The Dim-Post

September 6, 2016

Why are cabbage leaves wrinkled

Filed under: Uncategorized — danylmc @ 7:04 pm

One of the things I looked forward to about being a parent was answering questions about the world. What is the sun? Why is the sky blue, etc. And, I figured, even if I couldn’t answer my daughter’s questions I could look the answers up on the internet and then translate the explanations very lucidly.

This has hardly ever worked in practise. Today’s question: why are the leaves of a Savoy cabbage so wrinkled? ‘Uh . . . water retention?’ I guessed, before looking online and not finding an answer. Any botanists out there want to answer?

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25 Comments »

  1. Because that’s how God made them. Speaking of which, thoughts on Colin Craig?

    Comment by Jimmy — September 6, 2016 @ 7:17 pm

  2. My guess is unlike normal cabbage Savoy cabbage has a reticulate vein structure?

    Comment by Sanctuary — September 6, 2016 @ 7:33 pm

  3. They were a natural mutation that early plant breeders fixed as seperate variety?

    Comment by Ray — September 6, 2016 @ 7:44 pm

  4. Just a random mutation that the original breeders liked, I think. I don’t have kids myself, but someone on the internet mentioned a slow student who could never really understand why 1 divided by -1 was -1. He could memorise the result, but just wasn’t smart enough to understand the answer. Then I started wondering about it myself, and it took me a surprisingly long time to figure out the explanation.

    Comment by Gareth Wilson — September 6, 2016 @ 7:51 pm

  5. https://en.wikipedia.org/wiki/Brassica_oleracea

    “…Wild B. oleracea is a tall biennial plant, forming a stout rosette of large leaves in the first year, the leaves being fleshier and thicker than those of other species of Brassica, adaptations to store water and nutrients in its difficult growing environment…”
    So your guess was right, it has inherited fleshier leaves from B. oleracea in order to store more nutrients and water in a given area than flat leaves?

    Comment by Sanctuary — September 6, 2016 @ 7:54 pm

  6. There will be a Fibonacci sequence underlying it.

    Comment by Majella — September 6, 2016 @ 8:06 pm

  7. You’re reading your daughter Harry Potter, right? Magic. It’s just magic.

    Unless you feel some parental responsibility to tell her “the truth”. In which case – you monster, how could you deny her the tooth fairy?

    Comment by Andrew Geddis — September 6, 2016 @ 8:10 pm

  8. Could it be some form of defensive adaptation against parasites? A way of tricking parasites that it is the wrinkled skin of an animal and not a plant? (I’m thinking, as a rough analogy, of the way some butterflies evolved ‘eye’ patterns on their wings to deter predators).

    Comment by Nick — September 6, 2016 @ 9:47 pm

  9. Could it be some form of defensive adaptation against parasites?

    Maybe, but as it’s a characteristic that only seems to be maintained in cultivation it might be a selectively bred deformity, rather than a product of natural selection. Apparently most cultivated cabbages, along with broccoli and all of the cauliflowers, are selectively bred cultivars of Brassica oleracea. Botanically speaking they’re a single species. Like fancy pigeons and fluffy bunnies, without ongoing human intervention they’d likely revert to their wild ancestral form.

    Comment by Joe W — September 6, 2016 @ 11:53 pm

  10. The plant is evolving to resemble the human Scrotal sac. This adaptation is beneficial because it makes you less likely to want to pick up a big knife and slice into it.

    A.

    Comment by Antoine — September 7, 2016 @ 2:27 am

  11. These are the most nets where you just invent another just-so tale…

    Comment by Michael — September 7, 2016 @ 6:55 am

  12. *moments

    Comment by Michael — September 7, 2016 @ 6:56 am

  13. you’re missing a trick. i used to blame slow traffic on aliens stopping to take selfies

    the leaf is wrinkly because it’s the oldest of all the vegetables.

    Comment by Che Tibby — September 7, 2016 @ 7:08 am

  14. the leaf is wrinkly because it’s the oldest of all the vegetables.

    Not as green as it is cabbage-looking?

    Comment by Joe W — September 7, 2016 @ 7:28 am

  15. From what I can find on brassica leaf morphology on scholar.google.com I suspect the it increases the surface area available for photosyntheis to occur on. If it was about reducing transpiration you’d mre more likely to see fine hairs or a waxy epidermis.

    Comment by Robert Singers (@glassfugue) — September 7, 2016 @ 9:35 am

  16. It’s a common environmental adaptation for plants that thrive in exposed alpine low rainfall areas.
    Larger, thickened epidermis cells regulate water loss and sunken stomata are both protected from cold, dry air.

    Comment by Gregor W — September 7, 2016 @ 10:01 am

  17. If it didn’t have wrinkly leaves it wouldn’t be a savoy cabbage!

    Comment by Joanna — September 7, 2016 @ 1:22 pm

  18. Unless someone has studied it specifically, you likely won’t find an answer for Savoy cabbage in particular. And as seen from the range of ideas already given, the question could be answered in a variety of ways depending on the perspective: what is the function of the wrinkles and why did they evolve? How do the wrinkles form – what are the developmental, biophysical, biochemical, environmental, etc. causes? And what are the genetic factors that determine the wrinklyness?

    Your answer of water retention was mechanistic and intriguingly seems to draw parallels between the leaf form and human bathtime physiology? You could try an experiment and desiccate a Savoy leaf to see if it loses the wrinkles or put a regular cabbage leaf in water for a while and see if it goes wrinkly🙂

    Another possible physiological explanation is increased cell proliferation – pack more cells into an area and you get bulging. This has been proposed as an explanation for leaf curvature generally and genetic factors identified that cause it.

    From an evolutionary perspective, perhaps the easiest answer is that the wrinkles were selected for by humans because they liked the shape, colour and flavour, although they only selected for what was a natural mutation in the first place. Would that mutation have provided an advantage and persisted on its own? Other plants have wrinkly (rugose) leaves, so perhaps.

    Checking out the research online, it seems a lot of work still remains to be done to figure out the how and why of leaf shape – if you look at the huge diversity of leaf shapes it’s not hard to see why.

    Further reading ;p
    What determines a leaf’s shape? – http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4290414/

    The evolution and functional significance of leaf shape in the angiosperms – http://droyer.web.wesleyan.edu/Nicotra_leaf_shape_review_2011_Functional_Plant_Biology.pdf

    Leaf development: a cellular perspective – http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4116805/

    Comment by Antimorph — September 7, 2016 @ 2:06 pm

  19. One of my favourite games, answering my childrens’ questions. Try this one: Why is honey sticky? ‘Because it’s made of sugar and water’ just leads to ‘why is sugar in water sticky?’, which went on for some time and to some depth, considering there were no chemists present to give a definitive answer.

    Comment by Oliver Thompson — September 7, 2016 @ 4:42 pm

  20. One of my favourite games, answering my childrens’ questions. Try this one: Why is honey sticky? ‘Because it’s made of sugar and water’ just leads to ‘why is sugar in water sticky?’, which went on for some time and to some depth, considering there were no chemists present to give a definitive answer.

    That reminds me of a favourite passage in Kim Stanley Robinson’s Green Mars:

    About a year later Nirgal and the other children began to figure out how to deal with the days when they were taught by Sax. He would start at the blackboard, sounding like a particularly characterless Al, and behind his back they would roll their eyes and make faces as he droned on about partial pressures or infrared rays. Then one of them would see an opening and begin the game. He was helpless before it. He would say something like, “In nonshivering thermogenesis the body produces heat using futile cycles,” and one of them would raise a hand and say, “But why, Sax?” and everyone would stare hard at their lectern and not look at each other, while Sax would frown as if this had never happened before, and say, “Well, it creates heat without using as much energy as shivering does. The muscle proteins contract, but instead of grabbing they just slide over each other, and that creates the heat.”Jackie, so sincerely the whole class nearly lost it: “But how?”

    He was blinking now, so fast they almost exploded watching him. “Well, the amino acids in the proteins have broken covalent bonds, and the breaks release what is called bond dissociation energy.”

    “But why?”

    Blinking ever harder: “Well, that’s just a matter of physics.” He diagrammed vigorously on the blackboard: “Covalent bonds are formed when two atomic orbitals merge to form a single bond orbital, occupied by electrons from both atoms. Breaking the bond releases thirty to a hundred kcals of stored energy.”

    Several of them asked, in chorus, “But why?”

    This got him into subatomic physics, where the chain of whys and becauses could go on for a half hour without him ever once saying something they could understand. Finally they would sense they were near the end game. “But why?”

    “Well,” going cross-eyed as he tried to backtrack, “atoms want to get to their stable number of electrons, and they’ll share electrons when they have to.”

    “But why?”

    Now he was looking trapped. “That’s just the way atoms bond. One of the ways.”

    “But WHY?”

    A shrug. “That’s how the atomic force works. That’s how things came out—”

    And they all would shout, “in the Big Bang.”

    They would howl with glee, and Sax’s forehead would knot up as he realized that they had done it to him again

    Comment by danylmc — September 7, 2016 @ 7:11 pm

  21. Challenging as it is, the “why?” stage is still a lot more fun for parents than the “no” stage.

    Comment by McNulty — September 7, 2016 @ 8:19 pm

  22. A shrug. “That’s how the atomic force works. That’s how things came out—”

    And they all would shout, “in the Big Bang.”

    Which in turn doesn’t explain much which leads to eternal inflation, multiverses and the measure problem. Which leads to explanation not being something what we exist in is good at providing.

    Comment by NeilM — September 8, 2016 @ 12:11 am

  23. Wrinkles create a larger surface area for photosynthesis, resulting in more energy for the plant to use. Whether that’s the reason for the mutation or just a by-product of it is something for the more horticulturally-inclined to answer.

    Comment by Ataahua — September 8, 2016 @ 12:47 pm

  24. @danyl #20

    Louis C.K. from about 7:00 onwards.

    Actually the whole clip is gold.

    Comment by Gregor W — September 8, 2016 @ 12:57 pm

  25. In a sense, the reason may be “so you can tell it apart from normal cabbage”.

    That is, it’s not present in other plants bred from Brassica oleracea, and it’s not present in the wild form, so it’s clearly a result of selection by breeders, and usual evolutionary explanations probably don’t apply.

    Here’s a quote from an 1863 book http://www.underwoodgardens.com/fearing-burr-on-savoy-cabbage/


    This class of Cabbages derives its popular name from Savoy, a small district adjoining Italy, where the variety originated, and from whence it was introduced into England and France more than a hundred and fifty years ago. The Savoys are distinguished from the common head or closehearted Cabbages by their peculiar, wrinkled, or blistered leaves. According to Decandole, this peculiarity is caused by the fact that the pulp, or thin portion of the leaf, is developed more rapidly than the ribs and nerves.

    Besides the distinction in the structure of the leaves, the Savoys, when compared with the Common Cabbages, are slower in their development, and have more open or less compactly formed heads. In texture and flavor they are thought to approach some of the Broccolis or Cauliflowers; having, generally, little of the peculiar musky odor and taste common to some of the coarser and larger varieties of Cabbages.

    That explains mechanistically how the wrinkles come about, and it suggests that historically they are descended from a popular series of cultivars that happened to have wrinkled leaves.

    However they originated, the wrinkles would have been preserved in later breeding both because they look interesting and because they make it easier to distinguish Savoy cabbage from other, inferior types.

    Comment by Thomas Lumley — September 13, 2016 @ 6:02 pm


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