Flowering is one of the most important phenological periods, as it determines the timing of fruit maturation and seed dispersal.  To date, both nitric oxide (NO) and DNA demethylation have been reported to regulate flowering in plants.  However, there is no compelling experimental evidence for a relationship between NO and DNA demethylation during plant flowering.  In this study, an NO donor and a DNA methylation inhibitor were used to investigate the involvement of DNA demethylation in NO-mediated tomato (Solanum lycopersicum cv. Micro-Tom) flowering.  The results showed that the promoting effect of NO on tomato flowering was dose-dependent, with the greatest positive effect observed at 10 μmol L^–1 of the NO donor S-nitrosoglutathione (GSNO).  Treatment with 50 μmol L^–1 of the DNA methylation inhibitor 5-azacitidine (5-AzaC) also significantly promoted tomato flowering.  Moreover, GSNO and 5-AzaC increased the peroxidase (POD) and catalase (CAT) activities and cytokinin (CTK) and proline contents, while they reduced the gibberellic acid (GA3) and indole-3-acetic acid (IAA) contents.  Co-treatment with GSNO and 5-AzaC accelerated the positive effects of GSNO and 5-AzaC in promoting tomato flowering.  Meanwhile, compared with a GSNO or 5-AzaC treatment alone, co-treatment with GSNO+5-AzaC significantly increased the global DNA demethylation levels in different tissues of tomato.  The results also indicate that DNA demethylation may be involved in NO-induced flowering.  The expression of flowering genes was significantly altered by the GSNO+5-AzaC treatment.  Five of these flowering induction genes, ARGONAUTE 4 (AGO4A), SlSP3D/SINGLE FLOWER TRUSS (SFT), MutS HOMOLOG 1 (MSH1), ZINC FINGER PROTEIN 2 (ZFP2), and FLOWERING LOCUS D (FLD), were selected as candidate genes for further study.  An McrBC-PCR analysis showed that DNA demethylation of the SFT gene in the apex and the FLD gene in the stem might be involved in NO-induced flowering.  Therefore, this study shows that NO might promote tomato flowering by mediating the DNA demethylation of flowering induction genes, and it provides direct evidence for a synergistic effect of NO and DNA demethylation in promoting tomato flowering.

The Internet is believed to bring more technological dividends to vulnerable farmers during the green agriculture transformation.  However, this is different from the theory of skill-biased technological change, which emphasizes that individuals with higher levels of human capital and more technological endowments benefit more.  This study investigates the effects of Internet use on farmers’ adoption of integrated pest management (IPM), theoretically and empirically, based on a dataset containing 1 015 farmers in China’s Shandong Province.  By exploring the perspective of rational inattention, the reasons for the heterogeneity of the effects across farmers with different endowments, i.e., education and land size, are analyzed.  The potential endogeneity issues are addressed using the endogenous switching probit model.  The results reveal that: (1) although Internet use significantly positively affects farmers’ adoption of IPM, vulnerable farmers do not benefit more from it.  Considerable selection bias leads to an overestimation of technological dividends for vulnerable farmers; (2) different sources of technology information lead to the difference in the degree of farmers’ rational inattention toward Internet information, which plays a crucial role in the heterogeneous effect of Internet use; and (3) excessive dependence on strong-tie social network information sources entraps vulnerable farmers in information cocoons, hindering their ability to reap the benefits of Internet use fully.  Therefore, it is essential to promote services geared towards elderly-oriented Internet agricultural technology information and encourage farmers with strong Internet utilization skills to share technology information with other farmers actively.

Insufficient available phosphorus in soil has become an important limiting factor for the improvement of yield and quality in soybean.  The mining of QTLs and candidate genes controlling soybean phosphorus utilization related traits is a necessary strategy to solve this problem.  In this study, 11 phosphorus utilization related traits of a natural population of 281 typical soybean germplasms and a recombinant inbred line (RIL) population of 270 lines were evaluated under different phosphorus conditions at two critical stages: the four-leaf stage as the seedling critical stage was designated as the T₁ stage, and the six-leaf stage as the flowering critical stage was designated as the T₂ stage.  In total, 200 single nucleotide polymorphism (SNP) loci associated with phosphorus utilization related traits were identified in the natural population, including 91 detected at the T₁ stage, and 109 detected at the T₂ stage.  Among these SNP loci, one SNP cluster (s715611375, ss715611377, ss715611379 and ss715611380) on Gm12 was shown to be significantly associated with plant height under the low phosphorus condition at the T₁ stage, and the elite haplotype showed significantly greater plant height than the others.  Meanwhile, one pleiotropic SNP cluster (ss715606501, ss715606506 and ss715606543) on Gm10 was found to be significantly associated with the ratio of root/shoot, root and total dry weights under the low phosphorus condition at the T₂ stage, and the elite haplotype also presented significantly higher values for related characteristics under the phosphorus starvation condition.  Furthermore, four co-associated SNP loci (ss715597964, ss715607012, ss715622173 and ss715602331) were identified under the low phosphorus condition at both the T₁ and T₂ stages, and 12 QTLs were found to be consistent with these genetic loci in the RIL population.  More importantly, 14 candidate genes, including MYB transcription factor, purple acid phosphatase, sugar transporter and HSP20-like chaperones superfamily genes, etc., showed differential expression levels after low phosphorus treatment, and three of them were further verified by qRT-PCR.  Thus, these genetic loci and candidate genes could be applied in marker-assisted selection or map-based gene cloning for the genetic improvement of soybean phosphorus utilization.

Extreme meteorological disaster effects on grain production is mainly determined by the interaction between danger degree of hazard-induced factors and vulnerability degree of hazard-affected bodies.  This paper treats physical exposure, sensitivity of the response to the impact, and capabilities of disaster prevention and mitigation as a complex system for vulnerability degree of hazard-affected bodies, which included the external shocks and internal stability mechanism.  Hazard-induced factors generate external shocks on grain production systems though exposure and sensitivity of hazard-affected body, and the result can be represented as affected area of grain.  By quantile regression model, this paper depicts the quantitative relationship between hazard-induced factors of extreme meteorological disaster and the affected area in the tail of the distribution.  Moreover, the model of production function have also been utilized to expound and prove the quantitative relationship between the affected area and final grain output under the internal stability mechanism of the agricultural natural resources endowment, the input factors of agricultural production, and the capacity of defending disaster.  The empirical study of this paper finds that impact effects of drought disaster to grain production system presents the basic law of “diminishing marginal loss”, namely, with the constant improvement of the grade of drought, marginal affected area produced by hazard-induced factors will be diminishing.  Scenario simulation of extreme drought impact shows that by every 1% reduction in summer average rainfall, grain production of Jilin Province will fell 0.2549% and cut production of grain 14.69% eventually.  In response to ensure China’s grain security, the construction of the long-term mechanism of agricultural disaster prevention and mitigation, and the innovation of agricultural risk management tools should be also included in the agricultural policy agenda.