Self-pollinating impairing cross-pollinization ? [botany]

[Externet]

Hello.

If an apple orchard is populated with half a dozen varieties to favor cross-pollinization,  and an early bee lands on tree 'variety A'  and makes its pollen distribution among the flowers of such tree...

An hour later, a second bee that had been playing with 'variety B' blossoms somewhere else arrives to the 'variety A' tree which was already visited as explained previously.  What good or effect will the second bee provide with its 'better/foreign/varied' pollen to the flowers that were already self-pollinated by the first bee ?

Having proper tree varieties around to induce optimal fruiting does not mean success because some previous self pollinization by insects may already happened ?   

An apple tree does not 'discard' a previous pollinization for a new/later arrival of better characteristics; is that correct ?.  After pollinized once, 'door' shuts off; deal is done ?

If a branch with a dozen flowers, each gets a different bee carrying one of a dozen different variety pollens, will that produce a dozen different fruits in that same branch ?

[StringJunky]

Each individual fertilization event is unique and each pollen spore will provide its own genetics. A dozen different pollen varieties on a single tree will produce that many types of crosses.

Edited February 12 by StringJunky

[sethoflagos]

4 hours ago, Externet said:

What good or effect will the second bee provide with its 'better/foreign/varied' pollen to the flowers that were already self-pollinated by the first bee ?

I'll stand to be corrected but my understanding is that apples cannot self-pollinate.

4 hours ago, Externet said:

If a branch with a dozen flowers, each gets a different bee carrying one of a dozen different variety pollens, will that produce a dozen different fruits in that same branch ?

Cultivated apple trees are cloned varieties grafted onto an appropriate root stock. All fruit on a tree is true to the grafted cultivar, but the seeds will not sprout true to type - you'll get all sorts coming up, even from a single fruit.

[Externet]

36 minutes ago, sethoflagos said:

I'll stand to be corrected but my understanding is that apples cannot self-pollinate.

Thanks.  I did read that some varieties do self pollinate.  Granny, gala, golden, fuji... but yield better productions if cross-pollinated.

[John Cuthber]

4 hours ago, StringJunky said:

A dozen different pollen varieties on a single tree will produce that many types of crosses.

It's "worse" than that.
Even just one tree pollenating another will produce many different crosses from countless  possibilities-  in the same way that we are not (usually) the same as our brothers + sisters. Every year, every seed in every apple will be genetically unique.
That's (part of) the reason why they usually propagate commercial varieties from cuttings.

I understand that some plants will self pollenate, but leave it to the "last minute" They only do it if no other pollen is received.
They seem to have evolved to recognise that evolution is a good thing.
This makes them "better informed about evolution" than some people I know of.

[Externet]

14 hours ago, John Cuthber said:

I understand that some plants will self pollenate, but leave it to the "last minute" They only do it if no other pollen is received.

Thank you.  

  That implies the flower stigma 'analyzes' if the pollen arrived by an insect is foreign in order to accept it * for fertilization; and check if there is 'a time-or-maturity window' left to decide if taking the self-pollen is a last minute resource. 

*Of course, ignoring/rejecting other family/genus - which means another analysis of the pollen is not from a rose instead.

So much to learn !

[John Cuthber]

The simplest way to achieve the "if nothing else is available" pollination is simply to make sure the ovaries are active a while before the anthers are.