Having returned to veg growing after nearly 20 yers of not growing veg,
I thought I'd better refresh my mind on the theory, and I've come up
with things which have puzzled me.

From various books I have picked up that you should not grow indoor (all
female) and outdoor cucumbers in the same greenhouse, and sweet and
chilli peppers should not be grown together, in both cases because
'cross pollination' will cause undesirable results.

The cucumbers I think I understand - the all female plants not only do
not require fertilisation, the should *not* be fertilised - I think
because the presence of seeds would spoil the eating quality (and indeed
self fertilisation would have the same effect)

It's the peppers that puzzle me. I can see that, since they're closely
related, they are likely to cross pollinate and next year, if you save
seed, you will get all sorts of strange hybrids. But why should it
affect this year's fruit (which was the clear implication of the book I
read)? I can't see any mechanism by which this year's fruit could be
affected, and I'm inclined to disregard the advice (well, in fact I
already have)
--
Kay

In article ,
K wrote:

It's the peppers that puzzle me. I can see that, since they're closely
related, they are likely to cross pollinate and next year, if you save
seed, you will get all sorts of strange hybrids. But why should it
affect this year's fruit (which was the clear implication of the book I
read)? I can't see any mechanism by which this year's fruit could be
affected, and I'm inclined to disregard the advice (well, in fact I
already have)

It can happen - for example, I believe that it does for the 'extra
sweet and sickly' varieties of sweetcorn. But it has never happened
to my peppers, and I know that it is very rare.


Regards,
Nick Maclaren.

K wrote:
Having returned to veg growing after nearly 20 yers of not growing
veg, I thought I'd better refresh my mind on the theory, and I've
come up with things which have puzzled me.

From various books I have picked up that you should not grow indoor
(all female) and outdoor cucumbers in the same greenhouse, and sweet
and chilli peppers should not be grown together, in both cases because
'cross pollination' will cause undesirable results.

The cucumbers I think I understand - the all female plants not only do
not require fertilisation, the should *not* be fertilised - I think
because the presence of seeds would spoil the eating quality (and
indeed self fertilisation would have the same effect)

It's the peppers that puzzle me. I can see that, since they're closely
related, they are likely to cross pollinate and next year, if you save
seed, you will get all sorts of strange hybrids. But why should it
affect this year's fruit (which was the clear implication of the book
I read)? I can't see any mechanism by which this year's fruit could be
affected, and I'm inclined to disregard the advice (well, in fact I
already have)
Bees and butterflys will cross pollinate??
--
Pete C
London UK

Pete C writes


K wrote:
Having returned to veg growing after nearly 20 yers of not growing
veg, I thought I'd better refresh my mind on the theory, and I've
come up with things which have puzzled me.

From various books I have picked up that you should not grow indoor
(all female) and outdoor cucumbers in the same greenhouse, and sweet
and chilli peppers should not be grown together, in both cases because
'cross pollination' will cause undesirable results.

The cucumbers I think I understand - the all female plants not only do
not require fertilisation, the should *not* be fertilised - I think
because the presence of seeds would spoil the eating quality (and
indeed self fertilisation would have the same effect)

It's the peppers that puzzle me. I can see that, since they're closely
related, they are likely to cross pollinate and next year, if you save
seed, you will get all sorts of strange hybrids. But why should it
affect this year's fruit (which was the clear implication of the book
I read)? I can't see any mechanism by which this year's fruit could be
affected, and I'm inclined to disregard the advice (well, in fact I
already have)
Bees and butterflys will cross pollinate??

Sorry, I don't follow. Yes, the plants will be cross pollinated - but
how does this affect the fruit? The fruit is formed vegetatively from
the parent plant, as I understand it, it's the seed itself which
contains genetic material from both parents, so that any plant growing
from the seed will be the result of cross pollination.

So what I'm asking is whether there is a mechanism by which the genetic
material from pollen can affect the development of the fruit (as opposed
to any seeds that fruit contains), and, if so, what that mechanism is?
--
Kay

K wrote:
Pete C writes


K wrote:
Having returned to veg growing after nearly 20 yers of not growing
veg, I thought I'd better refresh my mind on the theory, and I've
come up with things which have puzzled me.

From various books I have picked up that you should not grow indoor
(all female) and outdoor cucumbers in the same greenhouse, and sweet
and chilli peppers should not be grown together, in both cases
because 'cross pollination' will cause undesirable results.

The cucumbers I think I understand - the all female plants not only
do not require fertilisation, the should *not* be fertilised - I
think because the presence of seeds would spoil the eating quality
(and indeed self fertilisation would have the same effect)

It's the peppers that puzzle me. I can see that, since they're
closely related, they are likely to cross pollinate and next year,
if you save seed, you will get all sorts of strange hybrids. But
why should it affect this year's fruit (which was the clear
implication of the book I read)? I can't see any mechanism by which
this year's fruit could be affected, and I'm inclined to disregard
the advice (well, in fact I already have)
Bees and butterflys will cross pollinate??

Sorry, I don't follow. Yes, the plants will be cross pollinated - but
how does this affect the fruit? The fruit is formed vegetatively from
the parent plant, as I understand it, it's the seed itself which
contains genetic material from both parents, so that any plant growing
from the seed will be the result of cross pollination.

So what I'm asking is whether there is a mechanism by which the
genetic material from pollen can affect the development of the fruit
(as opposed to any seeds that fruit contains), and, if so, what that
mechanism is?
Ahh, I see what you mean. Sorry, dunno.
--
Pete C
London UK

In article ,
K wrote:

Sorry, I don't follow. Yes, the plants will be cross pollinated - but
how does this affect the fruit? The fruit is formed vegetatively from
the parent plant, as I understand it, it's the seed itself which
contains genetic material from both parents, so that any plant growing
from the seed will be the result of cross pollination.

Nope. It ain't that simple. Nowhere NEAR that simple. When trying
to understand an explanation of Ipomoea indica/learii's complicated
infertility, I found out a little of this. My attempts to find out
a a coherent description of the fertilisation process in vascular
plants was a dismal failure :-(

It seems that the pollen grains germinate on their own, and some
haploid cells then move towards and merge with the ovary. Depending
on the plant, seeds can have components that are derived from the
combination, the ovary alone and the pollen grain alone, or even
all three. Maybe. Or maybe not. Trying to reverse engineer an
explanation of what is happening in a process that complicated from
incidental remarks in scientific papers in a field that one is not
an expert in is, shall we say, inclined to lead to misunderstandings.

So what I'm asking is whether there is a mechanism by which the genetic
material from pollen can affect the development of the fruit (as opposed
to any seeds that fruit contains), and, if so, what that mechanism is?

Yes, there is. Definitely. Whether the mechanism is unknown even to
the experts, or merely known only to such experts, I don't know.
Given my record of asking such questions, it's about as likely either
way.



Regards,
Nick Maclaren.

In message ,
writes
In article ,
K wrote:

Sorry, I don't follow. Yes, the plants will be cross pollinated - but
how does this affect the fruit? The fruit is formed vegetatively from
the parent plant, as I understand it, it's the seed itself which
contains genetic material from both parents, so that any plant growing
from the seed will be the result of cross pollination.

Nope. It ain't that simple. Nowhere NEAR that simple. When trying
to understand an explanation of Ipomoea indica/learii's complicated
infertility, I found out a little of this. My attempts to find out
a a coherent description of the fertilisation process in vascular
plants was a dismal failure :-(

It differs between different groups of plants. Flowering plants has
double fertilisation. Gnetophytes (if I've remembered the group
correctly) have a different form of double fertilisation. Other
gymnosperms don't. We don't necessarily know much about seed ferns, but
I'd guess that they were similar to gymnosperms. Other vascular plants
have macroscopic gametophytes, which produce free(ish) gametes which
unite to form sporophytes.

Among flowering plants, the details vary.

It seems that the pollen grains germinate on their own, and some
haploid cells then move towards and merge with the ovary. Depending
on the plant, seeds can have components that are derived from the
combination, the ovary alone and the pollen grain alone, or even
all three. Maybe. Or maybe not. Trying to reverse engineer an
explanation of what is happening in a process that complicated from
incidental remarks in scientific papers in a field that one is not
an expert in is, shall we say, inclined to lead to misunderstandings.

In the majority of flowering plants the embryo sac (female gametophyte)
ends up with 7 cells contained 8 haploid nuclei. The pollen grain (male
gametophyte) has 3 haploid cells - the vegetative cell, and two sperm
cells. When the pollen grain germinates the vegetative cell grows down
the style to reach the embryo sac, carrying the two sperm cells.

One sperm cell unites with one cell from the embryo sac. The resulting
diploid cell develops into the embryo. The other sperm cell unites with
the embryo sac cell with the extra nuclei. This develops into a triploid
tissue - the endosperm - which is many plants provides nourishment for
the embryo after seed germination. (In many other plants the endosperm
is vestigial. There might be complications about syncytia as well - I
don't recall.)

I don't know what happens to the other cells of the embryo sac, but I'd
guess that they degenerate. The remaining tissues of the seed (e.g. the
seed coat) develop from the ovule, and have the maternal genotype. In
true fruits the fruit is derived from the ovary, and has the maternal
genotype. In false fruits parts of the fruit are derived from other
parts of the flower, but still have the maternal genotype.

There's one species of androgenetic cypress in which the seed genotype
is from the parental plant only, but otherwise I expect that the
vegetative cell of the pollen grain doesn't contribute to the seed, and
that seeds have no components derived from the pollen grain alone.

So what I'm asking is whether there is a mechanism by which the genetic
material from pollen can affect the development of the fruit (as opposed
to any seeds that fruit contains), and, if so, what that mechanism is?

Yes, there is. Definitely. Whether the mechanism is unknown even to
the experts, or merely known only to such experts, I don't know.
Given my record of asking such questions, it's about as likely either
way.

Naively one might expect that embryo and endosperm properties are
controlled by both maternal and parental genotypes (so cross-pollination
does matter), and the remainder of the seed and the fruit to be
controlled by the maternal genotype.

So, cross pollination would be significant in maize, and insignificant
in sweet peppers.

But, embryo and endosperm development start with a cell loaded with
proteins specified by the maternal genotype, including regulatory
proteins. Even in the absence of genetic imprinting (as occurs in
mammals), it would take time for the parental genotype to exert an
influence.

On the other hand, traits in tissues of the maternal genotype might be
influenced by cellular messages produced in the embryo or endosperm, so
it's not impossible that the genetic material in the pollen might effect
the development of the fruit. Like Nick I don't know whether any
specific such mechanism are known.


Regards,
Nick Maclaren.

--
Stewart Robert Hinsley

Stewart Robert Hinsley writes
In message ,

In the majority of flowering plants the embryo sac (female gametophyte)
ends up with 7 cells contained 8 haploid nuclei. The pollen grain (male
gametophyte) has 3 haploid cells - the vegetative cell, and two sperm
cells. When the pollen grain germinates the vegetative cell grows down
the style to reach the embryo sac, carrying the two sperm cells.

One sperm cell unites with one cell from the embryo sac. The resulting
diploid cell develops into the embryo. The other sperm cell unites with
the embryo sac cell with the extra nuclei. This develops into a
triploid tissue - the endosperm - which is many plants provides
nourishment for the embryo after seed germination. (In many other
plants the endosperm is vestigial. There might be complications about
syncytia as well - I don't recall.)

Ah - right. This awakens memories of a long ago plant physiology course.
It all seemed very complicated, and I couldn't quite see the purpose for
making it so complicated, so buried it all in the back of my head
somewhere. So back to the text books for me! Thanks :-)


So, cross pollination would be significant in maize, and insignificant
in sweet peppers.

But, embryo and endosperm development start with a cell loaded with
proteins specified by the maternal genotype, including regulatory
proteins. Even in the absence of genetic imprinting (as occurs in
mammals), it would take time for the parental genotype to exert an
influence.

On the other hand, traits in tissues of the maternal genotype might be
influenced by cellular messages produced in the embryo or endosperm, so
it's not impossible that the genetic material in the pollen might
effect the development of the fruit. Like Nick I don't know whether any
specific such mechanism are known.

Oh well, I shall just have to hope. Hot sweet peppers I can cope with,
even non-hot chilli peppers. Strange tastes might be a different matter.

--
Kay

In article ,
Stewart Robert Hinsley wrote:

In the majority of flowering plants the embryo sac (female gametophyte)
ends up with 7 cells contained 8 haploid nuclei. The pollen grain (male
gametophyte) has 3 haploid cells - the vegetative cell, and two sperm
cells. When the pollen grain germinates the vegetative cell grows down
the style to reach the embryo sac, carrying the two sperm cells.

One sperm cell unites with one cell from the embryo sac. The resulting
diploid cell develops into the embryo. The other sperm cell unites with
the embryo sac cell with the extra nuclei. This develops into a triploid
tissue - the endosperm - which is many plants provides nourishment for
the embryo after seed germination. (In many other plants the endosperm
is vestigial. There might be complications about syncytia as well - I
don't recall.)

Then I definitely misunderstood! You haven't come across a coherent
description of this, anywhere, have you? I mean in more detail.

All of the textbooks I have found are at a considerable more basic
level - that looks horribly like details not normally taught to
undergraduates.


Regards,
Nick Maclaren.

In message ,
writes
In article ,
Stewart Robert Hinsley wrote:

In the majority of flowering plants the embryo sac (female gametophyte)
ends up with 7 cells contained 8 haploid nuclei. The pollen grain (male
gametophyte) has 3 haploid cells - the vegetative cell, and two sperm
cells. When the pollen grain germinates the vegetative cell grows down
the style to reach the embryo sac, carrying the two sperm cells.

One sperm cell unites with one cell from the embryo sac. The resulting
diploid cell develops into the embryo. The other sperm cell unites with
the embryo sac cell with the extra nuclei. This develops into a triploid
tissue - the endosperm - which is many plants provides nourishment for
the embryo after seed germination. (In many other plants the endosperm
is vestigial. There might be complications about syncytia as well - I
don't recall.)

Then I definitely misunderstood! You haven't come across a coherent
description of this, anywhere, have you? I mean in more detail.

All of the textbooks I have found are at a considerable more basic
level - that looks horribly like details not normally taught to
undergraduates.

Some time back I picked up a copy of Muller, Botany: A Functional
Approach (4th edn of 1979) from a library sale. This covers the topic in
about the degree of detail that I gave. It doesn't seem to have a
statement about the intended audience, but I had assumed that it was
targeted at freshmen life science students.

If you go to Google Book Search, and search for embryo sac in books with
Botany in the title (I searched for books published since 2000, to avoid
finding old journals) you find several books (limited preview) covering
this.

If you want much more detail you might have to go to the primary
literature - while the typical case is widely covered, all the various
variations aren't.


Regards,
Nick Maclaren.

--
Stewart Robert Hinsley

In article ,
Stewart Robert Hinsley wrote:

Some time back I picked up a copy of Muller, Botany: A Functional
Approach (4th edn of 1979) from a library sale. This covers the topic in
about the degree of detail that I gave. It doesn't seem to have a
statement about the intended audience, but I had assumed that it was
targeted at freshmen life science students.

Thanks very much.

My daughter completed a biology degree at Royal Holloway a short
while back, and none of her textbooks covered that.


Regards,
Nick Maclaren.

In message ,
writes
In article ,
Stewart Robert Hinsley wrote:

Some time back I picked up a copy of Muller, Botany: A Functional
Approach (4th edn of 1979) from a library sale. This covers the topic in
about the degree of detail that I gave. It doesn't seem to have a
statement about the intended audience, but I had assumed that it was
targeted at freshmen life science students.

Thanks very much.

My daughter completed a biology degree at Royal Holloway a short
while back, and none of her textbooks covered that.

Did she do any courses specifically on Botany? (Though Campbell, Biology
(4th edn of 1977) has if anything more detail. Perhaps with the growth
of molecular biology over the last 30 years other stuff has been
displaced from the courses.


Regards,
Nick Maclaren.

--
Stewart Robert Hinsley

In article ,
Stewart Robert Hinsley wrote:

My daughter completed a biology degree at Royal Holloway a short
while back, and none of her textbooks covered that.

Did she do any courses specifically on Botany? (Though Campbell, Biology
(4th edn of 1977) has if anything more detail. Perhaps with the growth
of molecular biology over the last 30 years other stuff has been
displaced from the courses.

Yup. You could be right about the reason.


Regards,
Nick Maclaren.

In message , K
writes
Stewart Robert Hinsley writes
In message ,

In the majority of flowering plants the embryo sac (female
gametophyte) ends up with 7 cells contained 8 haploid nuclei. The
pollen grain (male gametophyte) has 3 haploid cells - the vegetative
cell, and two sperm cells. When the pollen grain germinates the
vegetative cell grows down the style to reach the embryo sac, carrying
the two sperm cells.

One sperm cell unites with one cell from the embryo sac. The resulting
diploid cell develops into the embryo. The other sperm cell unites
with the embryo sac cell with the extra nuclei. This develops into a
triploid tissue - the endosperm - which is many plants provides
nourishment for the embryo after seed germination. (In many other
plants the endosperm is vestigial. There might be complications about
syncytia as well - I don't recall.)

Ah - right. This awakens memories of a long ago plant physiology
course. It all seemed very complicated, and I couldn't quite see the
purpose for making it so complicated, so buried it all in the back of
my head somewhere. So back to the text books for me! Thanks :-)


So, cross pollination would be significant in maize, and insignificant
in sweet peppers.

But, embryo and endosperm development start with a cell loaded with
proteins specified by the maternal genotype, including regulatory
proteins. Even in the absence of genetic imprinting (as occurs in
mammals), it would take time for the parental genotype to exert an
influence.

On the other hand, traits in tissues of the maternal genotype might be
influenced by cellular messages produced in the embryo or endosperm,
so it's not impossible that the genetic material in the pollen might
effect the development of the fruit. Like Nick I don't know whether
any specific such mechanism are known.

Oh well, I shall just have to hope. Hot sweet peppers I can cope with,
even non-hot chilli peppers. Strange tastes might be a different matter.

I'd be moderately surprised if cross-pollination significantly changed
the phenotype of sweet pepper and chile fruits (rather than the fruits
of the next generation), but I'm open to evidence to the contrary.
--
Stewart Robert Hinsley

In article ,
Stewart Robert Hinsley wrote:

I'd be moderately surprised if cross-pollination significantly changed
the phenotype of sweet pepper and chile fruits (rather than the fruits
of the next generation), but I'm open to evidence to the contrary.

As I said, I have not observed it, though my experience is not
immense. I have usually grown several types of chilli, though
all tend to be hot. In no case has the flavour or shape deviated
from what I would have expected.


Regards,
Nick Maclaren.