Effects of Long-Term Fertilization on Different Nitrogen Forms in Paddy along Soil Depth Gradient

The combined application of organic fertilizer and chemical fertilizer is an effective measure to increase nutrient content of soil plough layer, which must have a profound impact on the deep soil nutrients, especially the contents of nitrogen forms. The purpose of this study was to explore the characteristics of soil nitrogen forms in plough layer and along depth gradient in different fertilization treatments, so as to evaluate the soil quality in spatial dimension, further providing a theoretical basis for scientific fertilization and improvement of paddy soil fertility. Here, a 34-year field experiment was conducted with three treatments: without any fertilizer (CK), pure chemical fertilizer (NPK) and chemical fertilizer combined with organic fertilizer (NPKM). We analyzed the content of nitrogen forms in 0 - 100 cm soil depth and their ratios to total nitrogen (TN), and discussed the correlation between nitrogen forms contents and pH, CEC. Results showed that, compared with CK, both NPK and NPKM significantly increased the contents of nitrogen forms in topsoil (soil layer of 0 - 20 cm), especially nitrate nitrogen (NO3--N) content increased by 70% (NPK) and 111% (NPKM), respectively. Although the contents of different nitrogen forms decreased gradually along soil depth gradient, NPKS slowed down the decline rate of TN and alkali-hydrolysable nitrogen (AN) in 0 - 60 cm soil layer, compared to CK. Compared to NPK, NPKM significantly increased the NO3--N/TN ratio in 0 - 20 cm soil layer, but also decreased the content of -N in 20 - 40 cm, which was beneficial to reduce the risk of nitrogen leaching caused by nitrate leaching into deep layer. The increase of soil pH in NPKM treatment obviously alleviated the problem of soil acidification caused by long-term application of chemical fertilizer. Correlation analysis showed that there was a significant positive correlation between soil nitrogen forms and cation exchange capacity (CEC), but no significant correlation with soil pH. In conclusion, NPKM ensured the nutrients of soil plough layer (0 - 20 cm), also reduced the risk of nitrogen infiltration and nitrogen loss, thus ensuring the fertility of soil profile.

MIKC^(C)-type MADS-box genes in Rosa chinensis: the remarkable expansion of ABCDE model genes and their roles in floral organogenesis

MIKC^(C)-type MADS-box(MIKC^(C))genes encode transcription factors that have crucial roles in controlling floral organogenesis and flowering time in plants.Although this gene family has been well characterized in many plant species,its evolutionary and comprehensive functional analysis in rose is lacking.In this study,58 non-redundant MIKC^(C)uni-transcripts were extensively identified from rose transcriptomes.Phylogenetic analysis placed these genes into 12 clades with their Arabidopsis and strawberry counterparts,and revealed that ABCDE model(including AP1/FUL,AP3/PI,AG,and SEP clades),and SOC1 and AGL6 clade genes have remarkably expanded in Rosa chinensis,whereas genes from the FLC and AGL17 clades were undetectable.Sequence alignments suggest that the AP3/PI clade may contribute to more specific functions in rose due to a high variation of amino acid residues within its MADS-box domains.A comparative analysis of gene expression in specific floral organ differentiation stages and floral organs between R.chinensis cv.Old Blush and the closely related mutant genotype R.chinensis cv.Viridiflora(floral organs mutated into leaf-like structures)further revealed the roles of ABCDE model genes during floral organogenesis in rose.Analysis of co-expression networks provided an overview of the regulatory mechanisms of rose MIKC^(C)genes and shed light on both the prominent roles of AP3/PI clade genes in floral organogenesis and the roles of RcAGL19,RcAGL24,and RcSOC1 in regulating floral transition in rose.Our analyses provide an overall insight of MIKC^(C)genes in rose and their potential roles in floral organogenesis.

KSN heterozygosity is associated with continuous flowering of Rosa rugosa Purple branch

Rose(Rosa spp.)plants flower via two contrasting methods:once flowering(OF)and continuous flowering(CF).Purple branch is a rare continuously flowering variety of Rosa rugosa that is extensively cultivated in China.However,the genetic basis of its CF behavior is unknown.We demonstrated that Purple branch is heterozygous for the TFL1 homolog KSN.One KSN allele with a 9kb Copia insertion was found to be identical to that from continuously flowering Rosa chinensis Old blush.The other allele was found to be a functional wild-type allele.The overall expression of KSN was closely linked to the floral transition,and it was significantly repressed in continuously flowering Purple branch compared with OF Plena.The promoter region of the normal KSN allele was hypermethylated,and histone methylation at H3H4,H3K9,and H3K27 of the KSN gene locus was modified in continuously flowering Purple branch.Silencing of the DNA methyltransferase genes MET1 and CMT3 and the histone methyltransferase gene SUVR5 in Purple branch led to enhanced KSN expression,but silencing of the histone demethylase gene JMJ12 suppressed KSN expression.Therefore,the CF habit of Purple branch may be due to reduced expression of KSN caused by the halved dose and may be associated with epigenetic modifications together with retrotransposon insertions along the chromosome.Our study revealed a novel mechanism underlying the CF behavior of rose plants.

Application of New Water Flooding Characteristic Curve in the High Water-Cut Stage of an Oilfield

The oil production predicted by means of the conventional water-drive characteristic curve is typically affected by large deviations with respect to the actual value when the so-called high water-cut stage is entered.In order to solve this problem,a new characteristic relationship between the relative permeability ratio and the average water saturation is proposed.By comparing the outcomes of different matching methods,it is verified that it can well reflect the variation characteristics of the relative permeability ratio curve.Combining the new formula with a reservoir engineering method,two new formulas are derived for the water flooding characteristic curve in the high water-cut stage.Their practicability is verified by using the production data of Mawangmiao and Xijiakou blocks.The results show that the error between the predicted cumulative oil production and production data of the two new water drive characteristic curves is less than the error between the B-type water drive characteristic curve and the other two water drive characteristic curves.It is concluded that the two new characteristic curves can be used to estimate more accurately the recoverable reserves,the final recovery and to estimate the effects of water flooding.