Leaf Potassium Concentrations Research Articles

Nitrogen-fixing and non-nitrogen-fixing legume plants differ in leaf nutrient concentrations and relationships between photosynthetic and hydraulic traits.

Legumes account for a significant proportion of plants in the terrestrial ecosystems. Nitrogen-fixing capability of certain legumes is a pivotal trait that contributes to their ecological dominance. Yet, the functional traits and trait relationships between N-fixer and non-N-fixer legumes are poorly understood. Here, we investigated 27 functional traits associated with morphology, nutrients, hydraulic conductance, and photosynthesis in 42 woody legumes (19N-fixers and 23 non-N-fixers) in a common garden. Our results showed that N-fixers had higher specific leaf area, photosynthetic phosphorus (P) use efficiency, leaf nitrogen (N) and iron concentrations on both area and mass basis, N/P ratio, and carbon (C) to P ratio, but lower wood density, area-based maximum photosynthetic rate (Aa), photosynthetic N use efficiency, leaf mass- and area-based P and molybdenum and area-based boron concentrations, and C/N ratio, compared to non-N-fixers. The mass-based maximum photosynthetic rate (Am), stomatal conductance (gs), intrinsic water use efficiency (WUEi), mass- and area-based leaf potassium and mass-based boron concentrations, leaf hydraulic conductance (Kleaf), and whole-shoot hydraulic conductance (Kshoot) showed no difference between N-fixers and non-N-fixers. Significant positive associations between all hydraulic and photosynthetic trait pairs were found in N-fixers, but only one pair (Kshoot-Aa) in non-N-fixers, suggesting that hydraulic conductance plays a more important role in mediating photosynthetic capacity in N-fixers compared to non-N-fixers. Higher mass-based leaf N was linked to lower time-integrated gs and higher WUEi among non-N-fixer legumes or all legumes pooled after phylogeny was considered. Moreover, mass-based P concentration was positively related to Am and gs in N-fixers, but not in non-N-fixers, indicating that the photosynthetic capacity and stomatal conductance in N-fixers were more dependent on leaf P status than in non-N-fixers. These findings expand our understanding of the trait-based ecology within and across N-fixer and non-N-fixer legumes in tropics.

Alpha and beta diversity of functional traits in subtropical evergreen broad-leaved secondary forest communities

IntroductionIntra-speciic variation is the main source of functional trait diversity and has similar ecological effects as inter-speciic variation.MethodsWe studied 79 species and 3546 individuals from 50 ixed monitoring plots in subtropical evergreen broad - leaved secondary forests in Zhejiang Province, China. Using trait gradient analysis, we examined nine traits (speciic leaf area, leaf dry matter content, wood density, leaf area, chlorophyll content, leaf nitrogen content, leaf phosphorus content, leaf potassium content, and nitrogen-phosphorus ratio) by decomposing species functional traits into alpha (within-community) and beta (among-communities) measure the impact of environmental gradients and the presence of other species on the variation of traits.ResultAll nine functional traits showed some degree of differentiation in the forest communities, with a greater range of variation in alpha values than in beta values . Correlations were signiicantly different between the trait differences in the communities. The alpha values of each trait showed a higher correlation with other components than the beta values. The factors affecting intra-speciic trait variation were relatively complex. The alpha component had a more signiicant and stronger effect on intra-speciic trait variation compared to the beta component. Abiotic factors, such as soil nutrient content, soil nitrogen-phosphorus content, directly affected the beta component. In contrast, biotic factors, such as tree height variation, had a direct and stronger effect on the alpha component.DiscussionOur results demonstrate that alpha and beta components, as independent differentiation axes among coexisting species, have different sensitivities to different environmental factors and traits in different ecological strategies and spatial scales. Trait gradient analysis can more clearly reveal the variation patterns of species traits in communities, which will help to understand the scale effects and potential mechanisms of trait relationships.

Leaf stoichiometry of potassium, calcium, and magnesium in tropical plants: Responses to climatic and geographical variations—A case study from Hainan Island

AbstractGrasping how climate change will affect the tropical region's leaf potassium, calcium, and magnesium content is pivotal for enhancing our comprehension of plant stoichiometry. Currently, there is limited research on leaf potassium, calcium, and magnesium in tropical plants, which is particularly evident with the increasing importance of tropical rainforest biodiversity studies. This study investigated the impact of geographical and climatic factors on the leaf potassium, calcium, and magnesium content in 346 plants (including woody plants, herbs, and vines) on Hainan Island. The findings demonstrated that the average leaf potassium, calcium, and magnesium contents were 5.77, 11.86, and 2.92 mg·g−1, respectively, which were less than that in the Chinese flora. Mean annual precipitation (MAP) has a promoting effect on leaf potassium content (p < 0.05), suggesting that artificial potassium fertilization is needed due to the increasing MAP. Leaf potassium and magnesium content were positively correlated with latitude (p < 0.05) and longitude (p < 0.01); and there was a negative correlation between leaf calcium content and latitude (p < 0.05), showing that geographical factors have a significant impact on the potassium, calcium, and magnesium content of plant leaves. Additionally, the variables regulating leaf potassium, calcium, and magnesium varied across woody plants, herbs, and vines. Therefore, it is necessary to make corresponding adjustments according to local conditions and the plant functional types during nutrient management. In conclusion, this study sheds light on their potential responses to global changes and is instrumental in informing the management of these nutrients in tropical rainforest plants.

Estimation model of potassium content in cotton leaves based on hyperspectral information of multileaf position

Potassium (K) is a highly mobile nutrient element that continuously adjusts its demand strategy among and within cotton leaves through redistribution. This indirectly leads to variations in the leaf potassium content (LKC, %) at different leaf positions. However, owing to the interaction between light and leaf age, leaf sensitivity at different positions to this change varies, including the reflection and absorption of the spectrum. How to selecting the optimal monitoring leaf position is an important factor in quickly and accurately evaluation of cotton LKC using spectral remote sensing technology. Therefore, this study proposes a comprehensive multileaf position estimation model based on the vertical distribution characteristics of LKC from top to bottom. This is aimed at achieving an accurate estimation of cotton LKC and optimizing the strategy for selecting the monitored leaf position. Between 2020 and 2021, we collected hyperspectral imaging data of the main stem leaves at different positions from top to bottom (Li, i=1, 2, 3, …, n), during the cotton budding, flowering, and boll setting stages. Vertical distribution characteristics, sensitivity differences, and spectral correlations of LKC at different leaf positions were investigated. Additionally, the optimal range of the dominant leaf position for monitoring was determined. Partial least squares regression (PLSR), random forest regression (RFR), support vector machine regression (SVR), and the entropy weight method (EWM) were used to establish LKC estimation models for single leaf and multileaf positions. The results showed a vertical heterogeneous distribution of cotton LKC, with LKC initially increasing and then gradually decreasing from top to bottom, and the average LKC of cotton reaches its maximum value at flowering stage. The upper leaf position demonstrated greater sensitivity to K and exhibited a stronger correlation with the spectrum. The selected dominant leaf positions for the three growth stages were L1–L5, L1–L4, and L1–L2, respectively. Based on the dominant leaf position monitoring range, the optimal single leaf position models for estimating LKC during the three growth stages were PLSR-L4, PLSR-L1, and SVR-L2, with The coefficient of determination of the validation set (R2val) of 0.786, 0.580, and 0.768, and the root-mean-square error of the validation set (RMSEval) of 0.168, 0.197, and 0.191, respectively. The multileaf position LKC estimation model was constructed by EWM with R2val of 0.887, 0.728, and 0.703, and RMSEval of 0.134, 0.172, and 0.209, respectively. In contrast, the newly developed multileaf position comprehensive estimation model yielded superior results, improving the stability of the model on the basis of high accuracy, especially during the budding and flowering stages. These findings hold significant importance for investigating cotton LKC spectral models and selecting suitable leaf positions for field monitoring.

Crosstalk of sucrose, potassium, and magnesium on growth, yield, and carbohydrate partitioning in bell pepper (Capsicum annuum L.) under poor light conditions

Bell pepper has received high demand due to its high nutritional value and contained antioxidant compounds. This research aimed to evaluate the effects of sucrose and some minerals on morpho-physiological characteristics, yield parameters, and carbohydrate partitioning in the bell pepper. The pot experiment was outlined hydroponically in a factorial format based on a completely randomized design. The first factor, sucrose, was sprayed in two concentrations (0 and 0.5% w/v) and the second factor, mineral nutrition, consisted of four levels (control, magnesium nitrate 0.5% w/v, potassium nitrate 0.5% w/v, magnesium nitrate 0.25% w/v + potassium nitrate 0.25% w/v). Results indicated that sucrose 5 + combined magnesium & potassium nitrate was superior in all of the biomass and yield parameters. In this combined treatment, fruit yield per plant and fruit vitamin C increased up to 44.03% and 47.71% in comparison with control. The highest leaf-soluble carbohydrate was recorded in plants treated with sucrose 5 + combined magnesium & potassium nitrate which was not significantly different from other contained sucrose treatments. The highest fruit soluble carbohydrate was observed in sucrose 5 + combined magnesium & potassium nitrate treatment as well, but its difference was not significant from sucrose 5 + potassium nitrate. The highest leaf potassium concentration was seen in three treatments that combined sucrose and minerals. The treatment of combined magnesium & potassium nitrate contributed to more leaf magnesium concentration compared with other nutrient treatments. In total, sucrose spray alongside combined magnesium & potassium nitrate led to higher carbohydrate accumulation in fruit, causing yield increment and nutritional value enhancement in bell peppers.

Nutrient distribution in various tissues of Licorice (Glycyrrhiza glabra L.) and the influence of soil fertility on the levels of its bioactive compounds

This study aimed to optimize the production of licorice (Glycyrrhiza glabra L.) in field conditions using two licorice ecotypes and various types of nutrient sources. Licorice yield, leaf and root nutrient content, and its bioactive compounds were assessed. Mycorrhiza inoculation resulted in the highest rhizome dry weight in the Lalehzar (101.3 g) and Kermanshah (395.6 g) ecotypes in the first and second years, respectively. Rhizome dry weight was higher than the roots in both ecotypes. Two years old Kermanshah ecotype exhibited the highest root dry weight by using urea. The harvest index increased in Lalehzar ecotype by application of vermicompost in the first year and cow manure coupled with plant growth-promoting bacteria (PGPB) in the second year. Nitrogen content in leaves and roots significantly increased in the Kermanshah ecotype using cow manure and PGPB. Application of mycorrhiza (in Lalehzar ecotype) and cow manure combined with urea (in Kermanshah ecotype) led to leaf phosphorus (P) content improvement. The highest root P content in Lalehzar and Kermanshah ecotypes achieved by using cow manure and urea, respectively. Fertilization by urea and mycorrhiza led to higher leaf potassium (K) content in Kermanshah and Lalehzar, respectively, while urea yielded the highest root K content in the Kermanshah ecotype. Root glycyrrhizic acid (GA) content peaked in the Kermanshah ecotype with cow manure and PGPB (138 and 372.8 mg g-1 DW in the first and second years, respectively). Rhizome GA content performed better in the Lalehzar ecotype using cow manure and PGPB (191.34 mg g-1 DW, first year) and in the Kermanshah ecotype with cow manure and urea (239.62 mg g-1 DW, second year). Fertilizers had not significant effect on glabridin (GL) content. Notably, GA and GL exhibited a negative correlation with potassium and nitrogen. This study highlights the importance of balanced nutrient management for licorice cultivation.

AGRONOMIC EFFICIENCY OF REKAL REMINERALIZER IN SOYBEAN AND MAIZE CROPS

Remineralization regards using rocks as both conditioners and nutrient sources for agricultural soils; it also works as essential basis for degraded or depleted soil recovery. The aim of the present assay is to assess the performance of Rekal remineralizer and its effects on soybean and maize cultures, which were used as test plants. The following soil types were used in the experiment: Yellow Oxisol with sandy loam texture and Red Oxisol with clayey texture. The research was carried out in greenhouse, at the Agronomics School of Federal University of Goiás, Goiânia City, Goiás State. Experimental treatments consisted in using different Rekal remineralizer doses (0, 30, 60, 120 and 240 kg ha-1 K2O) to compare the results to those of FMX remineralizer products and potassium chloride (KCl), at the dose of 60 kg ha-1. Plant development variables (height, diameter and number of leaves), soil and leaf potassium content, calcium and magnesium content, CEC and soil base saturation, soybean grain yield, maize green mass yield and the relative efficiency of Rekal using in comparison to both FMX remineralizer and potassium chloride synthetic fertilizers were assessed. Results have shown that Rekal remineralizer presents agronomic efficiency comparable to that of KCl and FMX remineralizer. Using Rekal remineralizer can improve and keep important soil parameters, such as CEC, soil base saturation and calcium, magnesium and potassium content.

Nutritional changes in trees during drought‐induced mortality: A comprehensive meta‐analysis and a field study

AbstractBoth macronutrients and micronutrients are essential for tree growth and development through participating in various ecophysiological processes. However, the impact of the nutritional status of trees on their ability to withstand drought‐induced mortality remains inconclusive. We thus conducted a comprehensive meta‐analysis, compiling data on 11 essential nutrients from 44 publications (493 independent observations). Additionally, a field study was conducted on Pinus sylvestris L. trees with varying drought‐induced vitality loss in the “Visp” forest in southern Switzerland. No consistent decline in tree nutritional status was observed during tree mortality. The meta‐analysis revealed significantly lower leaf potassium (K), iron (Fe), and copper (Cu) concentrations with tree mortality. However, the field study showed no causal relationships between nutritional levels and the vitality status of trees. This discrepancy is mainly attributed to the intrinsic differences in the two types of experimental designs and the ontogenetic stages of target trees. Nutrient reductions preceding tree mortality were predominantly observed in non‐field conditions, where the study was conducted on seedlings and saplings with underdeveloped root systems. It limits the nutrient uptake capacity of these young trees during drought. Furthermore, tree nutritional responses are also influenced by many variables. Specifically, (a) leaf nutrients are more susceptible to drought stress than other organs; (b) reduced tree nutrient concentrations are more prevalent in evergreen species during drought‐induced mortality; (c) of all biomes, Mediterranean forests are most vulnerable to drought‐induced nutrient deficiencies; (d) soil types affect the direction and extent of tree nutritional responses. We identified factors that influence the relationship between tree nutritional status and drought survival, and proposed potential early‐warning indicators of impending tree mortality, for example, decreased K concentrations with declining vitality. These findings contribute to our understanding of tree responses to drought and provide practical implications for forest management strategies in the context of global change.

Response of Strawberry Plants to Foliar Application with Seaweeds Extract and Benzylaenine

This research was carried out in a greenhouse located south of Baghdad, Yusufiyah, Abu Halan area, in fall season at 20/10/2021, on Ruby gem strawberry cultivar. To find out the effect of spraying with growth regulator Benzyl adenine BA and seaweed extract on strawberry runners and some vegetative and fruiting characteristics. The study included implementation of a factorial experiment with two factors, first factor is spraying of growth regulator BA with three concentrations: 0, 50, 100 PPM as B0, B1, B2, respectively and second factor is seaweed extract spray with four concentrations: 0, 2, 4, 6 mg.L as A0, A1, A2, A3, respectively. treatments were distributed randomly in a randomized complete block design (RCBD) experiment. As experiment included 12 treatments with three replications and 12 plants for each experimental unit, thus the number of plants included in the experiment was 432 plants. The results showed that, seaweed extract spray at 6 mg/L.(A3) significantly increased in leaves number of 15.40 leaf.plant-1 and highest runner’s number of 4.77 runner.plant-1, highest leaf chlorophyll content of 0.825 %, highest leaf nitrogen content of 1.908 %, highest leaf phosphor content of 0.570 % and highest leaf potassium content of 1.87 %.

Response of some Growth Traits of Maize Plants to Conventional and Nano-Fertilizers

The Agricultural Research Station in the university city associated with the College of Agriculture at the University of Kufa undertook a fall 2022-2023 field experiment. The study examined the effects of zinc and iron nanoparticles at 2g.l-1 or 3g.l-1, conventional iron and zinc fertilizer at 3g.l-1, and distilled water on maize plant growth and development. A three-replication Randomized Completely Block Design (RCBD) factorial experiment was done. Nano-fertilization with nano-zinc at 3g.l-1 produced the best results across various vegetative development indicators. Plant height rate, stem diameter, leaf chlorophyll, nitrogen, and phosphorus content are these indicators. However, 3g.l-1 nano iron increased leaf area the highest, reaching 0.424 m2.plant-1. This treatment also produced the most rows per ear and the maximum leaf potassium concentration. In contrast, 1.5 g.L-1 traditional zinc and 1.5 gm.L-1 conventional iron fertilizer produced better vegetative growth and production. These included plant height, average stem diameter, leaf chlorophyll, and leaf elements (NPK). Additionally, 3 g.L-1 conventional iron produced the maximum leaf area. Overall, the 1.5 g.L-1 nano-zinc and 1.5 g.L-1 nano-iron fertilizer combination had higher vegetative growth rates than other combinations. However, the combination of 1 g.L-1 nano-iron and 1.5 g.L-1 nano-zinc had the maximum leaf area and potassium concentration.

How to Diagnose Potassium Abundance and Deficiency in Tomato Leaves at the Early Cultivation Stage

Potassium is one of the indispensable nutrient elements for plant growth, fruit development, and yield. The research and application of potassium nutrition diagnosis technology is the premise of scientific potassium management. However, potassium deficiency in tomato leaves, from vegetative to reproductive growth, is not easy to diagnose. To alleviate this problem, this paper proposes a suitable method of supplying potassium to tomatoes via a nutrient solution and diagnosing potassium abundance and deficiency through diagnosis methods based on ecological morphology, biological accumulation, and the photosynthetic characteristics of tomato plants. The relationship between the ecological morphology and biomass accumulation of tomatoes cultivated in the nutrient solution with potassium supply levels of 1, 4, 8, and 16 mmol/L is also discussed, and the potassium supply in the nutrient solution was studied 21 days after transplanting. The results showed that there was a significant quadratic correlation between the potassium supply in the nutrient solution and plant height and biomass accumulation, respectively. The most suitable level of potassium supply via the nutrient solution was deemed to be 10~13 mmol/L. However, if irreversible damage or severe stress to tomato plants has occurred because of potassium deficiency, there will be serious differences in the growth status of plants, and the diagnosis results will deviate greatly. In addition, the photosynthetic induction characteristics responding to the dark–light conversion of tomato leaves with potassium contents of 0.9%, 2.1%, 3.1%, and 3.3% cultivated with potassium supply amounts of 1, 4, 8, and 16 mmol/L in the nutrient solution were investigated. The results showed that tomato leaves with potassium contents of 3.1% and 3.3% had a more rapid response to dark–light conversion and higher first-order derivatives of net photosynthetic rate compared to those with potassium contents of 0.9% and 2.1%, but the first-order derivative of intercellular CO2 concentration showed an opposite trend. Additionally, a quadratic correlation between leaf potassium content and CO2 assimilation during 5 min of photosynthetic induction was established (R2 > 0.99). According to this correlation, the suitable leaf potassium content was estimated to be 2.3~2.7%, similar to that of tomatoes cultured in the nutrient solution with a 4~8 mmol/L potassium supply. Therefore, this method can realize the rapid, non-destructive, and real-time detection of potassium content in tomato leaves based on a portable photosynthetic measurement system by establishing the relationship between leaf potassium content and net CO2 assimilation during the photosynthetic induction period, therefore helping to avoid the irreversible damage caused by potassium deficiency at the later stages of plant cultivation and providing technical support for the precise fertilization of potassium in actual cultivation.

Drought-Tolerance Screening of Date Palm Cultivars under Water Stress Conditions in Arid Regions

Drought stress poses a considerable challenge to agriculture sustainability in arid regions. Water scarcity severely affects date palm growth and productivity in these regions. However, as water resources become increasingly scarce in arid regions, understanding the drought tolerance of date palm cultivars becomes imperative for developing drought-resistant cultivars and optimizing irrigation water usage for sustainable agriculture. This research examines the impact of different drought stress levels based on evapotranspiration (ETc), i.e., 40%, 60%, 80%, and 100% ETc, and time intervals (0, 6, 12, 18, and 24 months) on leaf growth, net photosynthesis, chlorophyll a and b content, and leaf relative water content (LRWC) of four prominent date palm cultivars, Khalas, Barhee, Hilali, and Ashrasee. In addition, the study also examines the effects of drought stress on dry weight, potassium and calcium content of leaf, stem, and root, and proline content in fresh leaves of these four cultivars. A solar-powered drip irrigation system with automated time-based irrigation scheduling was used to accurately control the irrigation water amount. To real-time estimate ETc in the study area, meteorological data were collected using a cloud-based IoT system. The findings of this study revealed that severe drought conditions (40 and 60 % ETc) significantly reduced leaf growth, plant dry biomass, and physiological and biochemical attributes; however, date palm cultivars can be grown under moderate drought conditions (80% ETc) with minimal effect on phenotypic, physiological, and biochemical traits to conserve water. The study also revealed that the drought-related characteristics decreased gradually with an increase in water stress time over 24 months. Comparing the date palm cultivars revealed that the Khalas and Barhee cultivars are more drought-tolerant, followed by Hilali, while Ashrasee is susceptible. The study elucidated a water conservation strategy employed in response to drought-induced stress based on the physiological and morphological parameters of date palm cultivars. It provides valuable insights into irrigation practices in arid regions. However, future studies can be focused on other nondestructive innovative techniques such as pulse-amplitude-modulation (PAM) fluorimetry, infrared radiation (IR), and video imaging system (VIS) methods to identify drought stress in date palms.

Twice Applications of Laying Hens Manure Produced the Highest Yield of Organic Okra Pods (Abelmoschus esculentus L. Moench.)

The optimal okra cultivation using organic fertilizers remains a subject of limited information. This study aimed to assess the impact of applying 18 t.ha-1 of laying hens' organic fertilizer on the morphological and physiological traits of the "Naila IPB" green okra variety. The study was conducted between September and December 2022 at the IPB organic experimental field at Cikarawang, Bogor, West Java, Indonesia. A randomized complete block design with a single factor namely frequency of organic fertilizer application, was employed. The factor consisted of four levels: no organic fertilization, 1-, 2-, and 3-times applications. The results demonstrated that a single application of organic fertilizer led to an increase in plant height at 5, 7, and 9 weeks after planting (WAP), leaf number at 5 WAP, root dry weight at 4 WAP, stem dry weight at 10 WAP, and an acceleration in the onset of flowering. This resulted in a flowering period lasting 29.6 days, with a total flowering duration of 69.33 days. In contrast, a two-times application of organic fertilizer resulted in elevated plant height at 11 WAP, an increased leaf number at 11 WAP, heightened leaf potassium content, a greater number of pods per plant, and a higher yield of young pod okra. These findings contribute to our understanding of the effects of organic fertilizer application frequency on the growth and yield of young pod okra, aiding in the formulation of improved cultivation strategies.

Mapping variability of soybean leaf potassium concentrations to develop a sampling protocol

AbstractThe spatial variability of soybean [Glycine max (L.) Merr.] leaf‐K (potassium) concentrations must be considered when collecting samples to monitor crop K status. Five commercial soybean fields were sampled at a 0.4‐ha grid resolution at two reproductive growth stages to quantify the trifoliolate tissue‐K concentration. The objectives of this study were to identify the potential field variability of soybean leaf‐K concentrations in typical Mid‐south US soybean production fields, evaluate interpolation methods, and develop a sampling protocol for in‐season soybean tissue monitoring. No consistent spatial dependencies were found in the leaf‐K concentrations across the fields and sample times, indicating that a soybean tissue‐K grid sampling protocol cannot be generalized to a specific area size. Inverse distance weighted (IDW) and rasterization interpolation methods were considered to predict leaf‐K concentrations between the sampled grid points at grid resolutions ranging from 0.4 to 4 ha. The IDW method consistently predicted leaf‐K concentrations between the known values with less error than rasterization. Rather than grid sampling, composite leaf samples should be collected based on management zones to provide a simplified sampling protocol. Within each management zone, a composite sample must consist of uppermost fully expanded trifoliolate leaves collected from at least 18 locations to ensure that the sample measures within the 95% confidence interval of the area average leaf‐K concentration. The developed sampling protocol coupled with the dynamic critical tissue‐K concentration curve will provide producers with the ability to effectively monitor soybean for potential hidden hunger and verify K deficiency symptoms in season.

Changes in Leaf Functional Traits Driven by Environmental Filtration in Different Monsoon Tropical Forest Types

Disturbances have created heterogeneous habitats for secondary and old-growth forests. Under the assumption that ecologically similar species have similar functional traits, numerous studies have attempted to use trait-based approaches to infer the abiotic and biotic factors that drive variations in community composition across different forests. However, the relative importance of these drivers in monsoon forests remains poorly understood. In this study, we randomly selected 86 plots and classified them into three forest types according to environmental factors: 1—secondary forests: secondary forest habitats at high elevation; 2—ecotone forests: general recovery and elevation; and 3—old growth forests: old growth at low elevations. We then compared the species and six leaf functional trait variations across the three forests and assessed their relationships with 15 environmental factors. The results showed that secondary and ecotone forests with a conservative strategy, exhibiting high dry matter content and leaf carbon content, tended to persist in stressful habitats, such as nutrient-poor soil, whereas old growth forests invested in trait values related to rapid resource acquisition with high specific leaf area, leaf nitrogen content, leaf phosphorous content, and leaf potassium content. Species with functional trait values between the secondary, ecotone, and old growth forests had clear signatures of their different strategies to persist in assemblages under distinct and opposite environmental filters. These plots were classified into three forest types according to environmental factors: (1) secondary forest at high elevation; (2) ecotone forests at general elevation; and (3) old growth forests at low elevation. Recovery time and elevation, followed by soil nutrients and light capture, were the most important factors shaping species and functional trait variations across forests. These results have demonstrated that environmental filters select plant species with distinct traits and ecological strategies. Acquisitive traits indicate higher competitive ability and faster resource acquisition for forest species that occur in areas with high soil fertility. Meanwhile, conservative traits promote the resistance of secondary species to environmental stressors in low soil fertility, suggesting that analyzing leaf functional-based trait variations to understand plant ecological strategies along an environmental gradient may improve understanding of forest dynamics in tropical monsoon forests.

Effect of shading and fertilization with iron and sulfur on some vegetative growth and leaves mineral content of Gardenia jasminoides Ellis.

This study was conducted in a glass house, Dept of Hort. and Landscape, College of Agriculture, Univ. Anbar, during the 2021-2022 growing season, to investigate the influence of shading and fertilization on the growth and leaf mineral content of gardenia plants. This study included two factors: two levels of shading at 0 (S0), shading 50 % (S1) and four treatments of fertilizations, control (F0), chelated iron spray at 2 ml.L-1 (F1), addition of magnesium sulfate to pots at 7 gm.plant-1 (F2) and chelated iron spray at 2 ml.L-1 + addition of magnesium sulfate to pots at 7 gm.plant-1 (F3) and their interaction. Treatments were replicated three times at Split plots design (Shading is the main plot) in an RCBD. The number of plants used was 36 plants. The results showed that interaction treatment (S1F3) significantly increased the plant height by 6.517 cm, the highest increase in shoot length of 11.267 cm, and the number of 94.107 leaves.plant-1 , highest leaf area of 9437.463 cm2 , highest leaf nitrogen content of 1.877 % and highest leaf potassium content of 0.561 %, while lower values of these traits were in interaction treatment (S0F0). Keywords: iron, sulfur, vegetative growth, Gardenia jasminoides Ellis

Prediction of Potassium Content in Rice Leaves Based on Spectral Features and Random Forests

The information acquisition about potassium, which affects the quality and yield of crops, is of great significance for crop nutrient management and intelligent decision making in smart agriculture. This article proposes a method for predicting the rice leaf potassium content (LKC) using spectral characteristics and random forests (RF). The method screens spectral characteristic variables based on the linear correlation analysis results of rice LKC and four transformed spectra (original reflectance (R), first derivative reflectance (FDR), continuum-removed reflectance (CRR), and normalized reflectance (NR)) of leaves and the PCA dimensionality reduction results of vegetation indices. Following a second screening of the correlated single band and vegetation index variables of the four transformed spectra, the RF is used to obtain the mixed variable (MV), and regression models are developed to achieve an accurate prediction of rice LKC. Additionally, the effect of potassium spectral sensitivity bands, indices, spectral transformation form, and different modeling methods on rice LKC prediction accuracy is assessed. The results showed that the mixed variable obtained with the second screening using the random forest feature selection method could effectively improve the prediction accuracy of rice LKC. The regression models based on the single band variables (BV) and the vegetation index variables (IV), FDR–RF and IV–RF, with R2 values of 0.62301 and 0.7387 and RMSE values of 0.24174 and 0.15045, respectively, are the best models. In comparison to the previous two models, the MV–RF validation had a higher R2 and a lower RMSE, reaching 0.77817 and 0.14913, respectively. It can be seen that the RF has a better processing ability for the MV that contains vegetation indices and IV than for the BV. Furthermore, the results of different variable screening and regression analyses also revealed that the single band’s range of 1402–1428 nm and 1871–1907 nm, as well as the vegetation indices constituted of reflectance 1799–1881 nm and 2276–2350 nm, are of great significance for predicting rice LKC. This conclusion can provide a reference for establishing a universal vegetation index related to potassium.

Modulation of nutritional and biochemical status of hydroponically grown Cucurbita pepo L. by Calcium Nitrate under saline conditions

Salinity is one of the critical environmental factors that decreases the water availability and induces nutritional imbalance in crops. In order to study the effect of calcium nitrate [(Ca(NO3)2] in the nutrient solution under salinity conditions, an experiment was designed with different salinity (0, 50, and 100 mM) and Ca(NO3)2 (2, 3, and 4 mM) levels on Cucurbita pepo (zucchini). Based on the results, an increase in the salinity from 0 to 100 mM caused a decrease in the leaf potassium and calcium concentration, whereas the iron, magnesium and zinc concentrations increased. The most effective Ca(NO3)2 level in increasing the nutritional quality and yield of zucchini was 3 and 4 mM. Salinity at 50 and 100 mM significantly increased the leaf sodium concentration and leaf area as well as the leaf number per plant, while the application of both Ca(NO3)2 levels modulated the harmful effects of salinity. The amount of malondialdehyde (MDA), proline and hydrogen peroxide (H2O2) as well as the catalase (CAT) activity increased under the severe salinity conditions, whereas the application of 4 mM Ca(NO3)2 had the potential of removing the negative effects of severe salinity. The catalase activity increased along with the increase in the Ca(NO3)2 concentration, which was independent from the salinity level. However, the amount of proline, MDA and H2O2 decreased in plants fed with 3 and 4 mM Ca(NO3)2 compared to the control in the presence of salinity. These findings suggest that both the 3 and 4 mM concentrations of Ca(NO3)2 under 50 mM salinity could be used to improve the zucchini performance by maintaining the ion homeostasis and inducing the antioxidant defence system.

Combined foliar application effect of iron and potassium on growth of okra and striped catfish using media bed based aquaponics

An experiment for 90 days was carried out to evaluate the combined effect of iron and potassium by foliar method on the growth of okra, Abelmoschus esculentus and striped catfish, Pangasianodon hypophthalmus using a media bed in aquaponics. The different iron dosages i.e. T1 (0.50 g/L), T2 (0.75 g/L), T3 (1.00 g/L), T4 (1.25 g/L), along with potassium at 5 g/L were applied in all the treatments twice a month. All four treatments and a control were in triplicate. No significant (P > 0.05) difference was noticed in the quality of water in all the treatments and control. The okra showed significantly better growth in the treatments than the control, especially in T3 and T4. The yield of okra found was to be significantly (P < 0.05) higher in T4 (36.67 ± 0.81 g/plant) as compared to control (17.16 ± 0.47 g/plant). The mineral composition and proximate analysis of the okra pod revealed considerably higher crude protein, potassium, and iron content in T3 and T4, and leaf potassium and iron content were observed to be higher in T4 as compared to other treatments. The growth performances, haematological and antioxidant enzymes analysis of fish, exhibited an insignificant variation (P > 0.05) among the treatments and control. From the findings of the present experiment, it can be concluded that the foliar application of iron dosage of 1.00 g/L in combination with 5 g/L potassium can improve the growth and yield of okra without any adverse effect on fish growth in aquaponics.

Genotypic Difference in Growth and Physiological Indices of Grain Amaranth Species under Salinity Stress

The present experiment was conducted during October to February of year 2019−20, to investigate the effect of salinity on  morpho-physiological traits and identify the genotype have higher salt tolerance among  ten genotypes belongs to three  grain Amaranth species. Plant growth traits viz., plant height, shoot and root dry weight decreases with increase in the salinity stress level (EC of 5 and 10 dS m-1) in all the genotypes, however significant (p&lt;0.01) genotypic difference were present among genotypes and GA-5 maintained the maximum growth under salinity. Percent decrease in SDW and RDW was lowest (10.61−23.86 and 10.37 and 26.59) in A. hypochondriachus while in A. cruentus (15.10-29.55 and 12.78-33.09) and A. caudatus (15.15−28.84 and 16.62-34.90). Salinity significantly (p&lt;0.01) decreases the membrane stability, relative water content and leaf potassium content while, leave sodium content increases. As compared to other genotype GA-5 have maximum membrane stability (53.30), relative water content (85.40%),  K+ accumulation and minimum Na+ accumulation in leaves.Morpho-physiological traits of grain Amaranthus species are significantly positively correlated with dry shoot biomass (0.649), MSI (0.770), RWC (0.768), chlorophyll (0.908), carotenoid (0.883) and leaf potassium (0.883).  It might be concluded that among studied genotypes GA-5 maintained the growth and have higher physiological efficiency results into maximum salt tolerance index also morpho-physiological traits like dry weight, RWC, MSI, Chlorophyll, Carotenoid and leaf potassium content might be utilised for selection of salt tolerant Amaranth genotypes.