Variation in Essential Oil Composition within Individual Leaves of Sweet Basil (Ocimum basilicum L.) Is More Affected by Leaf Position than by Leaf Age

Abstract

The aroma in sweet basil is a factor affecting the commercial value of the crop. In previous studies leaf age was considered to be a factor that influences the composition of essential oil (EO). In this study it was hypothesized that a single observation of the EO content in leaves from different positions on the main stem (young vs old) could predict the developmental changes in the plant during its life cycle. Plants harvested at week 16 demonstrated an exponential increase (R(2) = 0.92) in EO concentration in leaves on the main stem and lateral shoots, indicating higher EO concentrations in younger than in older leaves. Eugenol and methyleugenol predominated (28-77%) in the extract. Eugenol levels were higher in younger leaves (∼53%), and methyl-eugenol levels predominated in older leaves (∼68%). Linalool was lower in mature leaves than in younger leaves. This suggested that eugenol converted into methyleugenol and linalool decreased as leaf mature. However, in weekly monitored plants, the levels of these compounds in the EO had limited variation in the maturing leaf regardless of its position on the stem. This proposed that the EO composition in an individual leaf is mostly affected by the leaf position on the stem and not by its maturation process. Because leaf position is related to plant development, it is probable that the plant's physiological age at the time of leaf formation from the primordial tissue is the factor affecting the EO composition. It was concluded that interpretation of scientific observations should be carried out with caution and that hypotheses should be tested utilizing multifaceted approaches.

A Set of Regioselective O-Methyltransferases Gives Rise to the Complex Pattern of Methoxylated Flavones in Sweet Basil

“…Likewise, an opposite trend was observed in relative abundances of GARD B and pebrellin, a potential precursor of GARD B lacking only the 6-O-methyl group, which was attributed to changes in the expression of a F6OMT (Voirin and Bayet, 1992). This observation is in line with previous studies on terpene composition in basil (Johnson et al, 1999), peppermint (Brun et al, 1991), and thyme (Thymus vulgare; Yamaura et al, 1992) but contrasts with recent findings (Fischer et al, 2011) that the relative concentrations of several essential oil components in basil are strongly predetermined by the leaf position and vary little throughout leaf development.…”

Can Ocimum basilicum L. and Ocimum tenuiflorum L. in vitro culture be a potential source of secondary metabolites?

“…The lowest values of phenolic content were found in in vitro root, although this part contained almost twice as much eugenol compared to field grown roots. The diversity of the aromatic compounds in the leaves was affected significantly by the ageing of the leaf or the process of maturation (Fischer, Nitzan, Chaimovitsh, Rubin, & Dudai, 2011), and methylating enzymes (eugenol-O-methyltransferase and chavicol-O-methyltransferase) play a major role in the diversity and distribution of phenyl propene compounds (Lewinsohn et al, 2000), which could be the reason for the diverse eugenol content in the various analysed parts of the plant. A recent study demonstrated that some of the secondary metabolites detected in rapeseed have also different tissue-specific distribution patterns.…”

Geographical location is a key component to effective breeding of clary sage (Salvia sclarea) for essential oil composition

“…Freshly removed inflorescences (150 g/plot) were dissected into 1 cm long sections and were submitted to hydro-distillation in a Clevenger-type apparatus for 1.5 h. The essential oil composition was analyzed using the GC-MS procedure (Fischer et al 2011). …”