Effect of ammonia on sucrose synthase in pea roots

Abstract

The effects of ammonium on activity of sucrose synthase (SS) in the roots of pea (Pisum sativum L.) plants were studied. On the medium containing 14.2 mM (NH4)2SO4, SS activity increased by 20–200% for 10–20 days of plant growth as compared with the roots of plants growing without nitrogen. Illuminance affected the degree of effects. Under natural illumination, ammonium affected SS activity not only in sunny days (up to 25 klx) but also in cloudy days (3–6 klx) but to a lower degree. Under stable low light (2.5 klx), ammonium did not affect SS activity. In the in vitro experiments, at (NH4)2SO4 concentrations from 0 to 1 mM, SS activity was suppressed (up to 10%), whereas 1–37.5 mM (NH4)2SO4, it was increased (up to 50%).