Mineral Nutrient Concentrations Research Articles

Exogenously Applied Sulphur Improves Growth, Photosynthetic Efficiency, Enzymatic Activities, Mineral Nutrient Contents, Yield and Quality of Brassica juncea L.

Background: Due to increasing domestic and industrial demand, edible oil production is not keeping up with demand. To fill this gap, the productivity of oilseeds can be increased by applying adequate nutrients, particularly sulphur (S), at the crucial growth stage. Purpose: The present study aims to explore the best concentration of S for its foliar application on various cultivars of mustard. Methods: A factorial randomized pot experiment was conducted to investigate the role of leaf-applied S on growth, physiobiochemistry, yield and quality traits of three cultivars of Brassica juncea L. (mustard). Five levels of S viz. 0 (water), 15, 30, 45 and 60 ppm S constituted one variant, and the three cultivars (Chutki, Nath Sona and Rohini) were the other variants. The various levels of S were sprayed at 50 and 70 days after sowing (DAS). The growth and physio-biochemical characteristics were studied at 90 DAS, and yield and quality attributes at 120 DAS (harvest). Results: The data indicated that increasing S levels up to 45 ppm S improved all parameters of mustard and thereafter (at the level above 45 ppm S) decreased. Cultivar Nath Sona, followed by Rohini and Chutki, performed best. Among the foliar spray treatment of different levels of S, the application of 45 ppm S increased plant dry weight by 40.21, 35.65 and 30.96%, photosynthetic rate by 28.27, 27.44 and 36.29%, pods of a plant by 15.23, 12.12 and 10.80%, seed yield of a plant by 7.54, 3.89 and 4.91%, oil content by 48.70, 46.31 and 43.15% and oil yield of a plant by 24.56, 23.93 and 22.35% in cultivar Nath Sona, Rohini and Chutki, respectively, compared with their respective water-treated plants. Moreover, the oil was examined by GC-MS technique for its various components. The analysis revealed that there were 36 compounds in the oil of the non-treated plants and 44 compounds in the oil of plants treated with 45 ppm S. The extra compounds resulted from the application of 45 ppm S. Conclusion: It may be concluded that two sprays of 45 ppm S proved effective in improving the growth, physio-biochemical characteristics, yield and quality of cultivars of mustard, particularly Nath Sona.

Effects of supplementing green light to red and blue light on the growth and yield of lettuce in plant factories

Red and blue light-emitting diodes (LEDs) are widely used as light sources in plant factories. Plants grown under red and blue light only produces purplish-gray light environment where plant leaves look purplish-gray. Under that light condition, it makes difficulty to check health status of plants specially insect and disease infected leaves by human naked eye. But the leaf color turns green when inspected under full spectrum of light environment. In this regard, the use of green light to red and blue create a white light environment which is congenial for the grower. Likewise, CO2 assimilation of green light is usually lower compared to red and blue light because of its lower absorptance under low PPFD. But at higher PPFD (≥500 µmol m−2 s−1), green light shows higher CO2 assimilation rate compared to red and blue light through uniform distribution of full spectrum (red, green and blue) of light into the plant canopy and the lower leaves. In this study, optimal intensity of green light supplementation to the red and blue LEDs was evaluated for better growth, yield, and quality of lettuce. In experiment I and II, green light was added with red and blue light where total photosynthetic photon flux density (PPFD) was increased for the additional green light. In experiment III, 0, 10, 20, 30, 40, 50, 60, 70, 80 µmol m−² s−1 green (G) light was supplemented to 235 µmol m−² s−1 red (R) and 59 µmol m−² s−1 blue (B) light maintaining 294 µmol m−² s−1 total PPFD. Lettuce plants were cultivated hydroponically in three-step vertical grow beds using half-strength of Enshi nutrient solution. The temperature was maintained at 20 ± 2 °C at day and night and the day length was 16 h. In experiment I and II, the fresh mass of lettuce grown under the combination of R, B and G LEDs was found higher than those cultivated under R and B LEDs only. In experiment III, lettuce plants produced high fresh masses when 30 µmol m−² s−1 of G light was supplemented with R and B lights maintaining the ratio 211:30:53 (R:G:B). By supplementing excessive G light (≥50 µmol m−² s−1) with R and B lights, lettuce shoot fresh mass declined. The various combinations of irradiation of R, G and B LED did not significantly affect the contents of ascorbic acid and mineral nutrients. It is recommended to supplement 30 µmol m−2 s−1 of green light to red and blue light for a higher yield of lettuce. Therefore, the suitable LED (R:G:B) combination would be 72% of red, 10% of green and 18% of blue for lettuce cultivation following recycled hydroponics in plant factories.

Arbuscular mycorrhizal species vary in their impact on nutrient uptake in sweet corn (Zea mays) and butternut squash (Cucurbita moschata)

An increasing demand for organic produce, coupled with the need to reduce reliance on the diminishing resource of rock phosphate, has bolstered interest in the use of arbuscular mycorrhizae (AMF) as a biofertilizer. AMF are symbiotic fungi that colonize the roots of most crops and transfer nutrients from the soil to their hosts in exchange for carbon. While past studies have shown that mixed AMF communities grown from field soil can increase the yield of many crops, the targeted use of individual AMF species on host plants is a promising avenue to enhance nutrient uptake. We inoculated sweet corn (Zea mays) and butternut squash (Cucurbita moschata) seedlings with nine individual species of AMF and one mixed indigenous population to determine the most beneficial symbionts for enhancing mineral nutrient concentration and yield. Overall, level of root colonization was correlated with phosphorus (P) concentration of aboveground biomass. Corn and squash grown in association with AMF species in the Rhizophagus genus had the highest level of root colonization and tissue P concentration. Claroideoglumus etunicatum and Gigaspora margarita increased calcium (Ca) and magnesium (Mg) concentration in corn and Gigaspora rosea increased calcium in squash. S. constrictum and G. rosea positively impacted sweet corn seedling biomass. Based on this evidence, AMF species vary in their benefit to plant nutrient uptake and the most beneficial species depend on host. Further research on the effectiveness of inoculating individual AMF species across a range of hosts and ecosystems will prove useful in the development of host-targeted AMF biofertilizers.

Fruit collapse incidence and quality of pineapple as affected by biopesticides based on Pseudomonas fluorescens and Trichoderma harzianum

In this study the effect of Pseudomonas fluorescens and Trichoderma harzianum based biopesticides on fruit collapse disease incidence and pineapple quality was investigated. The experiment was implemented in a split-plot design with two factors, one involving two inoculation methods (spray and inject), and a second factor involving four treatments, A (control: no biopesticides used), B (Bio P32 from 13 weeks before harvest), C (Bio T10 from 13 weeks before harvest) and D (Bio P32 + Bio T10 from 13 weeks before harvest). The inoculated pathogen was Dickeya zeae. The incidence of fruit collapse, total soluble solids, total acidity, sucrose, ascorbic acid, mineral content, and electrolyte leakage were determined. The inject method caused more fruit collapse incidence than the spray method. Treatments C and D provided the best results having a low incidence of fruit collapse (spray: 5 and 1.7 %, inject: 20 % in both cases), high antioxidant capacity (regarding ascorbic acid), high mineral nutrient content (in terms of Ca and Mg), and low electrolyte leakage content (< 70 % in average), with a healthier cell wall characteristic. Meanwhile, treatments A and B were less efficient in these aspects and promoted the incidence of fruit collapse, especially when the inject method was used, as this was more harmful regarding the fruit physiology. In conclusion, the biopesticides employed can reduce the incidence of fruit collapse and positively affect the fruit quality.

Evaluation of substrates for cucumber production in the Dutch bucket hydroponic system

The Dutch bucket system is commonly used for production of high-wire crops such as tomatoes, peppers, and cucumbers in controlled environment agriculture. It is a hydroponic system that utilizes containers typically filled with perlite as the substrate. Perlite provides good aeration however has higher leachate in the systems. Furthermore, demand for regional and sustainable substrates is increasing. Our preliminary study showed growth parameters in vegetative and early fruiting stages of cucumber grown with five regionally accessible substrates are comparable to perlite. Thus, the current study evaluated the performance of five organic substrates in comparison to perlite in the Dutch bucket system for the full production cycle of cucumber (Cucumis sativus ‘Picolino F1’). The substrates evaluated were sphagnum peat, medium grade pine bark (Bark-M), coarse grade pine bark (Bark-C), coir, and wood fiber. Leachate rates in Bark-M, coir, and peat were lower than perlite by 18.0%, 24.0%, and 38.1%, respectively. Plant leaf area indicated better vegetative growth of cucumber with wood fiber, but pine bark had higher yield and fruit quality than perlite. Bark-M resulted in greater yield and fruit vitamin C content, which were 23.9% and 48.3% higher than perlite, respectively. On the other hand, although Bark-C had a similar yield to perlite, its fruit mineral nutrient content including nitrogen (except wood fiber), phosphorus, potassium, calcium (except Bark-M and wood fiber), sulfur (except Bark-M and wood fiber), iron (except Bark-M), zinc, boron, copper (except wood fiber), and manganese (except Bark-M), as well as total anthocyanin and total phenols were highest among all substrates. In summary, organic substrates investigated could provide equal or higher cucumber yields and quality than perlite in the Dutch bucket hydroponic system.

Effects of pruning on mineral nutrients and untargeted metabolites in fresh leaves of Camellia sinensis cv. Shuixian.

Pruning is an important strategy for increasing tea production. However, the effects of pruning on tea quality are not well understood. In this study, tea leaves were collected from Wuyi Mountain for both ionomic and metabolomic analyses. A total of 1962 and 1188 fresh tea leaves were respectively collected from pruned and unpruned tea plants sampled across 350 tea plantations. Ionomic profiles of fresh tea leaves varied significantly between pruned and unpruned sources. For tea plants, pruning was tied to decreases in the concentrations of mobile elements, such as nitrogen (N), phosphorus (P), potassium (K) and magnesium (Mg), and dramatic increases in the concentrations of the immobile ions calcium (Ca), aluminum (Al), manganese (Mn), boron (B) and cobalt (Co). Clustering and heatmap analysis showed that pruning also affected tea leaf metabolism. Among 85 metabolites that were significantly impacted by pruning, 30 were identified through random forest analysis as characteristic differential metabolites with a prediction rate of 86.21%. Redundancy analysis showed that pruning effects on mineral nutrient concentrations accounted for 25.54% of the variation in characteristic metabolites between treatments, with the highest contributions of 6.64% and 3.69% coming from Ca and Mg, respectively. In correlation network analysis, Ca and Mg both exhibited close, though opposing correlations with six key metabolites, including key quality indicators 1,3-dicaffeoylquinic acid and 2-O-caffeoyl arbutin. In summary, large scale sampling over hundreds of tea plantations demonstrated that pruning affects tea quality, mainly through influences on leaf mineral composition, with Ca and Mg playing large roles. These results may provide a solid scientific basis for improved management of high-quality tea plantations.

Comparative Effect of Seed Priming and Growing Media on Germination and Seedling Rootstocks of Mango (Mangifera indica)

The poor seedling rootstock is a key factor in mango yield reduction. Container-based study was conducted to evaluate the effect of seed priming and growing media on seedling rootstocks of mango. Hydropriming of seed was performed by using distilled water, while gibberellic acid (GA3) and NPK fertilizer (Solo plant) were used for hormonal and nutripriming, respectively. In second part, the primed and unprimed seeds were planted in four different growing media (GM) including GM1, GM2, GM3 and GM4. Data showed that seed germination (%), germination index (GI), seedling vigor index (SVI), height of seedling, stem diameter, chlorophyll content, electrolyte leakage of leaf, nutrient (N, P, K, Ca and Mg) contents in leaf tissue was significantly altered by both seed priming and growing media respectively. In case of priming treatments, hormonal primed seeds had the best seed germination (77.01%), stem diameter (9.65 mm) and electrolyte leakage of leaf (13.01%); while N (1.13%), P (0.14%), K (0.87%), Ca (2.40%) and Mg (0.34%) content of leaf tissue was observed maximum in nutripriming treatment. Whereas, seed germination (71.96%), germination index (11.15) and stem diameter (9.41 mm) had greater values in response to the GM2 treatment. While GM4 grown seedlings had higher seeding height (33.81 cm), N (1.17%), P (0.15%), K (0.98%), Ca (2.64%) and Mg (0.38%) content of leaf tissue. It is concluded that seed germination and seedling growth attributes had a greater influence of GA3, while mineral nutrient contents of leaf had a significant effect on nutripriming. Among growing media, GM2 was observed better for growth parameters while GM4 for mineral nutrient contents of leaf..

KNO3, Nano-Zn, and Fe Foliar Application Influence the Growth and Physiological Responses of Aloe vera under Salinity

Aloe vera L. is a perennial drought-tolerant plant that is commonly used in the pharmaceutical, food, and cosmetic industries. To evaluate the effects of the foliar application of KNO3, nano-Zn, and Fe (0 and 2 mgL−1) on Aloe vera plants under NaCl salinity stress (0, 50, 100 mM), a factorial experiment was conducted based on a completely randomized design. The results revealed that foliar applications influenced the root dry weight. The chlorophyll b content was affected by the salinity plus the foliar application. The total soluble solids content, chlorophyll a, phenolics, and flavonoids of the leaves, the gel content, catalase and superoxide dismutase activity, malondialdehyde, proline, and mineral nutrients content were impacted by the treatments as well. The highest values for the gel content (0.37 g per leaf) and plant dry weight (13.1 g per pot) were recorded at 0 mM NaCl + KNO3 + nano-Fe. The top K/Na ratio (35.2), and the largest K (69 g kg−1), P (6.6 g kg−1), Ca (31 g kg−1), and Mg (2.5 g kg−1) contents were recorded after the 0 mM NaCl + KNO3 treatment. The highest Fe content (383 g kg−1) was observed with 0 mM NaCl + nano-Fe treatment, and the maximum Zn content (37.6 mg kg−1) was measured after the 0 mM NaCl + nano Zn treatment. One hundred mM NaCl increased the malondialdehyde and Na contents. The largest amount of catalase activity was measured after the 50 mM NaCl + KNO3 + nano-Zn treatment. Salinity stress had adverse effects on the growth and physiological responses of Aloe vera. However, the foliar application of KNO3, nano-Zn and Fe mitigated the damaging effects of salinity. The results from more detailed studies would be advisable for pioneer farmers and the agricultural sector.

Effects of Nitrogen Deficiency and Resupply on the Absorption of Mineral Nutrients by Tangor Cultivar 'Shiranuhi' (Citrus unshiu × C. sinensis) Grown in a Hydroponic System.

Tangor (Citrus unshiu × C. sinensis) cultivars obtained through interspecific hybridization have gained popularity in various countries, including South Korea. However, tangor has a relatively short history of cultivation and thus has been less well researched in terms of physiology and opping technology compared to mandarin. In addition, although tangor grows more vigorously than mandarin and thus has high nutrient demands and longer harvest time, it is more prone to various physiological disorders. Furthermore, the demand for nutrients could vary depending on the cultivars even within the same species. Thus, the current study examined the effects of nitrogen deficiency and resupply on the uptake of mineral nutrients using a specific cultivar ‘Shiranuhi’ as a case study. In this study, the tangor cultivar ‘Shiranuhi’ was cultivated in a hydroponics system, which allows the control of nutrient contents, and changes in mineral nutrient contents under nitrogen deficiency and nitrogen resupply were examined. Based on this, the results show the straightforward relationship between nitrogen and other mineral nutrients under a hydroponic system applying the cultivation of tangor. This implies that the hydroponics system can be applied to tangor cultivation and efficiently and widely expanded in Northeast Asia, and the income of growers will increase through the production of high-quality fruits.

Effect and mechanism of exogenous selenium on selenium content and quality of fresh tea leaves

To study the effect and mechanism of selenium sources on the selenium content and quality of fresh tea leaves, tea seedlings (Camellia sinensis (L.) O. Kuntze) were the research object. A solution of 100 mg/L sodium selenate (Na2SeO4), sodium selenite (Na2SeO3), and selenium yeast (selenium yeast) were applied on the leaves surface of 5-week-old tea plants, and the selenium levels in the leaves, roots, and stems were determined at 20 weeks of age. The effects of different selenium sources on the mineral nutrient content, antioxidant enzyme activity, and quality parameters content in leaves were analyzed. The mechanism was analyzed by detecting the expression levels of related genes. The results showed that the three selenium sources can increase the growth of tea seedlings and the selenium content in leaves and stems, and the selenium yeast treatment had the most significant effect. Selenium spraying promoted the absorption of mineral nutrients such as nitrogen, phosphorus, and potassium, but had no significant impact on the absorption of calcium and magnesium. Spraying the three selenium sources dramatically increased the activities of APX, POD, and SOD antioxidant enzymes, among which the selenium yeast treatment had the most significant effect. However, there was no significant impact on the MDA level in this study. Selenium sources markedly increased leaves total amino acid levels, accompanied by up-regulation the genes of amino acid synthetic enzymes (CsGS, CsGOGAT, and CsGDH). Leaves glucose, tea polyphenol, total soluble protein, catechin, flavonoid contents, and sucrose were higher in selenium sources treatments than in control treatment seedlings. Moreover, selenium sources up-regulated expression of CsHMGR, CsAPX, and CsTCS1 genes. selenium yeast had the best comprehensive effect of the three selenium sources. These results confirmed that selenium sources play a positive role on the selenium content and quality of tea by increasing the antioxidant capacity of leaves, the absorption rate of mineral nutrients, and regulating expression of related genes in Camellia sinensis.

Kinetics of Macro and Micronutrients during Germination of Habanero Pepper Seeds in Response to Imbibition

The aim of this study was to evaluate the concentration and distribution of a number of macro- and micronutrients in response to imbibition in habanero pepper seeds extracted from fruits with different stages of maturity and postharvest storage times, as well as in their seedlings. Fruits were harvested unripe, half-ripe, and ripe, and were subjected to storage for 0 (control), 7, and 14 days postharvest prior to seed extraction. An X-ray microfluorescence analysis was carried out on seeds pre- and post-imbibition, as well as on seedlings at 10 and 14 days after sowing. K, Ca, Fe, P, Mg, and Mn were detected by elemental analysis. The results indicated that the elements had a higher concentration and distribution in seeds extracted from half-ripe fruits and ripe unstored fruits, as well as in seeds extracted from fruits stored for 7 and 14 days postharvest. K and Ca were the elements with the highest distributions and concentrations in seeds and seedlings pre- and post-imbibition compared to the other elements. At all maturity stages, postharvest storage increased the concentration and distribution of mineral nutrients in seeds and seedlings before and after imbibition. Storage translocated mineral elements to the radicle before germination, increased meristem growth in emerged seedlings, decreased electrical conductivity, and increased germination. Fourteen days of postharvest storage increased the distribution of macro- and micronutrients in immature seeds, decreasing electrical conductivity, potentiating germination, and improving mineral element distribution in seedlings.

Chalcogens reduce grain Cd accumulation by enhancing Cd root efflux and upper organ retention in wheat (Triticum aestivum L.)

A seedling-stage sand culture experiment and whole growth period pot experiment were conducted together to investigate the effects of chalcogenide elements (S, Se, Te) on the morphology, photosynthesis, Cd absorption, Cd and mineral nutrient transport, and transporter gene expression of wheat under Cd stress. Compared with S, Se and Te can alleviate wheat Cd toxicity and reduce Cd accumulation more efficiently. Compared with control conditions, S reduced the root Cd concentration by about 20 %, while SeIV and TeIV reduced the root Cd concentration by more than 60 % and the shoot Cd concentration by about 30 %. Chalcogens reduced Cd uptake by increasing root diameter (by about 50 %) and inhibiting lateral root formation under SeIV and TeIV treatments compared to Cd treatment alone. Moreover, chalcogens accelerated Cd efflux by up-regulating TaTM20 , thereby reducing Cd accumulation. Meanwhile, chalcogens enhanced Cd isolation in the cell wall and vacuole, reduced the active Cd proportion by increasing synthesis of chelates, and improved wheat Cd tolerance. Spraying Se and Te increased both the photosynthetic rate and yield, while also improving mineral nutrient contents (including magnesium, calcium, zinc, iron, manganese, copper, and molybdenum contents) in wheat grains. Selenomethionine (SeMet) was more effective in reducing upper organ Cd reactivation and inhibiting Cd transport from upper organs to grains, which was able to reduce grain Cd content by 27 % in the 5 mg/kg Cd treatment. Additionally, SeIV and TeIV reduced grain Cd content by 14 % and 16 %, respectively; while SeVI increased Cd content by 11 %. The current study reveals the mechanism by which chalcogens alleviate Cd toxicity and reduce grain Cd accumulation, which provides valuable insights for safe wheat production despite Cd soil contamination. • Se and Te alleviate Cd toxicity and increase wheat yield. • Chalcogens decrease Cd uptake by increasing root diameter and inhibiting lateral root growth. • Chalcogens reduce Cd accumulation by increasing root Cd efflux. • Increases in PC S -Cd complexes and up-regulation of HMA2 expression promote Cd transport to shoots. • SeMet reduces Cd transport to grains by reducing Cd reactivation in stem, leaf, and glume tissues.

Exogenous 5-aminolevulinic acid alleviates low-temperature damage by modulating the xanthophyll cycle and nutrient uptake in tomato seedlings

5-Aminolevulinic acid (ALA), an antioxidant existing in plants, has been widely reported to participate in the process of coping with cold stress of plants. In this study, exogenous ALA promoted the growth of tomato plants and alleviated the appearance of purple tomato leaves under low-temperature stress. At the same time, exogenous ALA improved antioxidant enzyme activities, SlSOD gene expression, Fv/Fm, and proline contents and reduced H2O2 contents, SlRBOH gene expression, relative electrical conductivity, and malondialdehyde contents to alleviate the damage caused by low temperature to tomato seedlings. Compared with low-temperature stress, spraying exogenous ALA before low-temperature stress could restore the indicators of photochemical quenching, actual photochemical efficiency, electron transport rate, and nonphotochemical quenching to normal. Exogenous ALA could increase the total contents of the xanthophyll cycle pool, the positive de-epoxidation rate of the xanthophyll cycle and improved the expression levels of key genes in the xanthophyll cycle under low-temperature stress. In addition, we found that exogenous ALA significantly enhanced the absorption of mineral nutrients, promoted the transfer and distribution of mineral nutrients to the leaves, and improved the expression levels of mineral nutrient absorption-related genes, which were all conducive to the improved adaptation of tomato seedlings under low-temperature stress. In summary, the application of exogenous ALA can increase tomato seedlings’ tolerance to low-temperature stress by improving the xanthophyll cycle and the ability of the absorption of mineral nutrients in tomato seedlings.

Assessing the Usefulness of Moringa oleifera Leaf Extract as a Biostimulant to Supplement Synthetic Fertilizers: A Review.

The extensive use of synthetic chemical fertilizers is associated with environmental pollution and soil degradation. In addition, the high costs of these fertilizers necessitate the search for alternative, eco-friendly and safe natural sources of phytonutrients. The liquid extracted from moringa (Moringa oleifera Lam.) leaves has been used in agriculture to improve the growth and productivity of several crops. The efficacy of moringa leaf extract (MLE) is attributed to its high content of mineral nutrients, protein, vitamins, sugars, fiber, phenolics and free proline. In addition, MLE contains significant amounts of phytohormones, such as auxins, cytokinins and gibberellins. Furthermore, MLE is a valuable product promoting seed germination, plant growth and deeper root development, delaying fruit senescence and increasing the yield and quality of crops grown under normal or stressful conditions. Here, we review the research on MLE as a biostimulant to enhance crop growth and productivity. Moreover, we emphasize its possible introduction to smallholder farming systems to provide phytonutrients, and we further highlight research gaps in the existing knowledge regarding MLE application. Generally, MLE is an inexpensive, sustainable, eco-friendly and natural biostimulant that can be used to improve the growth and productivity attributes of various crops under non-stressful and stressful conditions.

Transcriptome analysis revealed the expression levels of genes related to abscisic acid and auxin biosynthesis in grapevine (Vitis vinifera L.) under root restriction.

The root system is essential for the stable growth of plants. Roots help anchor plants in the soil and play a crucial role in water uptake, mineral nutrient absorption and endogenous phytohormone formation. Root-restriction (RR) cultivation, a powerful technique, confines plant roots to a specific soil space. In the present study, roots of one-year-old “Muscat Hamburg” grapevine under RR and control (nR) treatments harvested at 70 and 125 days after planting were used for transcriptome sequencing, and in total, 2031 (nR7 vs. nR12), 1445 (RR7 vs. RR12), 1532 (nR7 vs. RR7), and 2799 (nR12 vs. RR12) differentially expressed genes (DEGs) were identified. Gene Ontology (GO) enrichment analysis demonstrated that there were several genes involved in the response to different phytohormones, including abscisic acid (ABA), auxin (IAA), ethylene (ETH), gibberellins (GAs), and cytokinins (CTKs). Among them, multiple genes, such as PIN2 and ERF113, are involved in regulating vital plant movements by various phytohormone pathways. Moreover, following RR cultivation, DEGs were enriched in the biological processes of plant-type secondary cell wall biosynthesis, the defense response, programmed cell death involved in cell development, and the oxalate metabolic process. Furthermore, through a combined analysis of the transcriptome and previously published microRNA (miRNA) sequencing results, we found that multiple differentially expressed miRNAs (DEMs) and DEG combinations in different comparison groups exhibited opposite trends, indicating that the expression levels of miRNAs and their target genes were negatively correlated. Furthermore, RR treatment indeed significantly increased the ABA content at 125 days after planting and significantly decreased the IAA content at 70 days after planting. Under RR cultivation, most ABA biosynthesis-related genes were upregulated, while most IAA biosynthesis-related genes were downregulated. These findings lay a solid foundation for further establishing the network through which miRNAs regulate grapevine root development through target genes and for further exploring the molecular mechanism through which endogenous ABA and IAA regulate root architecture development in grapevine.

Crop Load and Thinning Methods Impact Yield, Nutrient Content, Fruit Quality, and Physiological Disorders in ‘Scilate’ Apples

Most apple cultivars produce too many flowers to enable consistent yields of high-quality fruit, thus, crop load management (thinning) is an integral part of orchard management in modern apple cultivation. Crop load is managed by thinning excess flowers and/or fruit from a tree, however ideal targets vary between cultivars. In this two-year study, the effect of thinning methods at different levels of crop load on fruit quality and production, post-harvest storability and physiological disorders, and fruit and leaf nutrient content in ‘Scilate’ apples were investigated in southern Tasmania, Australia. Two thinning methods, artificial bud extinction (ABE) and hand thinning (HT), were compared at three levels of crop load: 3, 6, or 12 fruit cm−2 limb cross-sectional area (LCSA), described as low, medium, and high, respectively. During the second season, all the ABE and HT treatments received additional chemical thinning (CT). The results demonstrated that ABE consistently outperformed HT in terms of improved fruit set, return bloom, and fruit weight. The fruit quality parameters, such as flesh firmness, total soluble solids, dry matter content, malic acid content, and fruit shape, were also improved under the ABE regime, with these positive effects being the clearest in the second season. In general, high-quality fruits were obtained from the low and medium crop loads, while the fruit quality was poor for the high crop load trees, but the low crop load fruit had a slightly higher incidence of internal flesh browning (predominantly radial) and fruit softening after regular atmosphere storage. The crop load also impacted on the fruit and leaf mineral nutrient content, where fruit N, Ca, Mn, and Zn, and leaf N, Fe, Zn, and Cu content increased while fruit and leaf K declined with a higher crop load. High crop load, irrespective of the thinning regime, and HT with a medium crop load, induced severe biennial bearing, whereas, the fruit yield was relatively consistent with ABE, even with a medium crop load. We conclude that ABE with a medium crop load (around six fruit cm−2 LCSA) is an effective method of managing crop load and optimizing the fruit quality in ‘Scilate’ apples.

Iron Source and Medium pH Affect Nutrient Uptake and Pigment Content in Petunia hybrida 'Madness Red' Cultured In Vitro.

Deficiency or excess of iron (Fe) and improper medium pH will inhibit the growth and development of plants, reduce the transfer and utilization of energy from the root to the leaf, and affect the utilization efficiency of inorganic nutrients. The most common symptom of Fe deficiency in plants is chlorosis of the young leaves. In this study, the effects of the iron source, in combination with the medium pH, on plant growth and development, plant pigment synthesis, and nutrient uptake in a model plant Petunia hybrida cultured in vitro were investigated. Iron sulfate (FeSO4·7H2O) or iron chelated with ethylenediaminetetraacetic acid (Fe-EDTA) were supplemented to the MNS (a multipurpose nutrient solution) medium at a concentration of 2.78 mg·L−1 Fe, and the treatment without any Fe was used as the control. The pH of the agar-solidified medium was adjusted to either 4.70, 5.70, or 6.70 before autoclaving. The experiment was carried out in an environmentally controlled culture room with a temperature of 24 °C with 100 µmol·m−2·s−1 photosynthetic photon flux density (PPFD) supplied by white light emitting diodes (LEDs) during a photoperiod of 16 h a day, 18 °C for 8 h a day in the dark, and 70% relative humidity. Regardless of the Fe source including the control, the greatest number of leaves was observed at pH 4.70. However, the greatest lengths of the leaf and root were observed in the treatment with Fe-EDTA combined with pH 5.70. The contents of the chlorophyll, carotenoid, and anthocyanin decreased with increasing medium pH, and contents of these plant pigments were positively correlated with the leaf color. The highest soluble protein content and activities of APX and CAT were observed in the Fe-EDTA under pH 5.70. However, the GPX activity was the highest in the control under pH 4.70. In addition, the highest contents of ammonium (NH4+) and nitrate (NO3−) were measured in the FeSO4-4.7 and EDTA-5.7, respectively. More than that, the treatment of Fe-EDTA combined with pH 5.70 (EDTA-5.7) enhanced nutrient absorption, as proven by the highest tissue contents of P, K, Ca, Mg, Fe, and Mn. The genes’ ferric reduction oxidase 1 and 8 (PhFRO1 and PhFRO8), iron-regulated transporter 1 (PhIRT1), nitrate transporter 2.5 (PhNRT2.5), and deoxyhypusine synthase (PhDHS) were expressed at the highest levels in this treatment as well. In the treatment of EDTA-5.7, the reduction and transport of chelated iron in P. hybrida leaves were enhanced, which also affected the transport of nitrate and catalyzed chlorophyll level in leaves. In conclusion, when the medium pH was adjusted to 5.70, supplementation of chelated Fe-EDTA was more conducive to promoting the growth and development of, and absorption of mineral nutrients by, the plant and the expression of related genes in the leaves.

Photon Distribution of Sole-Source Lighting Affects the Mineral Nutrient Content of Microgreens

In the study, we cultivated basil, beet, and mustard microgreens under different lighting treatments from light-emitting diodes (LEDs) and evaluated the contents of mineral nutrients. Microgreens grew under blue 447, red 638 and 665, far-red 731 nm LEDs, or the same spectrum but with partial substitution of 638 nm red with green 520 (BRG), yellow 595 (BRY), or orange 622 nm (BRO) LEDs (16 h photoperiod; total photon flux density of 300 μmol m −2 s −1). BRG, BRY, or BRO lighting had distinct effects on mineral contents among the microgreen species. BRG increased the content of mineral nutrients, especially in mustard and beet. In all microgreens, Ca and P were associated with BRG; in beet and mustard, Zn and Mg were associated with BRG; in basil, Zn was associated with BRY and Mg with BRO treatments. A broader photon spectrum increased Fe (up to 2.9–fold), K:Ca, P:Mg, and P:Zn in basil, and Fe:Zn in microgreens. We conclude that the partial replacement of red with green light was the most effective at enhancing the mineral nutrient content of microgreens, although responses varied among the crops studied.

Effect of Self- and Inter-Cultivar Grafting on Growth and Nutrient Content in Sweet Basil (Ocimum basilicum L.).

Vegetable grafting has been applied to fruiting crops, yet only to a limited extent in leafy greens and herbs which may also benefit from grafting. In this study, we examined the effect of reciprocal grafting two sweet basil (Ocimum basilicum L.) cultivars of differing vigor on plant growth and leaf mineral nutrient concentration to test whether differences in growth exist due to grafting and whether such differences are due to altered plant nutrient status in two trials. Two cultivars ‘Nufar’ (NU), a high vigor cultivar, and ‘Dolce Fresca’ (DF), a cultivar developed for compact growth, were selected. Four grafted treatments (scion/rootstock) were created by self-grafting (NU/NU and DF/DF) and reciprocal inter-cultivar grafting (DF/NU and NU/DF). Un-grafted plants (ug-NU and ug-DF) served as controls. Following grafting, plants were grown for 26 or 21 days in a greenhouse. DF rootstocks decreased NU shoot dry mass (19–29%) and stem length (12%) compared to ug-NU in both trials, while dry root mass was reduced (28%) in the second trial. In contrast, NU rootstocks did not affect DF growth in the first trial but significantly decreased dry shoot (18%) and root (31%) mass, compared to ug-DF in the second. Concentration of most inorganic nutrients examined was affected by both rootstock and scion genotype. For NU scions, DF rootstocks resulted in significantly higher (5–29%) levels of nitrogen, phosphorus, potassium, calcium, magnesium, sulfur, copper, and zinc in leaf tissue than ug-NU. For DF scions, NU rootstocks resulted in significantly higher (7–9%) levels of potassium and phosphorus but significantly lower (11–23%) levels of magnesium, sulfur, boron, copper, and zinc when compared to ug-DF. Results of this study show that inter-cultivar grafting sweet basil using a more vigorous cultivar as a rootstock did not enhance the growth of a less vigorous scion and reduced concentrations of certain nutrients. However, grafting a vigorous scion to a less vigorous rootstock reduced shoot growth but generally increased nutrient concentrations. This suggests that changes in growth in grafted basil are not due to altered nutrient status. Further research is needed to determine specific physiological processes influencing grafted basil growth.

Tomato Oxalyl-CoA Synthetase Degrades Oxalate and Affects Fruit Quality.

Acyl activating enzyme 3 (AAE3) encodes oxalyl-CoA synthetase involved in oxalate degradation. In this study, we investigated the role of AAE3 (SlAAE3) in the fruit quality of tomato (Solanum lycopersicum). The purified recombinant SlAAE3 protein from Escherichia coli exhibited a high activity toward oxalate, with a Km of 223.8 ± 20.03 μm and Vmax of 7.908 ± 0.606 μmol mg–1 protein min–1. Transient expression of SlAAE3-green fluorescent protein (GFP) fusion proteins suggests that SlAAE3 is a soluble protein without specific subcellular localization. The expression of SlAAE3 is both tissue- and development-dependent, and increased during fruit ripping. The Slaae3 knockout mutants had improved fruit quality as evidenced by the increased sugar-acid ratio and mineral nutrient content. To find the mechanism by which SlAAE3 affects fruit quality, transcriptome, and metabolome were employed on SlAAE3 over-expressed line and wide type fruits. The transcriptomic and metabolic profiles indicated that SlAAE3 in fruits mainly functions at 20 days post-anthesis (20 DPA) and mature green (MG) stages, resulting in up-regulation of amino acid derivatives, nucleotides, and derivatives, but down-regulation of lipid compounds. However, differentially expressed genes (DEGs) were mainly enriched at redox pathways. Taken together, both in vivo and in vitro results suggest that SlAAE3-encoded protein acts as an oxalyl-CoA synthetase, which also participates in redox metabolism. These data provide a further understanding of the mechanism by which SlAAE3 participates in tomato fruit quality.