Pinaceae
Pinaceae Temporal range:
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Larix (golden), Abies (central foreground) and Pinus (right foreground) | |
Scientific classification | |
Kingdom: | Plantae |
Clade: | Tracheophytes |
Clade: | Gymnospermae |
Division: | Pinophyta |
Class: | Pinopsida |
Order: | Pinales |
Family: | Pinaceae Lindley 1836 |
Genera | |
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Synonyms | |
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The Pinaceae (/pɪˈneɪsiːˌiː, -siˌaɪ/), or pine family, are conifer trees or shrubs, including many of the well-known conifers of commercial importance such as cedars, firs, hemlocks, piñons,
Description
Members of the family Pinaceae are
The female cones are large and usually woody, 2–60 centimetres (1–24 inches) long, with numerous spirally arranged scales, and two winged seeds on each scale. The male cones are small, 0.5–6 cm (1⁄4–2+1⁄4 in) 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 milligrams 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.[4] Pinaceae that persist in areas where tree squirrels are abundant do not seem to have evolved adaptations for bird dispersal.
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
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 subfamilies, 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 grouped into four subfamilies, based on the microscopical anatomy and the morphology of the cones, pollen, wood, seeds, and leaves:[5]
- Subfamily vessels) view, the seed is without resin vesicles, the seed wing holds the seed in a pair of claws, leaves have primary stomatal bands adaxial (above the xylem) or equally on both surfaces.
- Subfamily Picea): cones are annual, without a distinct umbo, the cone scale base is broad, concealing the seeds fully from abaxial view, seed is without resin vesicles, blackish, the seed wing holds the seed loosely in a cup, leaves have primary stomatal bands adaxial (above the xylem) or equally on both surfaces.
- Subfamily Larix, Pseudotsuga, and Cathaya): cones are annual, without a distinct umbo, the cone scale base is broad, concealing the seeds fully from abaxial view, the seed is without resin vesicles, whitish, the seed wing holds the seed tightly in a cup, leaves have primary stomatal bands abaxial only.
- Subfamily ): cones are annual, without a distinct umbo, the cone scale base is narrow, with the seeds partly visible in abaxial view, the seed has resin vesicles, the seed wing holds the seed tightly in a cup, leaves have primary stomatal bands abaxial only.
Phylogeny
A revised 2018 phylogeny places Cathaya as sister to the pines rather than in the Laricoidae subfamily with Larix and Pseudotsuga.
Ran et al. 2018[6] & Leslie et al. 2018[7][8] | Stull et al. 2021[9][10] | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
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Multiple molecular studies indicate that in contrast to previous classifications placing it outside the conifers, Gnetophyta may in fact be the sister group to the Pinaceae, with both lineages having diverged during the early-mid Carboniferous. This is known as the "gnepine" hypothesis.[11][12]
Evolutionary history
Pinaceae is estimated to have diverged from other conifer groups during the late
Defense mechanisms
External stresses on plants have the ability to change the structure and composition of forest ecosystems. Common external stress that Pinaceae experience are herbivore and pathogen attack which often leads to tree death.[22] In order to combat these stresses, trees need to adapt or evolve defenses against these stresses. Pinaceae have evolved a myriad of mechanical and chemical defenses, or a combination of the two, in order to protect themselves against antagonists.[23] Pinaceae have the ability to up-regulate a combination of constitutive mechanical and chemical strategies to further their defenses.[24]
Pinaceae defenses are prevalent in the bark of the trees. This part of the tree contributes a complex defensive boundary against external antagonists.[25] Constitutive and induced defenses are both found in the bark.[25][26][27]
Constitutive defenses
Constitutive defenses are typically the first line of defenses used against antagonists and can include sclerified cells, lignified periderm cells, and secondary compounds such as phenolics and resins.[28][25][26] Constitutive defenses are always expressed and offer immediate protection from invaders but could also be defeated by antagonists that have evolved adaptations to these defense mechanisms.[28][25] One of the common secondary compounds used by Pinaceae are phenolics or polyphenols. These secondary compounds are preserved in vacuoles of polyphenolic parenchyma cells (PP) in the secondary phloem.[29][27]
Induced defenses
Induced defense responses need to be activated by certain cues, such as herbivore damage or other biotic signals.[28]
A common induced defense mechanism used by Pinaceae is resins.
Active research: methyl jasmonate
The topic of defense mechanisms within family Pinaceae is a very active area of study with numerous studies being conducted. Many of these studies use methyl jasmonate (MJ) as an antagonist.[26][27][32] Methyl jasmonate is known to be able to induce defense responses in the stems of multiple Pinaceae species.[26][32] It has been found that MJ stimulated the activation of PP cells and formation of xylem traumatic resin ducts (TD). These are structures that are involved in the release of phenolics and resins, both forms of defense mechanism.[26][27]
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Close up of bishop pine cones
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Knobcone pine cone
References
- ISSN 1916-2790.
- ^ ISBN 978-1-900347-54-9.
- ^ Earle, Christopher J., ed. (2018). "Pinus merkusii". The Gymnosperm Database. Retrieved March 17, 2015.
- JSTOR 3545911.
- JSTOR 2419217.
- S2CID 52110440.
- PMID 30157290.
- )
- S2CID 232282918.
- )
- S2CID 236141481.
- PMID 29925623.
- ^ S2CID 52120430.
- S2CID 134849082.
- ^ ISSN 1058-5893.
- PMID 22491001.
- ^ S2CID 88292891.
- S2CID 54653621.
- PMID 22623610.
- S2CID 85402168.
- PMID 22988083.
- JSTOR 3072253.
- ^ S2CID 26043965.
- PMID 15998390.
- ^ a b c d Franceschi, V. R., P. Krokene, T. Krekling, and E. Christiansen. 2000. Phloem parenchyma cells are involved in local and distance defense response to fungal inoculation or bark-beetle attack in Norway spruce (Pinaceae). American Journal of Botany 87:314-326.
- ^ PMID 14704135.
- ^ PMID 17938111.
- ^ PMID 25261122.
- ^ PMID 16356912.
- ^ PMID 10718991.
- ^ PMID 16668184.
- ^ S2CID 21153303.
External links
- Arboretum de Villardebelle French Arboretum of conifers around the world
- Gymnosperm Database – Pinaceae
- Pinaceae on the web page of the Tree-of-Life project
- 40 Pine Trees From Around the World by The Spruce
- Jepson eFlora, The Jepson Herbarium, University of California, Berkeley, covers Californian species and much of western North America
- Pinaceae in Flora of North America
- Pinus in USDA Plants Database