103
After mimicking the desiccation that G. arbuscula thalli experienced during low
tides, the ethylene and the composition of gases emitted were also affected by treatments of exogenous ethylene (Garcia-Jimenez et al. 2013).
In broad-spectrum white light, most of the compounds generated by G. arbuscula
were methyl alkyl compounds, amines and derivatives of lipid oxidation, while in
darkness only methyl alkyl and amine compounds predominated. Despite the apparent similarity in the volatile emission profiles, white light affected the level of
amines, constituting 50% of relative area counts liberated, in a different manner
from those liberated in darkness (35% of relative area counts; Garcia-Jimenez et al.
2013). Comparing with the red light, we observed that not only did the profile of
volatiles differ, the relative area counts of compounds derived from lipid oxidation
also increased in red light (50% of relative area counts) compared to white light
(20% of relative area counts; Garcia-Jimenez et al. 2013).
Natural emissions of DMS, the most abundant sulphur-containing compounds
(Andreae et al. 1995), have also been determined for two green algae, Ulva intestinalis (Plettner et al. 2005) and Enteromorpha clathrata (Steinke et al. 1996), and for
the red alga Polysiphonia hendryi (Van Alstyne and Houser 2003). By all means,
DMS seems to play an important ecological role insofar as it contributes to the
albedo (van Rijssel and Gieskes 2002). Meanwhile, dipropyl disulphide in the
brown seaweed Dictyopteris prolifera has been differentially determined in protoplasts compared with thalli of this alga (Fujimura et al. 1994).
In Gelidium arbuscula, levels of dimethyl sulphide (DMS) were lower following
thalli exposure to darkness and red light compared to those obtained under broadspectrum white light. The in vivo emission of DMS in broad-spectrum white light
was estimated as 3.6 ± 0.2 nmol h
−1
g
−1
fw (Garcia-Jimenez et al. 2013). Moreover,
DMS was also affected by salinity in G. arbuscula. DMS breaks down dimethylsulphoniopropionate (DMSP) by the action of the enzyme DMSP lyase. Consequently,
the more DMSP is broken down, the more DMS is liberated. In algae, DMSP is
accumulated as an osmoticum to foster acclimation to high salinity (Otte et al. 2004;
Stefels 2000; Dacey et al. 1987). DMS in the red seaweed G. arbuscula has been
determined as 2.4 ± 0.02 nmol DMS h
−1
g
−1
fw at 60 psu, while when salinity fell to
36 psu, DMS liberation was 20.6 ± 0.015 nmol DMS h
−1
g
−1
fw (Garcia-Jimenez
et al. 2013).
We were also able to determine endogenous jasmonates levels in four different
seaweeds. Beyond the fact that production of jasmonates relies on the corresponding metabolism of seaweeds (availability of substrates, biosynthetic enzymes and
emission routes), brown algae emitted a high concentration of jasmonates compared with the green and red algae (Table 5.1). No comparative information on the
presence of methyl jasmonate between seaweeds has been reported previously,
although our results infer that methyl jasmonate could be involved in several tasks.
Without discerning the exact role of this compound among algal genera, the increment in volatile concentration in brown algae could be explained by the existence of
an environmental control (algae located in the upper-intertidal area, where desiccation and herbivory are intense and could produce more volatiles; Hay 1996) and by
the cellular structure (volatile compounds may be concentrated in the outer meristem; Tugwell and Branch 1989).
5 Volatiles in the Aquatic Marine Ecosystem: Ethylene and Related Plant Hormones…
After mimicking the desiccation that G. arbuscula thalli experienced during low
tides, the ethylene and the composition of gases emitted were also affected by treatments of exogenous ethylene (Garcia-Jimenez et al. 2013).
In broad-spectrum white light, most of the compounds generated by G. arbuscula
were methyl alkyl compounds, amines and derivatives of lipid oxidation, while in
darkness only methyl alkyl and amine compounds predominated. Despite the apparent similarity in the volatile emission profiles, white light affected the level of
amines, constituting 50% of relative area counts liberated, in a different manner
from those liberated in darkness (35% of relative area counts; Garcia-Jimenez et al.
2013). Comparing with the red light, we observed that not only did the profile of
volatiles differ, the relative area counts of compounds derived from lipid oxidation
also increased in red light (50% of relative area counts) compared to white light
(20% of relative area counts; Garcia-Jimenez et al. 2013).
Natural emissions of DMS, the most abundant sulphur-containing compounds
(Andreae et al. 1995), have also been determined for two green algae, Ulva intestinalis (Plettner et al. 2005) and Enteromorpha clathrata (Steinke et al. 1996), and for
the red alga Polysiphonia hendryi (Van Alstyne and Houser 2003). By all means,
DMS seems to play an important ecological role insofar as it contributes to the
albedo (van Rijssel and Gieskes 2002). Meanwhile, dipropyl disulphide in the
brown seaweed Dictyopteris prolifera has been differentially determined in protoplasts compared with thalli of this alga (Fujimura et al. 1994).
In Gelidium arbuscula, levels of dimethyl sulphide (DMS) were lower following
thalli exposure to darkness and red light compared to those obtained under broadspectrum white light. The in vivo emission of DMS in broad-spectrum white light
was estimated as 3.6 ± 0.2 nmol h
−1
g
−1
fw (Garcia-Jimenez et al. 2013). Moreover,
DMS was also affected by salinity in G. arbuscula. DMS breaks down dimethylsulphoniopropionate (DMSP) by the action of the enzyme DMSP lyase. Consequently,
the more DMSP is broken down, the more DMS is liberated. In algae, DMSP is
accumulated as an osmoticum to foster acclimation to high salinity (Otte et al. 2004;
Stefels 2000; Dacey et al. 1987). DMS in the red seaweed G. arbuscula has been
determined as 2.4 ± 0.02 nmol DMS h
−1
g
−1
fw at 60 psu, while when salinity fell to
36 psu, DMS liberation was 20.6 ± 0.015 nmol DMS h
−1
g
−1
fw (Garcia-Jimenez
et al. 2013).
We were also able to determine endogenous jasmonates levels in four different
seaweeds. Beyond the fact that production of jasmonates relies on the corresponding metabolism of seaweeds (availability of substrates, biosynthetic enzymes and
emission routes), brown algae emitted a high concentration of jasmonates compared with the green and red algae (Table 5.1). No comparative information on the
presence of methyl jasmonate between seaweeds has been reported previously,
although our results infer that methyl jasmonate could be involved in several tasks.
Without discerning the exact role of this compound among algal genera, the increment in volatile concentration in brown algae could be explained by the existence of
an environmental control (algae located in the upper-intertidal area, where desiccation and herbivory are intense and could produce more volatiles; Hay 1996) and by
the cellular structure (volatile compounds may be concentrated in the outer meristem; Tugwell and Branch 1989).
5 Volatiles in the Aquatic Marine Ecosystem: Ethylene and Related Plant Hormones…