Foliar spraying of indoleacetic acid (IAA) enhances the phytostabilization of Pb in naturally tolerant ryegrass by limiting the root-to-shoot transfer of Pb and improving plant growth.

Exogenous addition of IAA has the potential to improve the metal tolerance and phytostabilization of plants, but these effects have not been systematically investigated in naturally tolerant plants. Ryegrass (Lolium perenne L.) is a typical indigenous plant in the Lanping Pb/Zn mining area with high adaptability. This study investigated the phytostabilization ability and Pb tolerance mechanism of ryegrass in response to Pb, with or without foliar spraying of 0.1 mmol L-1 IAA. The results indicated that appropriate IAA treatment could be used to enhance the phytostabilization efficiency of naturally tolerant plants. Foliar spraying of IAA increased the aboveground and belowground biomass of ryegrass and improved root Pb phytostabilization. Compared to Pb-treated plants without exogenous IAA addition, Pb concentration in the shoots of ryegrass significantly decreased, then increased in the roots after the foliar spraying of IAA. In the 1,000 mg kg-1 Pb-treated plants, Pb concentration in the shoots decreased by 69.9% and increased by 79.1% in the roots after IAA treatment. IAA improved plant growth, especially in soils with higher Pb concentration. Foliar spraying of IAA increased shoot biomass by 35.9% and root biomass by 109.4% in 1,000 mg kg-1 Pb-treated plants, and increased shoot biomass by 196.5% and root biomass by 71.5% in 2,000 mg kg-1 Pb-treated plants. In addition, Pb stress significantly decreased the content of photosynthetic pigments and anti-oxidase activities in ryegrass, while foliar spraying of IAA remedied these negative impacts. In summary, foliar spraying of IAA could increase the biomass and improve the Pb tolerance of ryegrass.

A new species of Passaloecus Shuckard (Hymenoptera, Crabronidae) from China, with a key to Oriental species.

A new species of Passaloecus Shuckard, P.birugatus Bashir & Chen, sp. nov., is described and illustrated from Yunnan Province, China. The new species can be easily distinguished from known species of Passaloecus by its very long petiole, which is distinctly longer than wide, obscure scrobal suture, propodeum rugae and striations, body punctation, and coloration. An identification key to the Oriental species of Passaloecus is given.

Microbial fertilizer regulates C:N:P stoichiometry and alleviates phosphorus limitation in flue-cured tobacco planting soil.

Fertilization can be optimized and managed during the flue-cured tobacco growing period by studying the response of soil and microbial biomass stoichiometric characteristics to fertilization. In this study, we investigated the effect of compound fertilizers combined with microbial fertilizer treatments on the stoichiometric characteristics of the rhizosphere soil and the limitations of microbial resources during the flue-cured tobacco growing period. The results indicated that soil and microbial C:N:P varied greatly with the growing period. The effect of sampling time was usually greater than that of fertilization treatment, and microbial C:N:P did not vary with the soil resource stoichiometric ratio. The microbial metabolism of the tobacco-growing soil was limited by phosphorus after extending the growing period, and phosphorus limitation gradually increased from the root extension to the maturation periods but decreased at harvest. The rhizosphere soil microbial nitrogen and phosphorus limitations were mainly affected by soil water content, soil pH, microbial biomass carbon, and the ratio of microbial biomass carbon to microbial biomass phosphorus. Applying microbial fertilizer reduced phosphorus limitation. Therefore, applying microbial fertilizer regulated the limitation of microbial resources by affecting the soil and microbial biomass C:N:P in flue-cured tobacco rhizosphere soils.

Climatic factors determine the yield and quality of Honghe flue-cured tobacco.

Flue-cured tobacco (Nicotiana tabacum L.) is a major cash crop in Yunnan, China, and the yield, chemical components, and their proportions decide the quality of tobacco leaves. To understand the effects of environmental factors (soil and climatic factors) on the yield and quality of flue-cured tobacco and determine the main regulating factors, we selected three flue-cured tobacco cultivars [K326, Yunyan87 (Yun87), and Honghuadajinyuan (Hongda)] grown in the Honghe Tobacco Zone. Indices related to yield and economic traits, chemical component properties, soil physical and chemical properties, and climatic factors at different planting sites, were evaluated. We used variance analysis, correlation analysis, and redundancy analysis (RDA) in this study. The results showed that the yield and chemical component properties of flue-cured tobacco, except for the number of left leaves and plant total sugar (PTS) content, were significantly correlated with climatic factors. Particularly, the yield increased in drier and sunnier weather. In terms of the carbon supply capacity, PTS, petroleum ether (PPE), and starch contents (PS) were higher under high-altitude and high-latitude climatic conditions, whereas for the nitrogen supply capacity, plant nitrogen (PTN) and nicotine (PN) contents improved under low-altitude and low-latitude climatic conditions. PTS, reducing sugar (PRS), potassium (PTK), chlorine (PCL), and PPE contents were negatively related to soil clay content, soil pH, and soil organic matter, whereas PRS and PTK contents were positively correlated with alkali-hydrolyzed nitrogen (AN). According to RDA, the soil clay, AN, available phosphorus (AP), and soil chlorine content (SCL) strongly affected the quality of flue-cured tobacco. The quality of the K326 and Yun87 cultivars was mostly influenced by moisture, whereas the quality of the Hongda cultivar was mostly affected by temperature. In conclusion, compared with soil properties, climatic factors more significantly affect the yield and quality of Honghe flue-cured tobacco leaves.

High-Throughput Sequencing Analysis of Endophytic Bacteria Diversity in Fruits of White and Red Pitayas from Three Different Origins.

Pitaya contains various types of polyphenols, flavonoid and vitamins which are beneficial for health and it is among the most important commercial tropical fruits worldwide. Endophytic bacteria might be beneficial for plant growth and yield. However, bacterial diversity in pitaya is poorly characterized. In this study, fruits of white and red pitayas from three different origins (Thailand, Vietnam and China) were chosen for endophytic bacteria diversity investigation by using Illumina HiSeq second-generation high-throughput sequencing technology. Large number of endophytic bacteria were detected and 22 phyla, 56 classes, 81 orders, 122 families and 159 genera were identified. Endophytic bacteria diversity was uneven among pitaya fruits from different origins and bacteria structure was different between white pitaya group and red pitaya group. Phylum Bacteroidetes, classes Bacteroidia and Coriobacteriia, orders Bacteroidales and Coriobacteriales, families Prevotellaceae, Bacteroidaceae, Ruminococcaceae, Paraprevotellaceae, Rikenellaceae, Alcaligenaceae and Coriobacteriaceae, genera Prevotella, Bacteroides, Roseburia, Faecalibacterium and Sutterella were statistically significant different species (P < 0.05) between white and red pitayas. These findings might be useful for growth improvement, fruit preservation and processing of different pitaya species from different origins.