Biology Reference
In-Depth Information
(2001b) and found that in general, amino acid concentration appears to be
much higher in
phrygana
than in temperate systems (Petanidou et al., 2006).
Among all amino acids detected in the nectars of
phrygana
, the most
prevalent was phenylalanine, both in absolute content and in concentration
(Petanidou et al., 2006). Within all plant taxonomic groups, the most phenyla-
lanine-rich nectar was that of Lamiaceae, with an average phenylalanine
content of 47.2% of the total amino acids detected in all the species nectars
of the family. Almost all phenylalanine-rich plants were keystone species of
phrygana
including
Stachys cretica
,
Phlomis fruticosa
,
Satureja thymbra
,
Urginea maritima
,
Asphodelus aestivus
, and
Thapsia garganica
. In a similar
study carried out in an Israeli
batha
(i.e., a habitat that is equivalent to the
Greek
phrygana
) Dafni et al. (1988) also found extremely high proportions
of phenylalanine in the nectar of
Satureja thymbra
and
Salvia fruticosa
(71%
and 52%, respectively). The high proportion of phenylalanine therefore seems
to be characteristic of the phryganic plants in the Mediterranean region, as
this amino acid was not detected at high levels in the nectars of other species
from temperate and tropical systems (Baker & Baker, 1978, 1982, 1986;
Gardener & Gillman, 2001b).
Until the early commencement of flower senescence, most if not all of
the amino acids in nectar originate from phloem sap (Fahn, 1988). After the
beginning of senescence, amino acids increasingly result from nectary
breakdown (Petanidou et al., 1996). This type of proteolytic breakdown may
be limited by sugar concentration, as found in the nectar of the Mediterra-
nean species
Capparis spinosa
(Eisikowitch et al., 1986; Petanidou et al.,
1996), which implies that sometimes nectaries may restrict amino acid flow
through the nectar.
2.1.3
Minerals in floral nectars
Nectars have been found to contain K, P, Mg, Na, S, Ca, and many other miner-
als, with potassium prevailing in most cases (Waller et al., 1972; Kearns &
Inouye, 1993; Liu et al., 2004; Dafni et al., 2005). No studies on mineral con-
tent have been performed specifically on nectars from the Mediterranean, but
it is entirely probable that similar contents and concentrations are found in
this region.
2.1.4
Secondary compounds
Apart from the main ingredients of sugars and amino acids, nectars often
contain specific constituents or secondary compounds that may affect the
