The CR1 inbred line of Thlaspi arvense L. was used in most experiments. Plants were grown at 21 ℃ for 6 weeks before a 4-week vernalization treatment (6 ℃). In each experiment, control plants (grown at constant 21 ℃) were about the same chronological age (approximately 11 weeks) as vernalized plants.

The endogenous levels in shoot tips declined 10-fold by 2 d after the plants were returned to 21 ℃; this decline continued such that there was nearly 50-fold less kaurenoic acid by 10 d after the end of vernalization. No effect of vernalization on the endogenous levels of kaurenoic acid in leaves was observed.

The aerial parts of samples from collective populations of T. carnosus were collected during the vegetative phase (February 2000), at the beginning of the flowering phase (May 2000) and during the flowering phase (July 2000) at Quinta do Lago (Algarve). AQLM: collected in May, beginning of flowering phase; AQLJ: collected in July, flowering stage; AQLF: collected in Feb, vegetative stage.

All the oil samples collected in Quinta do Lago (QL) were dominated by borneol (26-31%) and camphene (9-18%), but the third main component varied according to the harvesting period. Bornyl acetate was the third main component (9-13%) in the flower oil and in the aerial parts oils collected in May and July, whereas terpinen-4-ol (8%) was the third main component in oil collected in February from vegetative phase plant material. A fourth main component, alpha-pinene (4-9%), was also present in relative high amounts in the QL oils.