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What makes a plant more or less likely to be pollinated by insect?

 
R Ranson
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What makes a plant more or less likely to be pollinated by insect?

Let's talk about bees, insects and buzzy things and how they interact with flowers to make seeds.

What qualities in a flower make it more or less likely to be pollinated by bees? This is important if we are trying to keep a plant variety 'pure' but also if we are seeking to create a landrace and rely on promiscuous pollination.

Squash for example, are almost completely dependent on outside help to move pollen about. One flower has the male (pollen producing) parts, another flower the female (fruit making) stuff. The pollen has to go from one flower to the other. Big, bright open flowers, seem to encourage bees to come and visit. Are there other elements that invite bees and pollinators?

Beans, on the other hand, are pretty resistant to cross pollination. Their flowers have both the male and female parts trapped inside their petals. The flower just needs to be jostled a bit to move the pollen to the right place. Even still, isolation of at least 100 meters is recommended for organic growing to prevent cross pollination.

What other strategies do plants have to encourage or discourage insects?
 
R Ranson
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The reason I ask is because I'm hoping to promiscuously pollinate some flax to develop a land race. The problem with flax is that the book says it only has a 3% cross by insect. Another book recommends we keep an isolation distance of 'a few meters' (more than they recommend for peas). As far as I can tell, neither book says if this is in organic conditions or in an industrial setting that uses pesticides (and thus has few, if any, pollinators). They also do not say if this is for oilseed flax or if this is for linen flax - same plant, different cultivars and characteristics.

I'm growing several different varieties and I've noticed that three of them attract bees and wasps, especially in the early afternoon (the flowers are only open for a few hours). Some open their flowers early morning, only to shut them by lunch time, other open in the late afternoon. The ones that attract the bees, open in the late morning and shut in the mid afternoon. They are also the more decorative and larger flowers. The ones that have no bee interest, have the ... can't remember the technical word... pollen loaf shaped thingy huddled next to the sticky out female bit. Whereas the bee friendly flowers have the male and female parts spread apart like welcoming arms.

Just because there are bugs, doesn't mean that I'm getting promiscuous pollination. The shape, timing, colour, and structure of the flower might not be the only thing that discourages insect pollination. So how can I tell if these plants are crossing by insect? Is there something else I can discover about the flowers, or do I need to wait to grow the seed to see if I've gotten any crosses?

 
Shawn Harper
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Another thing to keep in mind in insects see in colors of the light spectrum that are outside of the range of our eyes.
 
R Ranson
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Shawn Harper wrote:Another thing to keep in mind in insects see in colors of the light spectrum that are outside of the range of our eyes.


I was wondering about that too. Of all the blue-flowered flax, the insects prefer this one variety and leave the others alone. If I get the lighting just right, I can see there is a ... how do describe it?... a shimmer near the center of the flower that isn't there in the other blue flowers. I wondered if that was what the bugs saw that made them like that variety more than the others.
 
Shawn Harper
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R Ranson wrote:
Shawn Harper wrote:Another thing to keep in mind in insects see in colors of the light spectrum that are outside of the range of our eyes.


I was wondering about that too. Of all the blue-flowered flax, the insects prefer this one variety and leave the others alone. If I get the lighting just right, I can see there is a ... how do describe it?... a shimmer near the center of the flower that isn't there in the other blue flowers. I wondered if that was what the bugs saw that made them like that variety more than the others.


If the flowers stay open at night, then get a blacklight. It should reveal a small segment of the UV spectrum for you. I am not sure it will reveal the same exact chunk as insects see though.
 
Neil Layton
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The factors involved in pollination vary from species to species, variety to variety and sometimes plant to plant. Some species cannot self-pollinate, even between flowers on the same plant, either because they have only male or female flowers on each plant of for some other reason. Some species require a specialist pollinator. Others do not. The problem you have is that flax typically self-pollinates, and the only real solution to this problem would involve hand pollination.

Some varieties, mainly those attractive to insects under UV light, will attract more pollinators than others, but the fact that this plant has evolved to self-pollinate is working against you.

The best solution may be to get out on your hands and knees with a paintbrush.

You have picked a tricky plant to create a landrace from!
 
R Ranson
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Hmmm, I wonder...

If the bees aren't making a difference, then would a paint brush do the trick? It might be like a pea that drops its pollen before the flower fully opens.

Since the different varieties have different shaped flowers and the bees prefer half of them over the others, yet the wasps only want the pink ones... I wonder which of the 90 odd linaceae this 3% came from. What conditions are these numbers contrived in? I remember the isolation distance for beans and peas use to be a couple of meters (in the home garden) to keep the cultivar 'pure'. Now it's over 100m, depending on the conditions (organic v. spray). I think there must be a huge range of variables that affect pollination by insect.

The more I observe the different flowers, the more I'm fascinated by the structure and method for pollinating. Like Joseph's tomato project, how he can transform a usual self-pollinating plant into not just a promiscuous pollination, but also with a view to make it self-incompatible (like kale).

Flax got me started with this, but now I want to know more. It seems more complex than the seed saving books make it out to be. Every time one saves seeds, one selects in favour of one trait or another. Doing so consciously gives us the option to work with the plant to create a line that matches the local conditions as well as our needs. If pollinating by insect increases and/or preserve genetic diversity in a landrace, maybe selecting for the specific flowers is something I should be considering.
 
D. Klaer
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I would give the paintbrush a shot. I don't know a lot about flax but it is worth saying that as you no doubt know, bees are only one group of pollinators. The second largest group of pollinators is actually the flies and then we have beetles, butterflies etc and vertebrates. I wonder if there is some other pollinator that has evolved alongside flax? Again, I know little about flax but interesting topic.
 
Joseph Lofthouse
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I devote a lot of effort to finding and growing naturally occurring bean hybrids, and their descendants. I suspect that by doing so, I am also selecting for beans that are more promiscuously pollinating.

Eventually, I expect some interspecies crosses to show up in my common beans. Then the cross-pollination rate will skyrocket, since runner beans are so promiscuous.

 
R Ranson
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Glad you joined in Joseph.

I remember reading somewhere that some flowers are so designed that they can have as many bees or paintbrushes as we can toss at it, but the pollen still resists being transferred from one plant to another. Is it easy to tell if a plant is like this?
 
R Ranson
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Another influence flowers have on bees is what time of day they are open. Some are only open for an hour or two. What time of day that is, be it early morning, heat of the day, evening, night, will influence which pollinators, if any, visit the flower.

Some flowers have shape that requires the insect crawl deep into the flower, thus dislodging as much pollen as possible.
 
Joseph Lofthouse
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R Ranson wrote:I remember reading somewhere that some flowers are so designed that they can have as many bees or paintbrushes as we can toss at it, but the pollen still resists being transferred from one plant to another. Is it easy to tell if a plant is like this?


Flax has already been mentioned as a mostly inbreeding plant. I looked up the data for cross-pollination in flax, and the rate is about 2% to 5% crossing depending on a variety of factors. So today, I examined some domesticated fiber-flax flowers. The structure of the flowers is: The anthers are wrapped tightly around the style. Therefore, the stigma is highly likely to rub against the anthers of itself, and it's highly unlikely for foreign pollen to be able to get past the anthers and onto the stigma. So in the case of flax, the way to select for higher cross pollination rates would be to select for flowers in which the anther cone was held less tightly to the stigma. Today I planted the remaining blank spots in my garden into sweet corn, so I didn't spend the time to examine lots of flowers to see if there are differences between different plants. And I didn't examine the other species of flax that grows on my farm.

Domestic Flax Flower: Mostly inbreeding because the anthers wrap around the style.
 
Joseph Lofthouse
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A few years ago, I examined the flowers in my garden, after dark, with a short-wave ultraviolet lamp. The only flowers that I found that really stood out were lagenaria squash (which flowers at night), and some corn.

Lagenaria flower photographed under UV lighting.


That same night, I also photographed other flowers that had pollinators on them.


 
R Ranson
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The structure of the flowers is: The anthers are wrapped tightly around the style. Therefore, the stigma is highly likely to rub against the anthers of itself, and it's highly unlikely for foreign pollen to be able to get past the anthers and onto the stigma.


Thank you for having the words. This is what I've noticed in the proper fibre flax varieties - that the anthers and stigma are so close together that it looks like they are joined. A bit like this photo (borrowed from here)



Whereas the more decorative varieties have the anthers open and spread apart like the attached photo. The bees prefer these ones.
IMG_1155 (2).JPG
[Thumbnail for IMG_1155 (2).JPG]
open anthers
 
Joseph Lofthouse
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R Ranson wrote:Thank you for having the words.


You're welcome... I haven't had any formal instruction about botany in my life. So a few years ago, I took it upon myself to learn the parts of a flower so that I could write about them. And when I read strange words, I look them up, until eventually, after a few times, they get committed to memory.

 
R Ranson
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My problem is that I can recognize the words, but I can't seem to dig them out of memory to use them. Getting this fixed is next but one, on my list of projects.

Love the black lit flower. I couldn't imagine what would be pollinating at night. Interesting about the moths.
 
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Is there anyway to harvest the ones that the bees like separately ? Use this as your selection criteria as they are nmore likely to cross polinate ?
Are the bees on this crop solitary bees or honey bees ?

David
 
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I like to tie flags onto plants that have traits that I want to save separately later on. For example, this year, I tied red surveyors ribbon onto the fava beans that have red flowers. By the time I harvest the dry pods, the flowers will be long gone, but the flag will tell me which plants had red flowers.

A few years ago, I tied flags onto the corn plants. Different colored flag representing different traits that I valued.


I may write notes on the ribbon, and/or harvest the ribbon with the plant it was tied to:


I might tie two different colored flags to the same plant, if it has two traits that I want to call attention to. Also of note in this photo, is that I can cut off small pieces of cob to taste it, while allowing the rest of the seeds to reach full maturity.


p.s. I'm glad that I lost that knife!!!
 
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