Shengqun Liu

Melatonin alleviates low PS I limited carbon assimilation under elevated CO2 and enhances the cold tolerance of offspring in chlorophyll b-deficient mutant wheat

Melatonin is involved in the regulation of carbohydrate metabolism and induction of cold tolerance in plants. The objective of this study was to investigate the roles of melatonin in modulation of carbon assimilation of wild‐type wheat and the Chl b‐deficient mutant ANK32B in response to elevated CO2 concentration ([CO2]) and the transgenerational effects of application of exogenous melatonin (hereafter identified as melatonin priming) on the cold tolerance in offspring. The results showed that the melatonin priming enhanced the carbon assimilation in ANK32B under elevated [CO2], via boosting the activities of ATPase and sucrose synthesis and maintaining a relatively higher level of total chlorophyll concentration in leaves. In addition, melatonin priming in maternal plants at grain filling promoted the seed germination in offspring by accelerating the starch degradation and improved the cold tolerance of seedlings through activating the antioxidant enzymes and enhancing the photosynthetic electron transport efficiency. These findings suggest the important roles of melatonin in plant response to future climate change, indicating that the melatonin priming at grain filling in maternal plants could be an effective approach to improve cold tolerance of wheat offspring at seedling stage.

Effect of Different Arbuscular Mycorrhizal Fungi on Growth and Physiology of Maize at Ambient and Low Temperature Regimes

The effect of four different arbuscular mycorrhizal fungi (AMF) on the growth and lipid peroxidation, soluble sugar, proline contents, and antioxidant enzymes activities of Zea mays L. was studied in pot culture subjected to two temperature regimes. Maize plants were grown in pots filled with a mixture of sandy and black soil for 5 weeks, and then half of the plants were exposed to low temperature for 1 week while the rest of the plants were grown under ambient temperature and severed as control. Different AMF resulted in different root colonization and low temperature significantly decreased AM colonization. Low temperature remarkably decreased plant height and total dry weight but increased root dry weight and root-shoot ratio. The AM plants had higher proline content compared with the non-AM plants. The maize plants inoculated with Glomus etunicatum and G. intraradices had higher malondialdehyde and soluble sugar contents under low temperature condition. The activities of catalase (CAT) and peroxidase of AM inoculated maize were higher than those of non-AM ones. Low temperature noticeably decreased the activities of CAT. The results suggest that low temperature adversely affects maize physiology and AM symbiosis can improve maize seedlings tolerance to low temperature stress.

Melatonin Improves the Photosynthetic Carbon Assimilation and Antioxidant Capacity in Wheat Exposed to Nano-ZnO Stress

The release of nanoparticles into the environment is inevitable, which has raised global environmental concern. Melatonin is involved in various stress responses in plants. The present study investigated the effects of melatonin on photosynthetic carbon (C) assimilation and plant growth in nano-ZnO stressed plants. It was found that melatonin improved the photosynthetic C assimilation in nano-ZnO stressed wheat plants, mainly due to the enhanced photosynthetic energy transport efficiency, higher chlorophyll concentration and higher activities of Rubisco and ATPases. In addition, melatonin enhanced the activities of antioxidant enzymes to protect the photosynthetic electron transport system in wheat leaves against the oxidative burst caused by nano-ZnO stress. These results suggest that melatonin could improve the tolerance of wheat plants to nano-ZnO stress.

Cold Priming Induced Tolerance to Subsequent Low Temperature Stress is Enhanced by Melatonin Application during Recovery in Wheat

Cold priming can alleviate the effects of subsequent cold stress on wheat plant growth. Melatonin plays a key role in cold stress response in plants. In this study, the effects of foliar melatonin application during recovery on the cold tolerance of cold primed wheat plants were investigated. It was found that both melatonin and cold priming increased the photosynthetic rate and stomatal conductance, enhanced the activities of antioxidant enzymes, and altered the related gene expressions in wheat under cold stress. Melatonin application is helpful for the photosynthetic carbon assimilation and membrane stability of the cold primed plants under cold stress. These results suggested that foliar melatonin application during recovery enhanced the cold priming induced tolerance to subsequent low temperature stress in wheat.

Carbon and nitrogen metabolism in arbuscular mycorrhizal maize plants under low-temperature stress

Abstract. Effects of the arbuscular mycorrhizal (AM) fungus Glomus tortuosum on carbon (C) and nitrogen (N) metabolism of Zea mays L. grown under low-temperature stress was investigated. Maize plants inoculated or not inoculated with AM fungus were grown in a growth chamber at 25°C for 4 weeks and subsequently subjected to two temperature treatments (15°C, low temperature; 25°C, ambient control) for 2 weeks. Low-temperature stress significantly decreased AM colonisation, plant height and biomass. Total N content and activities of glutamate oxaloacetate transaminase and glutamate pyruvate transaminase of AM plants were higher than those of non-AM plants. AM plants had a higher net photosynthetic rate (Pn) than non-AM plants, although low temperature inhibited the Pn. Compared with non-AM plants, AM plants exhibited higher leaf soluble sugars, reducing sugars, root sucrose and fructose contents, and sucrose phosphate synthase and amylase activities at low temperature. Moreover, low-temperature stress increased the C : N ratio in the leaves of maize plants, and AM colonisation decreased the root C : N ratio. These results suggested a difference in the C and N metabolism of maize plants at ambient and low temperature regimes. AM symbiosis modulated C metabolic enzymes, thereby inducing an accumulation of soluble sugars, which may have contributed to an increased tolerance to low temperature, and therefore higher Pn in maize plants.

Cold Tolerance of Photosynthetic Electron Transport System Is Enhanced in Wheat Plants Grown Under Elevated CO2

The effects of CO2 elevation on sensitivity of photosynthetic electron transport system of wheat in relation to low temperature stress are unclear. The performance of photosynthetic electron transport system and antioxidant system in chloroplasts was investigated in a temperature sensitive wheat cultivar Lianmai6 grown under the combination of low temperature (2 days at 2/−1°C in the day/night) and CO2 elevation (800 μmol l−1). It was found that CO2 elevation increased the efficiency of photosynthetic electron transport in wheat exposed to low temperature stress, which was related to the enhanced maximum quantum yield for electron transport beyond QA and the increased quantum yield for reduction of end electron acceptors at the PSI acceptor side in plants under elevated CO2. Also, under low temperature, the activities of ATPases, ascorbate peroxidase, and catalase in chloroplasts were enhanced in wheat under elevated CO2. It suggested that the cold tolerance of photosynthetic electron transport system is enhanced by CO2 elevation.

Soil microbial community and activity are affected by integrated agricultural practices in China: Soil microbial community in agricultural practices

Sustainable agricultural management practices improve soil processes, prevent soil erosion and consequently enhance crop productivity. The integrated agricultural practice (IP) developed in northeast China, by altering row spacing of planting, adopting no-tillage and returning all crop residues, showed great benefit in sustaining crop yield. However, its effect on the soil microbiome remains largely elusive. This study evaluated the effect of 12-year integrated agricultural practice on the structure and activity of the soil microbial community at different soil depths in China’s Mollisols zone. The experiment consisted of integrated agricultural practice and conventional practice (CP) treatments in a split-plot arrangement. The soil microbial community was characterized by MiSeq sequencing. The results showed that agricultural practices affected 12 phyla, 24 classes, 32 orders and 75 families in the bacterial community and one phyla, four classes, 12 orders and 18 families in the fungal community. Integrated agricultural practice resulted in greater bacterial richness and diversity, and increased the relative abundances of Actinobacteria, Gemmatimonadetes, Verrucomicrobia and Ascomycota, but reduced Bacteroidetes, Firmicutes and Basidiomycota in the dominant bacterial and fungal phyla. These findings suggested that integrated agricultural practice modified the soil physiochemical properties and consequently altered microbial community structure and diversity, which in turn affected soil microbial biomass and enzyme activities. These changes under integrated agricultural practice could have contributed to the enhanced crop yield, suggesting that IP is a sustainable agricultural practice.

Tensile properties of seminal and nodal roots and their relationship with the root diameter and planting density of maize (Zea mays)

Abstract. The tensile property of roots is an important factor for anchorage and for resistance to root lodging. In this study, a root tensile test was applied to maize (Zea mays L.) grown in the field at three planting densities, 4.5 × 104, 6.75 × 104 and 9.0 × 104 plants ha–1, to quantify the maximum tensile force (Fmax) and tensile strength (Ts) of roots at the V10 stage (tenth leaf visible) and grain-filling stage. In addition, relationships among tensile properties, diameter and turgid weight : dry weight (TW : DW) ratio of roots were investigated. The results showed that the Fmax of primary and seminal adventitious roots was lower than of nodal roots. Among nodal roots, the Fmax of roots on upper nodes was higher. Planting density significantly affected the tensile force of nodal roots of the sixth to eighth tiers; their Fmax decreased with increasing planting density. A positive linear correlation between Fmax and root diameter and a power function between Ts and root diameter was observed. In addition, there was a positive linear correlation between the TW/DW ratio and root diameter and a negative exponential correlation between Ts and TW : DW ratio. Therefore, nodal roots with a lower TW : DW ratio could have a larger Ts, because their cells are smaller and cell walls are thicker. This result suggests that nodal roots with small and thick cells benefit the tensile properties of maize.

Integrated agricultural management practice improves soil quality in Northeast China

ABSTRACT Sustainable agricultural management practices have attracted increasing attention due to their significant roles in benefiting the functions and sustainability of agro-ecosystems. An integrated agricultural practice (IP) in a maize cropping system was developed by changing row spacing, adopting no-tillage and residue return in the Northeast China. A 12-year field study was carried out to evaluate the effect of IP and conventional practice (CP) on soil physical properties, microbial biomass and enzyme activity during the cropping season. The results showed that soil organic matter under IP was increased by 17.4, 9.88 and 6.69% in June, August and October, respectively, than CP. IP enhanced microbial biomass C (by 31.7, 25.1 and 30.4% in June, August and October) and activities of invertase, urease and phosphatase (by 27.2–38.0, 78.9–182 and 9.8–29.0%) compared to CP, possibly attributing to an increase in the soil microbial community. Furthermore, the soil pH, water content, nitrogen and phosphorus contents, microbial biomass and some specific enzyme activities varied with sampling time. It is concluded that IP improved soil quality and health by increasing organic matter content and microbial biomass and activity in maize field in Northeast China, suggesting that IP is a feasible management technology for sustainable agriculture.

Arbuscular mycorrhiza improves nitrogen use efficiency in soybean grown under partial root-zone drying irrigation

ABSTRACT Arbuscular mycorrhizal (AM) fungi can form symbiotic association with the roots of plants that acquire carbon (C) exclusively from the host plants and supply nitrogen (N) to the plants. In this study, our objective was to investigate the effects of the AM fungus on plant growth, C and N partitioning and accumulation of Glycine max L. grown under water stress in pot experiment. Soybean seedlings were inoculated or not inoculated with the AM fungus, and were exposed to three irrigation treatments including full irrigation, deficit irrigation and partial root-zone drying irrigation (PRD). The 15N isotope labeling was used to trace soybean N accumulation. Results showed that water stress significantly decreased plant dry weight. Compared with non-AM fungus, AM fungus increased root N and 15N concentration, and decreased stem, leaf and pod N and 15N concentrations under PRD. AM colonization decreased C and N partitioning into stem and leaf, and increased C and N partitioning into root under PRD. AM plants had greater C accumulation and N use efficiency than non-AM plants. It was concluded that AM symbiosis plays an important role in C and N dynamics of soybean grown under water stress.