Abietoid seed fatty acid composition—A review of the genera Abies, Cedrus, Hesperopeuce, Keteleeria, Pseudolarix, and Tsuga and preliminary inferences on the taxonomy of Pinaceae

Abstract

The seed fatty acid (FA) compositions of Abietoids (Abies, Cedrus, Hesperopeuce, Keteleeria, Pseudolarix, and Tsuga) are reviewed in the present study in conclusion to our survey of Pinaceae seed FA compositions. Many unpublished data are given. Abietoids and Pinoids (Pinus, Larix, Picea, and Pseudotsuga)-constituting the family Pinaceae-are united by the presence of several delta5-olefinic acids, taxoleic (5,9-18:2), pinolenic (5,9,12-18:3), coniferonic (5,9,12,15-1 8:4), keteleeronic (5,11-20:2), and sciadonic (5,11,14-20:3) acids, and of 14-methyl hexadecanoic (anteiso-17:0) acid. These acids seldom occur in angiosperm seeds. The proportions of individual delta5-olefinic acids, however, differ between Pinoids and Abietoids. In the first group, pinolenic acid is much greater than taxoleic acid, whereas in the second group, pinolenic acid is greater than or equal to taxoleic acid. Moreover, taxoleic acid in Abietoids is much greater than taxoleic acid in Pinoids, an apparent limit between the two subfamilies being about 4.5% of that acid relative to total FA. Tsuga spp. appear to be a major exception, as their seed FA compositions are much like those of species from the Pinoid group. In this respect, Hesperopeuce mertensiana, also known as Tsuga mertensiana, has little in common with Abietoids and fits the general FA pattern of Pinoids well. Tsuga spp. and H. mertensiana, from their seed FA compositions, should perhaps be separated from the Abietoid group and their taxonomic position revised. It is suggested that a "Tsugoid" subfamily be created, with seed FA in compliance with the Pinoid pattern and other botanical and immunological criteria of the Abietoid type. All Pinaceae genera, with the exception of Pinus, are quite homogeneous when considering their overall seed FA compositions, including delta5-olefinic acids. In all cases but one (Pinus), variations from one species to another inside a given genus are of small amplitude. Pinus spp., on the other hand, have highly variable levels of delta5-olefinic acids in their FA compositions, particularly when sections (e.g., Cembroides vs. Pinus sections) or subsections (e.g., Flexiles and Cembrae subsections from the section Strobus) are compared, although they show qualitatively the same FA patterns characteristic of Pinoids. Multicomponent analysis of Abietoid seed FA allowed grouping of individual species into genera that coincide with the same genera otherwise characterized by more classical botanical criteria. Our studies exemplify how seed FA compositions, particularly owing to the presence of delta5-olefinic acids, may be useful in sustaining and adding some precision to existing taxonomy of the major family of gymnosperms, Pinaceae.

Structures, practical sources (gymnosperm seeds), gas-liquid chromatographic data (equivalent chain lengths), and mass spectrometric characteristics of all-cis Δ5-olefinic acids

“…On the contrary, they are the rule. This was observed in earlier and more recent systematic studies of gymnosperm leaf [28,29] and seed lipids [30], and for the latter, extended to practically all species analysed so far (approximately 170 species analysed by author Wolff and co-workers [26,27,[31][32][33][34][35][36][37][38][39][40][41][42][43][44][45][46]). They also occur in wood [47][48][49][50][51][52] lipids, but the number of species analysed for these tissues is much more limited.…”

“…This profile may be used as a chemometric means for the taxonomy of conifer families and genera [33][34][35][44][45][46], that generally coincide with the same taxa characterised by botanical criteria. Though of apparent academic interest, this feature has practical implications in that it allows prediction of species in which a given category of ∆5-UPIFA is likely to be present, but unfortunately not systematically prediction of its abundance.…”

“…or cedar (Cedrus spp.) seeds can also be used, as they may contain up to 9% of taxoleic acid [46]. Surprisingly, the other genus of the Taxaceae family, Torreya, is almost devoid of taxoleic acid [36].…”

Characteristics of Lipid Fatty Acids in Calli of Two Geographic Populations of Larix gmelinii

“…In nongreen plant organs, such as seeds and roots, polyunsaturated FAs (PUFAs) are formed by ω 6 ( Fad 2 ) and ω 3 ( Fad 3 ) acyl-lipid desaturases of microsomal membranes [9,10]. PUFAs with an irregular double bond position were identified in the lipids of seeds and photosynthetic tissues of coniferous trees [11][12][13], Ranunculaceae seeds [14], and lower plants, such as mosses and ferns [15]; and ∆ 5 -acyl-lipid desaturase is involved in the biosynthesis of these PUFAs [5,16]. Several FAs are used as substrates for this biosynthesis.…”

“…Several FAs are used as substrates for this biosynthesis. Thus, oleic and cis -vaccenic acids are converted into dienoic acids, that is, ë18:2 ∆ 5,9 and ë18:1 ∆ 5,11 acids, respectively, while linoleic and di-homo-linoleic acids are converted into trienoic acids, ë18:3 ∆ 5,9,12 and ë20:3 ∆ 5,11,14 acids, respectively [13,17]. The ∆ 5 -unsaturated FAs with an irregular double-bond position, such as ë18:2 ∆ 5,9 (taxoleic), ë18:3 ∆ 5,9,12 (pinolenic), C 18:4 ∆ 5,9,12,15 (coniferonic), ë20:3 ∆ 5,11,14 (sciadonic), and others [12,13], were identified in the FA composition of lipids isolated from the seeds of various pine species and other coniferous plants.…”