Role of calcium nutrition in plant Physiology: Advances in research and insights into acidic soil conditions - A comprehensive review

Nutritional and Chemical Characterization of Red and Purple Potatoes Peels: A Polyphenol-Rich By-Product

Potato peel represents a major by-product of the potato-processing industry and a promising source of bioactive compounds with potential health benefits. This study investigates the biochemical and nutritional composition of peels from five purple and two red potato cultivars, with particular attention to their phytochemical profiles and antioxidant properties. Total phenolic content, carbohydrates, proteins, and lipids were quantified using UV-visible spectrophotometry. The phytochemical composition was further characterized via High-Performance Liquid Chromatography coupled with a Diode-Array Detector (HPLC-DAD). Antioxidant and radical-scavenging capacities of the extracts were assessed through Ferric Reducing Antioxidant Power (FRAP) and 2,2-diphenyl-1-picrylhydrazyl (DPPH) assays. Significant variability was observed across cultivars for all measured parameters. While all samples were rich in carbohydrates and proteins, they shared a common phenolic profile dominated by chlorogenic acid and its derivatives, as well as caffeic acid. Anthocyanin composition, however, was highly cultivar-specific. Notably, all extracts demonstrated strong antioxidant and antiradical activities, in agreement with their high total phenolic content. These findings highlight the potential of red and purple potato peels as valuable sources of functional ingredients for food and nutraceutical applications.

Growth variability of farm grown teak in response to climatic and soil factors across three agroclimatic zones of Tamil Nadu, India

Teak (Tectona grandis, Linn. f) is a prized hardwood species with remarkable properties that make it a favored material in various industries. In current trend, the cultivation of teak in farmlands is considered as a promising option. But the documentation and research on growth attributes and the studies on influence of climatic and edaphic factors on growth of teak raised in farmland condition is lacking. In this regard, the present investigation on farm grown teak was perpetrated in three agroclimatic zones viz., High Rainfall Zone, Southern Zone and Cauvery Delta Zone of Tamil Nadu in four different age classes (0-5, 5-10, 10-15 and 15-20 years). The study was carried forward with the prime motive of determining growth attributes and analyzing the impact of climatic and edaphic parameters on growth biometry of farm raised teak, both in block and boundary plantations. The soil physico-chemical parameters were analyzed both in surface (0-15 cm) and subsurface (15-30 cm) of plantations and the outcomes were presented in the form of cluster heat map, the results revealed that maximum organic carbon (0.62%), available nitrogen (197 kg ha-1), available phosphorous (22 kg ha-1), available potassium (340 kg ha-1), bulk density (1.34 g/cm3) and porosity (51.10%) were observed in surface soils of high rainfall zone. The follow-up of correlation studies between growth and climatic variables using R-software brought to light that tree volume positively correlated with climatic parameters viz., annual rainfall, mean minimum temperature and mean relative humidity, but showed negative correlation with respect to mean maximum temperature in both boundary and block plantations. Harmoniously, the correlation analysis between growth and edaphic parameters showed positive correlation with edaphic variables viz., organic carbon, available nitrogen, available phosphorous and available potassium, whereas growth depicted negative correlation with pH and electrical conductivity in both boundary and block plantations. In addition, principal component analysis was carried out to determine the most contributing factor among all and also to portray the highly suitable zone for teak cultivation. The overall study results portray that among climatic parameters, annual rainfall has significant impact on growth of teak and with respect to edaphic variables organic carbon play a crucial role in improving the growth of teak raised in farm settings. In regard to various zones surveyed, High Rainfall Zone exhibit favorable climatic and soil conditions, which in turn reflect better growth performance when compared to other zones taken into consideration.

Factors influencing heavy metal contamination in black pepper fields: a randomized study of the traditional chemical fertilized black pepper fields of South India concerning soil types

Despite the prevalence of heavy metal contamination in crop fields, targeted studies examining how factors like soil type affect contamination in chemically fertilized fields are scarce. This study assessed heavy metal contamination in Kerala's traditional black pepper fields, focusing on soil types-both soil order and series-and cultivation practices. We collected 266 soil samples from 70 diverse black pepper fields across five districts, which were categorized into 39 composite samples representing 13 soil series from two soil orders based on standard previous studies. Using Inductively Coupled Plasma-Mass Spectrometry, we quantitatively measured nine heavy metals (Cr, Mn, Fe, Co, Ni, Cu, Zn, Cd, and Pb) along with macronutrients (Mg and Ca). We analyzed heavy metal indices, including contamination factor, geo-accumulation index, pollution load index (PLI), and human health risk assessment, and explored correlations between heavy metals and soil nutrient parameters. It indicated that Cd, Zn, Cr, Pb, and Cu were the contaminants in the region's black pepper soils, while Fe and Mn levels were within natural limits. The PLI > 1 indicated significant contamination across both soil orders and most soil series. Mg levels were significantly higher (p > 0.05) in chemicalized fields, but Ca was undetectable in most samples, except from the Paippara series. Notable correlations were found between heavy metals and soil fertility parameters. This study underscores the extent of heavy metal contamination in black pepper fields relative to soil types and emphasizes the need for tailored soil fertility amendments and pesticide applications to promote sustainable agricultural practices.

Enhancing Yield, Physiological, and Quality Traits of Strawberry Cultivated Under Organic Management by Applying Different Non-Microbial Biostimulants

Organic farming is an environmentally friendly management practice that excludes the use of synthetic inputs, but at the same time is associated with lower yields than conventional production. In an attempt to compensate for yield reduction, resulting from foregoing the use of synthetic fertilizers, we hypothesized that the use of biostimulant products could provide much-desired food security. In light of this, a greenhouse experiment was conducted to compare and evaluate the effects of the foliar application of three different non-microbial biostimulants (a seaweed extract, a plant protein hydrolysate, and a plant extract) on the yield, mineral profile, and physiological response of strawberry (Fragaria × ananassa Duch.) grown in an organic farming context. Regardless of the type of biostimulant, treated plants showed significant improvement in photosynthetic performance. Specifically, the application of plant-derived protein hydrolysate increased ACO2 by 34.5% compared with control. Despite this, only the application of plant-derived protein hydrolysate significantly increased fruit yield per unit area (+13.5%). The improved performance of plants treated with plant-derived protein hydrolysate was associated with an overall improvement in mineral profile (compared to control +49.4 and 33.0% in NO3- and Mg2+ concentration, respectively). In contrast, application of the seaweed biostimulant increased (+17.4%) fruit antioxidant activity (DPPH) compared with control plants. These results underscore how the diverse origins of non-microbial biostimulants are responsible for specific responses in crops that can be exploited by organic growers to increase productivity.

Impact of Nutrient Stress on Plant Disease Resistance

Plants are constantly exposed to abiotic and biotic stresses that seriously affect crop yield and quality. A coordinated regulation of plant responses to combined abiotic/biotic stresses requires crosstalk between signaling pathways initiated by each stressor. Interconnected signaling pathways further finetune plant stress responses and allow the plant to respond to such stresses effectively. The plant nutritional status might influence disease resistance by strengthening or weakening plant immune responses, as well as through modulation of the pathogenicity program in the pathogen. Here, we discuss advances in our understanding of interactions between nutrient stress, deficiency or excess, and immune signaling pathways in the context of current agricultural practices. The introduction of chemical fertilizers and pesticides was a major component of the Green Revolution initiated in the 1960s that greatly boosted crop production. However, the massive application of agrochemicals also has adverse consequences on the environment and animal/human health. Therefore, an in-depth understanding of the connections between stress caused by overfertilization (or low bioavailability of nutrients) and immune responses is a timely and novel field of research with important implications for disease control in crop species. Optimizing nutrient management practices tailored to specific environmental conditions will be crucial in maximizing crop production using environmentally friendly systems.

Integrated metabolomics and transcriptomics reveal the role of calcium sugar alcohol in the regulation of phenolic acid biosynthesis in Torreya grandis nuts

BACKGROUND

Torreya grandis, a prominent tree species of the autochthonous subtropical region of China, possesses a drupe-like fruit containing a nut that is rich in nutrients and bioactive compounds. However, the effect of calcium (Ca2+) sugar alcohol (CSA), a newly developed chelated Ca2+-fertilizer, on the secondary metabolism of phenolics in T. grandis nuts is largely unknown, for which transcriptomic and metabolomic analysis was carried out.

RESULTS

Transcriptome sequencing detected 47,064 transcripts, and several phenolic acid biosynthesis pathway-related genes were identified. Correlation analysis showed that the four transcription factors, TgWRKY1, TgAP2-1, TgAP2-3, and TgAP2-4, were positively associated with the accumulation of phenolic acids. Furthermore, the binding of TgAP2-1 to the TgHCT promoter was confirmed using yeast one hybrid and dual-luciferase assays. Furthermore, the expression of TgHCT in Nicotiana enhanced the total flavonoid content.

CONCLUSIONS

Our results indicated that a new regulatory module, Ca2+-AP2-HCT, involved in the regulation of phenolic acid biosynthesis was revealed, expanding the understanding of the role of Ca2+ fertilizers in plant secondary metabolism.

Melatonin Enhances the Low-Calcium Stress Tolerance by Regulating Brassinosteroids and Auxin Signals in Wax Gourd

In plants, calcium (Ca) serves as an essential nutrient and signaling molecule. Melatonin is a biologically active and multi-functional hormone that plays an important role in improving nutrient use efficiency. However, its involvement in plant responses to Ca deficiency remains largely unexplored. This study aimed to assess the effects of melatonin on Ca absorption, the antioxidant system, and root morphology under low-Ca (LCa) stress conditions, as well as to identify key regulatory factors and signaling pathways involved in these processes using transcriptome analysis. Under LCa conditions, wax gourd seedling exhibited significant decreases in Ca accumulation, showed inhibition of root growth, and demonstrated the occurrence of oxidative damage. However, melatonin application significantly enhanced Ca content in wax gourd seedlings, and it enhanced the absorption of Ca2+ in roots by upregulating Ca2+ channels and transport genes, including BhiCNGC17, BhiCNGC20, BhiECA1, BhiACA1, and BhiCAX1. Furthermore, the application of exogenous melatonin mitigated the root growth inhibition and oxidative damage caused by LCa stress. This was evidenced by increases in the root branch numbers, root tips, root surface area, and root volume, as well as enhanced root vitality and antioxidant enzyme activities, as well as decreases in the reactive oxygen species content in melatonin treated plants. Transcriptome results revealed that melatonin mainly modulated the brassinosteroids (BRs) and auxin signaling pathway, which play essential roles in root differentiation, elongation, and stress adaptation. Specifically, melatonin increased the active BR levels by upregulating BR6ox (a BR biosynthesis gene) and downregulating BAS1 (BR degradation genes), thereby affecting the BR signaling pathway. Additionally, melatonin reduced IAA levels but activated the auxin signaling pathway, indicating that melatonin could directly stimulate the auxin signaling pathway via an IAA-independent mechanism. This study provides new insights into the role of melatonin in nutrient stress adaptation, offering a promising and sustainable approach to improve nutrient use efficiency in wax gourd and other crops.

Aging Dynamics of Polyvinyl Chloride Microplastics in Three Soils with Different Properties

Microplastic (MP) contamination in soil has been of great concern, but the dynamic aging process and potential pathways of MPs in natural soil systems remain poorly understood. Herein, poly(vinyl chloride) microplastics (5% w/w) were weathered for 12 months in sandy soil, silty clay, and silt loam. The results showed that the continuous increase of C═O and O-H groups (rate constant, k = 0.080-0.424 m-1) with time was observed on the surface of MPs aging in sandy soil due to the leading role of •OH induced by light irradiation. In the loam soil, the abundant coating of aluminosilicates and iron oxides on the MP surface by the formation of mineral-hydroxyl groups inhibited the generation of the C═O group (k < 0.165 m-1). The k of the characteristic bond C-Cl during the first 9 months was 9.51 and 1.93 times higher in clay compared to that in sandy and loam soil, respectively, revealing that dechlorination triggered the first step of the aging process for MPs in clay owing to the participation of degrading bacteria (Phenylobacterium and Caulobacteraceae). The results provide important insights into the aging dynamics of MPs in environmentally realistic circumstance, which account for understanding the different aging processes of MPs in different soils.

Network and stoichiometry analysis revealed a fast magnesium and calcium deficiency of mulched Phyllostachys violascens

The imbalanced fertilization and the consequential deterioration on the rhizosphere microbial community (RMC) were two potential reasons for the quick yielding degradation of Phyllostachys violascens (Lei-bamboo), a high-value shoot-oriented bamboo. However, most research only focused on nitrogen, phosphorus, and potassium; the studies on the dynamics of other nutrients, such as calcium and magnesium; and their driving mechanisms, lags far behind. Thus, Lei-bamboo fields of different mulching and recovery ages were selected to investigate the dynamics of calcium and magnesium in both soil and bamboo tissue, and to explore their relationship to RMC composition and network patterns. The results showed that mulching increased the content of soil acidification, total organic carbon, alkali-hydrolysable nitrogen, available phosphorus, and available potassium but reduced soil exchangeable magnesium and calcium in soil as well as the magnesium and calcium content in rhizome, stem, and leaf of Lei-bamboo, which indicated an increased relative limitation on magnesium and calcium. Mulching also enhanced the α-diversity and reshaped the composition of RMC, which had a close link to Mg rather than nitrogen, phosphorus, and potassium. As the mulching years increased, the RMC network became bigger and more complex, and the magnesium and calcium gradually appeared in the network center, which further support the magnesium and calcium deficiency to RMC. Nearly all the variation mentioned above could be revered after the removing of mulching. Structural equation modeling showed two main pathways that mulching leads to magnesium and calcium deficiency in Lei-bamboo, one is directly by lowering soil magnesium and calcium content, the other one is indirectly by improving RMC network interactions, a sign of weakened mutualism between RMC and plant roots that hampering the uptake of nutrients. This research highlights the quick magnesium and calcium deficiency caused by mulching in Lei-bamboo forest and the contribution of RMC in amplify the effects of soil magnesium and calcium deficiency, which offers valuable information on balancing fertilization pattern for future sustainable Lei-bamboo cultivation.

Silicon Nanomaterials Enhance Seedling Growth and Plant Adaptation to Acidic Soil by Promoting Photosynthesis and Antioxidant Activity in Mustard (Brassica campestris L.)

Soil acidity is a divesting factor that restricts crop growth and productivity. Conversely, silicon nanomaterials (Si-NMs) have been praised as a blessing of modern agricultural intensification by overcoming the ecological barrier. Here, we performed a sequential study from seed germination to the yield performance of mustard (Brassica campestris) crops under acid-stressed conditions. The results showed that Si-NMs significantly improved seed germination and seedling growth under acid stress situations. These might be associated with increased antioxidant activity and the preserve ratio of GSH/GSSG and AsA/DHA, which is restricted by soil acidity. Moreover, Si-NMs in field regimes significantly diminished the acid-stress-induced growth inhibitions, as evidenced by increased net photosynthesis and biomass accumulations. Again, Si-NMs triggered all the critical metrics of crop productivity, including the seed oil content. Additionally, Si-NMs, upon dolomite supplementation, further triggered all the metrics of yields related to farming resilience. Therefore, the present study highlighted the crucial roles of Si-NMs in sustainable agricultural expansion and cropping intensification, especially in areas affected by soil acidity.

Rhizospheric Bacteria of Cover Legumes from Acidic Soils Are Capable of Solubilizing Different Inorganic Phosphates

Due to its adsorption with aluminum and iron hydroxides, phosphorus viability is low in acidic soils; thus, the aim of this study was to isolate and identify bacteria from the rhizosphere of four legumes growing in acidic soils of the Cumbaza Sub-basin, San Martín, Peru, as well as to characterize their ability to solubilize aluminum phosphate and iron phosphate. The isolation process was conducted on TSA medium and the isolates were classified based on their origin and morphocolonial characteristics, with the bacillary shape being the most frequent, followed by cocci. To assess the solubilization of aluminum and iron phosphates, the liquid medium GELP was employed. Sixteen strains were selected, among which three stood out for their effectiveness in solubilizing AlPO4 (Sfcv-098-02, 22.65 mg L-1; Sfc-093-04, 26.50 mg L-1; and Sfcv-041-01-2, 55.98 mg L-1) and one for its ability to solubilize FePO4 (Sfcr-043-02, 32.61 mg L-1). These four strains were molecularly characterized, being identified as Enterobacter sp., Pseudomonas sp., and Staphylococcus sp. Additionally, a decrease in pH was observed in the reactions, with values ranging from 5.23 to 3.29, which enhanced the phosphate of solubilization. This suggests that the selected bacteria could be used to improve phosphorus availability in agricultural soils.