The Effect of Growth Medium Temperature on Corn Salad [Valerianella locusta (L.) Laterr] Baby Leaf Yield and Quality

Soil temperature has a crucial impact on physiological processes and growth of plants with important consequences for plant productivity and food safety including nitrate accumulation in leaf blades of leaf vegetables. Consumer demand for high-quality, fresh-cut vegetables has increased rapidly in the last decades, and temperature modulation can help control nitrate concentration in fresh vegetables, an important trait of product safety. Corn salad plants [Valerianella locusta (L.) Laterr., cultivar Galaj were grown at three root temperatures (15, 20, and 25 degrees C) in a floating system. This experimental setup allowed to directly evaluate the effect of root temperature on yield and plant quality excluding the effect on soil processes and properties. Nutrient solution was renewed weekly and kept aerated while air temperature was maintained constant at 20 degrees C for all treatments during the entire time of experiments. At harvest, plants were collected, the shelf life evaluated, and the nutrient uptake [NO(3)(-), iron (Fe) from (59)Fe-o,oEDDHA, and (35)SO(4)(2-)] and mineral content were determined. Results showed that growing conditions at 20 degrees C of the nutrient solution led to the best plant performance in terms of yield, nitrate content at leaf level, root biomass, leaf area, and greenness with positive effects on postharvest quality, i.e., less rapid leaf loss of greenness and leaf fresh weight (FW) loss during conservation at 4 degrees C. At this temperature condition of the nutrient solution, it has also been observed an enhanced functionality of mechanisms involved in the acquisition of nutrients like NO(3)(-), Fe, and SO(4)(2-), which are known to play an important role in nitrate level in leaf tissues of crops. Plants grown at 15 degrees C showed minor growth, whereas the nutrient solution at 25 degrees C caused stress for the plants affecting negatively the quality and yield. Overall, the results obtained showed that root temperature plays a fundamental role in several plant processes that affect yield and its quality; for hydroponic system cultivations, a level of growing-medium temperature close to that of the surrounding air seems suitable.