Effect of boron on nitrate reductase activity in young sunflower plants

Abstract
The effect of variable levels of B supply on the content of total N, nitrate and nitrate reductase activities in roots and shoots of young sunflower (Helianthus annuus L.) plants was investigated. It was found that both a deficiency and high toxic levels of B decreased the total N content and the activity of nitrate reductase and increased the content of nitrates in roots and shoots of the plants. The treatment of the excised segments of roots and leaves of plants supplied with insuficient levels of B and adequate levels of glucose significantly increased the activity of nitrate reductase. The study concluded that one of the factors influencing the primary assimilation of N is B supply to plants. Supported by these findings and corroborated by literature data, the possible effect of B on nitrate reductase activity via the metabolisms of nucleic acids and proteins and on energy turnover is discussed.