# How Biological and Environmental Factors Affect the Quality of Lavender Essential Oils
## 4 Conclusions  
Lavender essential oil is extensively used, not only in the aromatherapy, perfume, and the cosmetic industries but also in medicine and therapeutic applications, due to its antiviral and antibacterial activities. Furthermore, lavender monoterpenes perform essential physiological and ecological functions. This review summarises the environmental, developmental, and molecular factors contributing to EO composition in lavender flowers. These features predict the optimum harvesting period for high-quality lavender EO and highlight the environmental factors, such as rainfall and temperature during harvesting, and the developmental factors, like the circadian rhythm, that regulate linalool and linalyl acetate biosynthesis. Therefore, the highest quality of lavender EO is obtained when the flowers are harvested in the afternoon for the highest content of linalool and linalool acetate at the end of the flowering period.  
\begin{table}
\begin{tabular}{l l l} \hline \hline
**Genes** & **Factors** & **Reference** \\ \hline \multirow{4}{*}{_(R)-linalo synthase_ (_LaLinTS_)} & Inflorescence development & [62; 63] \\  & (flower stage 50\%) & [62; 63] \\ \cline{2-3}  & Genotype & [62] \\ \cline{2-3}  & Increased at mid-day & [64] \\ \hline _lavandulyl pyrophosphate synthesis_ (_LPPS_) & Genotype, unflorescence development (picked at bud II) & [62] \\ \hline _geranylgeranyl pyrophosphate synthase_ (_GGPPS_) & Genotype & [62] \\ \hline \multirow{4}{*}{_GPP synthase (GPPS)_} & Genotype, unflorescence development & [62] \\  & (picked at flower stage 50\%) & \\ \hline \multirow{4}{*}{_GPP synthase (GPPS)_} & Up-regulated by methyl & [66] \\  & jasmonate & [6] \\ \hline \multirow{4}{*}{_LIMS_} & Down-regulated during flower development & [6] \\ \cline{2-3}  & Increased at mid-day & [64] \\ \hline \multirow{2}{*}{_LaCINS_} & Up-regulated by methyl & [66] \\  & jasmonate & [66] \\ \hline _alcohol acetyltransferase transferase (AAT2)_ & Up-regulated before blossom & [6] \\ \hline \multirow{4}{*}{_LaAAT_} & Increased early flower development, decreased late flower development & [34] \\ \hline \multirow{4}{*}{_La05G1453/La05G1454 (TPS)_} & Up-regulated with methyl & [34] \\  & jasmonate & [34] \\ \hline \multirow{2}{*}{_La02G01528/La02G01529/La02G01630 (TPS)_} & Up-regulated with methyl & [34] \\  & jasmonate & [34] \\ \hline \multirow{2}{*}{_TPS-l_} & Increased at mid-day & [64] \\ \hline \hline \end{tabular}
\end{table}
Table 3: Effect of several environmental and developmental factors on gene expression of monoterpene biosynthesis in lavender.  
The regulation of the pathways involved in monoterpene biosynthesis in lavender is limited, which constrains the manipulation of VOC emission. In conjunction with new technologies, modern approaches will generate transgenic plants and improved genotypes with more precise, fine-tuned VOC emissions and high-quality lavender EO for industrial and medicinal purposes.  
Conceptualisation, C.N.H. and K.E.V.; data curation, C.N.H. and K.E.V.; writing--original draft preparation, C.N.H. and K.E.V.; writing--review and editing, C.N.H. and K.E.V.; visualisation, C.N.H.; supervision, K.E.V. All authors have read and agreed to the published version of the manuscript.  
This research received no external funding.  
Not applicable.  
Further inquiries can be directed to the corresponding author.  
The authors declare no conflicts of interest.