Borgognone Daniela, Rouphael Youssef, Cardarelli Mariateresa, Lucini Luigi, Colla Giuseppe
Department of Agricultural and Forestry Sciences, Tuscia University, ViterboItaly.
Department of Agricultural Sciences, University of Naples Federico II, PorticiItaly.
Front Plant Sci. 2016 Jun 30;7:978. doi: 10.3389/fpls.2016.00978. eCollection 2016.
Leaf extracts of cultivated cardoon (Cynara cardunculus L. var. altilis DC) are an important source of phenols. Soilless culture represents an important and alternative tool to traditional agriculture, since it allows a precise control of plant nutrition and the maximization of yield and quality of the product. Reducing N supply, while keeping quantity as high as possible is desirable for environmental and health-related reasons, especially that N deficiency can lead to improved concentrations of secondary plant metabolites. Two greenhouse experiments were carried out in order to determine the effect of a decreasing [Formula: see text]:Cl(-) ratio (80:20, 60:40, 40:60, or 20:80) and nitrate deprivation (0, 5, 10, or 15 days before harvest) on biomass production, leaf chlorophyll content and fluorescence, mineral composition, and phytochemicals in leaves of cardoon 'Bianco Avorio' grown in a floating system. Total phenols, flavonoids and antioxidant capacity increased linearly with Cl(-) availability, especially when nitrate was replaced by 80% of chloride (20:80 [Formula: see text]:Cl(-) ratio), without having a detrimental effect on yield. Total nitrogen and nitrate concentration in leaves decreased linearly with increasing Cl(-) in the nutrient solution. Total phenols and antioxidant capacity recorded after 15 days of nitrate deprivation were higher by 43.1, 42.8, and 44.3% and by 70.5, 40.9, and 62.2%, at 59, 97 and 124 days after sowing, respectively compared to the control treatment. The decrease in leaf nitrate content recorded under N-deprivation occurred more rapidly than the reduction in total nitrogen. Thus, up to 15 days of nitrate withdrawal can lower nitrates without sharply reduce total nitrogen or affecting growth and biomass of cultivated cardoon. The use of N-free nutrient solution prior to harvest or the replacement of nitrates with chlorides could be adopted among growers to improve the quality of the product and enhance sustainability of crop production system.
栽培刺菜蓟（Cynara cardunculus L. var. altilis DC）的叶片提取物是酚类物质的重要来源。无土栽培是传统农业的一种重要替代手段，因为它能精确控制植物营养，使产品产量和质量最大化。出于环境和健康方面的考虑，在尽可能保持总量的同时减少氮供应是可取的，尤其是因为氮缺乏会导致植物次生代谢产物浓度提高。进行了两项温室试验，以确定降低[公式：见原文]：Cl(-)比例（80:20、60:40、40:60或20:80）以及收获前硝酸盐剥夺（0、5、10或15天）对漂浮系统中生长的刺菜蓟‘Bianco Avorio’叶片生物量生产、叶绿素含量和荧光、矿物质组成以及植物化学物质的影响。总酚、黄酮类化合物和抗氧化能力随Cl(-)有效性呈线性增加，尤其是当硝酸盐被80%的氯化物替代时（20:80 [公式：见原文]：Cl(-)比例），且对产量没有不利影响。叶片中的总氮和硝酸盐浓度随营养液中Cl(-)增加呈线性下降。与对照处理相比，播种后59、97和124天，硝酸盐剥夺15天后记录的总酚和抗氧化能力分别高出43.1%、42.8%和44.3%以及70.5%、40.9%和62.2%。氮剥夺下叶片硝酸盐含量的下降比总氮的减少更快。因此，长达15天的硝酸盐去除可以降低硝酸盐含量，而不会大幅降低总氮或影响栽培刺菜蓟的生长和生物量。种植者可采用收获前使用无氮营养液或将硝酸盐替换为氯化物的方法来提高产品质量并增强作物生产系统的可持续性。
