Vujinović Tihana, Zanin Laura, Venuti Silvia, Contin Marco, Ceccon Paolo, Tomasi Nicola, Pinton Roberto, Cesco Stefano, De Nobili Maria
Dipartimento di Scienze Agroalimentari, Ambientali e Animali, University of Udine, Udine, Italy.
Faculty of Science and Technology, Free University of Bolzano, Bolzano, Italy.
Front Plant Sci. 2020 Jan 15;10:1652. doi: 10.3389/fpls.2019.01652. eCollection 2019.
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 soil 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 exerted 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, such as , , (coding for two high-affinity nitrate transporters and a PM H-proton pump), , , and (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 increase in the carboxylic groups content, as well as diverse structural modifications in OF vs. CF soils were observed. These changes were accelerated in planted soils. Similarity of chemical properties of DHS with the more easily obtainable water-soluble humic substance extracted from peat (WEHS) and the correspondence of their biostimulant actions confirm the validity of studies which employ WEHS as an easily available source of DHS to investigate biostimulant actions on agricultural crops.
传统农业（CF）向有机农业（OF）的转变据称有助于土壤资源的可持续管理，但关于其对溶解有机物（DOM）影响的信息却很少。在DOM的组分中，溶解腐殖质（DHS）对植物生长具有促进作用。从土壤柱状体收集的CF和OF土壤渗滤液中分离出DHS：首先在11月（裸土），然后在4月和6月（裸土和种植土）。DHS提高了玉米根中硝酸盐的吸收速率，并调节了几个与氮素吸收相关的基因。OF土壤中的DHS对硝酸盐吸收系统具有更强的生物刺激作用，但硝酸盐的第一步同化主要由CF土壤中的DHS激活。为了验证植物对DHS暴露的生理反应，对那些与硝酸盐吸收最相关的基因进行了实时RT-PCR分析，例如，，（编码两种高亲和力硝酸盐转运蛋白和一种质膜H +质子泵），，，和（编码硝酸盐还原酶和亚硝酸还原酶）。所有测试的DHS组分均诱导了硝酸盐还原酶（NR）的上调，特别是OF2 DHS刺激了编码两种NR同工型的两个测试转录本的表达。在实验过程中，OF和CF土壤中DHS的特性均发生了变化：OF土壤中高分子量组分减少，羧基含量普遍增加，并且观察到OF与CF土壤中存在不同的结构修饰。这些变化在种植土壤中加速。DHS的化学性质与从泥炭中提取的更容易获得的水溶性腐殖质（WEHS）的相似性及其生物刺激作用的对应关系证实了采用WEHS作为DHS的易获得来源来研究对农作物生物刺激作用的研究的有效性。
