Pinaceae

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Pinaceae
Glacier-Lyman-Tamarack.jpg
Larix (golden), Abies (center foreground) and Pinus (right foreground)
Scientific classification e
Kingdom: Plantae
Division: Pinophyta
Class: Pinopsida
Order: Pinales
Family: Pinaceae
Lindley 1836.
Genera

Subfamily Pinoideae
    Pinus - pines (about 115 species)
Subfamily Piceoideae
    Picea - spruces (about 35 species)
Subfamily Laricoideae
    Cathaya (one species)
    Larix - larches (about 14 species)
    Pseudotsuga - douglas-firs (five species)
Subfamily Abietoideae
    Pseudolarix - golden larch (one species)
    Abies - firs (about 50 species)
    Cedrus - cedars (two to four species)
    Keteleeria (three species)
    Nothotsuga (one species)
    Tsuga - hemlock (nine species)

The Pinaceae (pine family) are trees or shrubs, including many of the well-known conifers of commercial importance such as cedars, firs, hemlocks, larches, pines, and spruces. The family is included in the order Pinales, formerly known as Coniferales. Pinaceae are supported as monophyletic by their protein-type sieve cell plastids, pattern of proembryogeny, and lack of bioflavonoids. They are the largest extant conifer family in species diversity, with between 220 and 250 species (depending on taxonomic opinion) in 11 genera, and the second-largest (after Cupressaceae) in geographical range, found in most of the Northern Hemisphere with the majority of the species in temperate climates, but ranging from subarctic to tropical. The family often forms the dominant component of boreal, coastal, and montane forests. One species just crosses the equator in Southeast Asia. Major centres of diversity are found in the mountains of southwest China, Mexico, central Japan, and California.

They are trees (rarely shrubs) growing from 2 to 100 m tall, mostly evergreen (except Larix and Pseudolarix, deciduous), resinous, monoecious, with subopposite or whorled branches, and spirally arranged, linear (needle-like) leaves. The female cones are large and usually woody, 2-60 cm long, with numerous spirally arranged scales, and two winged seeds on each scale. The male cones are small, 0.5-6 cm long, and fall soon after pollination; pollen dispersal is by wind. Seed dispersal is mostly by wind, but some species have large seeds with reduced wings, and are dispersed by birds. Analysis of Pinaceae cones reveals how selective pressure has shaped the evolution of variable cone size and function throughout the family. Variation in cone size in the family has likely resulted from the variation of seed dispersal mechanisms available in their environments over time. All Pinaceae with seeds weighing less than 90 mg are seemingly adapted for wind dispersal. Pines having seeds larger than 100 mg are more likely to have benefited from adaptations that promote animal dispersal, particularly by birds.[1] Pinaceae that persist in areas where tree squirrels are abundant do not seem to have evolved adaptations for bird dispersal. The embryos of Pinaceae have three to 24 cotyledons.

Boreal conifers have many adaptions for winter. The narrow conical shape of northern conifers, and their downward-drooping limbs help them shed snow, and many of them seasonally alter their biochemistry to make them more resistant to freezing, called "hardening".

Classification[edit]

Classification of the subfamilies and genera of Pinaceae has been subject to debate in the past. Pinaceae ecology, morphology, and history have all been used as the basis for methods of analyses of the family. An 1891 publication divided the family into two subfamiles, using the number and position of resin canals in the primary vascular region of the young taproot as the primary consideration. In a 1910 publication, the family was divided into two tribes based on the occurrence and type of long-short shoot dimorphism. A more recent classification divided the subfamilies and genera based on the consideration of features of ovulate cone anatomy among extant and fossil members of the family. Below is an example of how the morphology has been used to classify Pinaceae. The 11 genera are divided into four subfamilies, based on the cone, seed, and leaf morphology:[2]

  1. Subfamily Pinoideae (Pinus): Cones biennial, rarely triennial, with each year's scale growth distinct, forming an umbo on each scale, cone scale base broad, concealing the seeds fully from abaxial view, seed without resin vesicles, seed wing holding the seed in a pair of claws, leaves with primary stomatal bands adaxial (above the xylem) or equally on both surfaces
  2. Subfamily Piceoideae (Picea): Cones annual, without a distinct umbo, cone scale base broad, concealing the seeds fully from abaxial view, seed without resin vesicles, blackish, seed wing holding the seed loosely in a cup, leaves with primary stomatal bands adaxial (above the xylem) or equally on both surfaces
  3. Subfamily Laricoideae (Larix, Cathaya, Pseudotsuga): Cones annual, without a distinct umbo, cone scale base broad, concealing the seeds fully from abaxial view, seed without resin vesicles, whitish, seed wing holding the seed tightly in a cup, leaves with primary stomatal bands abaxial (below the phloem vessels) only
  4. Subfamily Abietoideae (Abies, Cedrus, Pseudolarix, Keteleeria, Nothotsuga, Tsuga): Cones annual, without a distinct umbo, cone scale base narrow, with the seeds partly visible in abaxial view, seed with resin vesicles, seed wing holding the seed tightly in a cup, leaves with primary stomatal bands abaxial (below the phloem vessels) only

References[edit]

  1. ^ Benkman, C. W. 1995. Wind dispersal capacity of pine seeds and the evolution of different seed dispersal modes in pines. Oikos. 73:221-224.
  2. ^ Price, R. A., J. Olsen-Stojkovich, and J. M. Lowenstein. 1987. Relationships among the genera of Pinaceae: an immunological comparison. Syst. Bot. 12:91–97.

Further reading[edit]

  • Behnke, H. D. 1974. Sieve element plastids of Gymnospermae: Their ultra structure and relation to systematics. Pl. Syst. Evol. 123:1-12.
  • Farjon, A. 1998. World Checklist and Bibliography of Conifers. Royal Botanic Gardens, Kew. 300 p. ISBN 1-900347-54-7.
  • Greene, D. F. and Johnson, E.A. 1990. The dispersal of winged fruits and seeds differing in autorotative behavior. - Can. J. Bot. 68: 2693-2697.
  • Liston, A., Gernandt, D. S., Vining, T. F., Campbell, C. S. & Pinero, D. 2003. Molecular phylogeny of Pinaceae and Pinus. Pp. 107-114 in: Mill, R. R. (ed.). Proceedings of the International Conifer Conference. International Society for Horticultural Science, Brugge. [Acta Hort. No. 615.]
  • Zsolt Debreczy, Istvan Racz (2012). Kathy Musial, ed. Conifers Around the World (1st ed.). DendroPress. p. 1089. ISBN 9632190610. 

External links[edit]