Photosynthetica最新文献

Drought and heat stress significantly threaten forage crop development and photosynthetic activity in the Mediterranean region. This study investigated the physiological responses and photosynthetic activity of two Medicago truncatula lines TN6.18 and F83005.5 (F83), to single and combined heat and drought stress treatments. Biomass traits, leaf gas exchange, and photosystem activities were evaluated. Our findings indicate a reduction in biomass parameters under heat, drought, and combined stress on both lines, particularly in F83. The stomatal conductance and photosynthetic parameters exhibited differential responses, with F83 reducing its stomatal conductance under drought stress, while TN6.18 was adapted by opening its stomata. Moreover, in TN6.18, combined stress enhanced protection mechanisms in PSI, while F83 showed changes in PSII efficiency. These insights deepen our understanding of plant responses to abiotic stresses and offer strategies for improving tolerance and resilience in changing environmental conditions.

Transgenic tobacco, demonstrating bacterial cholesterol oxidase (CO) activity in the chloroplast, grown at PAR ~280 μmol(photon) m^-2s^-1 (low light), contained thylakoid membranes that include a greater variety of steroids and had reduced contents of sterol and sterol-esters per milligram chlorophyll in comparison to controls. The mature transgenic plants, grown at low light, demonstrate a ~3× larger root dry mass, ~3× larger stem dry mass, ~2× larger leaf dry mass, ~2× increased leaf number, and ~5× increased flower number than controls. Mature transgenic flowering plants, develop to first flower ~2× faster and grow ~30% taller than control flowering plants. The transgenic seedlings contain approximately 2× higher amounts of brassinolide (BR) per g fresh mass than controls. We propose that since the CO enzyme produces increased contents of oxidized steroids in the thylakoid membrane, this encourages enhanced photosynthesis, enhanced BR contents, and increased biomass accumulation.

This study evaluated the efficiency of green manure (+GM) on PSII efficiency throughout the day in Dalbergia ecastophyllum. The experiment was carried out in a disabled clay extraction deposit, located approximately 30 km south of São Mateus city (Espírito Santo State, Brazil). Chlorophyll (Chl) index, Chl a fluorescence, and plant growth were measured in the summer, after 12 months of planting. +GM improved the photochemical performance of D. ecastophyllum, reducing the occurrence of photoinhibition throughout the day. +GM increased the photochemical quantum yield, the probability of a photon absorbed to move beyond quinone Q_A ^-, and the total Chl index, resulting in higher plant height and stem diameter (+11.7 and +2.2%, respectively). The number of active reaction centers per cross-section and the performance index of PSII values were unchanged throughout the day. Full recovery of both K and L-bands occurred at night. In contrast, plants growing with -GM had higher energy losses as heat. In conclusion, these results contribute to improving revegetation techniques, to create better conditions for the planting of native tree species in degraded areas.

Strobilurin fungicides, such as pyraclostrobin (PCL), can impact plant metabolism and morphophysiological parameters. This study evaluated the effects of PCL on Phaseolus vulgaris L., subjecting seeds to imbibition in different concentrations (0, 112, 450; and 1,800 mg L^-1) for 10 and 30 min. After germination in a growth chamber, germination, growth, biomass, anatomical, and physiological characteristics were analyzed. The study confirmed that PCL interference was proportional to the concentration and seed imbibition time, affecting the percentage of germinated seeds in the first count, normal and abnormal seedlings, and dead seeds. There was a reduction in seedling growth and metaxylem diameter, resulting in lower biomass accumulation. However, lower concentrations (0 and 112 mg L^-1) favored the effective photochemical activity of PSII. We concluded that PCL influences seedling germination, anatomy, and physiology, with reduced concentrations potentially beneficial.

The regulation of stomatal movements is crucial for plants to optimize gas exchange and water balance. The plant hormone abscisic acid (ABA) triggers stomatal closure in response to drought, effectively minimizing water loss to prevent hydraulic failure. However, it significantly constrains photosynthesis, restricting plant growth and productivity. Therefore, rapid post-drought stomatal opening is crucial for earlier photosynthetic recovery. This review explores how phytohormones or plant growth regulators reverse ABA-induced stomatal closure. Phytomelatonin, 5-aminolevulinic acid, and brassinosteroids promote stomatal reopening by either ABA degradation or suppressing its biosynthesis through the downregulation of corresponding genes. This results in less ABA-induced H₂O₂ accumulation in guard cells, which lowers H₂O₂-triggered Ca²⁺ levels in guard cells, and promotes the opening of KAT1 (K⁺ _in channels). Insights from this review highlight the potential mechanisms of stomatal reopening for earlier post-drought gas exchange recovery, offering potential avenues to enhance plant productivity under changing environmental conditions.

We provide here the academic life of Dr. Autar Krishen Mattoo (1943-2024), including his role as a research leader at the United States Department of Agriculture and his outstanding contributions in photosynthesis, plant physiology and molecular biology with a focus to enhance nutrients. His work included ways to regulate Photosystem II (PSII) reaction center proteins, as well as to exploit, for our benefit, the role of polyamines in the plant world. Further, he provided the basis for beneficial aspects of sustainable agriculture systems and for selecting genes/proteins that provide better growth, higher disease resistance, and tolerance from abiotic stress. Autar K. Mattoo was a true international scholar and leader. We include below an overview of his selected research, his wonderful association with others, as well as a few reminiscences.

The 12^th International Conference "Photosynthesis and Hydrogen Energy Research for Sustainability 2024" was organised in honour of John Allen, Eva-Mari Aro, İbrahim Dinçer, Kazunari Domen, Elizabeth Gantt, and Andrey Rubin, by Bahçeşehir University in Istanbul from 13 to 19 October 2024. The International Society of Photosynthesis Research (ISPR) and the International Association for Hydrogen Energy (IAHE) supported the event. In the brief report, we provide a summary of the conference, the scientific contributions of honoured scientists, and a brief content of individual sessions. We specifically focused on the participation of young researchers, their presentations and awards.

Sensing rice drought stress is crucial for agriculture, and chlorophyll a fluorescence (ChlF) is often used. However, existing techniques usually rely on defined feature points on the OJIP induction curve, which ignores the rich physiological information in the entire curve. Independent Component Analysis (ICA) can effectively preserve independent features, making it suitable for capturing drought-induced physiological changes. This study applies ICA and Support Vector Machine (SVM) to classify drought levels using the entire OJIP curve. The results show that the 20-dimensional ChlF features obtained by ICA provide superior classification performance, with Accuracy, Precision, Recall, F1-score, and Kappa coefficient improving by 18.15%, 0.18, 0.17, 0.17, and 0.22, respectively, compared to the entire curve. This work provides a rice drought stress levels determination method and highlights the importance of applying dimension reduction methods for ChlF analysis. This work is expected to enhance stress detection using ChlF.

Afromontane forests are an important part of the KwaZulu Natal region of southern Africa, having a distinctive flora with a high proportion of endemic species, and lichens are keystone members. Unlike other continental areas, KwaZulu Natal climate change is predicted to increase rainfall and cloudiness. In the present study, hydrated Afromontane lichens from both exposed and shaded microhabitats were given either constant [100 µmol(photon) m^-2 s^-1] or fluctuating [0, 200, 0 µmol(photon) m^-2 s^-1] light for 8 h a day for 3 d and changes monitored in nonphotochemical quenching (NPQ) and rates of photosynthetic electron transport. In sun but not shade collections, NPQ strongly increased following treatment with constant and fluctuating light. It seems likely that CO₂ fixation may be reduced in moist thalli, and the increase in NPQ may reduce ROS formation during exposure to light while hydrated. Sun lichens can readily modify their NPQ in response to increased cloudiness and rainfall expected in KwaZulu Natal.

The strategies of Norway spruce [Picea abies (L.) Karst.] to increasing atmospheric CO₂ concentration (C _a) are not entirely clear. Here, we reconstructed centennial trajectories of leaf internal CO₂ concentration (C _i) and intrinsic water-use efficiency (WUE_i) from the amount of ¹³C in tree-ring cellulose. We collected 57 cores across elevations, soil, and atmospheric conditions in central Europe. Generally, WUE_i and C _i increased over the last 100 years and the C _i/C _a ratio remained almost constant. However, two groups were distinguished. The first group showed a quasi-linear response to C _a and the sensitivity of C _i to C _a (s = dC _i/dC _a) ranged from 0 to 1. Trees in the second group showed nonmonotonic responses with extremes during the peak of industrial air pollution in the 1980s and s increase from -1 to +1.6. Our study shows a marked attenuation of the rise in WUE_i during the 20^th century leading to invariant WUE_i in recent decades.