L-cysteine, a precursor of essential components for plant growth, is synthesized by the cysteine synthase complex, which includes O-acetylserine(thiol) lyase (OAS-TL) and serine acetyltransferase. In this work, we investigated how S-benzyl-L-cysteine (SBC), an OAS-TL inhibitor, affects the growth, photosynthesis, and oxidative stress of Ipomoea grandifolia plants. SBC impaired gas exchange and chlorophyll a fluorescence, indicating damage that compromised photosynthesis and reduced plant growth. Critical parameters such as the electron transport rate (J), triose phosphate utilization (TPU), light-saturation point (LSP), maximum carboxylation rate of Rubisco (V_cmax), and light-saturated net photosynthetic rate (P_Nmax) decreased by 19%, 20%, 22%, 23%, and 24%, respectively. The photochemical quenching coefficient (q_P), quantum yield of photosystem II photochemistry (ϕ_PSII), electron transport rate through PSII (ETR), and stomatal conductance (g_s) decreased by 12%, 19%, 19%, and 34%, respectively. Additionally, SBC decreased the maximum fluorescence yield (F_m), variable fluorescence (F_v), and chlorophyll (SPAD index) by 14%, 15%, and 15%, respectively, indicating possible damage to the photosynthetic apparatus. SBC triggered root oxidative stress by increasing malondialdehyde, reactive oxygen species, and conjugated dienes by 30%, 55%, and 61%, respectively. We hypothesize that dysfunctions in sulfur-containing components of the photosynthetic electron transport chain, such as the cytochrome b₆f complex, ferredoxin, and the iron–sulfur (Fe-S) centers are the cause of these effects, which ultimately reduce the efficiency of electron transport and hinder photosynthesis in I. grandifolia plants. In short, our findings suggest that targeting OAS-TL with inhibitors like SBC could be a promising strategy for the development of novel herbicides.

Chemical weed control is a significant agricultural concern, and reliance on a limited range of herbicide action modes has increased resistant weed species, many of which use C4 metabolism. As a result, the identification of novel herbicidal agents with low toxicity targeting C4 plants becomes imperative. An assessment was conducted on the impact of 3-cyanobenzoic acid on the growth and photosynthetic processes of maize (Zea mays), a representative C4 plant, cultivated hydroponically over 14 days. The results showed a significant reduction in plant growth and notable disruptions in gas exchange and chlorophyll a fluorescence due to the application of 3-cyanobenzoic acid, indicating compromised photosynthetic activity. Parameters such as the chlorophyll index, net assimilation (A), stomatal conductance (g_s), intercellular CO₂ concentration (C_i), maximum effective photochemical efficiency (F_v′/F_m′), photochemical quenching coefficient (q_P), quantum yield of photosystem II photochemistry (ϕ_PSII), and electron transport rate through PSII (ETR) all decreased. The A/PAR curve revealed reductions in the maximum net assimilation rate (A_max) and apparent quantum yield (ϕ), alongside an increased light compensation point (LCP). Moreover, 3-cyanobenzoic acid significantly decreased the carboxylation rates of RuBisCo (V_cmax) and PEPCase (V_pmax), electron transport rate (J), and mesophilic conductance (g_m). Overall, 3-cyanobenzoic acid induced substantial changes in plant growth, carboxylative processes, and photochemical activities. The treated plants also exhibited heightened susceptibility to intense light conditions, indicating a significant and potentially adverse impact on their physiological functions. These findings suggest that 3-cyanobenzoic acid or its analogs could be promising for future research targeting photosynthesis.

Enzymes of the sulfur assimilation pathway represent promising candidates for selective herbicide development. This study investigated the effects of O-benzyl-serine (OBS), a newly identified inhibitor of O-acetylserine(thiol)-lyase (OAS-TL), on two C3 weed species, Ipomoea grandifolia and Euphorbia heterophylla. Plants were cultivated hydroponically for 12 days in the presence of OBS (0–500 µM). OBS inhibited root growth in both species in a dose-dependent manner, with I. grandifolia being more sensitive. OAS-TL activity decreased in the roots of I. grandifolia but increased in the leaves of E. heterophylla. Nutrient profiling revealed significant alterations in sulfur, magnesium, and calcium contents, associated with chlorosis and reduced root and leaf development. While photosynthetic performance appeared unaffected at the lowest OBS concentration tested (62.5 µM), higher doses drastically reduced leaf expansion, preventing further measurements. Given this marked decline in foliar development, it is reasonable to infer that the overall photosynthetic capacity of the plants was also negatively affected under severe OBS exposure. OBS also disrupted apical dominance, promoting lateral shoot formation. These findings demonstrate that OBS differentially affects sulfur metabolism and growth in a species- and organ-specific manner, supporting its potential as a prototype molecule for herbicides targeting novel biochemical pathways.

Chemical weed control is a significant agricultural concern, and reliance on a limited range of herbicide action modes has increased resistant weed species, many of which use C4 metabolism. As a result, the identification of novel herbicidal agents with low toxicity targeting C4 plants becomes imperative. An assessment was conducted on the impact of 3-cyanobenzoic acid on the growth and photosynthetic processes of maize (Zea mays), a representative C4 plant, cultivated hydroponically over 14 days. The results showed a significant reduction in plant growth and notable disruptions in gas exchange and chlorophyll a fluorescence due to the application of 3-cyanobenzoic acid, indicating compromised photosynthetic activity. Parameters such as the chlorophyll index, net assimilation (A), stomatal conductance (gs), intercellular CO2 concentration (Ci), maximum effective photochemical efficiency (Fv'/Fm'), photochemical quenching coefficient (qP), quantum yield of photosystem II photochemistry (ϕPSII), and electron transport rate through PSII (ETR) all decreased. The A/PAR curve revealed reductions in the maximum net assimilation rate (Amax) and apparent quantum yield (ϕ), alongside an increased light-compensation point (LCP). Moreover, 3-cyanobenzoic acid significantly decreased the carboxylation rates of RuBisCo (Vcmax) and PEPCase (Vpmax), electron transport rate (J), and mesophilic conductance (gm). Overall, 3-cyanobenzoic acid induced substantial changes in plant growth, carboxylative processes and photochemical activities. The treated plants also exhibited heightened susceptibility to intense light conditions, indicating a significant and potentially adverse impact on their physiological functions. These findings suggest that 3-cyanobenzoic acid or its analogs could be promising for future research targeting photosynthesis.

L-cysteine, a precursor of essential components for plant growth, is synthesized by the cysteine synthase complex, which includes O-acetylserine(thiol) lyase (OAS-TL) and serine acetyltrans-ferase. In this work, we investigated how S-benzyl-L-cysteine (SBC), an OAS-TL inhibitor, affects the growth, photosynthesis, and oxidative stress of Ipomoea grandifolia plants. SBC impaired gas exchange and chlorophyll a fluorescence, indicating damage that compromised photosynthesis and reduced plant growth. Important parameters such as light-saturated net photosynthetic rate (PNmax), light saturation point (LSP), maximum carboxylation rate of Rubisco (Vcmax), electron transport rate (J), and triose phosphate utilization (TPU) decreased as a result. The quantum yield of photosystem II photochemistry (ϕPSII) and the electron transport rate through PSII (ETR) also decreased, as did the stomatal conductance (gs) and the photochemical quenching coefficient (qP). Additionally, SBC decreased the maximum fluorescence yield (Fm), variable fluorescence (Fv), and chlorophyll index, indicating possible damage to the photosynthetic apparatus. SBC triggered oxidative stress by increasing reactive oxygen species, malondialdehyde, and conjugated dienes. We hypothesize that dysfunctions in the sulfur-containing components of the photosynthetic electron transport chain, such as the cytochrome b6f complex, ferredoxin, and iron-sulfur (Fe-S) centers are the cause of these effects, which ultimately reduce the efficiency of electron transport and hinder photosynthesis in I. grandifolia plants. In short, our findings suggest that targeting OAS-TL with inhibitors such as SBC could be a promising strategy for the development of novel herbicides.