Top 10 Saddest Plant Programmed Cell Deaths

There’s truly no way to describe the feeling of seeing your favorite plant cell break apart and get engulfed by its neighbors.  Whether you’ve known the plant cell for a long time, or whether it’s newly emerged from the apical meristem, it can be hard to say goodbye.

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Welcome to planthumor.com.  Today we’re counting down the Top 10 Saddest Programmed Cell Deaths.  Programmed cell death (PCD) is part of the plant immune response, but it is also part of normal plant development.  We’re focusing on the latter.  Beware of spoilers and have your tissue boxes ready!

Here are our Top 10 Saddest PCDs:

10. Megaspores

We first met the megaspores in the ovule, after the meiosis of the megaspore mother cell.  These four identical little bundles of joy warmed our hearts.

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“Megaspore Mother Cell”, not “Mega Manga Convention”

Sadly, only one megaspore cell could develop into the female gametophyte that would later produce a plant egg cell.  The three other megaspores underwent PCD.

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“Functional Megaspore”, the sole survivor, will be racked with guilt when it reaches adulthood

We’ll miss you, little megaspores!

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9. Synergids

We saw the synergid cells all too briefly as they steadfastly guarded the entrance to the ovule.  The two loyal cells also did their duty in guiding the pollen tube towards the egg cell.

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Synergids are the orange cells; pollen tube enters through the micropylar end; we all can enjoy semicolons

Sadly, the loyal synergids were betrayed by their own leader when the pollen tube exploded into one synergid, causing the other synergid to die as well, as it tried to reach the egg.

We were shocked that a pollen tube could betray such loyal friends!

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8. Self-Incompatibility

Love can be beautiful, but it can also be painful if it doesn’t work out.  For poppy and other plants with self-incompatibility, a bad match is literally toxic.  If the pollen and stigma are from the same plant, or even if they’re from different plants but both have the same variant of the S-locus gene, then the pollen will die before it can grow a pollen tube and complete fertilization.

At least the incompatible pollen died for love…

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7. Embryonic Suspensor

The first division of the plant zygote produced two cells- the suspensor cell and the embryo cell.   These two sister cells were as different as night and day, but like yin and yang they complemented each other.  The suspensor, which was bigger and stronger, fixed the embryo in place within the seed and established the polarity of the embryo.

However, things did not last.  The embryo soon became bigger and stronger than the suspensor could ever be.

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Suspensor cells at the bottom- literally & metaphorically- as the embryo grows bigger

The embryo no longer needed the suspensor.  The suspensor, abandoned, withered away.  The death of this forgotten sister left us in tears.

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6. Seed Coat

We loved watching the ovule integuments train to become specialized cell types!   However, a new foe appeared: the outside world, with its extreme power to dehydrate a plant embryo.  It was too much to bear to watch the ovule integuments get slowly crushed together into a hard covering.

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In death, they became a legendary being more powerful than any of them could ever be in life: The Seed Coat.

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5. Endosperm

Under the seed coat, we were introduced to yet another unlikely hero.  The (literally) sweet endosperm cells looked unremarkable.  But they bravely sacrificed their starch reserves and underwent PCD when the embryo was starving.

 

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A “corny” diagram! (And a corny pun)

Endosperm is also frequently sacrificed into your stomach as the starchy part of wheat, barley, coconut, and corn.

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4. Root Cap

We were quickly impressed by the street smarts of root cap cells.  They may not have been upper-class, but they skillfully sensed gravity and protected root meristem cells.

That’s why we were infuriated when the plant root grew and unthinkingly sloughed off the root cap cells, causing their untimely deaths.

These senseless deaths introduced us to the grim underbelly of the root world.

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3. Leaf Shape

There was no greater sense of helplessness experienced than when we watched the mass deaths of cells during leaf development.  These cells were in the way and had to clear out to create leaf lobes and perforations, but we still mourned every passing.

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The lace plant (Aponogeton madagascariensis), an aquatic plant that was clearly the location of an epic death scene.

At least these cells left a beautiful testament to their legacy in the intricate patterns of leaves.

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2. Xylem Tracheary Elements

We were in awe while witnessing the transformation of the tracheary elements.  These cells showed complete mastery over their own bodies.  They purged their entire protoplasts and were left as a clean, hollow shell.

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These masters were then able to connect to each other and allow xylem to flow through them.  We sobbed as we watched them pass on to become part of the greater plant.

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Before we name our #1 most greatest most saddest tears-worthy PCD moment ever, let’s list a few honorable mentions:

  • the nucellus- nourishes the female gametophyte in the ovule
  • the antipodals- they also undergo death when the synergids do, around the fertilization of the ovule
  • the tapetum- it supports the microspores, then dies during pollen development
  • transmitting tract- it undergoes death to allow the pollen tube to pass through
  • pollen tube- it dies when it explodes
  • abscission- the technical term for shedding leaves, flowers, and fruits
  • dehiscence- the technical term for when fruits split open to release seeds, or when anthers split open to release pollen grains

There are also many types of cell death particular to certain plants, such as aerenchyma formation in aquatic plants, or the death of stamen primordia in unisexual flowers.

Now,

the ~top honor~

for *Saddest Plant Programmed Cell Death*,

the ABSOLUTE SADDEST THING that has happened to a plant cell,

goes to:

1. Senescence

When plant organs get really old, they die.  Anyway, it’s an example of PCD.

Thanks for reading and join us next time on planthumor.com!

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Key Source: 

Van Hautegem, T., Waters, A.J., Goodrich, J., Nowack, M.K.  2015.  Only in dying, life: programmed cell death during plant development.  Trends in Plant Science 20.2: 102-113.

Other Sources & Further Reading: 

Gunawardena, A., Greenwood, J.S., Dengler, N.G.  2004.  Programmed Cell Death Remodels Lace Plant Leaf Shape During Development.  The Plant Cell 16: 60-73.

Escamez, S., Tuominen, H.  Programmes of cell death and autolysis in tracheary elements: when a suicidal cell arranges its own corpse removal.  2014.  Journal of Experimental Botany 65.5: 1313-1321.

Haughn, G., Chaudhury, A.  2005.  Genetic analysis of seed coat development in Arabidopsis.  TRENDS in Plant Science 10.10: 1360-1385.

Pennell, R.I., Lamb, C.  1997.  Programmed Cell Death in Plants.  The Plant Cell 9: 1157-1168.

Reape, T.J., Molony, E.M., McCabe, P.F.  2008.  Programmed cell death in plants: distinguishing between different modes.  Journal of Experimental Botany 59.3: 435-444.

“Top Ten Saddest Anime Deaths.”  Youtube.  WatchMojo.com, 2014.   <https://www.youtube.com/watch?v=ukwLVDa8vKE&gt;

Zhao P., Zhou X.M., Zhang L.Y., Wang W, Ma L.G., Yang L.B., et al.  2013. A Bipartite Molecular Module Controls Cell Death Activation in the Basal Cell Lineage of Plant Embryos. PLoS Biology 11.9: e1001655.

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