Glucosinolate Content and Myrosinase Activity in Rapid-cycling Brassica oleracea Grown in a Controlled Environment

Abstract

Crops of the Brassicaceae contain glucosinolates(GSs), which when hydrolyzed by the enzyme myrosinase, generate products involved in cancer chemoprotection, plant defense, and plant-insect interactions. A rapid-cycling base population of B. oleracea L. was grown in a hydroponic system in a controlled environment to determine the roles of temperature, photosynthetic photon flux (PPF), and photoperiod in GS concentration and myrosinase activity. The concentration of total GSs in leaves was 44% and 114% higher at 12 and 32 °C respectively than at 22 °C under constant light of 300 μmol·m-2·s-1. The concentration of glucoraphanin, the precursor to sulforaphane, a compound with chemoprotective properties, was 5-fold higher at 32 than at 22 °C. Total GSs were ≈50% lower in roots at 12 °C and 32 than at 22 °C. Total GSs in leaves decreased 20% when PPF was increased from 200 to 400 μmol·m-2·s-1. Myrosinase activity on a fresh weight basis (activity-FW) was ≈30% higher in leaves and stems at 12 and 32 °C than at 22 °C, and ≈30% higher in leaves grown at 200 and 400 μmol·m-2·s-1 than at 300 μmol·m-2·s-1. Consideration of climatic factors that influence the glucosinolate-myrosinase system may be necessary to optimize the planting and cultivation of Brassica crops for maximum health benefits.