Geoscience Reference
In-Depth Information
significantly influence plant growth leading to yield and com-
position of medicinal and aromatic plants. According to Janzen
(1974), sandy soils, which are poor in nutrients, provide a
higher production of secondary metabolites compared with
clay soils, which are richer in nutrients. Studies carried out in
the Amazonas State, with authentic oil resins of
Copaifera mul-
tijuga
, show that there is a dependence between soil texture
(sandy or clay) and productivity of the oil resin, with production
being higher in clay soils than in sandy soils (Alencar, 1982).
However, there was no relationship observed between produc-
tion and soil type, but it was observed that the fractions of
non-oxygenated sesquiterpenes and diterpene acids are slightly
higher in clay soils, while the fraction of oxygenated sesquiter-
penes was higher in sandy soils (Medeiros and Vieira, 2008).
Moqbeli et al. (2011) reported that soil conditions have a signifi-
cant effect on yield and the essential oil of
Melissa officinalis.
.
It was further reported that in comparison to sand and clay, the
loam texture of soil recorded the highest biomass and essential
oil content in the plant.
The pH value has an impact on the production of secondary
metabolites (Yan et al., 2004; Medentsev et al., 2005; Babula
et al., 2006), for example, out of many soil parameters anal-
ysed, the highest correlation of the production of the glycoside
salidroside in
Rhodiola sachalinensis
was observed to the soil
pH (Yan et al., 2004).
There are contradictory reports in the literature concerning
the response of essential oil to salt stress. Salt stress decreased
essential oil yield in
Trachyspermum ammi
(Ashraf and Orooj,
2006). This negative effect of salt stress in oil yield was also
reported for other medicinal plants, for example,
Mentha
piperita
(Tabatabaie and Nazari, 2007); peppermint, penny-
royal, and apple mint (Aziz et al., 2008);
Thymus maroccanus
(Belaqziz et al., 2009); and basil (Said-Al Ahl and Mahmoud,
2010). Besides, salinity decreased the essential oil yield (Abd
El-Wahab, 2006) of fennel. It was also observed that the ane-
thole percentage was reduced with saline water. In marjo-
ram, the proportions of the main compounds were differently
affected by salt (Baatour et al., 2010), while, in
Matricaria
recutita
, the main essential oil constituents (α-bisabololoxide
B, α-bisabolonoxide A, chamazulene, α-bisabolol oxide A,
α-bisabolol, trans-β-farnesene) showed an increase under saline
conditions (Baghalian et al., 2008). Also, in
Origanum vulgare
,
it was found that the content of the main essential oil constitu-
ent (carvacrol) decreased under salt stress, while
p
-cymene and
γ-terpinene contents increased under non-salt stress treatments
