I emailed Bill Reid a couple days ago to see if he knows protandry of Fisher and Deerstand. He said he’s not grafted either, therefore doesn’t know.
I think, we’ll see though, my California friend will know.
Dax
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Dax, just a caution that the mechanism behind dichogamy is based on hours of chilling. Under some conditions, a normally protandrous variety will flip and become protogynous and vice versa. I know of one variety that flips from growing in South Georgia to North Alabama. In other words, it ain’t always what it always is! That Turkish study I posted about a couple of years ago listed several varieties that flipped in years where chill hours were under 200.
While completely flipping is unusual, it is far more common to see a variety that is normally protandrous become an overlap variety with near complete self-pollination. This also happens with protogynous varieties if taken into a colder climate.
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Fascinating. If I’m understanding correctly, is it that under high chill hours, the total bloom time is compressed such that the male and female blooms overlap? This reminds me of reports that bloom times of apricot, apple, etc overlap more in colder climates than warm. Or is it less predictable than that?
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That’s a hell of a pretty good answer, Jay. I understood Darrel but my mind couldn’t solve the mathematics.
This dichogamy had me thinking of Shepherd pecan right away. Fernald and I cannot understand why it has pistillate overlap (full) with staminite (full again.) We sort of wonder what the heck or how Dan Shepherd in Missouri is producing nuts that are full size. Shepherd being produced “north” with both Mullahy and Hark making a (3 trunk pecan tree) - each on its’ own trunk; Shepherd however produces nuts the size of thimballs up here.
I know Dan’s Dad got the rights or actually had the ortet Shepherd brought to his farm. I think it’s nothing more than a native MO. seedling so the parentage likely has nothing to do with its’ dichogamy. We just don’t get it, Darrel. Do you have an answer?
Dan Shepherd has no clue what is pollinating what and will laugh when asked. He just knows there’s so much pollen there that nothing could be compromised, ever. That’s all he needs to know as far as Dan is concerned.
I reached for Wes’ book to see he completely illustrates that problem being about Shepherd.
Thanks, Darrel.
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I answered my own question about Shepherd. It has to be hit at the exact right time with pollen from another cultivar or it isn’t gonna pollinate right.
Thanks,
Dax
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Pecans are a bit different because pistillate blooms wound up being activated by a slightly different set of genes than activate male catkin blooms. It works really well for pecan because dichogamy happens to favor cross pollination which tends to produce vigorous seedlings. On average, 1/2 to 3/4 of the trees in a native stand are protogynous and the remainder are protandrous. But since the bloom periods are different, most protogynous female blooms are pollinated by protandrous pollen and vice versa. It is one of those unusual genetic mechanisms that throw standard Mendelian inheritance for a loop. Contrast this with apple where various self-sterility mechanisms force cross pollination.
Protandrous (male flowers first) pecan varieties have a very strong tendency to overlap catkins (male flowers) with pistillate (female flowers). Several varieties are technically protandrous, but in the pecan spreadsheet are shown as O for Overlap. Protogynous (female flowers first) varieties can more easily be disrupted by changes in chilling hours. Going from 350 or more chilling hours to 200 or less can be enough to flip a protogynous variety to behave as though it is protandrous. It doesn’t stop there. Move that protogynous variety further north with too many chilling hours say 800 instead of normal 350 and the male flowers will be triggered to overlap with the female flowers. Short version, fewer chilling hours inhibit female flowers from opening and too many chilling hours speed up male flowers opening. This is a generalization and there are varieties that do not follow this pattern. Stuart is an example of a protogynous variety that needs very high chilling hours. Since it needs 500+ chilling hours to start with, moving it north with chilling hours above 1000 does not affect bloom sequence as much as a different protogynous variety that only needs 300 chilling hours. You can find this in the Turkish study which I linked in the Pecan thread, also in Herman Heinrich’s work with Dodd seedlings chilling hour requirements.
To answer the question about Shepherd, it is most likely a protandrous variety with relatively low chilling hour requirements. The result would be near 100% male/female flower overlap. When I say “relatively low”, this is in relation to the area where it is grown. Say it is growing in an area with 1000 chilling hours, but the tree only needs 500 hours to bloom normally, and it is protandrous, you would get exactly the reported results for Shepherd.
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Perfect. Well-explained…
Tank ya!
@Fusion_power is there a variation that occurs when northern, far-northern, or ultra-northern, provenance native-pecans are brought to the south where protandry is effected and if pistillate shed lines up again with staminite-flowers?
This “lining up” I’m speaking of shows influence it seems to me with male pollen (stigmas) and including their opening time - of generically speaking, “full protandry” (the meeting at the same time and ending of at the same time of when flowers are receptive and shedding).
Hey, thanks again.
You are asking questions currently with unknown answers. What I know or have read suggests that protandrous high chill varieties will tend to shift toward behaving as protogynous varieties when carried further south where their chilling hour requirements are not met. Some protogynous high chill varieties would most likely switch to behave as though they are protandrous. It is a question of which only the surface has been scratched.
I think I can give an example. Please emphasize that there are several variables so no two varieties will behave exactly the same. First, start with understanding how pecans got where they are growing. The last ice age was 11,000 years ago. at that time, there were no pecan trees in Illinois, Iowa, or other northern states because they were covered with glaciers and what was not covered in ice was too cold for pecans to grow. As the ice melted, pecans were carried further north and slowly adapted to new conditionns of season length, temperature, etc. Suppose there is a protandrous pecan tree that has a pistillate flower bud break requirement of 500 chilling hours and a male bud break requirement of 800 chilling hours. Now take that tree south far enough to get to an area with only 500 chilling hours. The female flowers will meet their requirements just about every year and will break buds as soon as temperatures moderate. The male flowers will not meet their chilling requirements, however, with pecan, high spring temperatures will eventually overcome the dormancy. Now we have a tree that is presenting female flowers prior to pollen shed from catkins, i.e. a protogynous tree. Do you see how the flip can occur?
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I sure do see that; I want to say I awoke this morning with complete understanding of yesterday’s lessons. Thank you so much!
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