1-Methylcyclopropene Modulates Physiological, Biochemical, and Antioxidant Responses of Rice to Different Salt Stress Levels

Salt stress in soil is a critical constraint that affects the production of rice. Salt stress hinders plant growth through osmotic stress, ionic stress, and a hormonal imbalance (especially ethylene), therefore, thoughtful efforts are needed to devise salt tolerance management strategies. 1-Methylcyclopropene (1-MCP) is an ethylene action inhibitor, which could significantly reduce ethylene production in crops and fruits. However, 1-MCPs response to the physiological, biochemical and antioxidant features of rice under salt stress, are not clear. The present study analyzed whether 1-MCP could modulate salt tolerance for different rice cultivars. Pot culture experiments were conducted in a greenhouse in 2016–2017. Two rice cultivars, Nipponbare (NPBA) and Liangyoupeijiu (LYP9) were used in this trial. The salt stress included four salt levels, 0 g NaCl/kg dry soil (control, CK), 1.5 g NaCl/ kg dry soil (Low Salt stress, LS), 4.5 g NaCl/kg dry soil (Medium Salt stress, MS), and 7.5 g NaCl/kg dry soil (Heavy Salt stress, HS). Two 1-MCP levels, 0 g (CT) and 0.04 g/pot (1-MCP) were applied at the rice booting stage in 2016 and 2017. The results showed that applying 1-MCP significantly reduced ethylene production in rice spikelets from LYP9 and NPBA by 40.2 and 23.9% (CK), 44.3 and 28.6% (LS), 28 and 25.9% (MS), respectively. Rice seedlings for NPBA died under the HS level, while application of 1-MCP reduced the ethylene production in spikelets for LYP9 by 27.4% compared with those that received no 1-MCP treatment. Applying 1-MCP improved the photosynthesis rate and SPAD value in rice leaves for both cultivars. 1-MCP enhanced the superoxide dismutase production, protein synthesis, chlorophyll contents (chl a, b, carotenoids), and decreased malondialdehyde, H2O2, and proline accumulation in rice leaves. Application of 1-MCP also modulated the aboveground biomass, and grain yield for LYP9 and NPBA by 19.4 and 15.1% (CK), 30.3 and 24% (LS), 26.4 and 55.4% (MS), respectively, and 34.5% (HS) for LYP9 compared with those that received no 1-MCP treatment. However, LYP9 displayed a better tolerance than NPBA. The results revealed that 1-MCP could be employed to modulate physiology, biochemical, and antioxidant activities in rice plants, at different levels of salt stress, as a salt stress remedy

Elevational Variation in Soil Amino Acid and Inorganic Nitrogen Concentrations in Taibai Mountain, China

<p>Fig 1. Concentrations of the different extractable N forms (A), free amino acids (B) and different hydrolyzable N forms (C) in the thirteen sampled elevations. Error bars represent standard error (n=3). </p> <p>Fig 2. Concentrations of soil individual hydrolyzable amino acids in the thirteen sampled elevations. Error bars represent standard error (n=3).  Fig 3. Elevational variations of the PC1 (A) and PC2 (B) score along a montane gradient. The best-fit lines, <i>F</i> values, goodness of fit (<i>r</i>) and <i>p</i>-values are provided. Fig 4. Simple linear regression of the relationships between the composition of individual amino acids contained in PC1 and elevation. The best-fit lines, <i>F</i> values, goodness of fit (<i>r</i>) and <i>p</i>-values are provided.  Fig 5. Proportions of the neutral, basic, acidic, and sulfur amino acids accounting for soil total hydrolyzable amino acids in the thirteen sampled elevations. Fig 6. Elevational variations of the proportion of hydrolyzable amino acids that accounted soil total N content across the thirteen sampled elevations. The best-fit lines, <i>F</i> values, goodness of fit (<i>r</i>) and <i>p</i>-values are provided.Fig.4. Simple linear regression of the relationships between the composition of individual amino acids contained in PC1 and elevation. The best-fit lines, F values, goodness of fit (r) and p-values are provided. Fig. 5. Proportions of the neutral, basic, acidic, and sulfur amino acids accounting for soil total hydrolyzable amino acids in the thirteen sampled elevations. Fig. 6. Mean concentrations of soil total N, total hydrolyzable N, hydrolyzable amino acids and un-hydrolyzable N (A), and their corresponding proportions that accounted for soil total N (B) across the thirteen sampled elevations. Error bars represent standard error (n=13).</p

Mixed-nitrogen nutrition-mediated enhancement of drought tolerance of rice seedlings associated with photosynthesis, hormone balance and carbohydrate partitioning

<p>Fig. 1 Leaf photosynthetic rate (<i>P_n</i>), stomatal conductance (g_s), intercellular CO₂ concentration (<i>C_i</i>), and transpiration rate (<i>T_r</i>) of rice plants subjected to different N forms and water regimens. N, NP, A, AP, NA and NAP represent the nitrate (NO₃^-), NO₃^-+PEG 6000, ammonium (NH₄⁺), NH₄⁺+PEG 6000, mixture of NO₃^- and NH₄⁺ (NO₃^-+NH₄⁺) and NO₃^-+NH₄⁺+PEG 6000 treatments, respectively. The same occurs below. </p> <p>Fig. 2 Rice leaf Chl, total N, and Rubisco contents under the different N form and water conditions</p> <p>Fig. 3 Concentrations of ABA, IAA, and CTKs, and the IAA/CTK in the leaves and roots of rice seedlings subjected to different N forms and water regimens</p> <p>Fig. 4 Concentrations of soluble sugar and starch in the leaves and roots of rice seedlings subjected to different N forms and water regimens</p> <p>Fig. 5 Activities of sucrose-phosphate synthase (SPS) and sucrose synthase in the synthetic direction (SSs) in the leaves of rice seedlings subjected to different N forms and water regimens</p> <p>Fig. 6 Activities of acid invertase (InvA), neutral/alkaline invertase (InvN), and sucrose synthase in the cleavage direction (SSc) in the leaves of rice seedlings subjected to different N forms and water regimens</p> <p>Fig. 7 Activities of acid invertase (InvA), neutral/alkaline invertase (InvN), and sucrose synthase in the cleavage direction (SSc) in the roots of rice seedlings subjected to different N forms and water regimens.</p

Why mixed-nitrogen nutrition increases drought tolerance in rice: from plant growth, to mesophyll conductance and photochemical efficiency

<div>Fig. 1 Rice xylem sap amount (A), root secretion rate (B) and water use efficiency (WUE) (C) of rice plants subjected to different N forms and water regimens. N, NP, A, AP, NA and NAP represent the nitrate (NO3-), NO3-+PEG 6000, ammonium (NH4+), NH4++PEG 6000, mixture of NO3- and NH4+ (NO3-+NH4+) and NO3-+NH4++PEG 6000 treatments, respectively. The same occurs below. </div><div>Fig. 2 Rice leaf Chl (A), total N (B) and Rubisco (C) contents of rice plants subjected to different N forms and water regimens. </div><div>Fig. 3 Concentrations of soluble sugars and starch in the leaves and roots of rice seedlings subjected to different N forms and water regimens.</div><div>Fig. 4 The CO2 response curves of rice plants subjected to different N forms and water regimens.</div><div>Fig. 5 Leaf photosynthetic rate (Pn), stomatal CO2 diffusion conductance (gs), intercellular CO2 concentration (Ci), and transpiration rate (Tr) of rice plants subjected to different N forms and water regimens under the 400 µmol mol-1 CO2 concentration. </div><div>Fig. 6 The relationships of net photosynthesis A) and water use efficiency (WUE) to the mesophyll diffusion conductance (gm), stomatal CO2 diffusion conductance (gs) and the ratio of gm to gs in rice leaves.</div><div><br></div

The response of mesophyll conductance and Rubisco activity to water stress vary with the rice supplied nitrogen nutrition

<p><b>Figure 1</b> Rice xylem sap amount (A), root secretion rate (B) and water use efficiency (C) under different N forms and water conditions. The data refer to the mean ±SE (<i>n</i>=4). N, NP, A, AP, NA and NAP represent the nitrate (NO₃^-), NO₃^-+PEG6000, ammonium (NH₄⁺), NH₄⁺+PEG6000, mixture of ammonium and nitrate (NO₃^-+NH₄⁺) and NO₃^-+NH₄⁺+PEG6000 treatments, respectively. Significant differences (<i>p</i><5%) between treatments of rice are indicated by different letters. The same as below. </p> <p><b>Figure 2</b> Rice leaf Chl (A), total N (B) and Rubisco (C) contents under the different N forms and water conditions. </p> <p><b>Figure 3</b> The relationships of net photosynthesis (<i>A</i>) and water use efficiency (WUE) to the mesophyll conductance (<i>g_m</i>), stomatal conductance (<i>g_s</i>) and ratio of g_m/g_s in rice leaves.</p

China Data Cube (CDC) for Big Earth Observation Data: Practices and Lessons Learned

In the face of tight natural resources and complex as well as volatile environments, and in order to meet the pressure brought by population growth, we need to overcome a series of challenges. As a new data management paradigm, the Earth Observation Data Cube simplifies the way that users manage and use earth observation data, and provides an analysis-ready form to access big spatiotemporal data, so as to realize the greater potential of earth observation data. Based on the Open Data Cube (ODC) framework, combined with analysis-ready data (ARD) generation technology, the design and implementation of CDC_DLTool, extending the support for data loading and the processing of international and Chinese imagery data covering China, this study eventually constructs the China Data Cube (CDC) framework. In the framework of this CDC grid, this study carried out case studies of water change monitoring based on international satellite imagery data of Landsat 8 in addition to vegetation change monitoring based on Chinese satellite imagery data of GF-1. The experimental results show that, compared with traditional scene-based data organization, the minimum management unit of this framework is a pixel, which makes the unified organization and management of multisource heterogeneous satellite imagery data more convenient and faster

Soil Fertility Management for Sustainable Crop Production

To feed the growing world population, which is expected to reach 9 [...

An optimized hexagonal quadtree encoding and operation scheme for icosahedral hexagonal discrete global grid systems

Although research on the discrete global grid systems (DGGSs) has become an essential issue in the era of big earth data, there is still a gap between the efficiency of current encoding and operation schemes for hexagonal DGGSs and the needs of practical applications. This paper proposes a novel and efficient encoding and operation scheme of an optimized hexagonal quadtree structure (OHQS) based on aperture 4 hexagonal discrete global grid systems by translation transformation. A vector model is established to describe and calculate the aperture 4 hexagonal grid system. This paper also provides two different grid code addition algorithms based on induction and $ijk$ coordinate transformation. We implement the transformation between OHQS codes and geographic coordinates through the $ij$, $ijk$ and $IJK$ coordinate systems. Compared with existing schemes, the scheme in this paper greatly improves the efficiency of the addition operation, neighborhood retrieval and coordinate transformation, and the coding is more concise than other aperture 4 hexagonal DGGSs. The encoding operation based on the $ijk$ coordinate system is faster than the encoding operation based on the induction and addition table. Spatial modeling based OHQS DGGSs are also provided. A case study with rainstorms demonstrated the availability of this scheme

Nitric oxide synthase-mediated early nitric oxide burst alleviates water stress-induced oxidative damage in ammonium-supplied rice roots

Abstract Background Nutrition with ammonium (NH4 +) can enhance the drought tolerance of rice seedlings in comparison to nutrition with nitrate (NO3 −). However, there are still no detailed studies investigating the response of nitric oxide (NO) to the different nitrogen nutrition and water regimes. To study the intrinsic mechanism underpinning this relationship, the time-dependent production of NO and its protective role in the antioxidant defense system of NH4 +- or NO3 −-supplied rice seedlings were studied under water stress. Results An early NO burst was induced by 3 h of water stress in the roots of seedlings subjected to NH4 + treatment, but this phenomenon was not observed under NO3 − treatment. Root oxidative damage induced by water stress was significantly higher for treatment with NO3 − than with NH4 + due to reactive oxygen species (ROS) accumulation in the former. Inducing NO production by applying the NO donor 3 h after NO3 − treatment alleviated the oxidative damage, while inhibiting the early NO burst by applying the NO scavenger 2-(4-carboxyphenyl)-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide (c-PTIO) increased root oxidative damage in NH4 + treatment. Application of the nitric oxide synthase (NOS) inhibitor N(G)-nitro-L-arginine methyl ester(L-NAME) completely suppressed NO synthesis in roots 3 h after NH4 + treatment and aggravated water stress-induced oxidative damage. Therefore, the aggravation of oxidative damage by L-NAME might have resulted from changes in the NOS-mediated early NO burst. Water stress also increased the activity of root antioxidant enzymes (catalase, superoxide dismutase, and ascorbate peroxidase). These were further induced by the NO donor but repressed by the NO scavenger and NOS inhibitor in NH4 +-treated roots. Conclusion These findings demonstrate that the NOS-mediated early NO burst plays an important role in alleviating oxidative damage induced by water stress by enhancing the antioxidant defenses in roots supplemented with NH4 +