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The increasing challenge posed by climate change necessitates a deeper understanding of the plant metabolic pathways that influence productivity under varying environmental conditions. In this context, investigating the impact of L-phenylalanine ammonia-lyase (PAL) inhibition on flag leaf physiology in winter triticale provides valuable insights into mechanisms that may affect crop productivity. This study investigated the physiological and molecular responses of the flag leaf following the application of 4-hydroxybenzoic acid hydrazide (HBH), a PAL inhibitor. It was hypothesized that PAL inhibition would redirect carbon flow towards carbohydrate synthesis at the expense of phenolic production, accompanied by alterations in photosynthetic performance and antioxidant responses. HBH was detected in flag leaf tissues and caused a significant reduction in phenolic content, along with a marked increase in soluble carbohydrate levels. HBH treatment strongly activated the antioxidant system, as evidenced by elevated levels of non-enzymatic antioxidants and the increased activity of antioxidant enzymes. Changes were also observed in chlorophyll fluorescence parameters and in the accumulation of proteins associated with CO₂ fixation and the photosynthetic apparatus function. These findings demonstrate that PAL inhibition can substantially affect the redox balance and photosynthetic activity of the flag leaf during a critical period of plant development and yield formation. Full article

Photosynthetic characteristics are critical for grape growth and development. Drought conditions in arid regions significantly affect these characteristics. To identify grape varieties better suited for cultivation in arid environments, this study evaluated the leaf phenotypes and photosynthetic characteristics of 27 table grape varieties in Hotan Prefecture, China. Results revealed significant variations in leaf phenotypes and chlorophyll content (SPAD) among varieties under Hotan’s drought conditions. ‘Kyoho’ exhibited the largest leaf area (254.34 cm²), while ‘Munage’ had the smallest (112.43 cm²), and ‘Manaizi’ showed the highest chlorophyll content (SPAD = 44.21). ‘Munage’ and ‘Flame Seedless’ recorded the highest net photosynthetic rates (P_Nmax = 16.24 and 16.23 μmol·m⁻²·s⁻¹, respectively), while ‘Thompson Seedless’ had the lowest respiratory loss (R_D = 1.15 μmol·m⁻²·s⁻¹) and light compensation point (I_c = 22.41 μmol·m⁻²·s⁻¹), with a highly significant positive correlation between R_D and I_c. ‘Crimson Seedless’ exhibited the highest light saturation point (I_sat = 2745.15 μmol·m⁻²·s⁻¹). Chlorophyll fluorescence analysis indicated that ‘Autumn Black’ had the highest PSII photochemical yield (F_v/F_m = 0.84), while ‘Zicuiwuhe’ showed high energy transfer indices (PI_abs = 1.78, PI_total = 1.66) and electron transfer efficiency (φ_Eo = 0.39). PIabs was significantly correlated with F_v/F_m, F_v/F_o, and energy flux parameters. ‘Molixiang’ demonstrated superior energy utilization, with the highest light absorption (ABS/CSm = 2440.8) and electron transfer flux (ETo/CSm = 874) and the lowest energy dissipation (DIo/CSm = 455.8), supported by a negative correlation between energy dissipation (DIo/CSm) and photochemical efficiency (φ_Eo). Principal component analysis revealed that ‘Molixiang’ had the highest comprehensive photosynthetic adaptability score (0.97), followed by ‘Zicuiwuhe’ (0.79) and ‘Hetianhong’ (0.73), under Hotan’s drought stress conditions. These findings provide valuable insights for selecting and breeding grape varieties adapted to arid environments and climate change. Full article

Photosynthesis is an essential plant biological process. The performance of photosynthesis in grafted plants is affected by either the scion or the rootstock. However, the effect of the scion, rootstock and their interaction in the scion–rootstock combinations on photosynthesis of the grafted trees was not clear. In this research, the photosynthesis was analyzed within 21 citrus scion–rootstock combinations derived from three navel oranges (Citrus sinensis cv. ‘Banfield’, ‘Chislett’ and ‘Powell’) grafted on seven rootstocks [(Swingle citrumelo (C. paradisi × Poncirus trifoliata), Carrizo citrange (C. sinensis × P. trifoliata), X639 (C. reticulata × P. trifoliata), MXT (C. sinensis × P. trifoliata), Hongju (C. reticulata), Ziyang xiangcheng (C. junos) and Trifoliate orange (P. trifoliata)]. Results indicated that photosynthesis of these grafted citrus plants was significantly affected by all the scion, rootstock and their interaction. The rootstock and scion–rootstock interaction had more effect on both chlorophyll fluorescence and photosynthetic parameters with lower p values than the scion. All the scions grafted on Swingle showed the highest electron transport rate at 132.24, 158.39 and 154.59 µmol electrons m⁻² s⁻¹, and a higher net CO₂ assimilation rate at 11.22, 10.77 and 11.69 µmol m⁻² s⁻¹, respectively. The rootstock is the predominant factor affecting the content of photosynthetic pigments, and the combinations using Ziyang xiangcheng as the rootstock had the highest content at 19.83, 20.97 and 20.39 μmol s⁻¹ Kg⁻¹ FW. Electron transport rate is probably the predominant factor determining the final photosynthesis of the grafted citrus trees. This research is the first to reveal the respective effect of the scion, rootstock and their interaction on photosynthesis of citrus scion–rootstock combinations and is valuable in enhancing the understanding of the different performances in citrus scion–rootstock combinations, which aids in selecting optimal scion–rootstock combinations. Full article

In this study, we aimed to evaluate physiological and agronomic traits in 120 sugarcane genotypes under early drought stress conditions in a field trial across various soil types. The experiment used a split-plot arrangement, with a randomized complete block design and two replications. Two different water regimes were assigned to the main plot: (1) non-water stress (CT) and (2) drought (DT) at the early growth stage, during which sugarcane was subjected to drought stress by withholding water for 4 months. The subplot consisted of 120 sugarcane genotypes. The stalk height, stalk diameter, number of stalks, photosynthetic traits including SPAD chlorophyll meter reading (SCMR) and maximum quantum efficiency of photosystem II photochemistry (Fv/Fm), and normalized difference vegetation index (NDVI) were measured at 3, 6, and 9 months after planting (MAP). Yield and yield component parameters were measured at 12 MAP. Drought treatments lead to significant changes in various physiological traits in the sugarcane. Clustering analysis classified 36 sugarcane varieties grown in sandy loam soil and 15 genotypes in loam soil into two main clusters. In sandy loam soils, Biotec4 and CO1287 exhibited outstanding performance in drought conditions, delivering high cane yields. Meanwhile, in loam soil, MPT13-118, MPT07-1, Q47, F174, MPT14-1-902, and UT1 exhibited the best drought tolerance. Under drought conditions, cluster 1 showed higher values for SCMR, NDVI, height growth rate (HGR), cane yield, and drought tolerance index compared to cluster 2. These findings suggest that breeders can utilize these genotypes to enhance drought resistance, and the identified physiological traits can assist in selecting stronger candidates for drought tolerance. Full article

This study compared the effects of two C3 forages (Italian ryegrass [RG], Timothy grass [TG]) and two C4 forages (Klein grass [KG], Bermuda grass [BG]) on growth performance, nutrient digestibility, and nitrogen (N) balance in Korean crossbred black goats to evaluate C4 warm-season forages as alternatives under changing climate conditions. Sixteen castrated goats (10 months old) were allocated to four treatments using a randomized complete block design. Diets contained 40% treatment-specific forage and 60% commercial concentrate. After adaptation periods, a 5-day metabolism trial measured performance and digestibility parameters. No significant differences occurred among treatments for growth performance or digestibility of dry matter, crude protein, neutral detergent fiber, ash, and non-fiber carbohydrate. C4 grasses showed significantly lower acid detergent fiber and ether extract digestibility than C3 grasses, with KG having the lowest ether extract digestibility. The KG group had higher N intake and absorption than the TG group, while BG showed lower urinary and total N excretion than KG. No differences existed in retained N, utilization efficiency, or biological value among groups. Both C3 and C4 forages supported comparable goat growth performance, providing a reference for utilizing different photosynthetic pathway forages under changing climatic conditions. Full article

High levels of dissolved salts in irrigation water sources limit melon cultivation in northeastern Brazil. In this context, nitrogen fertilization has been employed as one strategy to alleviate the effects of salt stress on plants. This study aimed to evaluate the effect of different nitrogen sources on cantaloupe melon cultivation under fertigation and irrigation with water of the same salinity and different cationic concentrations (Na⁺ and Ca⁺). The research consisted of two experiments, each following a randomized complete block design in a 4 × 2 factorial arrangement with four replicates. The treatments included four levels of electrical conductivity of the nutrient solution (2.0; 3.0; 4.0; and 5.0 dS m⁻¹) and two nitrogen sources of different origins: NO₃⁻ [Ca(NO₃) and KNO₃] and NH₄⁺ [CH₄N₂O and NH₄H₂PO₄]. The following factors were chlorophyll pigments, chlorophyll a fluorescence, and fruit weight. Nitrogen fertilization with NH₄⁺ mitigated salt stress by increasing the synthesis of chlorophyll a and carotenoids in plants irrigated with NaCl-based saline water. Furthermore, there was no influence of nitrogen sources on chlorophyll a fluorescence. Finally, NO₃⁻ fertilization reduced the effects of salt stress on the leaf mass ratio, specific leaf area under Ca²⁺ fertigation, and relative growth rate of leaf area in melons under cationic prevalences of Na⁺ or Ca²⁺ (associated with Cl⁻). Full article

Under refined management, high-yield cotton fields are approaching their maximum output. However, how to break this yield upper limit, specifically the source–sink relationship is still inadequately researched. This experiment was conducted to explore the interaction mechanism between yield formation and source–sink parameters (photosynthesis, nitrogen content, canopy structure and dry matter accumulation and distribution). The treatments consisted of a no cutting source and sink treatment (CK), cutting 1/2 leaves per plant (1/2L) and cutting 1/2 bolls per plant (1/2B) at the initial flowering stage (IFS), the flower and boll stage (FABS), and the full boll stage (FBS). The results showed that 1/2L treatment minimized yield losses to 2.3–5.9% by enhancing photosynthetic compensation, with FBS-1/2L showing the smallest reduction (2.3–2.9%) due to higher leaf N content and SPAD values, whereas, the 1/2B treatments resulted in significant yield losses attributable to fewer bolls, especially the FBS-1/2B treatments, which reduced yields by 35.7–41.9%, with a compensatory rate of only 8.1–14.3%. It is noteworthy that the compensation rates of IFS-1/2B and FABS-1/2B could reach 26.7–32.3% and 18.7–23.8% of their yields due to the higher leaf N content. In a word, the source damage can be buffered by physiological compensation, while the sink loss leads to yield collapse due to the irreversibility of reproductive development. Thus, the core regulator of high-yield cotton fields was sink strength. Accordingly, optimizing the sink quality was performed through moderate boll thinning at the IFS, enhancing water and fertilizer supply at the FABS and strengthening sink organ protection at the FBS in order to realize a breakthrough in yield limit. Full article

Pecan (Carya illinoinensis [Wangenh]. K. Koch) germplasm resources are abundant, yet the characteristics of each cultivar at the seedling stage remain insufficiently understood. This study systematically evaluated the growth parameters, photosynthetic traits, and anatomical structures of one-year-old grafted seedlings from five pecan cultivars: “Pawnee”, “Mandan”, “Nacono”, “Caddo”, and “Creek”. Principal component analysis (PCA) was employed to comprehensively assess 56 indicators. The results indicated that, in terms of vegetative growth, leaf area and biomass of “Nacono” and “Creek” were significantly greater than those of “Pawnee” (p < 0.05). “Mandan” ranked second. Additionally, the seedling quality index of “Creek” was markedly superior to all other cultivars (p < 0.05). Anatomically, “Pawnee” exhibited greater leaf thickness, more highly differentiated palisade tissue, and the development of the main vein. By contrast, “Mandan” displayed larger branch radius, cortex thickness, and pith radius, accompanied by finer vessels and large but sparsely distributed stomata (p < 0.05). Regarding photosynthetic performance, “Mandan” accumulated the highest concentrations of photosynthetic pigments and achieved the greatest photosynthetic efficiency, significantly outperforming the remaining cultivars (p < 0.05). The PCA-based comprehensive evaluation revealed that “Mandan” outperformed the other cultivars in seedling growth, making it the most suitable for promotion, followed by “Creek”, “Nacono”, “Caddo”, and “Pawnee”. This research offers a theoretical foundation for the breeding, promotion, and application of superior pecan cultivars. Full article

Cylindrospermopsis raciborskii is a toxin-producing cyanobacterium that is easy to overlook. It has strong environmental adaptability and is currently spreading around the world and gradually dominating to form a persistent bloom, causing ecological and environmental risks and drinking water safety issues. In this study, we systematically investigated the inhibitory effects of oleic acid on C. raciborskii and elucidated the underlying mechanisms through morphological observation, physiological assays, and bioinformatics analysis. Our results demonstrated that oleic acid strongly inhibits the growth of C. raciborskii, with a 72 h half-maximal effective concentration (EC₅₀) of 0.903 mg·L⁻¹. At 1.6 mg·L⁻¹, oleic acid achieved an inhibition rate of 99.5% within 48 h, indicating rapid suppression of cyanobacterial growth. Physiological analyses revealed that oleic acid severely impaired photosynthetic activity, as evidenced by significant reductions in key parameters (rETRmax, α, Fv/Fm, and Fv/Fo) and altered photosynthetic pigment composition, suggesting structural and functional damage to the photosynthetic apparatus. Morphological observations further showed that oleic acid disrupted filament integrity, inducing cell shrinkage, cytoplasmic vacuolation, cell wall detachment, membrane rupture, and eventual cellular disintegration. Kyoto Encyclopedia of Genes and Genomes pathway enrichment analysis indicated that oleic acid interferes with multiple metabolic processes, including nutrient and cofactor synthesis, membrane transport, and signal transduction, ultimately triggering algal cell death. This study highlights oleic acid as a promising eco-friendly agent for mitigating C. raciborskii blooms, offering potential applications in ecological prevention and emergency bloom control. Full article

Anthocyanins (ACNs) are flavonoid pigments that accumulate in plants and respond to environmental stimuli, including low phosphorus (LP). The synthesis and stable accumulation of ACNs rely on substantial carbohydrate investment, implying a potential role in carbon partitioning-mediated growth and resistance, in addition to the well-established antioxidant activity. To investigate cultivar-dependent differences in ACN accumulation and their relationship with photo-assimilate partitioning and growth adaptation under LP stress, seedlings of six representative maize cultivars were hydroponically cultured under both control and LP conditions. ACNs content, photosynthetic parameters, plant relative growth ratio, and tissue-specific carbohydrates were quantified. The results showed that LP reduced photosynthesis and biomass, while stimulating ACNs biosynthesis in leaves and sheaths. Cultivars were then classified as ACN-sensitive and -insensitive groups based on the ACNs accumulation in the newly unfolded leaves and corresponding sheaths. ACN-sensitive cultivars exhibited higher ACNs levels, which correlated positively with soluble sugars but negatively with starch reserves, suggesting preferential carbon partitioning to ACNs precursors rather than to starch. These cultivars also maintained higher relative growth ratios under LP, associated with less photosynthesis decline and starch accumulation compared with ACN-insensitive cultivars. We hypothesize that ACNs synthesis function as a diversion of photo-assimilates into secondary metabolism under LP, thereby improving photosynthetic efficiency by mitigating excess sugar accumulation that could impair plant growth. This carbon-partitioning adaptation could be exploited by selecting for ACNs accumulation as a breeding trait to enhance maize resilience to LP. Full article

The photochemical efficiency of photosystem II (PSII) was monitored in two-year-old seedlings from six Chilean woody sclerophyllous species differing in foliage habits (evergreen, deciduous, semi-deciduous) and leaf orientation. A common garden experiment was established in July 2020 in a Mediterranean-type climate site under two watering regimes (2 L⁻¹ seedling⁻¹ week⁻¹ for 5 months versus no irrigation). Chlorophyll a fluorescence rise kinetics (OJIP) and JIP test analysis were monitored from December 2021 to January 2022. The semi-deciduous Colliguaja odorifera (leaf angle of 65°) exhibited the highest performance in processes such as absorption and trapping photons, heat dissipation, electron transport, and level of photosynthetic performance (i.e., parameters PI_ABS F_V/F_M, F_V/F₀, and ΔV_IP). In contrast, the evergreen Peumus boldus (leaf rolling) exhibited the opposite behavior for the same parameters. On the other hand, the deciduous Vachelia caven (small compound leaves and leaf angle of 15°) showed the lowest values for minimal and maximal fluorescence (F₀ and F_M) and the highest area above the OJIP transient (S_m) during the study period. Irrigation decreased S_m and the relative contribution of electron transport (parameter ΔV_IP) by 22% and 17%, respectively, but no clear effects of the irrigation treatments were observed among species and dates of measurement. Overall, V. caven and C. odorifera exhibited the highest photosynthetic performance, whereas P. boldus seemed to be more prone to photoinhibition. We conclude that different foliar adaptations among species influence light protection mechanisms more than irrigation treatments. Full article

Speed breeding technology has been used as a promising approach to accelerate plant breeding cycles and enhance agricultural productivity. However, systematic research on optimizing speed breeding conditions for alfalfa (Medicago sativa L.) in controlled plant factory environments remains limited. This study aimed to optimize light intensity, nutrient solution formulations, and photoperiod conditions for alfalfa speed breeding in plant factories equipped with full-spectrum LEDs, and to validate the applicability of these conditions across cultivars with different fall dormancy levels. Results demonstrated that a light intensity of 250 μmol·m⁻²·s⁻¹ significantly enhanced photosynthetic parameters, antioxidant enzyme activities, and biomass accumulation while minimizing malondialdehyde (MDA). The 75% concentration of the Japanese garden-test formula (JGTF) outperformed the Hoagland solution in promoting growth and photosynthetic pigment synthesis. An extended photoperiod (22 h/d) substantially accelerated growth and shortened flowering time. Under optimized conditions (250 μmol·m⁻²·s⁻¹ light intensity, 22 h/d photoperiod, and 75% Japanese Garden Test Formula), alfalfa cultivars reached initial flowering in approximately 37 days, regardless of fall dormancy level. This study establishes an effective speed breeding protocol for alfalfa, and the optimized conditions demonstrate broad applicability across cultivars with varying fall dormancy characteristics, providing a valuable foundation for accelerated alfalfa breeding programs and contributing to enhanced forage crop development efficiency. Full article

A large population in Africa, particularly West Africa, depends on leafy vegetables such as red amaranth (Amaranthus cruentus), Lagos spinach (Celosia argentea), and African eggplant (Solanum macrocarpon) as affordable and readily available sources of nutrition. These vegetables are rich sources of phenolics, minerals, vitamins, and bioactive compounds, contributing significantly to dietary nutrition and providing an important source of revenue for farmers. However, the temperature rise due to climate change threatens their availability and nutritional value. This study assessed the effects of temperature regimes (23, 30, and 40 °C) on the growth and quality of these vegetables under greenhouse conditions for 48 (A. cruentus and C. argentea) and 54 (S. macrocarpon) days after sowing by measuring biomass (leaf, stem, shoot, root dry weight, root/shoot and leaf area), photosynthetic parameters, pigments, sugars, mineral content, antioxidant activity, total phenolic compounds, total flavonoids, and free amino acids. Temperature significantly affected biomass, with A. cruentus and C. argentea showing declines of 13.5–32.2% and 5.1–27.8%, respectively, at 40 °C compared to 23 °C, indicating sensitivity to heat stress. Photosynthetic rates increased with a rise from 23 to 30 °C by 2.1–29.2% across all species. Sugar contents remained generally stable, except for notable decreases in glucose and soluble sugars by 43.3% and 40.5%, respectively, in C. argentea between 30 and 40 °C, and a 52.6% reduction in starch in S. macrocarpon from 23 to 40 °C. Mineral nutrient responses varied by species; however, they exhibited similar increases in nitrogen and phosphorus, as well as decreases in calcium and manganese, at higher temperatures. Notably, antioxidant capacity and total phenolic compounds declined significantly in C. argentea (8.1% and 8.0%) and S. macrocarpon (4.7% and 13.3%). In contrast, free amino acid contents increased by 35.2% and 28.8% in A. cruentus and S. macrocarpon, respectively. It was concluded that A. cruentus and C. argentea suffer reduced growth and nutrients at 40 °C, while S. macrocarpon maintains biomass but has some biochemical declines; antioxidant capacity and phenolics drop at high temperatures, free amino acids rise, and 30 °C is optimal for all three. Full article

Low inner leaves in the thick canopy of dense Chinese fir plantations frequently show premature senescence and dieback regardless of age. To elucidate the underlying mechanisms, a 28-day growth chamber experiment was conducted under dark conditions to induce leaf senescence. Changes in leaf area, photosynthetic performance, and the responses of carbon metabolism and the antioxidant defense system were analyzed. Leaf area decreased significantly with time in darkness. The photosystem II reaction center was damaged, and fluorescence parameters and chlorophyll contents decreased, resulting in reduced light energy capture and conversion efficiencies. Photosynthetic rate, apparent quantum yield, stomatal conductance, transpiration rate, and light use efficiency all decreased, while the light compensation point and intercellular CO₂ concentration increased. Antioxidant enzyme activities initially increased but eventually collapsed as the stress continued and H₂O₂ and malondialdehyde accumulated, causing membrane conductivity, i.e., membrane permeability, to increase by 122%. Meanwhile, reduced non-structural carbohydrates, especially total non-structural carbohydrates content, decreased by 45.32%, triggering sugar starvation and accelerating aging. Our study provided new physiological evidence for light-stress response mechanisms in Chinese fir. Specifically, it revealed that dark-induced leaf senescence was mainly caused by irreversible damage to the photosynthetic apparatus and oxidative stress, which together led to carbon starvation and ultimately death. Full article

In order to identify saline–alkali-tolerant rapeseed varieties suitable for cultivation on moderately saline–alkali soils and to expand the use of such lands, six rapeseed varieties were selected as experimental materials. Field experiments were conducted to evaluate agronomic traits, photosynthesis, stress physiology, yield, and quality throughout the entire growth period. Statistical methods, including correlation analysis, principal component analysis, membership function analysis, and cluster analysis, were employed to evaluate and select saline–alkali-tolerant varieties. The results indicated that H62 and 20C14 yielded the highest seed production, reaching 2287.99 kg·hm⁻² and 2277.15 kg·hm⁻², respectively. During the mid-to-late growth stages, the majority of agronomic traits, photosynthetic parameters, and stress physiology indicators for 20C14 were significantly superior to those of the other varieties. The results of the principal component analysis showed that the total root length at maturity stage, root–shoot ratio at flowering stage, and proline content at maturity stage were the most important indicators for screening saline–alkali-tolerant rapeseed varieties. A comprehensive analysis of these indicators revealed the following descending order of saline–alkali tolerance among the varieties: 20C14 > 20C17 > 20C4 > H62 > H158 > 17C2. Cluster analysis was performed to classify the rapeseed into strong saline–alkali-tolerant type (20C14 and 20C17), moderate saline–alkali-tolerant type (20C4, H62, and H158), and weak saline–alkali-tolerant type (17C2). Consequently, 20C14 and 20C17 are recommended as suitable rapeseed varieties for cultivation on soda saline–alkali soils. Full article