Changes In Chloroplast Ultrastructure Research Articles

Unraveling subcellular functional traits: Adaptive insights into chloroplast ultrastructure in nonmodel species.

This essay discusses how the ultrastructural changes in chloroplasts, particularly the mechanisms of thylakoid membrane unstacking, help maintain the photosynthetic performance of photosystem II (PSII) under stress conditions. This phenomenon may facilitate the repair of damaged PSII by providing access to the repair machinery. It is argued that this PSII repair mechanism accelerates PSII recovery, optimizing photosynthetic processes in stressed plants. Although some studies demonstrate the relationship between thylakoid membrane unstacking in stress conditions, these studies were developed with model species under controlled conditions. Thus, this essay serves as a validation tool for these previous studies, because it demonstrates that the relationships between ultrastructural changes in chloroplasts and the functioning of PSII are essential acclimative strategies for nonmodel plants to survive the constant edaphoclimatic changes of natural environments. Understanding these subcellular dynamics can significantly inform biologists about the plastic potential of plants, especially in heterogeneous environments. An integrated approach in future studies is necessary, highlighting the importance of exploring plant functional traits at multiple scales, because subcellular characteristics have great potential to understand plant acclimatization.

Modified atmosphere packaging delays postharvest leaf senescence of Chinese flowering cabbage via suppressing chloroplast dismantling and alleviating mitochondrial oxidative damage

Onset of leaf senescence comes with biomolecule degradation and cellular organelle degeneration. Here, we examined the efficacy of modified atmosphere packaging (MAP) on reactive oxygen species (ROS) metabolism and ultrastructural changes of chloroplasts and mitochondria in Chinese flowering cabbage leaves during storage at 20 ± 1 ℃. MAP delayed chloroplast dismantling along with lower chlorophyll reduction and Fv/Fm ratio. Furthermore, the integrity of mitochondrial ultrastructure was maintained by MAP treatment during leaf senescence. MAP treatment also lowered accumulation of ROS and maintained higher levels of key components and enzyme activity of ascorbate–glutathione cycle, as well as expression of BrAPX5, BrGR, BrDHAR1 and BrMDHAR2. Additionally, MAP-treated cabbage leaves showed higher activity of peroxidase, superoxide dismutase, catalase and encoding gene expressions. Collectively, above findings suggest that MAP treatment could suppress chloroplast dismantling and maintain ROS homeostasis to mitigate mitochondrial oxidative damage and sustain mitochondrial structure, thereby postponing senescence of Chinese flowering cabbage.

Effect of chilling and salinity stress on photosynthetic performance and ultrastructure of chloroplast in faba beans (Vicia faba L.) leaves

Chilling (Ch) and salinity (S) are challenging stresses affecting plant physiology, growth, and productivity. The current study investigated the effects of these two stresses, singly and in combination, on photosynthetic performance and ultrastructure of chloroplast of faba beans (Vicia faba L. Cv. Aspani). Plants were exposed to 3 °C and 120 mM NaCl for 16 h in an optimized soil mixture (sand:clay 2:1) under optimized conditions. Results showed that both Ch and S significantly reduced photosynthetic rates, Fv/Fm, chlorophyll content, stomatal index, and stomatal conductance. Chilling caused changes in chloroplast ultrastructure (swelling, ruptured envelopes, and shrunk lamellae), while salinity caused more deformation of the thylakoid membrane and disorganization of the grana structure. However, there was an antagonistic effect between Ch x S. The tolerance of plant to 120 mM NaCl, in the present study, was improved by exposure to Ch which rather allowed the maintenance of chloroplast ultrastructure and morphology of stomata. Moreover, using SEM and TEM gave an effective insight of the ultrastructural damage in plant cells under stress and helps to consider the underlying mechanisms of stress effects. Our results suggest that Ch mitigates the noxious effect of S on the photosynthetic performance of Vicia faba plants.

Differential regulation of red light- and ethephon-induced degreening in postharvest kumquat fruit

Peel color is closely associated with the commercial value of citrus fruit. In early market or tropical regions, citrus fruit often show non-uniform coloration, which requires degreening practice at post-harvest stage. Here, we studied the degreening effect of red LED light, ethephon, and their combination treatment on kumquat fruit. Both red LED light and ethephon promoted fruit degreening, causing ultrastructural changes of chloroplasts accompanied by chlorophyll degradation. Transcriptome analysis revealed metabolic reprogramming in chloroplasts but the way how genes responded to red LED light and ethephon were remarkably different. Transient expression in Nicotiana benthamiana suggested that FcrCLH, FcrPPH and FcrSGR genes were potentially key factors in regulation of fruit degreening. Furthermore, red LED light promoted the catabolism of chloroplast components in vitro. This study provides novel insights into the molecular mechanism of fruit degreening and unravels an efficient practice for future post-harvest management of citrus fruit.

Saline Stress Impairs Lipid Storage Mobilization during Germination in Eruca sativa.

Soil salinization become worse in the last decades, leading to reduced crop yields, especially in the Mediterranean basin. Eruca sativa is a common species cultivated in this area with remarkable economic importance. This study aimed at investigating the effect of salinity on this plant, focusing on (i) seedling development in terms of variations in germination and growth parameters and (ii) anatomical and ultra-structural changes in the morphology of cotyledons. For this reason, seeds were treated with different salinity levels ranging from 137 to 548 mM NaCl. Seed germination was delayed by all the concentrations tested, but only above 137 mM seedling growth was impaired. Results showed a high occurrence of lipid bodies within the mesophyll cells of cotyledons of seedlings exposed to salt concentrations above 137 mM, suggesting an impairment in lipid mobilization caused by salinity during plant development. The cotyledons of treated seedlings showed reduced intercellular spaces and ultrastructural changes in chloroplasts and peroxisomes. Moreover, salt-induced autophagic processes were present in samples grown at the highest NaCl levels. Interestingly, at 137 mM NaCl, seedlings showed the highest values of mesophyll thickness and fresh weight, implying a possible mechanism of salt adaptation during germination.

Priming with gold nanoparticles leads to changes in the photosynthetic apparatus and improves the cold tolerance of wheat

Nanotechnologies provide a great platform for researching nanoparticles effects on living organisms including plants. This work shows the stimulating effect of seed priming with gold nanoparticles (AuNPs) on photosynthetic apparatus of Triticum aestivum seedlings. It was found using inductively coupled plasma-atomic emission and mass spectrometry that AuNPs (the average diameter of 15.3 nm, concentration of 20 μg ml−1) penetrated into the seeds, but were not found in seedling leaves. Ultrastructural changes in chloroplasts were found using transmission electron microscopy in plants grown from treated seeds: increases in the size of plastids, starch grains, grana in chloroplasts, and the number of thylakoids in grana. The intensity of photosynthesis, the content of chlorophylls, and the portion of unsaturated fatty acids in the composition of total leaf lipids were increased in treated AuNPs plants. This study demonstrates that revealed changes determined the increased tolerance of wheat to low temperature. The adaptive significance of these changes, possible mechanisms of the AuNPs effects on plants and future perspectives of study are discussed. This is the first report showing nanopriming with AuNPs as a new method to study the mechanisms of stress tolerance.

The effect of 100–200 nm ZnO and TiO2 nanoparticles on the in vitro-grown soybean plants

Engineered nanomaterials are increasingly used in everyday life applications and, in consequence, significant amounts are being released into the environment. From soil, water, and air they can reach the organelles of edible plants, potentially impacting the food chain and human health. The potential environmental and health impact of these nanoscale materials is of public concern. TiO2 and ZnO are among the most significant nanomaterials in terms of production amounts. Our study aimed at evaluating the effects of large-scale TiO2 (~100 nm) and ZnO (~200 nm) nanoparticles on soybean plants grown in vitro. The effect of different concentrations of nanoparticles (10, 100, 1000 mg/L) was evaluated regarding plant morphology and metabolic changes. ZnO nanoparticles showed higher toxicity compared to TiO2 in the experimental set-up. Overall, elevated levels of chlorophylls and proteins were observed, as well as increased concentrations of ascorbic and dehydroascorbic acids. Also, the decreasing stomatal conductance to water vapor and net CO2 assimilation rate show higher plant stress levels. In addition, ZnO nanoparticle treatments severely affected plant growth, while TEM analysis revealed ultrastructural changes in chloroplasts and rupture of leaf cell walls. By combining ICP-OES and TEM results, we were able to show that the nanoparticles were metabolized, and their internalization in the soybean plant tissues occurred in ionic forms. This behavior most likely is the main driving force of nanoparticle toxicity.

Cell-level anatomy explains leaf age-dependent declines in mesophyll conductance and photosynthetic capacity in the evergreen Mediterranean oak Quercus ilex subsp. rotundifolia.

Leaves of Mediterranean evergreen tree species experience a reduction in net CO2 assimilation (AN) and mesophyll conductance to CO2 (gm) during aging and senescence, which would be influenced by changes in leaf anatomical traits at cell level. Anatomical modifications can be accompanied by the dismantling of photosynthetic apparatus associated to leaf senescence, manifested through changes at the biochemical level (i.e., lower nitrogen investment in photosynthetic machinery). However, the role of changes in leaf anatomy at cell level and nitrogen content in gm and AN decline experienced by old non-senescent leaves of evergreen trees with long leaf lifespan is far from being elucidated. We evaluated age-dependent changes in morphological, anatomical, chemical and photosynthetic traits in Quercus ilex subsp. rotundifolia Lam., an evergreen oak with high leaf longevity. All photosynthetic traits decreased with increasing leaf age. The relative change in cell wall thickness (Tcw) was less than in chloroplast surface area exposed to intercellular air space (Sc/S), and Sc/S was a key anatomical trait explaining variations in gm and AN among different age classes. The reduction of Sc/S was related to ultrastructural changes in chloroplasts associated to leaf aging, with a concomitant reduction in cytoplasmic nitrogen. Changes in leaf anatomy and biochemistry were responsible for the age-dependent modifications in gm and AN. These findings revealed a gradual physiological deterioration related to the dismantling of the photosynthetic apparatus in older leaves of Q. ilex subsp. rotundifolia.

Ultrastructural Changes in Chloroplasts of Cucumis sativus L. and Secale cereale L. during Low-Temperature Hardening

Ultrastructural Changes in Chloroplasts of Cucumis sativus L. and Secale cereale L. during Low-Temperature Hardening

Manganese-induced oxidative stress, ultrastructural changes, and proteomics studies in rice plants.

Manganese (Mn) is an essential element for plant growth but it becomes phytotoxic at higher concentrations. The effect of Mn-excess in hydroponics medium was examined on growth, oxidative stress, and ultrastructural changes in chloroplasts and mitochondria as well proteomic alterations in rice (Oryza sativa L.) seedlings. Seedlings grown with 1mM and 2mM Mn in nutrient medium for 8days showed decline in length and fresh biomass, and decline in net photosynthetic rate, transpiration rate, and stomatal conductance. Shoots of the seedlings had higher Mn content than roots. Mn-treated seedlings showed increased production of O2·-, H2O2, and .OH, increased lipid peroxidation, increased carbonylation of proteins, and increased proteolytic activity compared to untreated seedlings. Mn-treated seedlings showed disorganization and swelling of chloroplasts with appearance of plastoglobuli in TEM images and deformity in shape of mitochondria. Using confocal microscopy depolarization of mitochondrial membrane was observed marked by green fluorescence of JC-1 dye monomers in Mn-treated roots. Proteomics studies from leaves of Mn-treated seedlings involving 2DE and PDQuest analysis showed differential expression of 23 proteins, among which MALDI-TOF/TOF mass spectrometry analysis revealed Mn-led downregulation of photosynthesis-related proteins, namely oxygen-evolving complex protein associated with PSII, PAP-3, enzyme involved in protein folding peptidyl-prolyl cis-trans isomerase (PPIase) and carbohydrate metabolizing enzymes hydrolase, fructose-bisphosphate aldolase, transketolase, and isocitrate dehydrogenase, whereas ATP-dependent Clp protease, peroxidase, and nucleic acid-binding proteins were downregulated due to Mn treatment. Results indicate that Mn-excess inhibits growth of rice plants with induction of oxidative stress, causing structural alterations in chloroplasts, mitochondria, inhibiting photosynthesis, and downregulating many photosynthesis and carbohydrate metabolism-related proteins.

Reactive oxygen species metabolism and photosynthetic performance in leaves of Hordeum vulgare plants co-infested with Heterodera filipjevi and Aceria tosichella

Key messageDefence responses of cyst nematode and/or wheat curl mite infested barley engage the altered reactive oxygen species production, antioxidant machinery, carbon dioxide assimilation and photosynthesis efficiency.The primary aim of this study was to determine how barley responds to two pests infesting separately or at once; thus barley was inoculated with Heterodera filipjevi (Madzhidov) Stelter (cereal cyst nematode; CCN) and Aceria tosichella Keifer (wheat curl mite; WCM). To verify hypothesis about the involvement of redox metabolism and photosynthesis in barley defence responses, biochemical, photosynthesis efficiency and chlorophyll a fluorescence measurements as well as transmission electron microscopy were implemented. Inoculation with WCM (apart from or with CCN) brought about a significant suppression in the efficiency of electron transport outside photosystem II reaction centres. This limitation was an effect of diminished pool of rapidly reducing plastoquinone and decreased total electron carriers. Infestation with WCM (apart from or with CCN) also significantly restricted the electron transport on the photosystem I acceptor side, therefore produced reactive oxygen species oxidized lipids in cells of WCM and double infested plants and proteins in cells of WCM-infested plants. The level of hydrogen peroxide was significantly decreased in double infested plants because of glutathione–ascorbate cycle involvement. The inhibition of nitrosoglutathione reductase promoted the accumulation of S-nitrosoglutathione increasing antioxidant capacity in cells of double infested plants. Moreover, enhanced arginase activity in WCM-infested plants could stimulate synthesis of polyamines participating in plant antioxidant response. Infestation with WCM (apart from or with CCN) significantly reduced the efficiency of carbon dioxide assimilation by barley leaves, whereas infection only with CCN expanded photosynthesis efficiency. These were accompanied with the ultrastructural changes in chloroplasts during CCN and WCM infestation.

Characterization of Photosynthetic Phenotypes and Chloroplast Ultrastructural Changes of Soybean (Glycine max) in Response to Elevated Air Temperatures.

Heat stress negatively affects photosynthesis in crop plants. Chlorophyll fluorescence provides information about the efficiency of the light-dependent reactions of photosynthesis and can be measured non-destructively and rapidly. Four soybean (Glycine max) genotypes were grown in controlled environments at 28/20°C (control), followed by imposition of control, 38/28°C, and 45/28°C day/night temperature regimes for 7 days. Coordinated chlorophyll fluorescence, gas exchange, and chloroplast ultrastructure measurements were conducted over the course of the 7-day temperature treatments and revealed contrasting responses among the different genotypes. Although generally similar, the extent of the impact of elevated temperatures on net photosynthesis differed among genotypes. Despite dramatic effects on photosynthetic light reactions, net photosynthetic rates were not reduced by exposure to 45°C on the 1st day of treatment imposition. Temporal dynamics of light reaction characteristics over the course of the 7-day heat-wave simulation revealed distinct responses among the genotypes. Similarly, chloroplast ultrastructure examination identified contrasting responses of DT97-4290 and PI603166, particularly with respect to starch characteristics. These changes were positively associated with differences in the percent area of chloroplasts that were occupied by starch grains. Elevated temperature increased number and size of starch grains on the 1st day of DT97-4290 which was coordinated with increased minimum chlorophyll fluorescence (F0) and reduced leaf net CO2 assimilation (A). Whereas on the 7th day the elevated temperature treatment showed reduced numbers and sizes of starch grains in chloroplasts and was coordinated with similar levels of F0 and A to the control treatment. Unlike starch dynamics of PI603166 which elevated temperature had little effect on. The genotypic differences in photosynthetic and chloroplast ultrastructure responses to elevated temperatures identified here are of interest for the development of more tolerant soybean cultivars and to facilitate the dissection of molecular mechanisms underpinning heat stress tolerance of soybean photosynthesis.

Ultrastructural Reorganization of Chloroplasts during Plant Adaptation to Abiotic Stress Factors

This review presents a comparative analysis of the literature and the authors’ data on the ultrastructural reorganization of plant chloroplasts adapting to abiotic factors of different nature—low temperature (factor of a physical nature) and chloride salinity (factor of a chemical nature). All ultrastructural changes in chloroplasts are considered in close relationship to the physiological, biochemical, and functional adaptive changes of the photosynthetic apparatus (PSA). The review discusses the adaptive value and emphasizes the nonspecific nature of ultrastructural transformations occurring in plant chloroplasts under abiotic stress. A separate section considers the effect of metal nanoparticles on the PSA and the nanoparticle-aided modeling of the PSA responses to stresses.

Chemically synthesized silver nanoparticles induced physio-chemical and chloroplast ultrastructural changes in broad bean seedlings

This study was conducted to explore the effects of priming of seven-year-old aged seeds with different concentrations of silver nanoparticles (AgNPs) on growth of broad bean (Vicia faba L.). Seeds were primed with different concentrations of AgNPs for 6 h before growing in the plastic trays. Different growth parameters like growth attributes, photosynthetic pigments, carbohydrates, antioxidant enzymes and chloroplast ultrastructure were estimated after 14 days of germination. Priming with AgNPs affected the root and shoot growth attributes as compared with control depending upon concentrations of AgNPs. In all treatments, photosynthetic pigments increased significantly above control levels, but total soluble sugars decreased in 10 and 50 ppm AgNPs and slightly increased in 100 ppm AgNPs as compared with control. Starch accumulation was apparent in all treated seedlings above that of control levels. Mesophyll cells of all treated seedlings were altered with electron dense particles than control. Priming with AgNPs affected the chloroplast structure which appeared in the form of less stacking of Greene, formation of protrusions and extensions, irregular shape of chloroplasts as compared with spindle shaped regular chloroplasts of control. In all treatments, total phenols were slightly affected as compared with control. The antioxidant enzyme activities in seedlings varied with the dose and type of antioxidants. Overall, AgNPs adversely affected the chloroplast ultrastructure, but increased growth of seedlings and starch accumulation. Further studies are required to explore the effects of AgNPs on the long-term on crop productivity of aged seeds.

Subcellular distribution and physiological responses of Potamogeton crispus to yttrium

Potamogeton crispus was exposed to a range of external yttrium (Y) concentrations (0–30 μM) for 20 days to investigate the effects of Y accumulation on the homeostasis of elements and the photochemistry of photosystem II (PS II). Yttrium accumulation increased in a concentration-dependent manner, with most Y being associated with polysaccharides. At all Y concentrations, significant declines in relative growth rates (fresh weight basis), photosynthetic pigments, and protein content were observed, as well as an increase in leaf area damage. Yttrium accumulation disrupted elemental homeostasis, with decrease observed for concentrations of micro- and macro-elements such as Cu, Zn, Mg, Mn, and K, and increases for S, Fe, and Ca. A significant reduction in PS II photochemistry occurred in Y-treated plants, as evidenced by decrease in Fv/Fm, Fv/Fo, Fv, ψo, φEo, φRo, φPo, and PIABS, and increases in Fo, Fo/Fv, and energy fluxes per reaction center (ABS/RC, ETo/RC, TRo/RC, and DIo/RC). In addition, Y treatment significantly reduced chloroplast ATPase activity and ATP level and induced changes in chloroplast ultrastructure including an increase in plastoglobule size and organelle shape. AsA and GSH content slightly increased at 10 µM Y and then declined and that of non-protein thiol was found to be enhanced at all the Y concentrations. The results suggest that Y exposure led to general disarray of cellular functions, similar to responses observed for other trace metals.

Photosynthetic capacity, osmotic adjustment and antioxidant system in sugar beet (Beta vulgaris L.) in response to alkaline stress

Photosynthetic characteristics of sugar beet cultivars KWS0143 and Beta464 were studied under alkaline conditions, including 0 (A0, control), 25 (A1), 50 (A2), 75 (A3), and 100 mM of mixed alkali (Na2CO3:NaHCO3, 1:2). A2, A3, and A4 reduced net photosynthetic rate (PN), stomatal conductance, and transpiration rate, but rose intercellular CO2 concentration. Reduction in PN occurred probably due to nonstomatal limitation. The decrease in efficiency of photosynthetic electron transport might be the main reason for the decrease of PN. The concentrations of photosynthetic pigments were significantly reduced by high (A3 and A4) alkalinity. Changes in chloroplast ultrastructure are the reason for the decrease in chlorophyll content. Sugar beet could resist injury from alkali owing to osmotic substances and antioxidant enzymes if alkaline stress was at a lower level. The better performance of KWS0143 under alkalinity might be associated with its more efficient osmotic and antioxidant systems to resist injury of photosynthetic apparatus caused by alkalinity.

Salt stress induces changes in genetic composition, proline content and subcellular organization in potato (Solanum tuberosum L.)

Several abiotic stresses including salinity impact plant growth and reduce the productivity of many plants and field crops. Plantlets produced in vitro by tissue culture technique offer a direct and fast approach to investigate the mechanism of stress adaptation. The present study estimated the survival percentage of two potato (Solanum tuberosum L.) cultivars (Spunta and Valor) under salt stress as abiotic stresses. Some biochemical alterations and ultrastructural responses of plantlets were examined. Moreover, genetic diversity was also studied using RAPD technique. The results showed that, with the increase of external stress there was a significant decrease in the survival percentage, significant accumulation of osmoprotectants (proline) and induction of DNA damages. Furthermore, there were closing of stomatal apertures, changesin chloroplast ultrastructure and cell intercellular spaces markedly decreased. Additionally,high salt stress (150 and 200mM NaCl) caused complete inhibition of plantlet growth. Thepresent work provides insight view for the adaptation of potato plantlets to salt stress throughaccumulating of osmoprotectants and change in molecular and ultrastructure traits.

Chloroplast ultrastructure and hormone endogenous levels are differently affected under light and dark conditions during in vitro culture of Guadua chacoensis (Rojas) Londoño & P. M. Peterson

Guadua chacoensis (Poaceae) is a woody bamboo native from the Atlantic forest biome. Morphogenetic and physiological studies are scarce in bamboos, and tissue culture-based biotechnologies tools can be used to investigate ultrastructure and physiological processes as well as to mass-propagate specific genotypes. This study evaluated the effect of light and dark conditions on chloroplast biogenesis as well as in the endogenous levels of zeatin (Z), abscisic acid (ABA), gibberellic acid (GA4), and jasmonic acid (JA) during in vitro culture of G. chacoensis. An increase was observed, followed by a decrease in starch content in response to light treatment, and in contrast, in darkness, an accumulation of starch which is associated to amyloplast formation at day 30 was observed. No etioplast formation was observed even in the dark and this was associated with the presence of fully developed chloroplast at the beginning of the experiment. Z levels quantified showed distinct behavior, as in light, no difference in the levels was observed, except at day 10, and in darkness, the levels increased along the evaluation time. ABA, GA4, and JA biosynthesis increased along the time of evaluation in light condition. In contrast, in darkness, the levels remained unaltered, excepted for an increase in JA levels at day 10, suggesting a strong relationship between light and these phytohormone levels. Possible reasons why light’s presence and absence cause changes in chloroplast ultrastructure and hormone endogenous levels in in vitro cultivated culms of G. chacoensis are discussed.

Physiological, ultrastructural and proteomic responses of tobacco seedlings exposed to silver nanoparticles and silver nitrate

Since silver nanoparticles (AgNPs) are a dominant nanomaterial in consumer products, there is growing concern about their impact on the environment. Although numerous studies on the effects of AgNPs on living organisms have been conducted, the interaction of AgNPs with plants has not been fully clarified. To reveal the plant mechanisms activated after exposure to AgNPs and to differentiate between effects specific to nanoparticles and ionic silver, we investigated the physiological, ultrastructural and proteomic changes in seedlings of tobacco (Nicotiana tabacum) exposed to commercial AgNPs and ionic silver (AgNO3) from the seed stage. A higher Ag content was measured in seedlings exposed to AgNPs than in those exposed to the same concentration of AgNO3. However, the results on oxidative stress parameters obtained revealed that, in general, higher toxicity was recorded in AgNO3-treated seedlings than in those exposed to nanosilver. Ultrastructural analysis of root cells confirmed the presence of silver in the form of nanoparticles, which may explain the lower toxicity of AgNPs. However, the ultrastructural changes of chloroplasts as well as proteomic study showed that both AgNPs and AgNO3 can affect photosynthesis. Moreover, the majority of the proteins involved in the primary metabolism were up-regulated after both types of treatments, indicating that enhanced energy production, which can be used to reinforce defensive mechanisms, enables plants to cope with silver-induced toxicity.

2,4-Di-tert-butylphenol-induced leaf physiological and ultrastructural changes in chloroplasts of weedy plants

2,4-Di-tert-butylphenol (2,4-DTBP), a natural compound from plants, causes severe chlorosis and necrosis on Hedyotis verticillata and Leptochloa chinensis leaf blades by inducing oxidative stress through the generation of reactive oxygen species, leading to lipid peroxidation and membrane damage in leaf and root tissues. However, its effects on the physiology of photosynthesis through ultrastructural alterations in chloroplasts remain unclear. Therefore, this study examined the phytotoxic effects of 2,4-DTBP on chloroplast ultrastructure and leaf physiology of H. verticillata and L. chinensis in a 3-day assay. The results revealed that treating H. verticillata and L. chinensis seedlings with 2,4-DTBP significantly decreased shoot fresh weight on day 3 after treatment. 2,4-DTBP increased electrolyte leakage in H. verticillata, but no notable electrolyte leakage was detected in L. chinensis. Ultrastructural damage to chloroplasts was evident in both species, with a disorganised thylakoid system and undulating membranes, coupled with the absence of starch grains and an increased number of plastoglobuli. Damage to the chloroplast ultrastructure subsequently reduced the leaf greenness, quantum yield and stomatal conductance values. These results suggest that 2,4-DTBP has potent herbicidal properties that can alter chloroplast ultrastructure, thereby reducing physiological activity of these weedy plants.