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Understanding soil phosphorus (P) distribution and its key drivers is fundamental for sustainable P management. In this study, a 21-year fertilization experiment on black soil was carried out, setting up five fertilization treatments: unfertilized control (CK), nitrogen and potassium (NK), nitrogen, P and potassium (NPK), NPK plus straw (NPKS), and NPK plus manure (NPKM). The distribution and effecting factors of P pools within soil aggregates were investigated. Compared to CK, the NK and NPK treatments decreased calcium-associated P concentration in all aggregate fractions. Meanwhile, the NPK treatment significantly increased the organic P extracted from NaOH in unaggregated particles (<0.053 mm). This was mainly due to the reduction in soil pH. The NPKS and NPKM treatments increased almost all P forms in aggregates, especially Ca-P. For the NPKM treatment, inorganic P extracted from resin, NaHCO3, and NaOH increased as aggregate size increased. This was mainly because straw or manure addition promoted soil organic carbon (SOC) storage in aggregates, creating more sorption sites via association with amorphous metallic minerals, and, thus, facilitating P accumulation. In conclusion, decreasing soil pH by chemical fertilizers is an effective strategy for mobilizing soil P, whereas increasing SOC by straw or manure facilitates P accumulation. [ABSTRACT FROM AUTHOR]

Plant NAPDH oxidase (NOX) gene family members are critical producers of ROS and play crucial roles in plant signaling, development, and stress responses. Opisthopappus taihangensis is a pivotal wild genetic resource in Asteraceae. To date, little knowledge exists about the functions of NOXs in O. taihangensis. In this study, seven typical NOXs and seven ferric reduction oxidases (FROs) were identified in O. taihangensis. Dispersed duplication might play a critical role in the expansion of the NOX/FRO gene family in O. taihangensis, and most of the NOX/FRO homologous pairs have undergone purifying selection. Although the results of the collinearity analysis show that these genes were relatively conserved, the gain and loss of members in this gene family occurred frequently during the evolution of Asteraceae. Phylogenetic analysis indicated that the FROs are relatively ancient, and the earliest diverged branch was revealed by the maximum likelihood (ML) tree. The Asteraceae NOXs were divided into six subgroups according to their relationship with Arabidopsis and rice members. The transcriptome profile unveiled tissue-specific expression patterns and complex response modes under drought and salt stresses. OtNOX6 and OtNOX7 could be recognized as important candidates to respond to drought and salt stress. Our results provide clues and references for further in-depth exploration of NOX/FRO function in O. taihangensis and other horticulture plants. [ABSTRACT FROM AUTHOR]

Phosphorus (P) leaching from excessive P application is the primary pathway of P losses in agricultural soils. Different P fertilizer practices have mixed effects on P leaching. We conducted a meta-analysis of the relevant literature regarding the response of crop yields, soil-available P (AP), and total P (TP) leaching to reduced P input (RP) and an inorganic-organic combination fertilizer (NPKM) for different agricultural land-use types. Compared to conventional P application (CP), RP (10~90% reduction) did not reduce crop yields in vegetable fields (experiments were 1~4 years) but significantly reduced cereal yields by 4.57%. Compared to chemical fertilizer (NPK), NPKM significantly increased cereal yields by 12.73%. Compared to CP, RP significantly reduced AP at 0~60 cm in vegetable and cereal fields. The greatest reduction occurred at 20~40 cm in vegetable fields (40.29%) and 0~20 cm in cereal fields (34.45%). Compared to NPK, NPKM significantly increased the AP at 0~60 cm in vegetable fields, with the greatest increase (52.44%) at 20~40 cm. The AP at 0~40 cm in cereal fields significantly increased under the NPKM treatment, with the greatest increase at 0~20 cm (76.72%). Compared to CP, RP significantly decreased TP leaching by 16.02% and 31.50% in vegetable and cereal fields, respectively. Compared to NPK, NPKM significantly increased TP leaching in vegetable fields (30.43%); no significant difference in leaching occurred in cereal fields. P leaching, in response to RP, was influenced by the P amounts applied (34.49%); soil organic matter (14.49%); and TP (12.12%). P leaching in response to NPKM was influenced by multiple factors: rainfall (16.05%); soil organic matter (12.37%); soil bulk density (12.07%); TP (11.65%); pH (11.41%). NPKM was more beneficial for improving yields in cereal fields with low soil fertility and lower P-leaching risks. [ABSTRACT FROM AUTHOR]

Understanding the effects of a fertilization regime on the long-term accumulation and transformation of soil phosphorus (P) is essential for promoting the development of sustainable management of soil P. Based on a 29-year field experiment in Mollisol, the compositions and changes of P forms using a modified Hedley sequential extraction method, solution 31P-NMR and P K-edge XANES and soil properties were investigated under continuous mono maize with and without manure (NPKM and NPK). Results showed a stronger positive related coefficient between soil total P and labile P, and mid-labile P fraction was found in NPKM than in NPK treatment. It indicated NPKM could improve the availability of soil accumulated P and reduce its transformation to stable P. Accumulated inorganic P (Pi) was dominated by aluminum phosphate (Al-P) and monobasic calcium phosphate monohydrate (MCP) for NPK treatment, Al-P, MCP, and tricalcium phosphate for NPKM treatment with XANES analysis, which contributed to the P availability in Mollisol. Moreover, the proportion of IHP with XANES and ratio of orthophosphate diesters to monoesters in NPK compared to NPKM indicated the higher Po lability with NPK treatment. Pi, especially NaHCO3-Pi and NaOH-Pi, were the potential sources of resin-Pi. Soil organic matter (SOM), organic-bound iron, and alumina oxide (Fep + Alp) showed significant influence on the transformation of P forms. Our research suggested that due to the rise in SOM and Fep + Alp, the fertilization regime significantly increased most highly active soil P fractions, especially in NPKM treatment. This work gives new insight into sustainable P management, which benefits the reduction in soil P accumulation. [ABSTRACT FROM AUTHOR]

An elucidation of how the selection pressures caused by habitat environments affect plant plastid genomes and lead to the adaptive evolution of plants, is a very intense area of research in evolutionary biology. The genus Paphiopedilum is a predominant group of orchids that includes over 66 species with high horticultural and ornamental value. However, owing to the destructive exploitation and habitat deterioration of wild germplasm resources of Paphiopedilum, it needs more molecular genetic resources and studies on this genus. The chloroplast is cytoplasmically inherited and often used in evolutionary studies. Thus, for this study, we newly sequenced, assembled and annotated five chloroplast genomes of the Paphiopedilum species. The size of these genomes ranged from 155,886 bp (P. henryanum) to 160,503 bp (P. 'GZSLKY' Youyou) and they contained 121–122 genes, which consisted of 76 protein coding genes, eight ribosomal RNAs, and 37–38 transfer RNAs. Combined with the other 14 Paphiopedilum species, the characteristics of the repeat sequences, divergent hotspot regions, and the condo usage bias were evaluated and identified, respectively. The gene transfer analysis showed that some fragments of the ndh and ycf gene families were shared by both the chloroplast and nucleus. Although the genomic structure and gene content was conserved, there was a significant boundary shift caused by the inverted repeat (IR) expansion and small single copy (SSC) contraction. The lower GC content and loss of ndh genes could be the result of adaptive evolutionary responses to its unique habitats. The genes under positive selection, including accD, matK, psbM, rpl20, rps12, ycf1, and ycf2 might be regarded as potential candidate genes for further study, which significantly contribute to the adaptive evolution of Paphiopedilum. [ABSTRACT FROM AUTHOR]