is pervasive throughout the Southern Great Plains, USA. The ability of woody plants to dissipate excess solar radiation - dynamically over the day and sustained periods without recovery overnight - is key for maintaining photosynthetic performance during dry stretches, but our understanding of these processes remains incomplete. Photosynthetic performance and energy dissipation were assessed for co-occurring encroachers on the karst Edwards Plateau (Juniperus ashei, Prosopis glandulosa, and Quercus fusiformis) under seasonal changes in water status. Only J. ashei experienced mild photoinhibition from sustained energy dissipation overnight while experiencing the lowest photochemical yields, minimal photosynthetic rates, and the highest dynamic energy dissipation rates at midday during the dry period - indicating susceptibility to photosynthetic downregulation and increased dissipation under future drought regimes. Neither other encroacher experienced sustained energy dissipation in the dry period, though P. glandulosa did experience marked reductions in photosynthesis, photochemical yields, and increased regulatory dynamic energy dissipation.

In many crops, including grapevine, the distribution of reflecting dust on foliage is a practice potentially leading to the mitigation of environmental stresses such as excessive light and limited water supply. This study aimed to evaluate whether the presence of dust on the leaves may affect PSII photochemical efficiency and gas-exchange measurements, thus leading to biased results. The study was conducted in a winery located at Benevento (Italy) on Vitis vinifera L. subsp. vinifera 'Falanghina' where the application of basalt dust was tested on the canopy to alleviate the effects of water stress. The results showed that there is no difference in PSII photochemistry or gas-exchange parameters measured in the presence of dust or after cleaning the leaves. Therefore, we conclude there is no need to remove dust from leaves before performing the ecophysiological investigations, thus fastening and simplifying the data collection.

Natural SiO₂ nanoparticles (SiO₂-NPs) are widely distributed in the environment, and at the same time, synthetic SiO₂-NP may be applied in agriculture. Evaluations of physiological responses to SiO₂-NPs treatment of plants are controversial. They are often performed at adaxial leaf sides whereas NPs permeate leaf tissues through stomata located at the abaxial leaf side in the majority of bifacial plants. We measured coefficients of the functional dorsoventral asymmetry of NPs-stressed Chelidonium majus leaves, S, by values of the CO₂ assimilation rate (SP _N), dark respiration (SR), maximal and operating quantum yields of photosystem II (SF_v/F_m, SF_v'/F_m'; using PAM-fluorometry), and oxygen coefficients of photosynthesis (SΨ_O2; using photoacoustics). The results indicated that SP _N and SΨ_O2 were significantly influenced by SiO₂-NPs treatment, since P _N and Ψ_O2 were declining more markedly when the light was directed to the abaxial side of leaves compared to the adaxial side. Overall, SiO₂-NPs-induced stress increased 'anoxygenity' of photosynthesis.

The study aims to understand the effect of UV exclusion and arbuscular mycorrhizal fungi (AMF) inoculation on the photosynthetic parameters of soybean. The study was conducted in nursery bags and plants were grown under iron mesh covered with UV cut-off filters. The plants grown under the exclusion of UV with AMF inoculation (I) showed higher photosynthetic pigments, carbonic anhydrase activity, reduced internal CO₂ concentration, enhanced transpiration rate, and stomatal conductance as well as improved photosynthetic rate over uninoculated plants. Moreover, -UVB+I and -UVAB+I plants exhibited an increased performance index, the activity of the water-splitting complex on the donor side of PSII, and the concentration of active PSII reaction centers per excited cross-section. Overall, UV-excluded and AMF-inoculated plants showed the highest quantum yield of PSII and rate of photosynthesis. Our study will pave the way for future investigation to identify the possible role of UV exclusion and AMF in improving the photosynthetic performance for better yield of soybean.

The mesophyll anatomical traits are essential factors for efficient light capture, CO₂ diffusion, and hydraulics in leaves. At the same time, leaf hydraulics are governed by the xylem anatomical traits. Thus, simultaneous analyses of the mesophyll and xylem anatomy will clarify the links among light capture, CO₂ capture, and water use. However, such simultaneous analyses have been scarcely performed, particularly on non-seed plants. Using seven fern species, we first showed that fern species with a large mesophyll thickness had a high photosynthetic rate related to high light capture, high drought tolerance, and low leaf hydraulic conductance. The chloroplast surface area (S_c) per mesophyll thickness significantly decreased with an increase in mesophyll thickness, which may increase light diffusion and absorption efficiency in each chloroplast. The photosynthetic rate per S_c was almost constant with mesophyll thickness, which suggests that ferns enhance their light capture ability via the regulation of chloroplast density.

We examined the morphological and physiological responses of Osmanthus fragrans 'Yingui' (Yin) and O. fragrans 'Jingui' (Jin) to different NaCl concentrations. NaCl concentrations significantly affected plant height and leaf mass per area. Total biomass decreased by 22.8-41.8% under moderate and high NaCl which inhibited O. fragrans growth. The ratio of root to shoot biomass in Yin was 44.3% higher than that in Jin at high NaCl concentrations which suggested that Yin possesses conservative resource acquisition strategies to resist salt stress. Compared to Yin, Jin showed higher net photosynthesis, stomatal conductance, and intercellular CO₂ concentration under high NaCl treatment. Jin exhibited also relatively higher proline, soluble sugar, K⁺ content, and K⁺/Na⁺ under the treatments implying that acquisitive resource acquisition may be the main strategy for salt resistance in Jin. Our results demonstrated that Yin and Jin could be cultivated in saline land in a short time and the two cultivars respond to salinity by different morphological and physiological mechanisms.