Conifers
David Beeson
Conifers are a magnificent group of gymnosperm plants that produce seeds without the need of fruit or flowers. They include some incredible trees such as the Giant Sequoias of North America that can grow over 110 m tall.
Conifers do not have flowers that a child would recognise. Instead they bear male and female cones, with the seeds being released eventually from the female cone.
These plants belong to a group called the Gymnosperms, meaning: naked seeds as they are not within a fruit but open to the air when the female cone is mature.
Gymnosperms include our own conifers, plus cycads and various odds-and-sods such as the Ginko tree.
These plants hit their distribution peak in the dino-era and have since been overshadowed in many parts of the world by the flowering trees, although the conifers still hold sway in many colder regions.
You will immediately think, why have they lost ground in that way? I would suggest that the thin, needle-like leaves are less well designed (adapted) to capture sunlight energy but especially their water transport system is far below par. Their xylem tubes (woody tissues mainly involved in water transport)have many cross walls with only holes to allow the movement of water. The Angiosperms, flowering plants, have true tubes in their xylem with, consequently, minimal resistance to water flow.
Hence, conifer wood (softwood) has a different structure to Angiosperm wood (hard wood). Mainly small,cross-walled xylem tracheids in conifers, mainly wide xylem vessels in the Angiosperms.
Water movement in conifers is around 1mm per second. In Angiosperms it is 11mm per second. Ten times better, allowing them to cope in a wider range of habitats.
Spring is the time to search out the male cones. They are at the growing tips and you should spot clusters of pollen filled bags and eventually they will burst to liberate clouds of air-carried grains. (One source of spring hay fever.) To give the grains lift they have two air bladders, so spread long distances.
Below: single pine pollen grain. Microscopic image showing the two air bladders.
The female cones on the Scots Pine (Pinus sylvestris) are about 3cm long and it is, in fact, already a year old. Once the egg cell is fertilized it needs to grow for another full year before the seeds are released.
Locally squirrels and crossbills feed extensively on the pine seeds. Both species are to be seen in Harewood where there are exotic Douglas firs.
(With all plants the reproductive system is not as straightforward as in animals. Real botanists need to look up their breeding strategy when feeling bright and alert! It isn’t what you think it should be!)
Scots Pine leaves (needles) are covered on their upper surface with a waxy layer to reduce water loss, and the stomata (breathing pores) are sunk down for the same reason. Their wood is resinous in an attempt to reduce insect damage, they often grow on acidic soils (So, not many occur naturally near Andover), their bark is nutrient-poor and that ensures they are little colonised by mosses or lichens.
INTERESTING FACTS
Scots pine can live for up to 700 years. It is the only true native pine in the UK. Mature trees can grow up to 35m in height. Its bark is scaly and orange-brown in colour. Scots pine timber is one of the strongest softwoods available and is widely used in the construction industry and in joinery. It is used in the manufacture of telegraph poles, pit props, gate posts and fencing. The tree can also be tapped for resin to make turpentine. Other uses include rope made from the inner bark, tar from the roots and a dye from the cones. Dry cones can be used as kindling for fires.
Conifer trees are immense and hold the records for the world’s tallest, widest, oldest and largest trees.
Tallest: Coast redwood (Sequoia sempervirens) – 115 m
Widest: Montezuma cypress (Taxodium mucronatum) – 11.42 m
Oldest: Great Basin bristlecone pine (Pinus longaeva) – 4,700 years old
Largest: General Sherman, a giant sequoia (Sequoiadendron giganteum) – ~1487 m³
Do add the WOODLAND TRUST tree app to your smart phone. It is free and there are no adverts.
Wildlife and Ecology, the Wildlife Encyclopaedia 