Tree Flowering and Reproduction

Tree Flowering and Reproduction
by John Calyx

Wind-pollinated plants produce vast amounts of pollen because most of it falls by the way and does not reach the flower and pistil. When the pine or spruce are in bloom huge clouds of pollen are carried by the wind and a layer of yellow dust covers the surface of nearby puddles and ponds. The pollen grains of most wind-pollinated trees have air sacs which make it possible for them to be carried as much as ten to twenty kilometres.

The commonest types are Spike, including Catkin – petalless flowers attached directly to an unbranched stem either erect or pendulous (alder, birch); Raceme similar to spike, but each flower having a separate stalk or pedicel (bird cherry); Panicle – a branched flowering stem bearing several flowers (horse-chestnut); Umbel – several stalked flowers arising together and forming a flattened or convex head (cornelian cherry); Dichasium – a branched inflorescence, the branches of which terminate in a flower and two lateral stems, each one of which may also terminate in a flower and further lateral branches; Corymb – similar to a raceme, but the lower flowers have longer pedicels (stalks) bringing all the flowers up together to form a flattened or convex head (lime).

Plant Stuff

When the anther is ripe it bursts and releases the pollen grains, i.e. the actual male cells which are of microscopic dimensions. The pistil is formed of an ovary, containing the ovules, and a stigma, with either a sticky or a hairy surface, to trap the pollen grains. Quite often, the stigma is attached to the ovary by a stalk or style which may be very short, or long and slender.

The quantity of seeds produced depends not only on the number of flowers but also on the weather conditions during the period of flowering and seed maturation. Frosts or rainy weather can prevent pollination or fertilization so that few or no seeds are set. Furthermore, some trees do not bear a good crop of seeds every year, for this requires a large quantity of reserve food supplies which the tree must build up over a period of time.

Trees producing large seeds and thus requiring larger food reserves (oak, beech, walnut) may only bear them at two to four year intervals. Again, in harsher climates, e.g. in high mountain regions or in the north, where a longer time is required to accumulate the necessary food stores, the seed-bearing intervals may be longer.

Insect-pollinated trees such as the lime, black locust or cherry blossom later when the crown comes into leaf.

About the Author:

Permalink to ‘Tree Flowering and Reproduction’

Click here for more information about 'Tree Flowering and Reproduction'.

Category: Plant Stuff

Leave a Reply

%d bloggers like this: