Induction of cucumber leaf urease by cobalt

Abstract

Formation of urease (EC. 3.5.1.5) in higher plants was strictly controlled by the concentration of nickel (Ni) in the culture medium. The urease activity of cucumber leaves was markedly suppressed at a Ni concentration of less than 100 ng L^-1 in the culture medium. When cobalt (Co) chloride was fed instead of NiCl₂ , the urease activity in leaves appeared, although the Co-induced urease showed a lower specifit activity than that of Ni-induced urease. When plants cultured in the nutrient solution containing Co were supplied with Ni, the urease activity in leaves rapidly increased. The activity of both enzymes from Ni-cultured and Co-cultured plants was inhibited by acetohydroxamic acid in the same manner.

Key Words:

• cobalt
• cucumber plant
• nickel
• substitution, urease