3.1.1 Scent volatiles variations from in situ flowers
Benzenoids and terpenoids were shown to be the major volatile compounds emitted from J. auriculatum flowers. To understand variations in emission patterns at different stages of floral growth and maturation until senescence, the contents of major volatiles was evaluated from intact in situ flowers at six defined stages starting from early bud stage to senescence stage. The emission of benzyl alcohol, 2-phenylethanol, linalool and farnesol was highest at flower blooming (S4) stage whereas the emission of benzyl acetate and α-farnesene was much higher at fully bloomed (S5) stage (Figure 1 ).
3.1.2 Activities ofmajor pathway enzymes of volatile biosynthesis at different floral maturation stages
To find out any correlation between enzyme activities and scent volatiles synthesis and emission, we attempted to measure the amount of active enzymes (in terms of their in vitro activities) involved in the scent biosynthetic pathways throughout floral lifespan. The major volatile compounds in J. auriculatum are benzyl acetate, 2-phenylethanol and phenylethyl acetate, derived from the phenylpropanoid pathway. PAL is the entry point enzyme of phenylpropanoid pathway that catalyzes the formation oftrans -cinnamic acid from L-phenylalanine. Most of the benzenoid volatile compounds are subsequently formed from trans -cinnamic acid via C2 side chain shortening. Higher PAL activities were recorded at time of flower blooming (S4) stage (Figure 2a ), which showed a gradual decline with subsequent stages of petal growth and maturation until senescence. The enzyme BEAT catalyzes the formation of benzyl acetate from the substrate benzyl alcohol in presence of acetyl CoA. Out of the six stages the activity of BEAT was found to be highest at flower blooming (S4) stage (Figure 2c ). The PAR enzyme is responsible for formation of 2-phenylethanol (2PE) from phenylacetaldehyde. Upliftment of PAR activities was observed at late bud stage (S3) which gradually declined after the flower blooms (Figure 2d ). Terpenoid volatiles also contribute to the floral scent bouquet of J. auriculatum . Linalool is the major emitted monoterpene compound. The activity of MTS responsible for formation of linalool was also measured; MTS showed highest peak at late bud (S3) stage followed by a gradual decline after flower blooming (S4) (Figure 2e ). Chromatograms indicating product formation by BEAT, PAR and MTS are presented in Figure 2f, g, h .
Many volatile compounds in J. auriculatum are present as glycosyl-bound form. In this species, it was observed that the release of scent volatiles started at higher rate within first few hours of flower opening. Little is known about the enzymes involved in the de-glycosylation process. The β-glucosidase activity was measured at different floral maturation stages; a higher activity observed at the flower blooming (S4) stage (Figure 2b ), which indicated the cleavage of glucosyl moiety for easy release of volatile compounds.