Photosynthetica最新文献

The impact of salt stress is becoming more prevalent each year, largely due to the effects of climate change. Limited availability of salt-free water is rising concern for hydroponics lettuce production. Despite evidence supporting salt stress-induced quality losses and physiological changes, studies on romaine lettuce salt-stress tolerance are limited. This study examined the mechanism underlying the sodium chloride (NaCl) tolerance (0, 50, 100, and 150 mM) of lettuce on its growth and nutrition at late-rosette and early head-formation stages. Results revealed 76% fresh mass reduction under increased NaCl at both stages. The study also found unchanged carbon assimilation with reduced stomatal conductance under increased NaCl. Salt-stressed lettuce accumulated more boron and iron but had reduced phosphorus and calcium. Phenolics and sugars increased linearly under salt stress, suggesting that lettuce responds to increased oxidative stress at both stages. A positive association between salt treatment and sodium to potassium ion ratio indicated lettuce sensitivity to salt stress at both stages.

A manipulative experiment with two different water regimes was established to identify the variability of physiological responses to environmental changes in 5-year-old Norway spruce provenances in the Western Carpathians. While variations in the growth responses were detected only between treatments, photosynthetic and biochemical parameters were also differently influenced among provenances. Following drought treatment, an obvious shrinkage of tree stems was observed. In most provenances, drought had a negative effect on leaf gas-exchange parameters and kinetics of chlorophyll a fluorescence. Secondary metabolism was not affected so much with notable differences in concentration of sabinene, o-cimene, and (-)-alpha-terpineol monoterpenes. The most suitable indicators of drought stress were abscisic acid and fluorescence parameters. Seedlings from the highest altitude (1,500 m a.s.l.) responded better to stress conditions than the other populations. Such provenance trials may be a valuable tool in assessing the adaptive potential of spruce populations under changing climate.

Cyclocarya paliurus has been traditionally used as a functional food in China. A hydroponic experiment was conducted to determine the effects of N and P additions on photosynthesis and chlorophyll fluorescence (ChlF) of C. paliurus seedlings. N and P additions significantly altered photosynthesis and ChlF in the seedlings, but responses of these parameters to the N and P concentrations varied at different developmental stages. The greatest net photosynthetic rate (P _N) and actual photochemical efficiency of PSII (Ф_PSII) occurred in the treatment of 150.0 mg(N) L^-1 and 25.0 mg(P) L^-1 addition, whereas the highest maximum quantum yield of PSII (F_v/F_m) and water-use efficiency (WUE) were recorded with 150.0 mg(N) L^-1 and 15.0 mg(P) L^-1 on the 60^th day after treatment. Significantly positive correlations of P _N with leaf relative chlorophyll content, transpiration rate, WUE, F_v/F_m, and Φ_PSII, as well as the Ф_PSII with the F_v/F_m, were found. Our results indicated that an optimal addition of N and P nutrients depends on their coupling effects on the photosynthetic capacity and PSII photochemistry.

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.