Nitrogen Balance Index Research Articles

Mitigating saturation effects in rice nitrogen estimation using Dualex measurements and machine learning

Nitrogen is essential for rice growth and yield formation, but traditional methods for assessing nitrogen status are often labor-intensive and unreliable at high nitrogen levels due to saturation effects. This study evaluates the effectiveness of flavonoid content (Flav) and the Nitrogen Balance Index (NBI), measured using a Dualex sensor and combined with machine learning models, for precise nitrogen status estimation in rice. Field experiments involving 15 rice varieties under varying nitrogen application levels collected Dualex measurements of chlorophyll (Chl), Flav, and NBI from the top five leaves at key growth stages. Incremental analysis was performed to quantify saturation effects, revealing that chlorophyll measurements saturated at high nitrogen levels, limiting their reliability. In contrast, Flav and NBI remained sensitive across all nitrogen levels, accurately reflecting nitrogen status. Machine learning models, particularly random forest and extreme gradient boosting, achieved high prediction accuracy for leaf and plant nitrogen concentrations (R2 > 0.82), with SHAP analysis identifying NBI and Flav from the top two leaves as the most influential predictors. By combining Flav and NBI measurements with machine learning, this approach effectively overcomes chlorophyll-based saturation limitations, enabling precise nitrogen estimation across diverse conditions and offering practical solutions for improved nitrogen management in rice cultivation.

Effect of Foliar Boron and Proline Applications on Physiological and Biochemical Properties in Soybean (Glycine max L.)

Background: In this study, boron which is an important element in many fields such as defense industry, energy, food and cleaning in the world, was studied. It is also an important plant nutritional element. However, like other important elements, it has some effects on plants and the environment. Türkiye has 76% of the world¢s boron reserves. In this study, proline applications were tried to determine the toxic effect of boron in soybeans, which is a strategic product and to reduce the damage. Methods:This study was carried out to determine the effects of boron (0, 2.5, 5 and 10 ppm) and proline (0, 10 and 20 ppm) applications on plant growth parameters and biochemical properties in soybean (Glycine max L.). The study was carried out in the fully controlled climate room of our faculty's field crops.This trial was carried out according to the randomized plots experimental design in a factorial arrangement with 4 replications. Result: In the research, after the applications, soybean plant height (22.7-33.3 cm), root length (26.2-38.7 cm), stem fresh weight (1.77-3.20 g), stem dry weight (0.59-0.71 g), root fresh weight (1.43-2.72 g), root dry weight (0.15-0.24 g), leaf area index (10.4-11.1 cm2), ion leakage in leaf tissues (20.4- 24.9%), nitrogen balance index (47.3-92.2 dx), anthocyanin (0.04-0.08 dx). flavonoid (34.9-55.6 dx) and chlorophyll (22.5-42.4 mg cm-2) were examined. In the results of working; Boron applications first increased and then decreased the values of plant height, root length, stem fresh and dry weight and root fresh and dry weight in soybean plants. There was a direct decrease in leaf area index, NBI and total chlorophyll values. Other parameters followed a fluctuating course. It has been determined that boron applications increase flavonoid and anthocyanin values. In this study, it was determined that proline applications had a positive and regulatory effect on root length, stem fresh weight, root fresh weight, root dry weight, nitrogen balance index and flavonoid values against boron toxicity.

Serendipita indica: A Promising Biostimulant for Improving Growth, Nutrient Uptake, and Sugar Accumulation in Camellia oleifera

Serendipita indica is a very promising root-associated endophytic fungus that is widely used on various plants; however, whether it affects the growth and physiological activity of an oilseed crop (Camellia oleifera) under field conditions remains unclear. In this study, we analyzed the effects of S. indica inoculation on root colonization rate, growth rate, photosynthetic parameters, mineral element concentrations and related gene expression, and sugar concentrations and expression of their transporter genes in four-year-old C. oleifera trees in the field. The results showed that the root colonization rate of C. oleifera increased from 3.37% to 9.42% following being inoculated with S. indica. Inoculation with S. indica significantly increased the plant height (46.81%), net photosynthetic rate (69.16%), nitrogen balance index (14.44%), chlorophyll index (21.08%), leaf K (7.4%), leaf Ca (13.52%), root P (17.75%), root K (12.80%), soil NH4+-N (17.78%), available K (26.66%), Olsen-P (184.30%), easily extractable glomalin-related soil protein (39.26%), and soil organic carbon (16.25%) concentrations compared to the uninoculated treatment. Inoculation with S. indica also significantly up-regulated the expression of CoHKT1;1 and CoCAX1;2 in the leaves and roots and CoPht1;1, CoPht1;2, and CoPht1;3 in the leaves. Plants inoculated with S. indica also presented significantly higher leaf glucose, fructose, and sucrose concentrations, accompanied by up-regulated expression of CoSWEET2a, CoSWEET7, CoSWEET9b, CoSWEET17a, and CoSWEET17b. These results suggest that S. indica has significant potential as a biostimulant for enhancing the growth and nutritional profile of C. oleifera, thereby contributing to sustainable oilseed production.

Yield Trait and Stability of Chickpea Genotypes for Intensification of Drought‐Prone Rice Fallows of South Asia

ABSTRACTThere is a need for increasing cropping intensity in South Asia including India to ensure food security of burgeoning population. Accordingly, increasing cropping intensity in rainfed rice fallows can be a futuristic strategy. Identification of suitable cultivar and exploration of genetic variability of specific crops/traits are imperative for genetic improvement, drought resistance and yield gain in rice fallows. We evaluated the morphophysiological, yield traits and stability of 15 chickpea genotypes in randomised complete block design for three consecutive years on a drought‐prone rainfed condition of Fluvisol in Kanpur, India. Among genotypes, ‘IPC 2014‐55’, ‘IPC 2015‐44’ and ‘IPC 2011‐92’ had 2%–10% higher relative water content (RWC) over ‘ICC‐92944’ (check cultivar). These genotypes did not differ for total chlorophyll content, root dry weight and nodule dry weight with ‘ICC‐92944’ and ‘KWR 108’ (wider adaptable cultivar of the region). The nitrogen balance index was higher in ‘IPC 2011‐92’, ‘IPC 2014‐88’ and ‘IPC 2014‐55’ by 5%–44% over check cultivar (p < 0.05). The membrane stability index was higher for ‘IPC 2014‐55’ (30%, p < 0.05) and ‘IPC 2011‐92’ (17%, p < 0.05) than ‘ICC‐92944’. ‘IPC 2011‐92’, ‘IPC 2014‐88’ and ‘IPC 2014‐55’ (3 years mean) had 3%–24% higher plant dry weight than ‘ICC‐92944’. Notably, ‘IPC 2014‐55’, ‘IPC 2015‐44’, ‘IPC 2014‐88’ and ‘IPC 2011‐92’ had higher yield attributes such as pods plant−1 by 9%, grain weight plant−1 by 13% and 100‐seed weight by 3% than ‘ICC‐92944’ and ‘KWR 108’ (mean of years). These genotypes had higher mean seed yield than ‘ICC‐92944’ by 23%–42% and ‘KWR 108’ by 7%–23% (p < 0.05). The yield of ‘IPC 2014‐55’, ‘IPC 2015‐44’, ‘IPC 2014‐88’ and ‘IPC 2011‐92’ were stable over years across variable soil and environmental condition as indicated by the genotype × year biplot. Membrane stability index, pods plant−1 and 100‐seed weight were the determinants for increased seed yield of chickpea under drought‐prone condition. Evidently, genotype ‘IPC 2014‐55’, ‘IPC 2015‐44’, ‘IPC 2014‐88’ and ‘IPC 2011‐92’ were better under rainfed rice fallows. These genotypes could be tested under specific drought condition for developing varieties and promoted in rice fallows of South Asia for yield advantage and drought resistance.

Photoperiod Regulates Aerobic Methane Emissions by Altering Plant Growth and Physiological Processes

Previous studies have shown that light quality and quantity affect methane emissions from plants. However, the role of photoperiod in plant-derived methane has not been addressed. We studied the effects of two photoperiods—long-day (16 h light/8 h dark), and short-day (8 h light/16 h dark)—on growth and methane emissions of lettuce (a long-day plant), mung bean (a short-day plant), and tomato (a day-neutral plant) under a temperature regime of 22/18 °C. All species were grown under both light durations. First, seeds were germinated in Petri dishes for one week, then plants were transferred to pots and randomly assigned to one of the two experimental conditions. Under each condition, twelve plants were grown for 21 days; at that time, plant growth and physiological traits, including plant dry mass, growth index, photosynthesis, chlorophyll fluorescence, total chlorophyll, nitrogen balance index, flavonoids, and anthocyanin, were measured. Lettuce plants under the short-day photoperiod had the highest methane emissions. Long-day plants that were exposed to short-day conditions and short-day plants that were exposed to long-day conditions were stressed; day-neutral plants were also stressed under short days (p < 0.05). All three species had decreased total dry mass under short-day conditions, most likely because of decreased photosynthesis and increased transpiration and stomatal conductance. Methane emission was positively correlated with shoot/root mass ratio, nonphotochemical quenching and anthocyanin; but was negatively correlated with stem height, dry mass, photosynthesis, water-use efficiency, total chlorophyll, and flavonoids (p < 0.05). This study revealed that, besides light intensity and quality, light duration can also affect methane emissions from plants.

Supplemental nitrogen alleviates the negative effects of higher temperature on the vegetative growth of canola regardless of carbon dioxide concentration

Climate change components, including carbon dioxide (CO2) and temperature, can influence crop productivity and nutritional value, posing a threat to food security. Many studies have investigated the mitigation of climate change factors by nitrate and/or ammonium application, but there has been little focus on the role of urea in the interactive effects of these factors. We examined the effects of temperature, CO2, and supplemental nitrogen (N in the urea form) on growth and physiological traits of canola (Brassica napus). Plants were grown under two temperature regimes (22/18 °C and 28/24 °C, 16 h light/8 h dark), two CO2 concentrations (400 and 700 µmol mol−1), and three levels of N (zero, no supplement; low, based on 50 kg ha−1; high, based on 100 kg ha−1) for 21 days after one week of initial growth under 22/18 °C. In this study, gas exchange, chlorophyll fluorescence, chlorophyll, flavonoids, nitrogen balance index (NBI), plant growth and biomass, and tocopherols, were measured. Higher temperatures decreased net CO2 assimilation (AN), water use efficiency, effective quantum yield of photosystem II, nonphotochemical quenching (qNP), chlorophyll, flavonoids, stem height and diameter, leaf area and number, dry mass, and β-, γ-, and δ-tocopherols, but increased stomatal conductance. Elevated CO2 increased AN, qNP and leaf area ratio, but decreased stomatal conductance (gs). Supplemental nitrogen alleviated the effects of temperature stress by increasing gs, chlorophyll, NBI, stem height and diameter, leaf area, growth rate, and dry mass. Overall, these findings suggest that under climate change, N supplementation may be used to alleviate environmental stress on plants.

Cultivar effect on proximal optical sensor measurements and estimation of leaf N content in muskmelon and sweet pepper

In intensive vegetable crops, there is a requirement for monitoring tools that assess crop nitrogen (N) status to reduce N use and the potential for nitrate (NO3-) leaching loss. Monitoring with proximal optical sensors can regularly provide information to vegetable growers to assist with optimal crop N management. Reference values for proximal optical sensor measurements that indicate crop N sufficiency or deficiency are increasingly available in the literature. Available values are species specific; however, their use may be problematic if proximal optical sensor measurements are affected by cultivar. Little is known on whether differences between cultivars, within a species, affect optical sensor measurements and their relationships with crop N status, particularly in vegetable crops. This study evaluated the effect of cultivar on a) measurements with the SPAD-502 chlorophyll meter, Normalized Difference Vegetation Index (NDVI) measured with the Crop Circle ACS 470 canopy reflectance sensor, and Nitrogen Balance Index (NBI-R) measured with the Multiplex fluorimeter, and b) the relationships of these measurements with leaf N content. The study was conducted with four cultivars of muskmelon (Tezac, Bosito, Magiar and Jacobo) and three of sweet pepper (Melchor, Machado and CLX PLRJ 731). In both muskmelon and sweet pepper, there were significant differences between cultivars in SPAD and in NBI-R. The range of differences between the cultivars was 2.2−9.7 and 0.6−2.8 SPAD units in muskmelon and sweet pepper, respectively, and 0−0.16 and 0.020.08 NBI-R units in muskmelon and sweet pepper, respectively. Significant differences between cultivars in the NDVI were only obtained in muskmelon; the range of differences between the four cultivars was 0.01–0.04 NDVI units. The relatively large cultivar effect with SPAD and NBI-R values with muskmelon may limit the use of reference values in this species. For avoiding cultivar effects in the two species evaluated, NDVI is preferrable to SPAD and NBI-R. In general, the slopes and intercepts of linear relationships between optical sensor measurements and leaf N content, for each cultivar of each species, were not significantly different to the slope and intercept of the relationship calculated with pooled data of all cultivars of each species. This indicated that the sensitivity of optical sensors to assess leaf N content was similar between cultivars of each species.

Integration of QTL and transcriptome approaches for the identification of genes involved in tomato response to nitrogen deficiency.

Optimizing plant nitrogen (N) usage and inhibiting N leaching loss in the soil-crop system is crucial to maintaining crop yield and reducing environmental pollution. This study aimed at identifying quantitative trait loci (QTLs) and differentially expressed genes (DEGs) between two N treatments in order to list candidate genes related to nitrogen-related contrasting traits in tomato varieties. We characterized a genetic diversity core-collection (CC) and a multi-parental advanced generation intercross (MAGIC) tomato population grown in a greenhouse under two nitrogen levels and assessed several N-related traits and mapped QTLs. Transcriptome response under the two N conditions was also investigated through RNA sequencing of fruit and leaves in four parents of the MAGIC population. Significant differences in response to N input reduction were observed at the phenotypic level for biomass and N-related traits. Twenty-seven QTLs were detected for three target traits (leaf N content, leaf nitrogen balance index, and petiole NO3- content), 10 and six in the low and high N condition, respectively, while 19 QTLs were identified for plasticity traits. At the transcriptome level, 4752 and 2405 DEGs were detected between the two N conditions in leaves and fruits, respectively, among which 3628 (50.6%) in leaves and 1717 (71.4%) in fruit were genotype specific. When considering all the genotypes, 1677 DEGs were shared between organs or tissues. Finally, we integrated DEG and QTL analyses to identify the most promising candidate genes. The results highlighted a complex genetic architecture of N homeostasis in tomato and novel putative genes useful for breeding tomato varieties requiring less N input.

Optimized sand tube irrigation combined with nitrogen application improves jujube yield as well as water and nitrogen use efficiencies in an arid desert region of Northwest China

Efficient water-saving irrigation techniques and appropriate nitrogen (N) application are keys to solving the problems of water scarcity and irrational fertilization in jujube cultivation. In this study, first, the effects of sand tube irrigation (STI) on surface and subsurface wetted characteristics were investigated using in-situ infiltration tests in a jujube garden. Compared with surface drip irrigation (SD), STI reduced surface wetted area by 57.4% and wetted perimeter of the surface wetted circle by 37.1% and increased subsurface maximum infiltration distance of wetting front by 64.9%. At the optimal sand tube depth of 20 cm, surface wetted area of the surface wetted circle decreased by 65.4% and maximum infiltration distance of the wetting front increased by 70.9%, compared with SD. Two-year field experiments then investigated the effects of STI and SD on soil water storage, jujube leaf chlorophyll, net photosynthetic rate, actual water consumption, fruit yield, and water (WUE) and N (NUE) use efficiencies at four levels of N (pure nitrogen: N1, 0; N2, 286 kg ha–1; N3, 381 kg ha–1; N4, 476 kg ha–1) at the same irrigation amount (45 mm irrigation–1, total of 8). Compared with SD, STI increased soil water storage 18.0% (2021) and 15.6% (2022) during the entire growth period and also chlorophyll content, nitrogen balance index, and net photosynthetic rate, with both increasing and then decreasing with increasing N. Compared with SD, STI increased yields by 39.1% and 36.5% and WUE by 44.3% and 39.7% in 2021 and 2022, respectively. Nitrogen use efficiency was 2.5 (2021) and 1.6 (2022) times higher with STI than with SD. STI combined with N3 had the highest yield, WUE, NUE, and net income and is thus recommended as the optimal water–N combination. In conclusion, STI combined with appropriate N application can be an effective water-saving irrigation technology alternative to SD in jujube cultivation in arid areas.

Physiological Characterization of Cold Tolerant and Susceptible Pigeon Pea [Cajanus cajan (L.) Millsp.] Genotypes

Background: The cold stress adversely affects the growth, survival and reproductive capacity of plants if the minimum temperature falls below 5°C. Information’s regarding cold stress and its impact on morphological characters, physio-biochemical constituents and yield attributes in cold tolerant and susceptible pigeon pea genotypes are very limited. Keeping the above facts in to consideration, the experiments were conducted. Methods: Field experiments were conducted during 2018-19 and 2019-20 with 34 genotypes of pigeon pea including checks (NDA-1, Bahar, IPA203, NDA-2, MAL-13, ICP2275, IPACT-2, MA-6, IPACT-3, IPACT-24, Rajendra Arhar, IPA15F, Dholi-D, JBT46/27, IPACT-6, IPACT-14, IPAD1-17, IPAC 68, IPACT 22, ICPL 7035 IPA19-101, IPA19-102, IPA19-103, IPA19-104, IPA19-105, IPA19-106, IPA19-107, IPA19-108, IPA19-109, IPA19-110, IPA19-111, IPA19-112, IPA19-113, IPA19-114) in RBD at ICAR-IIPR, Kanpur. Morphological and yield Characters including plant height, scoring of cold injury in exposed plants and Number of flower drop and pod set during the cold period in tagged plants were recorded. In biochemical/ crop efficiency parameters viz: Nitrogen balance index, chlorophyll, flavonols, anthocyanin’s and NDVI were measured. The photosynthetic rate, stomatal conductance, and transpiration rate were measured at the pod formation stage. Anti-oxidant enzymes activity was assayed as per standard methods. Meteorological observations during Cold stress were recorded. Result: Based on flower/pod drop and retention the genotypes like IPA 15F, Dholi dwarf, JBT46/27, IPACT-6, IPACT-14, IPAC-1-17, IPACT-68, IPACT-22, IPA 19-101, IPA 19-102, IPA 19-103, IPA 19-104, IPA 19-105, IPA 19-107, IPA 19-108, IPA 19-109, IPA 19-110, IPA 19-111 and IPA 19-113 were found susceptible to cold stress and retaining an average 51.67 % flowers/pods. Genotypes like NDA-2, MAL-13, ICP2275, IPACT-2, MA-6, IPACT-3, IPACT-24, Rajendra arhar, IPA19-106, IPA19-112 and IPA19-114 have retained more than an average of 67.48% flowers/pods are considered tolerant to cold stress. Amongst the tolerant group NDA-2, MAL-13, ICP2275, IPACT-2, IPA19-106, IPA19-112 retained the flower/pod more than the average of check genotypes (67.57%). Biochemical/plant efficiency parameters were superior in tolerant group over susceptible group.

Optimizing rice yield: evaluating the nitrogen supply characteristics of slow- and controlled-release fertilizers using the leaf nitrogen balance index

Synchronizing the nitrogen (N) supply of slow- and controlled-release N fertilizers (SCRNFs) with rice N demand is pivotal in substituting multiple urea applications by a single basal application of SCRNFs. Traditional assessment of N supply characteristics focuses mainly on N release patterns, which are only applicable to coated SCRNFs and ignore N transformation mechanisms, thus raising the need for a more universal and reliable index. Based on the ability of crop N status to detect N deficiency or excess, we hypothesized that employing leaf N balance index (NBI) as a measure of N status could provide new insights into assessing N supply characteristics of SCRNFs. We conducted field experiments involving four individual SCRNFs-humic acid urea (HAU), sulfur-coated urea (SCU), urease inhibitor urea (UIU), and polymer-coated urea (PCU)- and their four combined forms, along with the high-yield urea split application as control (CK). The results showed that NBI dynamics relative to CK could reflect the N supply potential of different SCRNFs while classifying them as short-, medium-, and long-acting fertilizers. Combinations that incorporated the long-acting SCRNF (PCU) consistently outperformed others in yield (by 5.5%) and N use efficiency (by 42.8%) by providing a more consistent and efficient N supply throughout the rice growth cycle. Grain yield showed negative correlation with the difference in NBI dynamics between SCRNFs and CK, indicating synchronizing N supply between one-time application of SCRNFs and conventional high-yield fertilization is the key for high yield. Our findings identify the potential of N status diagnosed by leaf NBI to evaluate N supply characteristics of SCRNFs and emphasize the significant role of synchronized N supply for a one-time SCRNF application.

Growth Performance and Osmolyte Regulation of Drought-Stressed Walnut Plants Are Improved by Mycorrhiza

This study aims to evaluate whether a selected arbuscular mycorrhizal fungus, Diversispora spurca, improves growth in drought-stressed walnut (Juglans regia L. cv. Qingxiang) plants and whether this improvement is associated with changes in osmolyte (fructose, glucose, sucrose, soluble protein, proline, and betaine) levels. After 60 days of soil drought treatment (50% of maximum field water-holding capacity), root D. spurca colonization rate and soil mycelium length decreased by 13.57% and 64.03%, respectively. Soil drought also inhibited the growth performance of aboveground (stem diameter, leaf number, leaf biomass, and stem biomass) and underground (root projected area, surface area, and average diameter) parts, with uninoculated plants showing a stronger inhibition than D. spurca-inoculated plants. D. spurca significantly increased these growth variables, along with aboveground part variables and root areas being more prominent under drought stress versus non-stress conditions. Although drought treatment suppressed the chlorophyll index and nitrogen balance index in leaves, mycorrhizal inoculation significantly increased these indices. Walnut plants were able to actively increase leaf fructose, glucose, sucrose, betaine, and proline levels under such drought stress. Inoculation of D. spurca also significantly increased leaf fructose, glucose, sucrose, betaine, proline, and soluble protein levels under drought stress and non-stress, with the increasing trend in betaine and soluble protein being higher under drought stress versus non-stress. Drought stress dramatically raised leaf hydrogen peroxide (H2O2) levels in both inoculated and uninoculated plants, while mycorrhizal plants presented significantly lower H2O2 levels, with the decreasing trend higher under drought stress versus non-stress. In conclusion, D. spurca symbiosis can increase the growth of drought-stressed walnut plants, associated with increased osmolyte levels and decreased H2O2 levels.

Comparative Response of Arbuscular Mycorrhizal Fungi versus Endophytic Fungi in Tangor Citrus: Photosynthetic Efficiency and P-Acquisition Traits

Citrus plants are prone to phosphorus (P) deficiency, especially in acidic soil, making them more dependent on root-associated endophytic fungi for growth and development. Beni-Madonna, a hybrid of Citrus nanko × C. amakusa, is a citrus known as “tangor” that is highly popular in China and other parts of the world due to its deep red color and jelly-like flesh. In this study, the inoculation response to two arbuscular mycorrhizal fungi (Diversispora versiformis, Dv; Funneliformis mosseae, Fm) and an endophytic fungus (Serendipita indica, Si) with regard to the growth, leaf gas exchange, light energy efficiency, P levels, acid phosphatase activity, and expression of the purple acid phosphatase (PAP) and phosphate transporter (PT) genes through a potted experiment using Beni-Madonna (tangor) citrus plants grafted on trifoliate orange (Poncirus trifoliata) was studied. Two years following inoculation, the root fungal colonization rates of inoculated plants were significantly increased, accompanied by an increase in plant height and stem diameter, with Si presenting the best effect. Fungal inoculations also significantly increased the leaf chlorophyll index, nitrogen-balance index, photosynthesis rate, stomatal conductance, transpiration rate, photosynthetic efficiency, and quantum yield of PSII, while it reduced photoinhibition and heat dissipation, with Si having the best effect on light energy efficiency. Si significantly increased leaf and root P levels, as well as root CsPAP1‒3, CsPT2, CsPT3, and CsPT7 expression and soil acid phosphatase activity; Fm in mycorrhizal fungi significantly increased leaf and root P levels, as well as root CsPT1 and CsPT7 expression and root/soil acid phosphatase activity. These observations suggested an advantage of Si over the other two AMF in terms of improved plant growth and P acquisition, while Fm displayed prominent effects on increased photosynthetic efficiency.

Investigation of the chlorophylls and flavonoids content in apple leaves under conditions of various scab protection systems

As part of the study of the effect of fungicides on the development of apple scab in an orchard in the Solnechnogorsk district of the Moscow region, changes in the optical parameters of apple leaves depending on protection systems and varieties were studied. The effectiveness of the express method using the Dualex chlorophyll meter has been proven. This method has the same effectiveness as the traditional spectrophotometric determination of the chlorophylls a and b, but it is faster and easier. The choice of the method of working with the N-tester is justified. Leaves 5-9 of average age, located in the middle of the shoot, were selected as plant samples. They are considered to be the most optimal for assessing the state of the nitrogen status of plants. It has been experimentally proven that the treatment of plants with fungicides based on captan, dithianon, trifloxystrobin and ciprodinil has the positive effect on increasing the plant nitrogen balance index (NBI). The greatest effect of an increase in the NBI index was observed on the Mantet variety, the most susceptible to the development of scab in the conditions of the experiment.

Enhancing salinity stress tolerance in chickpea (Cicer arietinum L.) genotypes through foliar application of spermidine

Chickpea (Cicer arietinum), the 2nd most important legume after dry beans, known for its protein content, is an important crop agronomically as well as economically. The present study aimed to determine the effect of foliar application of spermidine (spd) on various aspects of chickpea genotypes under salt stress. The chickpea genotypes were cultivated under 4 and 8 dSm-1 Cl- dominated salinity followed by the spermidine application of 0.5 and 1.0 mM. Salinity stress inhibited the plant height and root length, reducing plant biomass (fresh and dry weight). Furthermore, it also decreased the chlorophyll and nitrogen content of the plant. Results obtained from spermidine (spd) application indicated that both concentrations of spermidine are good in enhancing the tolerance in chickpea genotypes against salt stress. Spermidine application increased the plant's height as well as biomass. It also enhanced the chlorophyll content (32.93%), increasing the Nitrogen Balance Index (77.37%) at 1.0 mM.It further increased the flavonoid and anthocyanin content in plant leaf. In addition, the application of spermidine retained more moisture (25.81%) and increased seed fiber (13.30%) in all chickpea genotypes at 1.0 mM. It reduces the Cl- ion accumulation and maintains the ionic balance in chickpea seeds. The effect of spermidine application (0.5 and 1.0mM) was more pronounced, but 1.0 mM had a more positive effect in salt-sensitive chickpea genotypes.

Arbuscular Mycorrhizal Fungi, Especially Rhizophagus intraradices as a Biostimulant, Improve Plant Growth and Root Columbin Levels in Tinospora sagittata

Tinospora sagittata is a columbin-rich medicinal plant, but its columbin levels are reduced under artificial cultivation conditions. The objective of this study was to analyze the effects of inoculations with Diversispora versiformis (Dv), Funneliformis mosseae (Fm), Rhizophagus intraradices (Ri), and mixed inoculation (Dv + Fm + Ri) (Mix) on growth performance, root morphology, leaf photosynthetic physiology, and root columbin levels in T. sagittata. These arbuscular mycorrhizal fungi (AMF) were able to colonize the roots, as evidenced by a root mycorrhizal colonization rate ranging from 17% to 48% and soil hyphal lengths ranging from 17.51 cm/g to 32.02 cm/g, with the Mix treatment being the greatest. AMF inoculations improved plant height (16–151%), leaf number (119–283%), shoot (37–211%), and root biomass (22–318%) to varying extents, with Ri and Mix treatments being the most prominent. AMF-treated plants presented relatively greater root total length, projected area, surface area, volume, and average diameter, especially those treated with Ri and Mix. AMF inoculations also significantly improved the leaf nitrogen balance index, transpiration rate, and stomatal conductance, while the photosynthesis rate and chlorophyll index varied by AMF species, along with a decrease in intercellular CO2 levels. Root columbin levels ranged from 0.524 mg/g to 5.389 mg/g, and AMF inoculation significantly increased root columbin levels by 228–928%, with Ri being the most significant. Root columbin levels were significantly positively correlated with soil hyphal length, root total length, root projected area, root surface area, root volume, and root average diameter, but not root AMF colonization rate. This study demonstrates for the first time that AMF, especially Ri, can be employed as a biostimulant to promote growth as well as root columbin levels in T. sagittata, where AMF-triggered improvement in root morphology is an important reason for promoting root columbin levels.

Application of Encapsulation Technology: In Vitro Screening of Two Ficus carica L. Genotypes under Different NaCl Concentrations

Salinity stress represents an increasing issue for agriculture and has a great negative impact on plant growth and crop production. The selection of genotypes able to tolerate salt stress could be a suitable solution to overcome the problem. In this context, in vitro cultures can represent a tool for identifying the NaCl tolerant genotypes and quickly producing large populations of them. The possibility of exerting selection for tolerance to NaCl by using encapsulation technology was investigated in two genotypes of fig: ‘Houmairi’ and ‘Palazzo’. The effects of five concentrations of NaCl (0, 50, 100, 150 and 200 mM) added to the artificial endosperm were tested on the conversion of synthetic seeds and on the growth of derived shoots/plantlets. Moreover, proline (Pro) and malondialdehyde (MDA), the enzymatic activities of catalase (CAT), guaiacol peroxidase (POD), and EL (Electrolytic Leakage), as well as the chlorophyll content, flavanols, anthocyanins, and Nitrogen Balance Index (NBI) were determined on shoots/plantlet. The obtained results clearly showed that ‘Houmairi’ and ‘Palazzo’ could tolerate salt stress, although a strong difference was found depending on each specific physiological pathway. Indeed, ‘Houmairi’ was revealed to be more tolerant than ‘Palazzo’, with different response mechanisms to salt stress. The use of encapsulated vitro-derived explants proved to be a useful method to validate the selection of genotypes tolerant to salinity stress. Further investigation in the field must validate and confirm the legitimacy of the approach.

Positive Changes in Fruit Quality, Leaf Antioxidant Defense System, and Soil Fertility of Beni-Madonna Tangor Citrus (Citrus nanko × C. amakusa) after Field AMF Inoculation

Citrus plants rely heavily on arbuscular mycorrhizal fungi (AMF) due to their lack of root hairs. Most experiments have been conducted with AMF inoculation under potted conditions, while field inoculation of AMF on citrus, especially a high economic hybrid tangor variety Beni-Madonna (Citrus nanko × C. amakusa), has been rarely recorded. This study aimed to analyze the effects of two AMF inoculations (a single Funneliformis mosseae and a mixture of F. mosseae, Diversispora versiformis, and Rhizophagus intraradices) on the internal and external fruit quality, leaf antioxidant defense system, and soil fertility and structure of top-worked Beni-Madonna tangor citrus trees. Three and a half years after AMF inoculations, soil hyphal length and root mycorrhizal colonization rate increased by 61.2–101.8% and 15.85–29.6% in inoculated plants, respectively. Inoculated trees had higher external fruit coloration value, fruit horizontal diameter, and fruit weight, and lower fruit rigidity than uninoculated trees. AMF-inoculated trees had higher glucose levels of fruit peels, fructose and sucrose levels of fruit fleshes, and the ratio of fruit soluble solids/titratable acids, as well as lower titratable acids concentrations than non-AMF-inoculated trees. AMF inoculation significantly increased leaf nitrogen balance index, chlorophyll index, peroxidase, catalase, superoxide dismutase, and glutathione reductase activities, as well as reduced glutathione and oxidized glutathione concentrations, resulting in lower hydrogen peroxide and malondialdehyde levels when compared to the uninoculated treatment. In addition, inoculated trees presented higher soil nutrient levels, including organic carbon, available K, and Olsen-P as, well as soil aggregate stability (based on mean weight diameter) than uninoculated trees. This study concluded that field AMF inoculation improved fruit quality, enhanced leaf antioxidant defense system, and improved soil fertility of Beni-Madonna trees, with mixed AMF being prominent in improving fruit quality and F. mosseae being prominent in enhancing leaf antioxidant defense system and improving soil fertility.

Non-Destructive Assessment of Leaf Chlorophyll and Epidermal Flavonoids in Two Tomato Cultivars (Solanum lycopersicum L.) Grown Under Different Trichoderma Spp. Treatments

Summary The purpose of this study is to examine the effects of different Trichoderma spp. treatments (T1: Trichoderma harzianum, T2: Trichoderma brevicompactum, and T3: T1 + T2) on two tomato cultivars (‘Narvik’ and ‘Gružanski zlatni’) by the non-destructive monitoring of chlorophyll (Chl) and epidermal flavonol (Flav) indices and nitrogen balance index (NBI) in their leaves. The main objectives were to compare the responses of tomato cultivars considered (grown in a greenhouse) to different Trichoderma strains and a combination of Trichoderma strains. Variations in the Chl, Flav, and NBI values obtained were significantly influenced by nearly all the factors examined (namely the tomato cultivar, experimental week, and treatment), the interaction of which was found significant for all the parameters analyzed. The results obtained indicate that the combinations of strains in the T3 treatment markedly enhanced the Chl content in the ‘Narvik’ cultivar in some experimental weeks. Moreover, reduced NBI values were determined in the Trichoderma-treated ‘Narvik’ plants due to the increased flavonol content, which indicates a shift from primary to secondary metabolism. Further research, including the same cultivars and treatments, is warranted under field conditions to evaluate the physiological responses of the ‘Narvik’ and ‘Gružanski zlatni’ tomato cultivars in a multiple-stressor environment.

Serendipita indica mitigates drought-triggered oxidative burst in trifoliate orange by stimulating antioxidant defense systems.

Soil drought is detrimental to plant growth worldwide, particularly by triggering reactive oxygen species (ROS) burst. Serendipita indica (Si), a culturable root-associated endophytic fungus, can assist host plants in dealing with abiotic stresses; however, it is unknown whether and how Si impacts the drought tolerance of citrus plants. To unravel the effects and roles of Si on drought-stressed plants, trifoliate orange (Poncirus trifoliata L. Raf.; a citrus rootstock) seedlings were inoculated with Si and exposed to soil drought, and growth, gas exchange, ROS levels, antioxidant defense systems, and expression of genes encoding antioxidant enzymes and fatty acid desaturases in leaves were measured. Soil drought suppressed plant biomass, whereas Si inoculation significantly increased plant biomass (10.29%-22.47%) and shoot/root ratio (21.78%-24.68%) under ample water and drought conditions, accompanied by improved net photosynthetic rate (105.71%), water use efficiency (115.29%), chlorophyll index (55.34%), and nitrogen balance index (63.84%) by Si inoculation under soil drought. Soil drought triggered an increase in leaf hydrogen peroxide and superoxide anion levels, while Si inoculation significantly reduced these ROS levels under soil drought, resulting in lower membrane lipid peroxidation with respect to malondialdehyde changes. Furthermore, Si-inoculated seedlings under soil drought had distinctly higher levels of ascorbate and glutathione, as well as catalase, peroxidase, and glutathione peroxidase activities, compared with no-Si-inoculated seedlings. Si inoculation increased the expression of leaf PtFAD2, PtFAD6, PtΔ9, PtΔ15, PtFe-SOD, PtCu/Zn-SOD, PtPOD, and PtCAT1 genes under both ample water and soil drought conditions. Overall, Si-inoculated trifoliate orange plants maintained a low oxidative burst in leaves under drought, which was associated with stimulation of antioxidant defense systems. Therefore, Si has great potential as a biostimulant in enhancing drought tolerance in plants, particularly citrus.