Weeping peaches
Weeping willows and other trees that grow their branches downward appear to give up their fight against gravity. But American researchers show that this is not the case, the hanging branches of peach trees are just as strong.
The branches of most trees grow towards the sky. But some trees like weeping willows let their branches hang downwards. The underlying cause is not really clear. That is why the researchers decided to study this in more detail. They used a peach variant that was missing the WEEP gene. This loss resulted in hanging branches.
The first thing the researchers studied was the sturdiness of its branches of peach trees with or without the WEEP gene. For this they analysed the structure of the cell wall. This appeared not to differ much. They also analyse the reaction of the peach plants when these were hanging upside down, and when they were after a while righted again. It turned out that WEEP missing plants were behaving exactly the opposite to WEEP containing plants. Upside down new branches would still grow downwards. And after being righted, these new branches kept growing upwards. Notting wrong with the sturdiness of the branches.
WEEP missing plants react differently on purpose
But what is causing the branches of WEEP missing plants to grow downwards? To find out the researchers studied which genes were turned on in the branches. Hereby they compared the genes that were on in the top and bottom side of the branch. Surprisingly the genes that were on at the top side of the branch in WEEP containing plants were on at the bottom side of the branch in WEEP missing plants. And the other way around.
Studying those genes the researches noticed that a some of those genes that were differently turned on in WEEP-missing and WEEP-containing plants had to do with how much a cell can stretch itself. Those are differently tuned at the top and bottom of the branch. Are they more turned on in the bottom of the branch, then these cells will stretch more allowing the branch to grow upwards. But are they, like in WEEP-missing plants, more turned on in the cells at the top of the branch, then the branch will grow downwards.
Showing that it isn’t that trees with hanging branches giving op their fight with gravity. They are reacting differently on purpose. Enabling that also weeping peach trees can bear delicious fruits on their hanging branches. Which in turn makes for easy picking.
Literature
Andrea R Kohler, Andrew Scheil, Joseph L Hill, Jeffrey R Allen, Jameel M Al-Haddad, Charity Z Goeckeritz, Lucia C Strader, Frank W Telewski, Courtney A Hollender (2024) Defying gravity: WEEP promotes negative gravitropism in peach trees by establishing asymmetric auxin gradients. Plant Physiology; kiae085, https://doi.org/10.1093/plphys/kiae085
Plant en Zo 