Sugar Pine

''Pinus lambertiana'' (commonly known as the sugar pine or sugar cone pine) is the tallest and most massive pine tree, and has the longest cones of any conifer. The species name ''lambertiana'' was given by the Scottish botanist David Douglas, who named the tree in honour of the English botanist, Aylmer Bourke Lambert. It is native to coastal and inland mountain areas along the Pacific coast of North America, as far north as Oregon and as far south as Baja California in Mexico.

Description

Growth

The sugar pine is the tallest and largest ''Pinus'' species, commonly growing to tall, exceptionally to tall, with a trunk diameter of , exceptionally . The tallest recorded specimen is tall, is located in Yosemite National Park, and was discovered in 2015. The second tallest recorded was "Yosemite Giant", an tall specimen in Yosemite National Park, which died from a bark beetle attack in 2007. The tallest known living specimens today grow in southern Oregon and Yosemite National Park: one in Umpqua National Forest is tall and another in Siskiyou National Forest is tall. Yosemite National Park also has the third tallest, measured to tall as of June 2013; the Rim Fire affected this specimen, but it survived.

The bark of ''Pinus lambertiana'' ranges from brown to purple in color and is thick. The upper branches can reach out over . Like all members of the white pine group (''Pinus'' subgenus ''Strobus''), the leaves ("needles") grow in fascicles ("bundles") of five, with a deciduous sheath. They are long. Sugar pine is notable for having the longest cones of any conifer, mostly long, exceptionally to long (although the cones of the Coulter pine are more massive); their unripe weight of makes them perilous projectiles when chewed off by squirrels. The seeds are long, with a long wing that aids their dispersal by wind. Sugar pine never grows in pure stands, always in a mixed forest and is shade tolerant in youth.

Distribution

The sugar pine occurs in the mountains of Oregon and California in the Western United States, and Baja California in northwestern Mexico; specifically the Cascade Range, Sierra Nevada, Coast Ranges, and Sierra San Pedro Martir. It is generally more abundant towards the south and can be found growing in elevations between above sea level.

Genome

The massive 31 gigabase mega-genome of sugar pine has been sequenced in 2016 by the large PineRefSeq consortium. This makes the genome one of the largest sequenced and assembled so far.

The transposable elements that make up the megagenome are linked to the evolutionary change of the sugar pine. The sugar pine contains extended regions of non-coding DNA, most of which is derived from transposable elements. The genome of the sugar pine represents one extreme in all plants, with a stable diploid genome that is expanded by the proliferation of transposable elements, in contrast to the frequent polyploidization events in angiosperms.

Embryonal growth

In late stage of embryonal development, the sugar pine embryo changes from a smooth and narrow paraboloid to a less symmetric structure. This configuration is caused by a transverse orientation of division planes in the upper portion of the embryo axis. The root initial zone is established, and the epicotyl develops as an anlage flanked by regions of that define the cotyledonary buttresses. At this stage, the embryo is composed of the suspensor, root initials and root cap region, hypocotyl-shoot axis, and the epicotyl. The upper (distal) portion of the embryo, which gives rise to the cotyledons and the epicotyl, is considered to be the shoot apex.

Shoot apex

The apex has the following four zones:
#The apical initials produce all cells of the shoot apex through cell division. It is located at the top of the meristem and the cells are larger in size compared to other cells on the surface layer.
#The central mother cell generates the rib meristem and the inner layers of the peripheral tissue zone through cell division. It presents a typical gymnosperm appearance and is characterized by cell expansion and unusual mitosis that occurs in the central region. The rate of mitosis increases on its outer edge.
#The peripheral tissue zone consists of two layers of cells that are characterized by dense cytoplasm and mitosis of high frequency.
#Lastly, the rib meristem is a regular arrangement of vertical files of cells which mature into the pith of the axis.

Etymology

Naturalist John Muir considered sugar pine to be the "king of the conifers". The common name comes from the sweet resin, which Native Americans used as a sweetener. John Muir found it preferable to maple sugar