Effects of Salinity and Nutrients in Seawater on Hydroponic Culture of Red Leaf Lettuce

Abstract

Among various environmental factors, the effects of light quality and quantity on growth of vegetables and ornamental plants were investigated thoroughly in closed plant factories, whereas how solutes and minerals in hydroponics affect on growth of vegetables were poorly understood. In this study, we investigated the effects of salinity and nutrients on the growth of red leaf lettuce (Lactuca sativa L. cv. Mother-red). A closed plant factory with hydroponic cultures supplemented with sodium salt (NaCl) or seawater was employed for cultivation of lettuce. The fresh weight of lettuce grown in culture with NaCl was dramatically reduced when compared to those grown in standard culture or culture with seawater. The lettuces grown in the culture with NaCl or seawater contained higher amounts of sugar and anthocyanin, and the lettuce plants grown in the culture with seawater accumulated highest levels of photosynthetic pigments, chlorophylls and carotenoids. These results indicate that the addition of some solutes (e.g. NaCl) to the culture medium affect the size of plant as well as the levels of sugars and pigments in the plant, and suggest that the addition of seawater (20%) to the medium is effective to produce lettuces with higher quality and nutritional value.

Enhancing Quality of Fresh Vegetables Through Salinity Eustress and Biofortification Applications Facilitated by Soilless Cultivation

“…Although under soil conditions this technique for improving product quality poses a high risk of plant overstress ( Hidaka et al, 2008 ), soilless culture may be an effective tool for modulating secondary metabolites without curbing growth and yield, through proper management of the nutrient solution’s composition ( Schwarz et al, 2009 ; Tomasi et al, 2015 ). Several studies have demonstrated that NaCl in the nutrient solution raises the levels of sugars, organic acids, and amino acids in several vegetable crops, like tomato ( Zushi and Matsuzoe, 2015 ; Moya et al, 2017 ), pepper ( Marin et al, 2009 ), melon ( Rouphael et al, 2012b ), watermelon ( Colla et al, 2006 ), eggplant ( Savvas and Lenz, 1996 ), lettuce ( Sakamoto et al, 2014 ), and cauliflower ( Giuffrida et al, 2017 ) thereby improving their organoleptic quality. The salt-induced osmoregulatory mechanism in hydroponically grown vegetables involves the biosynthesis of specific osmolytes (sugars, minerals, and amino acids such as proline and GABA) believed to function as osmoprotectants by counterbalancing the increase in vacuolar osmotic potential caused by the toxic accumulation of sodium and chloride ions ( Hasegawa et al, 2000 ).…”

Morpho-Anatomical and Physiological Responses Can Predict the Ideal Period for the Transplantation of Hydroponic Seedlings of Hymenaea courbaril, a Neotropical Fruit Tree

“…Given this, any reduction in the SD, which is reflected in a decrease in the transpirational flux (e.g., [ 43 , 44 , 45 ]), may help the plant to avoid the potentially damaging effects of high ion concentrations in hydroponic systems. A number of studies have shown that plants cultivated in these systems are more able to adapt to conditions of high salinity than plants cultivated using conventional methods [ 46 ], which may reflect a potential for the use of brackish water, or even seawater in hydroponic systems (e.g., [ 47 , 48 , 49 , 50 ]). This adaptation may be related directly to the anatomical and physiological adjustments observed in the H. courbaril seedlings in the present study.…”

Development of Future’s Two Model Plant (Lettuce and Potato) in Diluted Seawater In Vitro and In Vivo Conditions

“…Increasing the EC from 0.80 to 1.93 dS m -1 resulted in a 28.5% increase in shoot fresh mass, whereas rising the EC level from 1.93 to 4.72 dS m -1 declined the fresh mass by 16.5%. Sakamoto et al (2014) reported that the addition of NaCl and other some solutes to the hydroponic growing medium affect plant size, and levels of pigments and sugars. They concluded that, addition of diluted seawater (20%) on the growing medium were produced higher quality and nutritional value lettuces.…”

“…Ünlükara et al, (2008) and Karakoç and Kale (2016) have obtained good plant growth in lettuce at low salt concentrations similar to the results of our research. It is well known that, in the seawater containing minerals like chlorite magnesium can be stimulate growth and development (Sakamoto et al, 2014), the overabundant concentration of mineral salts (mostly sodium chloride) present in seawater is an important source of salt stress (Atzori et al, 2016).…”

“…In the world of soilless cultivation, hydroponic culture has been made along with a world-wide vegetable production expanding around 35,000 hectares (Hickman, 2011;Atzori et al, 2016). Some of these studies have shown that the use of seawater in growing environments does not adversely affect efficiency up to certain concentrations and has maximum thresholds that vary by species (Sakamoto et al, 2014;Turhan et al, 2014). In any case, although the scientific literature provides a variety of information about the effects of salt for more than 130 plant species (Shannon and Grieve, 1998), there are still missing data about others, especially considering the production of nutrient contents as a response to salinity stress (Atzori et al, 2016).…”