Soil Nutrient Status and Leaf Nutrient Diagnosis in the Main Apple Producing Regions in China

Soil and leaf nutrient analysis are widely used as effective methods of diagnosing nutrient deficiency in fruit trees, the results of which are used to properly manage fertilizer application. Therefore, a survey was conducted for assessment of the soil nutrient status and leaf nutrient concentration in 2 827 apple orchards in the Bohai Bay and Loess Plateau apple production regions of China. The soil organic matter, alkali hydrolyzable N, available P, and available K were 10.91 g·kg−1, 73.21 mg·kg−1, 70.22 mg·kg−1, and 169.23 mg·kg−1 in the Bohai Bay region, respectively, and 11.72 g·kg−1, 56.46 mg·kg−1, 14.91 mg·kg−1, and 135.78 mg·kg−1 in the Loess Plateau region, respectively. Soil organic matter was at a medium-to-low level in both regions, whereas the soil alkali hydrolyzable N was low. In the Bohai Bay region, soil available P was high, but soil available K was deficient. In contrast, both soil available P and K were insufficient in the Loess Plateau region. The Diagnosis and Recommendation Integrated System (DRIS) diagnostic results indicated that the most deficient elements were Ca and K in low-yielding orchards (<35 t·hm−2) of the Bohai Bay region followed by Fe, N, and Zn; however in the Loess Plateau region, the most deficient elements were P and K followed by N, Zn, and Cu. The findings imply that the application of Ca, K, Fe, N, and Zn fertilizer should be increased in the Bohai Bay region, whereas P, K, N, Zn, and Cu fertilizer should be enhanced in the Loess Plateau region. Meanwhile, use of organic manure is recommended to improve soil quality in the two apple producing regions. Keywords: apple, soil nutrition, leaf nutrient, nutrient deficiency, diagnosi

Effects of Soil C/N Ratio on Apple Growth and Nitrogen Utilization, Residue and Loss

Soil C/N ratio is an important influencing factor in soil nitrogen cycling. Two-year old apple trees (Borkh. cv. ‘Fuji’/ Malus hupehensis) were used to understand the effect of soil C/N ratio [6.52 (CK), 10, 15, 20, 25, 30, 35 and 40] on apple growth and nitrogen utilization and loss by using 15N trace technique. The results showed that, with the increasing of soil C/N ratio, apple shoot length and fresh weight increased at first, and then decreased; the higher apple shoot length and fresh weight appeared in C/N=15, 20 and 25 treatments, and there were no significant differences among these three treatments, but significantly higher than the other treatments. Statistical analysis revealed that there was significant difference in nitrogen utilization rate between the different treatments, the highest N utilization rate was occurred in soil C/N=25 treatment which value was 22.87%, and there was no significant difference between soil C/N=25 and C/N=20 treatments, but both the two treatments were significantly higher than the other treatments; Soil C/N=40 had the lowest N utilization rate which value was 15.43%, and this value was less than CK (16.65%). The proportion of plant absorption nitrogen from fertilizer was much higher when the value of soil C/N ratio in the range of 15-25, but the percentage of plant absorption nitrogen from soil was much higher when the soil C/N ratio was too low (<15) or high (<25). Amount of residual nitrogen in soil increased gradually with the soil C/N ratio increasing, the amount of residual nitrogen in C/N=40 treatment was 1.32 times than that in CK. With the increasing of soil C/N ratio, fertilizer nitrogen loss decreased at first, and then increased, fertilizer nitrogen loss was the minimum in C/N=25 treatments (49.87%) and the maximum were occurred in CK (61.54%). Therefore, regarding the apple growth and nitrogen balance situation, the value of soil C/N ratio in the range of 15-25 would be favorable for apple growth and could increase effectively nitrogen fixed by soil, reduce nitrogen loss, and improve the nitrogen utilization ratio

Glucose Increases the Abundance of Phosphate Solubilizing Bacterial Community for Better Apple Seedling Growth and Phosphate Uptake

Phosphorus-solubilizing microorganisms play an important role in soil nutrient phosphorus cycling. In order to clarify the effect of glucose (C6H12O6) on soil phosphorus transformation, the effects of glucose additions on the bacterial community, soil phosphorus status, and plant phosphorus uptake in apple rhizosphere soil were investigated. A 90-day pot experiment was carried out, and the experiment was repeated three times. Glucose additions were 0, 2.5, 5, 7.5, 10, and 12.5 g glucose per kg of soil. We measured soil bacteria and phosphorus related indexes using Illumina MiSeq sequencing technology and chemical methods. The results showed that when the glucose application rate was 2.5–7.5 g·kg−1, the soil total phosphorus content decreased by 4.4–7.3%; however, the soil acid phosphatase activity increased by 0.5–1.3 times, and the microbial biomass phosphorus increased by 29.1% and 37.0%. The content of Al-P and Fe-P in the rhizosphere soil decreased by 14.4 to 32.7 mg·kg−1 and 16.04 to 28.7 mg·kg−1, respectively. The compositional difference of the bacterial community became larger, and the relative abundance of 11 bacterial phyla changed significantly, among which the most significant change was found in Proteobacteria. This study also found that the relative abundances of Bacillus, Pseudomonas, Arthrobacter, and Cuprococcus increased by 0.9%, 2.2%, 2.4%, and 0.8%, respectively. Applying 7.5 g glucose per kg of soil can significantly increase the relative abundance of phosphorus solubilizing bacteria (Bacillus, Pseudomonas, Arthrobacter et al.) in rhizosphere soil, activate Al-P and Fe-P, and improve the availability of soil phosphorus

Magnesium alleviates aluminum-induced growth inhibition by enhancing antioxidant enzyme activity and carbon–nitrogen metabolism in apple seedlings

Previous studies have determined that magnesium (Mg) in appropriate concentrations prevents plants from suffering from abiotic stress. To better understand the mechanism of Mg alleviation of aluminum (Al) stress in apple, we investigated the effect of Mg on plant growth, photosynthetic fluorescence, antioxidant system, and carbon (C) and nitrogen (N) metabolism of apple seedlings under Al toxicity (1.5 mmol/L) via a hydroponic experiment. Al stress induced the production of reactive oxygen in the leaves and roots and reduced the total dry weight (DW) by 52.37 % after 20 days of treatment relative to plants grown without Al, due to hindered photosynthesis and alterations in C and N metabolism. By contrast, total DW decreased by only 11.07 % in the Mg-treated plants under Al stress. Supplementation with 3.0 mmol/L Mg in the Al treatment decreased Al accumulation in the apple plants and reduced Al-induced oxidative damage by enhancing the activity of antioxidant enzymes (superoxide dismutase, catalase, and peroxidase) and reducing the production of H2O2 and malondialdehyde (MDA). Under Al stress, the Mg-treated plants showed a 46.17 % higher photosynthetic rate than the non-treated plants. Supplementation with Mg significantly increased the sucrose content by increasing sucrose synthase (SS) and sucrose-phosphate synthase (SPS) activities. Moreover, Mg facilitated the transport of 13C-carbohydrates from the leaves to roots. Regarding N metabolism, the nitrate reductase (NR), glutamine synthase (GS), and glutamate synthase (GOGAT) activities in the roots and leaves of the Mg-treated plants were significantly higher than those of the non-treated plants under Al stress. Compared with the non-treated plants under Al stress, the Mg-treated plants exhibited a significantly high level of NO3- and soluble protein content in the leaves, roots, and stems, but a low level of free amino acids. Furthermore, Mg significantly improved nitrogen accumulation and enhanced the transport of 15N from the roots to leaves. Overall, our results revealed that Mg alleviates Al-induced growth inhibition by enhancing antioxidant capacity and C-N metabolism in apple seedlings

Oxidative stress induced by zearalenone in porcine granulosa cells and its rescue by curcumin in vitro.

Oxidative stress (OS), as a signal of aberrant intracellular mechanisms, plays key roles in maintaining homeostasis for organisms. The occurrence of OS due to the disorder of normal cellular redox balance indicates the overproduction of reactive oxygen species (ROS) and/or deficiency of antioxidants. Once the balance is broken down, repression of oxidative stress is one of the most effective ways to alleviate it. Ongoing studies provide remarkable evidence that oxidative stress is involved in reproductive toxicity induced by various stimuli, such as environmental toxicants and food toxicity. Zearalenone (ZEA), as a toxic compound existing in contaminated food products, is found to induce mycotoxicosis that has a significant impact on the reproduction of domestic animals, especially pigs. However, there is no information about how ROS and oxidative stress is involved in the influence of ZEA on porcine granulosa cells, or whether the stress can be rescued by curcumin. In this study, ZEA-induced effect on porcine granulosa cells was investigated at low concentrations (15 μM, 30 μM and 60 μM). In vitro ROS levels, the mRNA level and activity of superoxide dismutase, glutathione peroxidase and catalase were obtained. The results showed that in comparison with negative control, ZEA increased oxidative stress with higher ROS levels, reduced the expression and activity of antioxidative enzymes, increased the intensity of fluorogenic probes 2', 7'-Dichlorodihydrofluorescin diacetate and dihydroethidium in flow cytometry assay and fluorescence microscopy. Meanwhile, the activity of glutathione (GSH) did not change obviously following 60 μM ZEA treatment. Furthermore, the underlying protective mechanisms of curcumin on the ZEA-treated porcine granulosa cells were investigated. The data revealed that curcumin pre-treatment significantly suppressed ZEA-induced oxidative stress. Collectively, porcine granulosa cells were sensitive to ZEA, which may induce oxidative stress. The findings from this study clearly demonstrate that curcumin is effective to reduce the dysregulation of cellular redox balance on porcine granulosa cells in vitro and should be further investigated for its protective role against ZEA in animals

Transcriptome and Metabolome Analysis Reveals the Effect of Nitrogen–Potassium on Anthocyanin Biosynthesis in “Fuji” Apple

Nitrogen (N) and potassium (K) have significant effects on apple peel color. To further understand the molecular mechanism of N–K regulation of apple color, we analyzed the apple peel under different N and K treatments using isotope labeling, transcriptomics, and metabolomics. Under high N treatments, fruit red color and anthocyanin content decreased significantly. High N decreased the 13C distribution rate and increased the Ndff values of fruits, while K increased the expression of MdSUTs and MdSOTs and promoted 13C transportation to fruits. Anthocyanin-targeted metabonomics and transcriptome analysis revealed that high N downregulated the expression of structural genes related to the anthocyanin synthesis pathway (MdPAL, Md4CL, MdF3H, MdANS, and MdUFGT) and their regulators (MdMYBs and MdbHLHs), and also decreased some metabolites contents. K alleviated this inhibition and seven anthocyanins were regulated by N–K. Our results improve the understanding of the synergistic regulation of apple fruit coloring by N–K

Intracellular ROS levels assayed using DCFH-DA and DHE fluorescent probes in porcine granulosa cells treated with curcumin.

<p>A-B, Intracellular ROS was measured by flow cytometry (DCFH-DA and DHE). For better clarity, a guidance line (red) is drawn through histograms for comparison. C-D, Average intensity of DCFH-DA and DHE fluorescence in porcine granulosa cells treated with curcumin. The results are presented as mean ± SD. Asterisk (*) indicates significant difference (P<0.05)</p

The expression levels of endogenous antioxidative enzymes Sod1, Cat and Gpx1 in porcine granulosa cells treated with ZEA for different times (8–24 h).

<p>A-C. Gene expression in ZEA-treated cells at 8 h, 16 h and 24 h. The expression level was normalized to that of β-actin as internal control. Compared to the control group, relative fold changes were presented as mean ± SD. All experiments were repeated at least three times independently. Asterisk (*) indicates significant difference (P < 0.05), while asterisk (**) represents highly significant difference (P < 0.01).</p

Intracellular ROS levels assayed with DCFH-DA fluorescent probe in porcine granulosa cells treated with ZEA.

<p>A (A’), Control (untreated); B (B’), 15 μM ZEA; C (C’), 30 μM ZEA; D (D’), 60 μM ZEA. Intracellular ROS was measured by flow cytometry (A-D) and fluorescent imaging (A’-D’) using DCFH-DA probe. For better clarity, a guidance line (red) is drawn through histograms for comparison. E, Average intensity from DCFH-DA. The results are presented as mean ± SD. Asterisk (*) indicates significant difference (P<0.05).</p