Dip. Scienze Agrarie e Ambientali, University of Udine, 33100 Udine, Italy.
Plant Physiol Biochem. 2012 Jul;56:14-23. doi: 10.1016/j.plaphy.2012.04.002. Epub 2012 Apr 20.
Soil-less cultivation of horticultural crops represents a fairly recent innovation to traditional agriculture which has several advantages including higher water-use efficiency. When plants are grown with this system, their roots come in contact with nutrients solely via the hydroponic solution. Although its beneficial effects have been widely demonstrated, silicon (Si) is mostly omitted from the composition of nutrient solutions. Therefore, the objective of this study was to assess the beneficial effect of Si addition to hydroponic solution on quali-quantitative aspects of edible production of two cultivars of corn salad (Valerianella locusta (L.) Laterr.) grown in soil-less floating system. Impacts on shelf life of this food were also studied. Results show that the supply of Si increased the edible yield and the quality level reducing the nitrate concentration in edible tissues. This result might be attributed to changes either in the metabolism (such as the nitrate assimilation process) or to the functionality of root mechanisms involved in the nutrient acquisition from the outer medium. In fact, our results show for the first time the ability of Si to modulate the root activity of nitrate and Fe uptake through, at least in part, a regulation of gene expression levels of the proteins involved in this phenomenon. In addition, the presence of Si decreased the levels of polyphenoloxidase gene expression at harvest and, in post-harvest, slowed down the chlorophyll degradation delaying leaf senescence and thus prolonging the shelf life of these edible tissues. In conclusion, data showed that the addition of Si to the nutrient solution can be a useful tool for improving quali-quantitatively the yield of baby leaf vegetable corn salad as well as its shelf life. Since the amelioration due to the Si has been achieved only with one cultivar, the recommendation of its inclusion in the nutrient solution does not exclude the identification of cultivars suitable for this cultivation system and the comprehension of agronomical and environmental factors which could limit the Si benefits.
无土栽培园艺作物是对传统农业的一项相当新的创新，具有许多优点，包括更高的水利用效率。当植物用这种系统种植时，它们的根仅通过水培溶液与养分接触。尽管硅（Si）的有益效果已得到广泛证明，但它在营养溶液的组成中大多被省略。因此，本研究的目的是评估在无土漂浮系统中添加硅对两种羽衣甘蓝（Valerianella locusta（L.）Laterr.）栽培品种的可食用产量和质量方面的有益影响。还研究了对这种食品货架期的影响。结果表明，硅的供应增加了可食用产量和质量水平，降低了可食用组织中的硝酸盐浓度。这一结果可能归因于代谢变化（如硝酸盐同化过程）或参与从外部介质中获取营养的根机制的功能变化。事实上，我们的研究结果首次表明，硅能够通过调节硝酸盐和铁吸收的根活性来调节根活性，至少部分是通过调节参与这一现象的蛋白质的基因表达水平来调节的。此外，硅的存在降低了收获时多酚氧化酶基因表达水平，并在收获后，通过减缓叶绿素降解来延缓叶片衰老，从而延长这些可食用组织的货架期。总之，数据表明，向营养液中添加硅可以成为提高羽衣甘蓝可食用产量和货架期的有用工具。由于仅用一个品种就可以实现 Si 的改良，因此建议将其纳入营养液中，并不排除确定适合这种栽培系统的品种，并理解可能限制 Si 益处的农业和环境因素。
