The effect of various levels and combinations of molybdenum and tungsten on the growth and nitrate accumulation in lettuce (Lactuca sativa L.) grown in nutrient solution

absorption de substances nutritives assorbimento di elementi nutritivi colture idroponiche colture in serra crecimiento crescita croissance cultivos de invernadero culture hydroponique fitotoxicidad greenhouse crops growth hydroponics lactuca sativa molibdeno molybdenum nitrate nitrates nitrati nitratos nutrient uptake phytotoxicity plante de serre tungsten tungsteno