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Gymnosperm Pollination #2From: Biological Science. Scott Freeman. 3rd ed. Pearson Education Inc., 2008.

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Gymnosperm Pollination #3

http://onnaturemagazine.com/field-trip-coniferous-trees.html

Field Trip: Coniferous treesby Dan Schneider and Peter Pautler

Confined, for the most part, to habitats shaped by cold, dry, windy climates, coniferous trees dominate the enormous northern boreal forest, a region that blankets 11 percent of the earth’s surface. North of Ontario’s Great Lakes, this vast coniferous forest occupies 75 million hectares, nearly half of the land mass of the province. Pines, hemlocks and eastern white-cedars thrive in the mixed-forest region, which extends from Lake Superior west and east to the Manitoba and Quebec borders, respectively, and south to the deciduous forest zone along Lakes Ontario and Erie.

All of Ontario’s 12 coniferous trees and three shrubs retain their narrow needle- or scale-like leaves beyond one growing season, except the tamarack (see “The deciduous coniferous tree,” opposite page). Red pine needles may remain on the tree for three years; the needles of balsam fir may last up to seven years. Because conifers do not grow new leaves each spring, these species are able to conserve energy and scarce resources. Moreover, photosynthesis can begin with the first sign of spring and continue well into autumn, even at temperatures as low as –7 C.Conifers have evolved so as to maximize a brief growing season and withstand harsh winters. To prevent desiccation, the narrow or flat leaves of coniferous species expose minimal surface area to the dry Arctic winds. A thick, transparent cuticle envelops the needles, preventing moisture loss year-round.

Coniferous trees have descended from an ancient lineage of plants – the gymnosperms (the term derives from the Greek word meaning “naked seeds”). These trees are cone bearers and most grow two types of cones. Male cones release copious amounts of pollen, which winds carry to the exposed ovules on the scales of the larger, female cones. After fertilization the seeds mature as the scales grow tightly together, forming the familiar looking cones. In spring the scales loosen and, with a gentle breeze, the winged seeds are released and twirl to a suitable site for germination. For some species, such as the jack pine, only the intense heat from a fire frees the seeds.

Use these tips to identify coniferous trees: Pines and larches have needles in clusters of two, three, five or more. Firs and hemlocks have flat, single needles, sometimes with a slender leaf-stalk joining the main needle to the branch, and sometimes without one. The needles of spruces have edges. Junipers and cedars have leaves composed of overlapping scales.

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RED PINE (PINUS RESINOSA)Red pine reaches 25 metres in height, has two long (10–16 cm) needles per cluster and reddish or pinkish scaly bark. This species grows in areas of low soil fertility, from Lake Ontario and southern Lake Huron north to Lake Nipigon and Lake of the Woods. With its tall, straight trunk, red pine was used for the masts of British ships during colonial times.

EASTERN HEMLOCK (TSUGA CANADENSIS)The needles of eastern hemlock are blunt and flat with a narrow leaf stalk joining the needle to the branch. This species can be found in cool, moist areas throughout southern Ontario to just north of Lake Huron and along the Minnesota border between Lake Superior and Manitoba. Deer often overwinter in the shallow surface snow beneath the horizontal branches of hemlocks, the dense needles of which catch and hold most of the snowfall.

EASTERN WHITE-CEDAR (THUJA OCCIDENTALIS)Eastern white-cedar has flattened, scale-like leaves and tiny, one-centimetre-long cones with leathery scales. Reaching heights of about 15 metres, this species grows in both wet and dry sites throughout Ontario, except in the extreme north and northwest. Eastern white-cedars, some several hundred years old, have been discovered growing out of cliff faces in southern Ontario. The oldest living cedar in Ontario is an astonishing 1,320 years old.

RED SPRUCE (PICEA RUBENS)Red spruce has four-sided, yellowish green, 10- to 16-millimetre-long needles and cones three to five centimetres long. Its range in Ontario is limited to the Canadian Shield in the Algonquin Provincial Park area, Lake Nipissing, extreme eastern Ontario and near Parry Sound on Georgian Bay, all moist, upland areas. Red spruce is the provincial tree of Nova Scotia.

BALSAM FIR (ABIES BALSAMEA)The needles of the balsam fir are fl at and blunt with no narrow leaf stalk, and the top of the tree tapers gradually to a distinctive point. Able to thrive in a variety of soils from Lake Ontario north to near Hudson Bay, balsam fir is a popular Christmas tree because its needles remain on the branch long after cutting.

WHITE SPRUCE (PICEA GLAUCA)The most widespread tree in Canada, the white spruce has four-sided, bluish green, 15- to 22-millimetre-long needles and cones three to six centimetres long. Its bark is pink when freshly exposed. This tree grows in a variety of habitats from the southern limit of the Canadian Shield, Lake Simcoe and the Bruce Peninsula north to Hudson Bay. Native people often used the springy boughs for bedding.

JACK PINE (PINUS BANKSIANA)Jack pine is a small conifer with two very short (2-4 cm) needles in a cluster. This tree is found mostly in areas disturbed by fire or logging, and ranges from Georgian Bay north, extending nearly to Hudson Bay. The cones of the jack pine are tightly sealed by resin and remain on the

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tree for as long as 25 years. The cones open only when subjected to fire or on the infrequent occasions when temperatures rise above 47 C in direct sunlight.

BLACK SPRUCE (PICEA MARIANA)Restricted to boggy areas in the southern parts of its range, which extends from Lake Ontario and southern Lake Huron north to Hudson Bay, black spruce has four-sided, grayish green, eight- to 15-millimetre-long needles and cones two to three centimetres long. It is Ontario’s most common tree and is the provincial tree of Newfoundland and Labrador.

EASTERN WHITE PINE (PINUS STROBUS)Eastern white pine is Ontario’s tallest tree – reaching heights of 30 metres or higher – and the only conifer of the 12 native to the province that possesses five needles per cluster. This majestic tree is found throughout southern Ontario and north to Lake of the Woods and along northern Lake Superior. Britain could claim victory over Napoleon’s navy thanks to our eastern white pines, which made superior masts for sailing ships. In colonial times, white pines were reserved specifically for the use of Britain’s Royal Navy by decree of the king.

PITCH PINE (PINUS RIGIDA)Reaching 20 metres in height, pitch pine is a smaller tree and Ontario’s only conifer with three needles per cluster. Its range here is restricted to the eastern end of Lake Ontario along the St. Lawrence River. Pitch pine is well adapted to forest fires. Once scorched, the dormant buds in its burned trunk begin to grow into new, green branches.

EASTERN RED CEDAR (JUNIPERUS VIRGINIANA)A small tree, growing only about 10 metres high, eastern red cedar has both scale-like and needle-like leaves, with dark blue seed cones that resemble berries. This species flourishes in poor soils in rocky and sandy areas near lakes Ontario and Huron and on the Canadian Shield from Georgian Bay to the Ottawa area. This tree is often one of the first trees to become established in old pastures and former farm fields.

TAMARACK (Larix laricina)Tamarack is Ontario’s only deciduous conifer and has many short needles in a cluster. This tree inhabits cold, wet, poorly drained sites such as bogs and muskeg. Its range extends throughout Ontario except along stretches of the Hudson Bay coast. The tamarack is a particularly stunning tree in autumn when its needles turn gold before falling, usually long after other deciduous trees have lost their leaves.

THE DECIDUOUS CONIFEROUS TREEThe beautiful tamarack tree (also called American larch) is an anomaly among Ontario’s coniferous trees, as it is our only native species of conifer that is deciduous. Tamaracks and other larches are cone-bearing trees that lose and re-grow their needles each year.This would appear to be an odd survival strategy. Why, when the development of tough, cold- and drought-resistant leaves has given most conifers a competitive edge in cold, dry climates,

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are larches deciduous? More intriguing still, these tough trees form the treeline in Asia (Siberian larch) and are often found in mountainous regions (Alpine larch).In these extreme climates, even conifer leaves might freeze in winter. So, rather than investing energy into thick, freeze-resistant leaves, tamaracks expend less energy producing thin, soft needles. Further, tamarack needles are usually the first leaves of all our trees to appear in spring and are among the last to fall in autumn, extending the annual photosynthetic period of larches beyond that of most deciduous trees.

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Gymnosperm Pollination #4

Go to: http://www.youtube.com/watch?v=D9byVQxvMXs and watch the video

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Gymnosperm Pollination #5From: Eaglesham, B. (2003, March). Flower Power: Odyssey Adventures in Science, 12, 6-7.

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Seed Germination #1From: Plant Physiological Ecology. Hans Lambers, F. Stuart Chapin III, Thijs L. Pons. Springer-Verlag, 1998.

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Seed Germination #2From: Growing Seeds! Linda D. Harris. Fulcrum Publishing, 1999.

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