![]() ![]() As a group they are also tolerant of dry conditions, in particular seasonally dry conditions. lodgepole pine in the western US, Swiss pine in the Alps). Many are tolerant of extreme cold and can live at upper elevations (e.g. They are particularly abundant in mountain habitats, as are other conifers. Pines are primarily distributed in the northern hemisphere, and primarily occur at latitudes north of the tropics. Two other features are significant to the matter and energy relations of pines (and other evergreen conifers): (1) their evergreen life-style allows for year-round photosynthesis if conditions are appropriate, (2) leaves with longer lifespans are potentially beneficial to nutrient status because absorbed nutrients have a longer residence time in the plant. In spite of the fact that individual leaves of pines and most other conifers have a much smaller surface area than broad-leaved plants, the total leaf area per branch may exceed that of broad-leaved plants because there often are lots of needles. The shape of of conifer leaves (cylindrical), coupled with a thick cuticle reduces water loss but also slows carbon dioxide acquisition when compared to a broad-leafed plant with a much greater surface area to volume ratio and thinner cuticles. Pines are typical photosynthetic autotrophs, acquiring carbon dioxide from the air and converting it into carbohydrates to be converted back to carbon dioxide in cellular respiration (yielding ATP) or to be used to synthesize biomolecules. Most species of pines have seeds that are winged and dispersed by the wind, but a few species have adapted to dispersal by birds (see below). Significant to the story is that pines, like ferns and mosses and also like wheat and aspen, do produce spores, i.e. ![]() Both these entities are packaged in a seed coat constructed of cells derived from the tree that produced the cone. Pines reproduce by seed, a multigenerational unit, which in the case of conifers contains both an embryo and the female gametophyte that produced the egg that was fertilized to form the zygote that grew into the embryo. While some pines and most other conifers (spruces, firs and douglas fir) produce a ‘Christmas tree’ form, with triangular crowns that are usually quite steep, pines often have a broader base and less steep sides. ![]() They are the largest genus within the phylum, containing over 100 of the approximately 600 species in the group.Īlmost all pines are typical woody trees (a few might be considered large shrubs) with a branched, dendritic form that through time and with secondary growth produces the typical form that we recognize as trees. ![]() Conifers are by far the most commonly encountered gymnosperm and pines (the genus Pinus) are probably the most frequently encountered conifer. they are not a group unified by their evolutionary history. cycads and ginkgo) are grouped as gymnosperms but most workers do NOT consider this to be a sound phylogenetic entity, i.e. Sometimes conifers and the other seed plants without flowers (e.g. They have vascular tissue and produce seeds but do not produce flowers. Pines belong to a distinct phylogenetic entity, the conifers, a group that is usually placed at the phylum level (Pinophyta). Most pines are distinct from other evergreens by the fact that their needles are longer, often 10 cm long or more, and they almost always occur in clusters (bundles), typically in groups of two, three or five with the number of needles per group being a useful identification aid. Pine trees should be familiar to just about everyone although some might confuse them with other evergreen trees. ![]()
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