Articles
ESSENTIAL OILS AND GLANDULAR TRICHOMES OF PERILLA SEEDLINGS AS AFFECTED BY LIGHT INTENSITY
Akachirimen) seedlings, a condimental plant named as mejiso in Japan, were grown on a fertilizer-free volcanic ash soil under four light treatments covered with silver film or cheesecloths in a greenhouse, as follows: 0%, 15%, 50% and 100% of natural daylight.
Plants were harvested at cotyledon stage (6 days after emergence) and at the first true leaf stage (15 days after emergence).
Essential oil concentrations in the top of perilla seedlings increased with the increase of light intensity at both stages.
In cotyledons, peltate glandular trichomes were mostly observed on the adaxial surface, not on the abaxial one, and also more in the leaf margin than in the central portion regardless of light intensity.
On the other hand, in true leaves, most peltate glandular trichomes were found on the abaxial surface.
In both stages of leaves, the relationship between light intensity and the number of peltate glandular trichomes per a leaf was not clear.
However, the higher the light intensity, the smaller the number of peltate glandular trichomes per unit leaf area.
It seems that the decrease of trichomes was caused by a dilution effect with increase of leaf area (1 mm2). The diameter of the head of peltate glandular trichomes tended to increase with the increase of light intensity.
These results suggest that the increase of essential oil concentrations with the increase of light intensity is not due to the number of peltate glandular trichomes, but the increased accumulation of essential oils in glands.