Photosynthetic Characteristics Research Articles

Effect of Arbuscular Mycorrhizal Fungi (AMF) on photosynthetic characteristics of cotton seedlings under saline-alkali stress.

The study aimed to find the best Arbuscular Mycorrhizal Fungi (AMF) strain for cotton growth in Xinjiang's salinity and alkali conditions. Cotton (Xinluzao 45) was treated with Funneliformis mosseae (GM), Rhizophagus irregularis (GI), and Claroideoglomus etunicatum (GE) as treatments, while untreated cotton served as the control (CK). Salinity stress was applied post-3-leaf stage in cotton. The study analyzed cotton's reactions to diverse saline-alkali stresses, focusing on nutrient processes and metabolism. By analyzing the growth and photosynthetic characteristics of plants inoculated with Funneliformis mosseae to evaluate its salt tolerance. Saline-alkali stress reduced chlorophyll and hindered photosynthesis, hampering cotton growth. However, AMF inoculation mitigated these effects, enhancing photosynthetic rates, CO2 concentration, transpiration, energy use efficiency, and overall cotton growth under similar stress levels. GM and GE treatments yielded similar positive effects. AMF inoculation enhanced cotton plant height and biomass. In GM treatment, cotton exhibited notably higher root length than other treatments, showing superior growth under various conditions. In summary, GM-treated cotton had the highest infection rate, followed by GE-treated cotton, with GI-treated cotton having the lowest rate (GM averaging 0.95). Cotton inoculated with Funneliformis mosseae, Rhizophagus irregularis, and Claroideoglomus etunicatum juvenile showed enhanced chlorophyll and photosynthetic levels, reducing salinity effects. Funneliformis mosseae had the most significant positive impact.

Nano calcium carbonate improves wheat nitrogen accumulation and grain yield by enhancing soil nitrogen supply and flag leaf photosynthetic characteristics

ContextOver-application of chemical fertilizers to attain optimal crop yields has resulted in an environmental issue of global concern. To mitigate this, reducing nitrogen (N) application and enhancing fertilizer use efficiency is crucial, and nano-fertilizers offer a promising solution. However, there is a paucity of studies examining the use of nano-fertilizers in fields. ObjectivesThis study aimed to assess the impact of different dosages of nano calcium carbonate (NCC) mixed with compound fertilizer (CF) on soil N supply, enzyme activity, microbial ecology, as well as photosynthetic characteristics, N accumulation and yield of wheat plants. MethodsThe effects were examined through a soil column leaching experiment and a two-year field experiment conducted from 2020 to 2022. Five treatment groups were established, namely CK (CF), T1 (CF + 0.15% NCC), T2 (CF + 0.30% NCC), T3 (CF + 0.45% NCC), and T4 (CF + 0.60% NCC), to determine the optimal ratio of NCC to CF. ResultsAll NCC treatments resulted in reduced leaching of soluble N. Nevertheless, the 0.45% and 0.60% NCC treatments (T3 and T4) posed a risk of migration through water runoff, leading to nutrient losses. The simultaneous application of NCC and CF increased the content of soil nitrate N (NO3--N), as well as the activity levels of urease and protease during the anthesis stage. Additionally, it elevated the abundance of various microbial communities, including Actinobacteria, Acidobacteria, Chloroflexi, Cyanobacteria, and Nitrospirae. NCC application reduced the content of Na+/K+ and malondialdehyde (MDA), while elevating the activities of flag leaf superoxide dismutase (SOD), catalase (CAT), ascorbate peroxidase (APX), nitrate reductase (NR), and glutamine synthetase (GS). Additionally, it increased stomatal conductance (Gs) and net photosynthetic rate (Pn). The 0.30% NCC treatment showed significantly higher N accumulation in the stem, leaf, and spike compared to CK at the maturity stage. Moreover, 0.30% NCC treatment exhibited a significant increase in the number of grains per spike and higher yields compared to CK. In particular, 0.30% and 0.45% NCC treatments accomplished yield boosts of 29.6–34.7% and 19.9–26.0%, respectively. ConclusionNCC enhanced wheat plant N accumulation and yield through regulation of N release rate and increased soil N content, enzyme activity, and microbial community diversity and abundance. Additionally, NCC boosted flag leaf photosynthesis rate during the anthesis to maturity stage of wheat. This research highlights the potential of NCC to improve wheat crop production. And 0.30% NCC is the optimal application concentration for NCC.

Contribution of Photosynthetic, Root and Phenotypic Traits to Soybean Plant Height

Breeding new high-yield and high-quality forage soybean cultivars is an effective approach to addressing the shortage of feed protein and sustainable agricultural development. Plant height is a key indicator of forage soybean genotypes and is closely related to forage yield. However, the determinants affecting soybean plant height remain highly uncertain. In order to analyze the factors contributing to plant height differences among soybean cultivars, two tall-stemmed soybean cultivars (“Neinong S001” and “Neinong S002”) and two short-stemmed soybean cultivars (“Neinong 0004” and “Neinong 0005”) were used in this study as test materials for examining aboveground phenotypic characteristics, root traits, and photosynthetic characteristics. The test materials were planted in 2018 at Chakintai Ranch (122°15′ E, 43°38′ N) using the potting method, and the indicators were measured in June. The results showed that the leaf area, root volume, and root surface area of high-stemmed soybean cultivars were significantly (p < 0.05) lower than those of short-stemmed soybean cultivars. Additionally, the dry weight of a single plant and transpiration rate were significantly (p < 0.05) higher in high-stemmed soybean cultivars compared to short-stemmed soybean cultivars. It was found that soybean plant height was significantly (p < 0.05) correlated with leaf area, leaf shape index, intercellular CO2 concentration, transpiration rate, SPAD, root weight, root length, root surface area, and root volume. Further path analyses revealed that intercellular CO2 concentration and root surface area had a direct impact on plant height, with direct effect coefficients of 0.22 and −0.91, respectively. These results provide new insights into the sustainability development and genetic enhancement of plant height characteristics in forage soybean.

Enhancing Drought Resistance and Yield of Wheat through Inoculation with Streptomyces pactum Act12 in Drought Field Environments

Drought stress is the primary abiotic factor affecting wheat growth, development, and yield formation. The application of plant growth-promoting rhizobacteria (PGPR) represents an environmentally sustainable approach to mitigate the impacts of drought stress on wheat. This study conducted field experiments using two winter wheat varieties, the drought-sensitive variety Jimai 22 and the drought-resistant variety Chang 6878, aiming to investigate the effects of Streptomyces pactum Act12 inoculation on photosynthetic characteristics, physiological parameters, and yield traits during the jointing, heading, and middle-filling stages under drought stress. The results revealed that drought stresses significantly reduced chlorophyll content, leaf area, biomass, and yield in wheat, while Act12 inoculation significantly increased chlorophyll content, photosynthetic efficiency, antioxidant enzyme activity such as superoxide dismutase (SOD) and peroxidase (POD), osmolyte content (proline and soluble proteins), and decreased malondialdehyde (MDA) content. These combined effects alleviated drought stress, resulting in increased biomass and yield in wheat. Under drought stress, an increase in leaf proline content of 13.53% to 53.23% (Jimai 22) and 17.17% to 43.08% (Chang 6878) was observed upon Act12 inoculation. Moreover, a decrease in MDA content was recorded of 15.86% to 53.61% (Jimai 22) and 13.47% to 26.21% (Chang 6878). Notably, there was a corresponding increase in yield of 11.78% (Jimai 22) and 13.55% (Chang 6878). In addition, grain quality analysis revealed a significant improvement in grain hardness with Act12 inoculation. Therefore, Act12 demonstrates the potential for enhancing the sustainable development of wheat production in arid and semi-arid regions.

Exogenous strigolactone enhanced the drought tolerance of pepper (Capsicum chinense) by mitigating oxidative damage and altering the antioxidant mechanism.

Exogenous SL positively regulates pepper DS by altering the root morphology, photosynthetic character, antioxidant enzyme activity, stomatal behavior, and SL-related gene expression. Drought stress (DS) has always been a problem for the growth and development of crops, causing significant negative impacts on crop productivity. Strigolactone (SL) is a newly discovered class of plant hormones that are involved in plants' growth and development and environmental stresses. However, the role of SL in response to DS in pepper remains unknown. DS considerably hindered photosynthetic pigments content, damaged root architecture system, and altered antioxidant machinery. In contrast, SL application significantly restored pigment concentration modified root architecture system, and increased relative chlorophyll content (SPAD). Additionally, SL treatment reduced oxidative damage by reducing hydrogen peroxide (H2O2) (24-57%) and malondialdehyde (MDA) (79-89%) accumulation in pepper seedlings. SL-pretreated pepper seedlings showed significant improvement in antioxidant enzyme activity, proline accumulation, and soluble sugar content. Furthermore, SL-related genes (CcSMAX2, CcSMXL6, and CcSMXL3) were down-regulated under DS. These findings suggest that the foliar application of SL can alleviate the adverse effects of drought tolerance by up-regulating chlorophyll content and activating antioxidant defense mechanisms.

Additional far-red light promotes the healing and quality of double-root-cutting grafted watermelon seedlings

Graft healing is an important factor that determines the survival of the double-root-cutting (DRC) grafted plants. Recent studies have shown that adding far-red light (FR) to change the red/far-red (R/FR) ratio plays a crucial role in plant growth and development. However, there have been few studies on how R/FR ratio affects the grafting union healing process of DRC grafted seedling. In this study, we applied four light quality treatments: dark (D), white (R/FR=6.0, W), R/FR ratios of 3 (H) and 0.3 (L). The effects of different ratios of R/FR on the survival rate, photosynthetic fluorescence characteristics, graft union healing and growth of DRC grafted watermelon seedlings during the healing period were analyzed using darkness (D) as a control. The results showed that compared with the control L treatment could significantly improve the survival rate, growth indicators and photosynthetic capacity of grafted seedlings, significantly increased the activities of SOD and POD, and contents of soluble sugar and protein in the graft union, and significantly reduced the accumulation of O2−, H2O2 and MDA, which was conducive to the production of callus cell and the healing of grafted union. Meanwhile, qRT-PCR results showed that the expression levels of graft healing-related genes, ClaIAA, ClaSOD, ClaPOD, ClaWOX4, ClaGH9B14 and ClaGH9B1 were significantly induced L treatment. The current study can contribute to speeding up the development of industrialized production with high-quality watermelon grafted seedlings.

Effects of Penoxsulam on Photosynthetic Characteristics and Safety Evaluation of Foxtail Millet

Foxtail millet planting has a long history and profound role in agricultural civilization. However, weeds have become one of the obstacles restricting the development of the foxtail millet industry. Penoxsulam, as an early post-emergence herbicide for controlling gramineous weeds in paddy fields, is effective for some broadleaf weeds. In this study, six different doses (CK, 0.5X, 1X, 2X, 3X, 4X) of penoxsulam were sprayed at the 3–5 leaf stage of the conventional variety Jingu 21 to study its effect on the growth and development of foxtail millet, in order to screen out the appropriate spraying concentration. The main results are as follows: Within 15 days after spraying penoxsulam, the plant height and leaf area of foxtail millet decreased with the increase in spraying dose, and gradually recovered 15–25 days after spraying, but there were still significant differences compared with CK. The photosynthetic pigment content, net photosynthetic rate (Pn), transpiration rate (Tr), stomatal conductance (Gs), the maximum photochemical efficiency (Fv/Fm), photosynthetic system II actual photochemical efficiency (Y(II)), and photochemical quenching coefficient (qP) of foxtail millet decreased with an increase in the penoxsulam spraying dose, while the intercellular CO2 concentration (Ci) and non-photochemical quenching coefficient (NPQ) showed an upward trend. There was almost no significant difference in each index between the spraying dose of 0.5X and 1X and CK, but the photosynthesis of foxtail millet leaves was still significantly inhibited under a spraying dose of 3X and 4X. Penoxsulam had certain growth-inhibiting effects on Echinochloa crus-galli (L.) Beauv. (E. crus-galli), Digitaria sanguinalis (L.) Scop. (D. sanguinalis), Chenopodium album L. (C. album), and Amaranthus retroflexus L. (A. retroflexus) which increased as the spraying dosage increased. Our study found that spraying dose groups of 0.5X and 1X penoxsulam were safe for foxtail millet growth and could be used to control gramineous weeds in fields. Other spraying doses are not recommended in the field due to their serious phytotoxicity to foxtail millet, which provides a new measure for weed control in foxtail millet fields.

Effect of arbuscular mycorrhizal symbiosis on growth and biochemical characteristics of Chinese fir (Cunninghamia lanceolata) seedlings under low phosphorus environment.

The continuous establishment of Chinese fir (Cunninghamia lanceolata) plantations across multiple generations has led to the limited impact of soil phosphorus (P) on tree growth. This challenge poses a significant obstacle in maintaining the sustainable management of Chinese fir. To investigate the effects of Arbuscular mycorrhizal fungi (AMF) on the growth and physiological characteristics of Chinese fir under different P supply treatments. We conducted an indoor pot simulation experiment in the greenhouse of the Forestry College of Fujian Agriculture and Forestry University with one-and-half-year-old seedlings of Chinese fir from March 2019 to June 2019, with the two P level treatment groups included a normal P supply treatment (1.0 mmolL-1 KH2PO4, P1) and a no P supply treatment (0 mmolL-1 KH2PO4, P0). P0 and P1 were inoculated with Funneliformis mosseae (F.m) or Rhizophagus intraradices (R.i) or not inoculated with AMF treatment. The AMF colonization rate in the root system, seedling height (SH), root collar diameter (RCD) growth, chlorophyll (Chl) photosynthetic characteristics, enzyme activities, and endogenous hormone contents of Chinese fir were estimated. The results showed that the colonization rate of F.m in the roots of Chinese fir seedlings was the highest at P0, up to 85.14%, which was 1.66 times that of P1. Under P0 and P1 treatment, root inoculation with either F.m or R.i promoted SH growth, the SH of R.i treatment was 1.38 times and 1.05 times that of F.m treatment, respectively. In the P1 treatment, root inoculation with either F.m or R.i inhibited RCD growth. R.i inhibited RCD growth more aggressively than F.m. In the P0 treatment, root inoculation with F.m and R.i reduced the inhibitory effect of phosphorus deficiency on RCD. At this time, there was no significant difference in RCD between F.m, R.i and CK treatments (p < 0.05). AMF inoculation increased Fm, Fv, Fv/Fm, and Fv/Fo during the chlorophyll fluorescence response in the tested Chinese fir seedlings. Under the two phosphorus supply levels, the trend of Fv and Fm of Chinese fir seedlings in different treatment groups was F.m > R.i > CK. Under P0 treatment, The values of Fv were 235.86, 221.86 and 147.71, respectively. The values of Fm were 287.57, 275.71 and 201.57, respectively. It increased the antioxidant enzyme activity and reduced the leaf's malondialdehyde (MDA) content to a certain extent. It is concluded that AMF can enhance the photosynthetic capacity of the host, regulate the distribution of endogenous hormones in plants, and promote plant growth by increasing the activity of antioxidant enzymes. When the P supply is insufficient, AMF is more helpful to plants, and R.i is more effective than F.m in alleviating P starvation stress in Chinese fir.

Tolerance to mild shading levels in cattail as related to increased photosynthesis and changes in its leaf area and anatomy.

Shading is an environmental factor that has been little investigated regarding its effects on emergent aquatic plants. Typha domingensis Pers. is an emergent macrophyte that demonstrates some plasticity for self-shading, and as it can shade other species in the same area, the effect of shading on its traits deserves further investigation. The objective of the present study was to evaluate the gas exchange, leaf anatomy, and growth of T. domingensis cultivated under increasing shading intensities. The plants were collected and propagated in a greenhouse, and the clones were subjected to four shading intensities: 0% (unshaded), 35%, 73%, and 83% shading created by black nets. Growth traits, clonal production, photosynthesis, transpiration, and leaf anatomy were evaluated. The 73% and 83% shading promoted the death of all plants, but all plants survived in the 35% and unshaded treatments. Compared with the unshaded treatment, the 35% shading treatment promoted a higher photosynthetic rate and greater transpiration, supporting increased growth and production of clones. The increase in the photosynthetic rate in the 35% shading was related to the increase in leaf area which increased the photosynthesis of the whole plant. The 73% and 83% treatments inhibited the development of photosynthetic parenchyma and stomata in T. domingensis, leading to a drastic reduction in photosynthesis and energy depletion. Therefore, T. domingensis does not tolerate intense shading, but its photosynthetic characteristics and growth are favored by mild shading, a factor that may be of great importance for its competitiveness and invasive behavior.

Physiological and Transcriptional Characteristics of Banana Seedlings in Response to Nitrogen Deficiency Stress

Nitrogen is a crucial element for the growth and development of plants, directly affecting crop growth and yield. To investigate the physiological and molecular mechanism of nitrogen-deficiency stress, we conducted an investigation into the effects of different nitrogen levels on the growth, photosynthetic characteristics, and gene transcription levels of banana seedlings. Compared with the control group with normal nitrogen levels (NN), the height of plants receiving Reduced-N (NR), Low-N (LN), and N-Free (NF) treatments was decreased by 0.45 cm, 2.5 cm, and 3.25 cm, respectively. Their dry weight was reduced by 1.63 g, 2.99 g, and 2.88 g, respectively. Conversely, the dry weight of the underground plant part in the LN and NF treatment groups exhibited an increase of 0.13 g and 0.16 g, respectively. Regarding photosynthetic characteristics, the Specialty Products Agricultural Division (SPAD) values of the NR, LN, and NF treatments showed reductions of 15.5%, 30.4%, and 35.9%, respectively, compared with those of the control treatments. The values of maximum photosynthetic efficiency (Fv/Fm), actual photosynthetic efficiency (Y(Ⅱ)), and relative electron transfer (ETR) of the banana seedlings decreased to different degrees after NR, LN, and NF treatment, and their values were positively correlated with N levels. Gene transcription analysis showed that N transport-related proteins, including NRT1.7, NRT2.3a, NRT2.3b, and NRT2.5, were significantly up-regulated to increase the nitrogen absorption capacity of plant roots. On the other hand, various transcription factors including GRAS, MYB, and WRKY were notably up-regulated, facilitating root growth and the expanding root absorption area, thereby enhancing nitrogen uptake. Furthermore, genes associated with endogenous hormone metabolic pathways such as gibberellin (GA), strigolactone (SL), and brassinosteroids (BR) were activated in banana plants subjected to low nitrogen stress, enhancing the plant’s ability to adapt to nitrogen-deficient conditions. These findings offer valuable insights into understanding the transcriptional regulatory mechanisms governing banana responses to low nitrogen stress and breeding new varieties with improved nutrient utilization.

Niche and phenotypic differentiation in fern hybrid speciation, a case study of Pteris fauriei (Pteridaceae).

Niche differentiation is a critical issue in speciation. Although it has a well-known role in adaptive processes of hybrid angiosperms, it is less understood in hybrid ferns. Here we investigate whether an intermediate ecological niche of a fern hybrid is a novel adaptation that provides insights into fern hybrid speciation. Pteris fauriei (Pteridaceae) is a natural hybrid fern, occurring environments between its parent species. The maternal P. minor is found in sunny areas, but the habitat of the paternal P. latipinna is shady. We combined data from morphology, leaf anatomy, and photosynthetic traits to explore adaptation and differentiation, along with measuring the environmental features of their niches. We also performed experiments in a common garden to understand ecological plasticity. The hybrid P. fauriei is intermediate between the parent species in stomatal density, leaf anatomical features, and photosynthetic characteristics in both natural habitats and a common garden. Interestingly, the maternal P. minor showed significant environmental plasticity and was more similar to the hybrid P. fauriei in the common garden, suggesting that the maternal species experiences stress in its natural habitats but thrives in the environments similar to the hybrid's. Based on the similar niche preferences of the hybrid and parents, we propose hybrid superiority. Our results indicate that the hybrid P. fauriei exhibits greater fitness and can compete with and occupy the initial niches of the maternal P. minor. Consequently, we suggest that the maternal P. minor has experienced a niche shift, elucidating the pattern of niche differentiation in this hybrid group. These findings offer a potential explanation for the frequent occurrence of hybridization in ferns and provide novel insights into fern hybrid speciation, enhancing our understanding of fern diversity.

Photosynthetic physiological characteristics, growth performance, and element concentrations reveal the calcicole-calcifuge behaviors of three Camellia species.

We grew three yellow Camellia species (the calcifuge C. nitidissima and C. tunghinensis, and the calcicole C. pubipetala) in acidic and calcareous soils for 7 months and assessed their photosynthetic physiological characteristics, growth performance, and element concentrations in this developmental context. The calcifuge C. nitidissima and C. tunghinensis species exhibited poor growth with leaf chlorosis, growth stagnation, and root disintegration in calcareous soils, and with their P n, G s, T r, F v/F m, ΦPSII, ETR, qP, leaf Chla, Chlb, and Chl(a + b) concentrations, and root, stem, leaf, and total biomass being significantly lower when grown in calcareous soils relative to in acidic soils. In contrast, the calcicole C. pubipetala grew well in both acidic and calcareous soils, with few differences in the above parameters between these two soil substrates. The absorption and/or transportation of nutrient elements such as N, K, Ca, Mg, and Fe by the two calcifuge Camellia species plants grown in calcareous soils were restrained. Soil type plays a major role in the failure of the two calcifuge Camellia species to establish themselves in calcareous soils, whereas other factors such as competition and human activity are likely more important limiting factors in the reverse case. This study furthers our understanding of the factors influencing the distribution of these rare and endangered yellow Camellia species, allowing for improved management of these species in conservation projects and horticultural production.

Mechanism of salt tolerance in the endangered semi-mangrove plant Barringtonia racemosa: anatomical structure and photosynthetic and fluorescence characteristics.

To elucidate the mechanisms governing the salt tolerance of the endangered semi-mangrove plant Barringtonia racemosa, the biomass, photosynthetic and fluorescent characteristics, and anatomical structure of B. racemosa were studied under low, medium and high salt stress. The results showed that the stem dry weight, net photosynthetic rate, intercellular CO2 concentration, Fv/Fm, and ΦPSI of B. racemosa decreased under high salt stress, which led to a significant reduction in total dry weight. Stem dry weight was significantly positively correlated with the thickness of palisade tissue and significantly negatively correlated with the thickness of the epidermis of roots and xylem of stems. Therefore, a stable net photosynthetic rate and intercellular CO2 concentration, an increase in Fv/Fm and ΦPSI, an increase in or stable palisade tissue and spongy mesophyll of leaves and an increase in xylem thickness of the stem and epidermis, outer cortex, and stele diameter of roots could contribute to the salt tolerance of B. racemosa.

Effects of Long-Term High Temperatures in the Root Zone on the Physiological Characteristics of Grapevine Leaves and Roots: Implications for Viticulture Practices

Ridging cultivation and root restriction cultivation are beneficial due to their improvement of the soil permeability in the root zone of grapevine, and they are widely used in southern China, Japan, and other countries. However, with the intensification of global warming, when using ridging or root restriction cultivation, the soil temperature in the root zone can often reach 30 °C or even more than 35 °C during the summer, which is not conducive to the growth of grapevines. The aim of this study was to explore the effects of high root zone temperatures on the photosynthetic fluorescence characteristics of grapevine leaves, root respiration, and degree of lignification of roots and shoots, as well as to provide a theoretical foundation for the management of grapevine production and cultivation. One-year-old potted ‘Kyoho’ was used as the study material. Three root temperature treatments were implemented for 15 days (9:00–16:00): 25 °C (CK), 30 °C (T1), and 35 °C (T2). The results showed that the malondialdehyde and H2O2 levels in leaves increased, while the chlorophyll content decreased. The oxygen-evolving complex was inactivated, and PSII donor and acceptor sides were blocked, thus reducing the photosynthetic gas exchange capacity at high root zone temperatures. The grapevine root activity and root/shoot ratio decreased. Simultaneously, the lignin content in the roots and shoots increased. In addition, there was a significant increase in the expression of key genes (PAL, C4H, 4CL, F5H, COMT, CCR, and CAD) in the root lignin synthesis pathway. Heightened root zone temperatures increased cyanide-resistant respiration in roots and heat release in the PPP pathway to alleviate stress damage. Therefore, it is recommended to use grass, mulching, and other cultivation management methods to maintain root zone temperatures below 30 °C in order to ensure the normal growth of grapevines and promote a high and stable yield.

Effects of Rainfall Exclusion Treatment on Photosynthetic Characteristics of Black Locust in the Sub-Humid Region of the Loess Plateau, China.

The mesic-origin species Robinia pseudoacacia L. (black locust) is widely planted in the semiarid and sub-humid areas of the Loess Plateau for the reforestation of vegetation-degraded land. Under the scenario of changing precipitation patterns, exploring the response of photosynthesis to drought allows us to assess the risk to sustainable development of these plantations. In this study, paired plots were established including the control and a treatment of 30% exclusion of throughfall (since 2018). The photosynthetic characteristics were investigated using a portable photosynthesis system for four periods in the full-leaf growing season of 2021-2022, the fourth and fifth years, on both treated and controlled sampling trees. Leaf gas exchange parameters derived from diurnal changing patterns, light response curves, and CO2 response curves showed significant differences except for period II (9-11 September 2021) between the two plots. The photosynthetic midday depression was observed in 2022 in the treated plot. Meanwhile, the decline of net photosynthetic rate in the treated plot was converted from stomatal limitation to non-stomatal limitation. Furthermore, we observed that black locust adapted to long-term water deficiency by reducing stomatal conductance, increasing water use efficiency and intrinsic water use efficiency. The results demonstrate that reduction in precipitation would cause photosynthesis decrease, weaken the response sensitivity to light and CO2, and potentially impair photosynthetic resilience of the plantations. They also provide insights into the changes in photosynthetic functions under global climate change and a reference for management of plantations.

Improving sugarcane agronomy: Field evidence for ultrasonic treatment enhancing yield, growth, and physiological and biochemical characteristics

Ultrasonic treatment (UT) is a safe and efficient physical stimulus used to improve crop germination and growth. However, previous studies have concentrated on the germination and seedling stages of ultrasonically treated crops, while field tests of the effects of ultrasound on sugarcane growth have not been reported. In this study, we compared the growth, photosynthetic characteristics, and antioxidant properties of three sugarcane varieties, ‘ROC22’, ‘LC05–136’, and ‘YT93–159’, under no UT (T1), UT (20–40 kHz mixed frequency, dry treatment) for 1 min (T2), UT for 2 min (T3), and UT for 5 min (T4). The field experiments were conducted from January 2021 to January 2023.The effect of UT on newly-planted sugarcane was greater than on ratoon sugarcane for all measured parameters in both years. Compared with the T1 treatment, in 2021 the increases in cane yield and sugar yield under UT (T3 and T4) were 9.76%–28.57% and 7.80%–21.21%, respectively, while in 2022, the increases were 1.19%–12.64% and 2.16%–8.39%, respectively. From the two-year data, compared with the T1 treatment, the sucrose content of sugarcane under the T3 treatment in V1 increased by 0.38%–15.26%; the T3 and T4 treatments in V2 increased the sucrose content by 0.48%–4.90%, and the T4 treatment in V3 increased the content by 1.17%–5.85%. Moreover, suitable UT increased plant height, stem diameter, root length, and germination rate. Suitable UT also increased the chlorophyll content, net photosynthetic rate, stomatal conductance, transpiration rate, superoxide dismutase activity, peroxidase activity, catalase activity, soluble protein content, and soluble sugar content while decreasing the malondialdehyde content in sugarcane leaves. Meanwhile, a multi-analysis showed that a more developed root system, a more efficient photosynthetic rate, and better antioxidant properties after UT treatment led to increased sugar yield of sugarcane. This study is the first to demonstrate that suitable UT (2–5 min, 20–40 kHz mixed frequency, dry treatment) can significantly increase the yield and quality of sugarcane based on field tests. Furthermore, this study shows that ultrasonic seed treatment technology has promising applications in sugarcane cultivation and significant potential in agricultural production.

Rubisco and sucrose synthesis and translocation are involved in the regulation of photosynthesis in wheat with different source-sink relationships.

Source-sink relationships influence photosynthesis. So far, the limiting factors for photosynthesis of wheat cultivars with different source-sink relationships have not been determined. We aimed to determine the variation patterns of photosynthetic characteristics of wheat cultivars with different source-sink relationships. In this study, two wheat cultivars with different source-sink relationships were selected for photosynthetic physiological analyses. The results showed that YM25 (source-limited cultivar) had higher photosynthetic efficiency compared to YM1 (sink-limited cultivar). This is mainly due to a stronger photochemical efficiency, electron transfer capacity, and Rubisco carboxylation capacity of YM25. YM25 accumulated less soluble carbohydrates in flag leaves than YM1. This is mainly due to the stronger sucrose synthesis and transport capacity of YM25 by presenting higher sucrose-related enzyme activities and gene expression. A PCA analysis showed that Rubisco was the main factor limiting the photosynthetic capacity of YM25. The soluble sugar accumulation in flag leaves and sink limitation decreased the photosynthetic activity of YM1. Increased N application improved source-sink relationships and increased grain yield and source leaf photosynthetic capacity in both two wheat cultivars. Taken together, our findings suggest that Rubisco and sucrose synthesis and translocation are involved in the regulation of photosynthesis of wheat cultivars with different source-sink relationships and that source and sink limitation effects should be considered in photosynthesis.

Yield and Photosynthesis Related to Growth Forms of Two Strawberry Cultivars in a Plant Factory with Artificial Lighting

Appropriate growth forms for strawberry production in a plant factory with artificial lighting (PFAL), which is a recently developed production system, remain undetermined. Improving strawberry productivity in a PFAL requires insights into the interplay between production characteristics (growth and photosynthesis) and growth forms, such as plant height and leaf area (LA), which are major determinants of crop yield. Growth status, yield, and photosynthetic characteristics of the two cultivars of strawberries (Fragaria ×ananassa Duch. Tochiotome and Koiminori) with different growth forms were examined. ‘Koiminori’ exhibited a 1.9-fold higher yield and a 2.0-fold greater total dry weight of respective organs compared with ‘Tochiotome’. The single-plant photosynthetic rate (AP), serving as an index for both cultivars, was 2.2-times higher for Koiminori than for Tochiotome. The photosynthetic rates of a single leaf (AL) and LA were also analyzed as important factors that influence the AP. The AL for ‘Koiminori’ surpassed that of ‘Tochiotome’ by 1.4 times. This was attributed to the elevated photosynthetic photon flux density received by the upper leaves of Koiminori, which is a consequence of its higher plant height in proximity to the light source. Evaluation of four photosynthetic capacities, maximum rate of carboxylation, maximum rate of electron transport, photosynthetic rate under saturating light, and light utilization efficiency, which are potential factors that affect AL, revealed no differences in these capacities between cultivars. ‘Koiminori’ exhibited a significantly larger LA (2.3- to 3.1-times) than ‘Tochiotome’, indicating that the former’s higher AP resulted mainly from its higher AL and larger LA. Thus, strawberry production in a PFAL can be improved by growing cultivars with growth forms such as higher plant height and larger LA.

The Microphytobenthos are Abundant and Mediate Key Carbon Fluxes in Tropical Mangroves

AbstractThe microphytobenthos (MPB) are known to play important ecological roles in estuarine ecosystems. While tidal flat MPB are widely studied, mangrove MPB are often overlooked due to the common belief that the light-limited environment under the mangrove canopy is not conducive to MPB growth. We assessed the biomass and community characteristics of the MPB in two contrasting mangrove forests (silty substrate and brackish influence versus sandy substrate and oceanic influence), their seasonal photosynthetic performance, as well as their role in mediating porewater carbon flux. Biomass measured as chlorophyll a concentration indicated that MPB abundance was equal, if not higher, in mangroves than on tidal flats. While mangrove sediments fostered an equally rich assemblage of MPB (estimated 23 to 45 genera) as the adjacent tidal flat, the MPB genus composition was different across all habitats, sites, and seasons, indicating the strong environmental influence on MPB assemblages. This study identified porewater salinity, temperature, and pH, as well as irradiance level and surface soil temperature to be accountable for 23.5% of this variation. MPB in all sampling locations were dominated by pennate diatoms, while cyanobacteria were common in the estuarine (as opposed to oceanic) site. Compared to tidal flat MPB, mangrove MPB exhibited photosynthetic performance characteristic of lower light acclimation. A mesocosm experiment using enriched stable isotopes of carbon and nitrogen indicated that a tight coupling exists between mangrove-derived carbon and MPB. Mangrove MPB are abundant and different from tidal flat MPB, and are functional photosynthetic entities with a regulatory role in nutrient cycling in mangrove ecosystems.

Effects of summer pruning on the growth and photosynthetic characteristics of pepper (Capsicum annuum L.)

The objective of the study is to investigate the mechanism by which summer pruning enhances the growth of pepper plants, as indicated by growth and fruit appearance indicators, photosynthetic rate and gas exchange parameters, rapid light response and induction kinetics curves and the related chlorophyll fluorescence parameters. The results indicated that the leaf growth rate, the individual pepper fruit weight, and the fruit longitudinal and cross diameters of the pruned group were significantly higher than those of the control. The stomatal conductance (Gs), intercellular CO2 concentration (Ci) and transpiration rate (Tr) of the pruned group were significantly higher than those of the control. The initial slope of the rapid light response curve, which represents light energy utilisation efficiency (α), the maximum electron transfer rate (Jmax) and saturated light intensity (PARsat) were all higher in the summer pruning group than in the control group. The F0 of the pruned group decreased by 16.83%, Fv/F0 increased by 23.69%, PIabs increased by 58.33%, and DIo/RC decreased by 22.09% compared to the control group. In summary, summer pruning significantly improves the leaf growth rate and fruit appearance quality of pepper, effectively promotes the photosynthesis of functional leaves, and reduces the degree of stress under adverse environmental conditions.