Localization of methyl benzoate synthesis and emission in Stephanotis floribunda and Nicotiana suaveolens flowers

The emission of fragrances can qualitatively and quantitatively differ in different parts of flowers. A detailed analysis was initiated to localize the floral tissues and cells which contribute to scent synthesis in STEPHANOTIS FLORIBUNDA (Asclepiadaceae) and NICOTIANA SUAVEOLENS (Solanaceae). The emission of scent compounds in these species is primarily found in the lobes of the corollas and little/no emission can be attributed to other floral organs or tissues. The rim and centre of the petal lobes of S. FLORIBUNDA contribute equally to scent production since the amount of SAMT (salicylic acid carboxyl methyltransferase) and specific SAMT activity compensate each other in the rim region and centre region. IN SITU immunolocalizations with antibodies against the methyl benzoate and methyl salicylate-synthesizing enzyme indicate that the adaxial epidermis with few subepidermal cell layers of S. FLORIBUNDA is the site of SAMT accumulation. In N. SUAVEOLENS flowers, the petal rim emits twice as much methyl benzoate due to higher total protein concentrations in the rim versus the petal centre; and, both the adaxial and abaxial epidermis house the BSMT (salicylic acid/benzoic acid carboxyl methyltransferase).