Biostimulant Action of Dissolved Humic Substances From a Conventionally and an Organically Managed Soil on Nitrate Acquisition in Maize Plants

作者：Tihana Vujinović, Laura Zanin, Silvia Venuti, Marco Contin, P. Ceccon, Nicola Tomasi, Roberto Pinton, Stefano Cesco, Maria De Nobili · 发表于：Frontiers in Plant Science · 年份：2020 · DOI：10.3389/fpls.2019.01652 · 被引用次数：65 · 研究领域：Soil Carbon and Nitrogen Dynamics、Plant Growth Enhancement Techniques、Legume Nitrogen Fixing Symbiosis

Conversion of conventional farming (CF) to organic farming (OF) is claimed to allow a sustainable management of soil resources, but information on changes induced on dissolved organic matter (DOM) are scarce. Among DOM components dissolved humic substances (DHS) were shown to possess stimulatory effects on plant growth. DHS were isolated from CF and OF soils leacheates collected from soil monolith columns: first in November (bare soils), and then in April and June (bare and planted soils). DHS caused an enhancement of nitrate uptake rates in maize roots and modulated several genes involved in nitrogen acquisition. The DHS from OF soil exert a stronger biostimulant action on the nitrate uptake system but the first assimilatory step of nitrate was mainly activated by DHS derived from CF soil. To validate the physiological response of plants to DHS exposure, real-time RT-PCR analyses were performed on those genes most involved in nitrate acquisition, as ZmNRT2.1, ZmNRT2.2, ZmMHA2 (coding for two high-affinity nitrate transporters and a PM H+-proton pump) and ZmNADH:NR, ZmNADPH:NR and ZmNiR (coding for nitrate reductases and nitrite reductase). All tested DHS fractions induced the upregulation of nitrate reductase (NR), and in particular the OF2 DHS stimulated the expression of both tested transcripts encoding for two NR isoforms. Characteristics of DHS varied during the experiment in both OF and CF soils. A decrease of high molecular weight fractions in the OF soil; a general in...