102
enzyme activities. More specifically, volatile compounds from long-chain aldehydes have been quantified and detected simultaneously with nitrogen compounds
in the seagrass Zostera marina (Kawasaki et al. 1998) and in the red seaweed
Gelidium arbuscula (Garcia-Jimenez et al. 2013). The presence of LCA-forming
activities, both in seagrasses and seaweeds, has been hypothesised as part of the
evolution from green algae to land plants (Kawasaki et al. 1998).
Consequently, studies of volatile organic compounds released by algae have
focused more on the identities of all of the compounds produced than on their metabolic origins or potential functions. Moreover, the scarcity of standardised data
obscures the exact role of these volatile compounds. Volatile screening varies enormously with respect to the amounts released, time monitoring and trapping methods
used, making comparison difficult and generating confusion and producing speculative results.
Different approaches have been taken to clarify how far different experimental
factors and biosynthesis pathways can influence the production of these volatile
compounds. All of the myriad volatiles identified derive from different precursors,
including amino acids, fatty acids and carotenoids, whose biosynthetic pathways
are shared with the non-volatile secondary metabolites. Hence, several authors have
established a classification of volatiles released depending on their functional
groups, as a benchmark to improve the comprehension of the role of these compounds, in order to further infer the putative functions of these volatiles and their
enzyme pathways. In the red seaweed Gelidium arbuscula, for instance, six volatile
compound groups were generated—compounds consisting of methyl alkyl, amines,
lipid oxidation derivatives, halides, sulphur and ethylene—in order to classify volatiles released under different experimental conditions and to further study their roles
(Garcia-Jimenez et al. 2013).
5.3 Complexity of Factors Drives Volatile Emission by Algae
A set of factors affects the production of the myriad of volatiles reported. Light
availability, desiccation, tissue age, kind of algae, wounded algae and grazing can
influence production and rates of release of volatiles , moreover, with defined periods of temporal evolution (Leedham Elvidge et al. 2015). For instance, algae with
large surface fronds, as Laminaria digitata from intertidal area, have been reported
to release nearly 514–742 ng total volatiles detected g
−1
dw after 4–6 h of desiccation, compared with other algae as Fucus and Enteromorpha, which retain water for
longer periods, with rates of 110–170 ng total volatiles detected g
−1
dw (BravoLinares et al. 2010). Moreover, in the brown alga Laurencia dendroidea, the accumulation and transport of secondary metabolites were associated with the presence
of vesicle transport into the cells (Reis et al. 2013).
Additionally, when in vitro production of volatiles was analysed under different
light and salinity conditions, the profiles of volatile organic compounds generated
by the red seaweed Gelidium arbuscula differed with the light and salinity treatments tested (Garcia-Jimenez et al. 2013).
P. Garcia-Jimenez and R.R. Robaina
enzyme activities. More specifically, volatile compounds from long-chain aldehydes have been quantified and detected simultaneously with nitrogen compounds
in the seagrass Zostera marina (Kawasaki et al. 1998) and in the red seaweed
Gelidium arbuscula (Garcia-Jimenez et al. 2013). The presence of LCA-forming
activities, both in seagrasses and seaweeds, has been hypothesised as part of the
evolution from green algae to land plants (Kawasaki et al. 1998).
Consequently, studies of volatile organic compounds released by algae have
focused more on the identities of all of the compounds produced than on their metabolic origins or potential functions. Moreover, the scarcity of standardised data
obscures the exact role of these volatile compounds. Volatile screening varies enormously with respect to the amounts released, time monitoring and trapping methods
used, making comparison difficult and generating confusion and producing speculative results.
Different approaches have been taken to clarify how far different experimental
factors and biosynthesis pathways can influence the production of these volatile
compounds. All of the myriad volatiles identified derive from different precursors,
including amino acids, fatty acids and carotenoids, whose biosynthetic pathways
are shared with the non-volatile secondary metabolites. Hence, several authors have
established a classification of volatiles released depending on their functional
groups, as a benchmark to improve the comprehension of the role of these compounds, in order to further infer the putative functions of these volatiles and their
enzyme pathways. In the red seaweed Gelidium arbuscula, for instance, six volatile
compound groups were generated—compounds consisting of methyl alkyl, amines,
lipid oxidation derivatives, halides, sulphur and ethylene—in order to classify volatiles released under different experimental conditions and to further study their roles
(Garcia-Jimenez et al. 2013).
5.3 Complexity of Factors Drives Volatile Emission by Algae
A set of factors affects the production of the myriad of volatiles reported. Light
availability, desiccation, tissue age, kind of algae, wounded algae and grazing can
influence production and rates of release of volatiles , moreover, with defined periods of temporal evolution (Leedham Elvidge et al. 2015). For instance, algae with
large surface fronds, as Laminaria digitata from intertidal area, have been reported
to release nearly 514–742 ng total volatiles detected g
−1
dw after 4–6 h of desiccation, compared with other algae as Fucus and Enteromorpha, which retain water for
longer periods, with rates of 110–170 ng total volatiles detected g
−1
dw (BravoLinares et al. 2010). Moreover, in the brown alga Laurencia dendroidea, the accumulation and transport of secondary metabolites were associated with the presence
of vesicle transport into the cells (Reis et al. 2013).
Additionally, when in vitro production of volatiles was analysed under different
light and salinity conditions, the profiles of volatile organic compounds generated
by the red seaweed Gelidium arbuscula differed with the light and salinity treatments tested (Garcia-Jimenez et al. 2013).
P. Garcia-Jimenez and R.R. Robaina