UV-B is Required for Normal Development of Oil Glands in Ocimum basilicum L. (Sweet Basil)

Abstract

Plants of Ocimum basilicum L. grown under glass were exposed to short treatments with supplementary UV-B. The effect of UV-B on volatile essential oil content was analysed and compared with morphological effects on the peltate and capitate glandular trichomes. In the absence of UV-B, both peltate and capitate glands were incompletely developed in both mature and developing leaves, the oil sacs being wrinkled and only partially filled. UV-B was found to have two main effects on the glandular trichomes. During the first 4 d of treatment, both peltate and capitate glands filled and their morphology reflected their 'normal' mature development as reported in the literature. During the following days there was a large increase in the number of broken oil sacs among the peltate glands as the mature glands broke open, releasing volatiles. Neither the number of glands nor the qualitative or quantitative composition of the volatiles was affected by UV-B. There seems to be a requirement for UV-B for the filling of the glandular trichomes of basil.

Plantas medicinais: fatores de influência no conteúdo de metabólitos secundários

“…Foi demonstrado, por ex., que no manjericão (Ocimum basilicum) e no tomilho (Thymus vulgaris), duas plantas utilizadas na medicina popular e como condimentos, o completo desenvolvimento de tricomas glandulares, onde os óleos essenciais são armazenados, é luz-dependente 123,126 .…”

Seasonal Variation of the Chemical Composition and Antimicrobial and Cytotoxic Activities of the Essential Oils from Inga laurina (Sw.) Willd.

“…The terpenoids accounted for 33.84% and were found in higher amount when compared with oil obtained during the dry season (4.32%) ( Tables 2 and 4). The synthesis of some terpenoids occurs specifically in leaf structures called glandular trichomes [28] and studies have shown that in some plants the full development of these structures is light-dependent [29,30]. A greater or lesser light intensity can explain the variation of terpenoids (Tables 2 and 4) when oils from leaves of I. laurina are compared at different collection periods.…”

Comparative analysis of essential oil composition and oil containing glands in Ocimum sanctum L. (Holy basil) under ambient and supplemental level of UV-B through gas chromatography–mass spectrometry and scanning electron microscopy

“…Though, some of the earlier studies have already reported a substantial induction of essential oil and secondary metabolites in different medicinal plants due to UV-B (Ioannidis et al 2002;Chang et al 2009). Findings of the present investigation are of importance, as it seems to be the first report evaluating the impact of sUV-B exposure on holy basil under natural field conditions.…”

“…Smaller number of studies indicates towards the positive effects of UV-B on volatile oil production in different medicinal plants (Kumari et al 2009a, b;Nitz and Schnitzler 2004;Johnson et al 1999;Maffei and Scannerini 2000). According to Ioannidis et al (2002), UV-B might be required for filling of oil glands in sweet basil (Ocimum basilicum L.). In another study, Chang et al (2009) have also reported a positive enhancement of total volatile content in the essential oil of O. basilicum L. under supplemental dose of UV-B.…”