Site author Richard Steane
The BioTopics website gives access to interactive resource material, developed to support the learning and teaching of Biology at a variety of levels.

Apples, sexual and asexual reproduction

Apples are classified by botanists as pomes: "accessory fruits".
The part which is eaten is produced from the end of the flower stalk - "the floral cup". The inner section - the core, containing pips (seeds) - is actually the true fruit.
Many varieties of apples exist, and there are categories such as eating (dessert) apples, cooking apples, as well as cider apples.

See if you can name some apple varieties:
> crab apples, Cox's, Granny Smith, Bramley, golden delicious, discovery, gala etc

Although apples are fruits and they contain seeds, new apple trees are not normally produced by growing on from seeds.

In fact apple varieties are usually propagated by transferring buds or shoots from established varieties onto other trees which are not allowed to produce their own fruit. This is called grafting, and the fruiting variety is called the scion. The other variety of apple is called the rootstock. Often the rootstock influences the growth of the tree above. There are some varieties (dwarfing rootstocks) which cause the tree to remain at a manageable height for easy picking rather than growing into a large tree where ladders are required.

Not all apples are edible; crab apples are extremely sour, but can be turned into crab apple jelly when cooked with lots of sugar.

Crab apples grow wild in lots of places, but they have been cultivated for the beauty of the trees in flower. Crab apples are probably the original source from which cultivated apple varieties have been developed, and are sometimes used to provide rootstock.

Pollination and fertilisation

Apples will not develop on an apple tree unless the tree is pollinated. This is normally carried out by bees or bumble bees, not by wind as in some crops. Bees visit the flowers (apple blossom) in order to collect the sugary liquid nectar, and pollen from the male parts (stamens, consisting of anthers held up by filaments) attaches to their body by accident. When they visit other flowers, some of this pollen rubs off onto the stigma, the receptive surface of the female parts. If the pollen is of the correct variety, it will grow a tube down the style and into the ovary where it releases a pair of nuclei, one of which fuses with the nucleus of the ovule (female cell). This is fertilisation.

In fact bees will clean off some of the pollen that sticks to their body, collect it into "pollen baskets" on their hind legs and take it back to the hive to be stored and eaten. It is said to contain protein.

Some apple varieties need to receive pollen from another variety (cross-pollination), although some can be self-pollinated. If there is not an appropriate variety in the area, fewer apples will be produced.

Why do fruit growers place bee hives on the edges of their orchards?
> To ensure pollination of flowers by bees, to maximise fruit production
> (secondary reason) to get honey which will have a distinctive flavour from the fruit tree blossom

Why do fruit growers sometimes plant a few trees of different apple varieties on the edge of their orchards?
> As a pollen source - to ensure cross-pollination of flowers to maximise fruit production

Why are bees more important as pollinators than other insects?
> They have bristles on their body which catch pollen
> They systematically visit the same sort/species of flowers so they will pollinate more effectively

Case history - Cox's Orange Pippin

The word pippin means a tree grown from an apple pip or seed. Arising as a result of sexual reproduction, such plants or seedlings will show some variation from (the variety of) their parents, which may not be known for certain. It is only when the seedling has grown into a mature tree that it will flower and bear fruit. Sometimes the resulting apples will be better in some way or, just as likely, worse in other ways. Cox's Orange Pippin was found to have a good flavour as well as extended keeping qualities.

In about 1825 Richard Cox planted two seeds from a Ribston Pippin which he is thought to have pollinated with a Blenheim Orange. Some years later, when the trees had fruited, he realised they had potential. These were later to be known as the Cox's Orange Pippin and Cox's Pomona. In 1836 he supplied some grafts to a local nurseryman who sold the first trees in 1840. The varieties remained nationally unknown until Charles Turner of the Royal Nurseries, Slough, started to promote them in 1850. The original Cox's Orange Pippin tree is thought to have blown down in a gale in 1911, but two sixty year old trees were seen still standing in the garden in 1933, presumably direct grafts from the original.

These apples come from two varieties which are thought to be the parents of the original Cox's Orange Pippin.

Are apple seedlings the result of sexual or asexual reproduction?
>sexual - there are both male and female parts in the flower, and a male nucleus from pollen must fuse with a female nucleus in the ovule

Why was it relatively certain that one parent of the Cox's Orange Pippin was a Ribston Pippin?
> That was the variety of apple on one of the original trees in his garden.

Why was it relatively less certain that the other parent of the Cox's Orange Pippin was a Blenheim Orange?
> This must have provided the pollen, which could have come (by bee!) from any other tree in the area

It must be said that nowadays most people do not raise seedlings on the offchance that they might be worthwhile. Instead they tend to buy young plants of known varieties which will grow to a certain size and hopefully bear fruit with known characteristics. But there are plenty of amateur gardeners who enjoy this endeavour.
There are also many plant research institutes worldwide who are carrying out controlled crosses and developing new varieties and growing techniques to suit the market today.

Web references

Apples: British to the Core (BBC iPlayer link)
Broadcast on BBC Four, 1:25AM Fri, 24 Jun 2011
Probably no longer available, but with several useful links to clips.
Horticulturalist Chris Beardshaw uncovers the British contribution to the history of our most iconic fruit. He reveals the 'golden age', when the passion and dedication of Victorian gardeners gave us more varieties than anywhere else in the world. Chris also finds out how the remarkable ingenuity of a small group of 20th century British scientists helped create the modern mass market apple.

Cox's Orange Pippin From Wikipedia, the free encyclopedia

Cox's Orange Pippin apple
subtitled as the comprehensive resource for apples and orchards, this site has a wider appeal than its title implies, but like this page it draws its inspiration from a popular fruit!

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