THE EFFECT OF LIGHT AND TEMPERATURE ON GLUCOSINOLATE CONCENTRATION INTHE LEAVES AND ROOTS OF CABBAGE SEEDLINGS

In previous studies it was shown that the concentration of total and i ndividual glucosinolates in brassicaceous plants can vary significantl y over a 24-h period grown either in the field or under controlled con ditions. The present study shows total and individual glucosinolate va riation during a single day. Seedlings of cabbage grown under controll ed conditions and at 14 and 15 days after emergence were moved to 20 d egrees C (Exp A) and 30 degrees C (Exp B), with a constant photosynthe tic photon flux density of 480 mu mol m(-2) s(-1) and 75% relative hum idity, over a 2-day period, during which time aerial parts and roots w ere sampled at regular intervals. Whilst the glucosinolate patterns of the aerial part of the plant and of the roots remained the same, the levels of major glucosinolates in the aerial part, averaged over all s ampling times and 2 days, were 233 +/- 60 mu mol 100 g(-1) DW for 3-me thylsulphinylpropyl and 72 +/- 22 for 2-propenyl; in the roots, 2-phen ylethyl and 1-methoxyindol-3-ylmethyl showed the highest average conce ntrations, with 678 +/- 355 mu mol 100 g(-1) DW and 411 +/- 122, respe ctively. Total and individual glucosinolate levels showed very high si gnificant differences between the two plant parts. Despite the constan t temperature, light and relative humidity, glucosinolates varied with in a 24-h period, showing ultradian rhythms that are common to several metabolic processes in plants. The results confirm previous observati ons that at a temperature of 20 degrees C, close to the optimum for gr owth and development, the diurnal variation in glucosinolate concentra tion, was smaller than at 30 degrees C. (C) 1998 Society of Chemical I ndustry.