Using leaf veins to hindcast climate

Leaf lamina. The leaf architecture probably ar...

Leaf lamina. The leaf architecture probably arose multiple times in the plant lineage (Photo credit: Wikipedia)

From the University of California – Los Angeles

Hacking code of leaf vein architecture solves mysteries, allows predictions of past climate

UCLA life scientists have discovered new laws that determine the construction of leaf vein systems as leaves grow and evolve. These easy-to-apply mathematical rules can now be used to better predict the climates of the past using the fossil record.

The research, published May 15 in the journal Nature Communications, has a range of fundamental implications for global ecology and allows researchers to estimate original leaf sizes from just a fragment of a leaf. This will improve scientists’ prediction and interpretation of climate in the deep past from leaf fossils.

Leaf veins are of tremendous importance in a plant’s life, providing the nutrients and water that leaves need to conduct photosynthesis and supporting them in capturing sunlight. Leaf size is also of great importance for plants’ adaptation to their environment, with smaller leaves being found in drier, sunnier places.

However, little has been known about what determines the architecture of leaf veins. Mathematical linkages between leaf vein systems and leaf size have the potential to explain important natural patterns. The new UCLA research focused on these linkages for plant species distributed around the globe.

“We found extremely strong, developmentally based scaling of leaf size and venation that has remained unnoticed until now,” said Lawren Sack, a UCLA professor of ecology and evolutionary biology and lead author of the research.

How does the structure of leaf vein systems depend on leaf size? Sack and members of his laboratory observed striking patterns in several studies of just a few species. Leaf vein systems are made up of major veins (the first three branching “orders,” which are large and visible to the naked eye) and minor veins, (the mesh embedded within the leaf, which makes up most of the vein length).

Federally funded by the National Science Foundation, the team of Sack, UCLA graduate student Christine Scoffoni, three UCLA undergraduate researchers and colleagues at other U.S. institutions measured hundreds of plant species worldwide using computer tools to focus on high-resolution images of leaves that were chemically treated and stained to allow sharp visualization of the veins.

The team discovered predictable relationships that hold across different leaves throughout the globe. Larger leaves had their major veins spaced further apart according to a clear mathematical equation, regardless of other variations in their structure (like cell size and surface hairiness) or physiological activities (like photosynthesis and respiration), Sack said.

“This scaling of leaf size and major veins has strong implications and can potentially explain many observed patterns, such as why leaves tend to be smaller in drier habitats, why flowering plants have evolved to dominate the world today, and how to best predict climates of the past,” he said.

These leaf vein relationships can explain, at a global scale, the most famous biogeographical trend in plant form: the predomination of small leaves in drier and more exposed habitats. This global pattern was noted as far back as the ancient Greeks (by Theophrastus of Lesbos) and by explorers and scientists ever since. The classical explanation for why small leaves are more common in dry areas was that smaller leaves are coated by a thinner layer of still air and can therefore cool faster and prevent overheating. This would certainly be an advantage when leaves are in hot, dry environments, but it doesn’t explain why smaller leaves are found in cool, dry places too, Sack noted.

Last year, Scoffoni and Sack proposed that small leaves tend to have their major veins packed closely together, providing drought tolerance. That research, published in the journal Plant Physiology, pointed to an advantage for improving water transport during drought. To survive, leaves must open the stomatal pores on their surfaces to capture carbon dioxide, but this causes water to evaporate out of the leaves. The water must be replaced through the leaf veins, which pull up water through the stem and root from the soil. This drives a tension in the leaf vein “xylem pipes,” and if the soil becomes too dry, air can be sucked into the pipes, causing blockage.

The team had found, using computer simulations and detailed experiments on a range of plant species, that because smaller leaves have major veins that are packed closer together — a higher major vein length per leaf area — they had more “superhighways” for water transport. The greater number of major veins in smaller leaves provides drought tolerance by routing water around blockages during drought.

This explanation is strongly supported by the team’s new discovery of a striking global trend: higher major vein length per leaf area in smaller leaves.

The Nature Communications research provides a new ability to estimate leaf size from a leaf fragment and to better estimate past climate from fossil deposits that are rich in leaf fragments. Because of the very strong tendency for smaller leaves to have higher major vein length per leaf area, one can use a simple equation to estimate leaf size from fragments.

Major vein length per leaf area can be measured by anyone willing to look closely at the large and small leaves around them.

“We encourage anyone to grab a big and a small leaf from trees on the street and see for yourself that the major veins are larger and spaced further apart in the larger leaf,” Scoffoni said.

Because leaf size is used by paleobiologists to “hindcast” the rainfall experienced when those fossil plants were alive and to determine the type of ecosystem in which they existed, the ability to estimate intact leaf size from fragmentary remains will be very useful for estimates of climate and biodiversity in the fossil record, Sack said.

The research also points to a new explanation for why leaf vein evolution allowed flowering plants to take over tens of millions of years ago from earlier evolved groups, such as cycads, conifers and ferns. Because, with few exceptions, only flowering plants have densely packed minor veins, and these allow a high photosynthetic rate — providing water to keep the leaf cells hydrated and nutrients to fuel photosynthesis — flowering plants can achieve much higher photosynthetic rates than earlier evolved groups, Sack said.

The UCLA team’s new research also showed that the major and minor vein systems in the leaf evolve independently and that the relationship between these systems differs depending on life size.

“While the major veins show close relationships with leaf size, becoming more spaced apart and larger in diameter in larger leaves, the minor veins are independent of leaf size and their numbers can be high in small leaves or large leaves,” Sack said. “This uniquely gives flowering plants the ability to make large or small leaves with a wide range of photosynthetic rates. The ability of the flowering plants to achieve high minor-vein length per area across a wide range of leaf sizes allows them to adapt to a much wider range of habitats — from shade to sun, from wet to dry, from warm to cold — than any other plant group, helping them to become the dominant plants today.”

The strength of the mathematical linkage of leaf veins with leaf size across diverse species raises the question of cause.

The UCLA team explains that these patterns arise from the fact of a shared script or “program” for leaf expansion and the formation of leaf veins. The team reviewed the past 50 years of studies of isolated plant species and found striking commonalities across species in their leaf development.

“Leaves develop in two stages,” Sack said. “First, the tiny budding leaf expands slightly and slowly, and then it starts a distinct, rapid growth stage and expands to its final size.”

The major veins form during the first, slow phase of leaf growth, and their numbers are complete before the rapid expansion phase, he said. During the rapid expansion phase, those major veins are pushed apart, and can simply extend and thicken to match the leaf expansion. Minor veins can continue to be initiated in between the major veins during the rapid phase, as the growing leaf can continue to lay down new branching strands of minor veins.

In the final, mature leaf, it is possible for minor veins to be spaced closely, even in a large leaf where the major veins would be spaced apart.

“The generality of the development program is striking,” Sack said, “It’s consistent with the fact that different plant species share important vein development genes — and the global scaling patterns of leaf vein structure with leaf size emerge in consequence.”

These vein trends, confirmed with high-resolution measurements, are “obvious everywhere under our noses,” Sack and Scoffoni said.

Why had these trends escaped notice until now?

“This is the time for plants,” Sack said. “It’s amazing what is waiting to be discovered in plant biology. It seems limitless right now. The previous century is known for exciting discoveries in physics and molecular biology, but this century belongs to plant biology. Especially given the centrality of plants for food and biosphere sustainability, more attention is being focused, and the more people look, the more fundamental discoveries will be made.”

###

UCLA is California’s largest university, with an enrollment of nearly 38,000 undergraduate and graduate students. The UCLA College of Letters and Science and the university’s 11 professional schools feature renowned faculty and offer 337 degree programs and majors. UCLA is a national and international leader in the breadth and quality of its academic, research, health care, cultural, continuing education and athletic programs. Six alumni and five faculty have been awarded the Nobel Prize.

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102 Responses to Using leaf veins to hindcast climate

  1. Richard M says:

    This whole subject leaves me cold. Best to leave this subject for now.

  2. If one were to subtract ‘climate’ from this tale…..oh never mind. What are they really saying? That climate changes? D’uh, we know that, silly!

  3. gopal panicker says:

    plants in drier environments have smaller leaves to conserve water…xerophytic adaptation…at the extreme we have cacti with no leaves…stuff from high school biology 40 years ago

  4. gopal panicker says:

    vein patterns on leaves are like fractals…i wonder if these UCLA have heard of them

  5. Ally E. says:

    This is brilliant. It will be fascinating to apply this to fossils. One of those “But of course!” moments when once stated, it makes perfect sense. I look forward to reading what discoveries can be found on this basis.

  6. Clique2 says:

    Sounds like real science! Hooray!

  7. Duncan says:

    Tea leaves perhaps…

  8. Beth Cooper says:

    Plant adaptation is amazing … like human adaptatation to what’s out there. Crossing the Nullarbor Plain in Australia, stands of narrow leafed sclerophyl shrubs vary from place to place, soil changes, topography, growing in a hollow or roadside ditch that catch moisture, low growing fan shaped growth to maximize opportunities … so we all try to seize the day. )

  9. Geoff Sherrington says:

    In human beings, the distance between the hip joint and the knee joint is correlated with overall person height. So is the length of the external carotid artery.
    So what?

  10. Jace F says:

    A step up from reading tea leafs?

  11. As I see it there is a problem using leaves as a proxy for climate. Many leaf fossils are found in old river sediments. They fall from a bankside tree and float down stream. So the leaf does not show the climate where it is found but the climate somewhere upstream which could be many miles. Also a leaf, like tree rings, display some signature of the microclimate where it grew not the general climate of an area that is of interest.

  12. steveta_uk says:

    Someone needs to explain to Lawren Sack, a UCLA professor of ecology, that “how to best predict climates of the past” is simply nonsensical, Alice-in-Wonderland stuff.

    Or perhaps he’ll soon be remembering the climate at the end of the 21st century.

  13. Shevva says:

    Old hat, we’ve been using tea-leaves for years, my mum and sister had theirs done beginning of the year and told there brother/son would be rich and famous.

    “The previous century is known for exciting discoveries in physics and molecular biology, but this century belongs to plant biology. Especially given the centrality of plants for food and biosphere sustainability, more attention is being focused, and the more people look, the more fundamental discoveries will be made.” – Please send grant cheques to PO Box.

  14. Shevva says:

    Just an after-thought but would every single leaf have to be the same?

  15. Tony McGough says:

    Fascinating – was there ever a toddler who did not gaze intently at a leaf? And now there is a great deal to learn from them. How little we know…

  16. Ed Zuiderwijk says:

    Wow! Tea leaves have always been used to predict the future. Now I read they can tell us the past; that’s half of the task done. I will look at my neighbour with her crystal ball with new eyes: perhaps she really does know something I don’t.

  17. Roger Carr says:

    Nice! Intriguing. Specimens readily at hand for amateur and professional alike. Easy to show the kids and pique their interest (or not). Just inside my scientific envelope (meaning anyone can do it). And if, in pursuing it, I begin feeling hot all over, nothing in the paper says I am suffering from CO2 poisoning, so I’ll just assume it’s the excitement of discovery…

  18. Jim Barker says:

    Puts new meaning to reading tea leaves:)

  19. Don Keiller says:

    Off topic, I know but this;

    http://hauntingthelibrary.wordpress.com/2012/05/23/global-warming-author-says-bar-code-everyone-at-birth/

    shows the frightening “1984″ mentality of the Greens

  20. genemachine says:

    This is great work but there are other factors that help explain the rise of flowering plants such as their co-evolution with their insect pollinators which is likely conducive to speciation. The orchids may be an especially good example of this.

  21. guidoLaMoto says:

    Leaf growth is not a simple “zoom out” transformation. Cells get more numerous, not larger, as a leaf grows, so this phenomenon described could have easily been deduced before it was observed. Water flows up from the roots & out thru the leaf in the process of transpiration, a siphoning effect, so to speak. In drier climates, it’s logical to assume the water evaporates completely closer to the base of the leaf, limiting further growth. A pitfall in using this newly described info is that even in a given individual plant, leaf size often varies according to the leaf’s distance from the roots & its age, so sampling error will enter into data collection, not to mention other factors affecting growth, like nitrogen or light availability. It’s also a bit simplistic to suggest that the dominance of angiosperms over other plant forms depended only on water usage. There are many adaptive advantages that evolved to favor them.

  22. Tony Mach says:

    Another study overselling a potential proxy’s ability to hindcast temperatures vs. precipitation?

  23. Bob says:

    New laws? We skipped hypotheses and theorems and went straight to laws?

  24. ddpalmer says:

    Nice to see people doing real science.

    “The team had found, using computer simulations and detailed experiments…”
    This is the way it is suppose to work. Computer simulations (a much better term them ‘models’) are useless without complementary physical experiments/data. The simulation may point to areas to be studied or what type real world data is needed, but by themselves they don’t show or prove anything (well except what biases the programmer put into them).

  25. polistra says:

    Bigger animals have bigger spaces between bones. By measuring the gap between two ribs you can get a pretty good sense of the animal’s size.

    Bigger leaves have bigger “leaf bones”. Sort of a no-brainer. The leaf needs to have a fairly consistent number of veins overall, so the spacing has to be closer in a small leaf.

  26. LevelGaze says:

    Umm… How exactly do you predict the past?
    Or am I dead and have gone to an alternative universe?

  27. David says:

    “This will improve scientists’ prediction and interpretation of climate in the deep past from leaf fossils.”

    Strange words to use’ “prediction” and “interpretation”, instead of “improving our UNDERSTANDING of past climate”. One does not “predict” the past. However, if one is looking for a particular result, then one can look for (cherry pick) from a data set, and find the “predicted” answer. So, how many factors make a tree ring grow, or a leaf also for that matter?

  28. durango12 says:

    99% hype

  29. My thoughts (observations and emotions) are like the comments above. Mixed–excited, yet cautious and skeptical. It is hard to get past the sense behind the writing that the authors are primarily excited that they have something they think justifies their time and money spent, but also justification for continuing funding. Well, one has to pay the bills. I’m okay with that, but it does seem the climate factor is what really excites them. The pool of possible grants gets much larger for plant-climate research. The pool must be much smaller for basic plant-biology research. Perhaps we shall see. Mostly, it may be practical, as they suggest, but I doubt we gain significant insight to the past. The rocks tell us most of what we can know, and the geologists have been doing that for many decades already.

  30. Stephen Wilde says:

    Plant stomata are already a better proxy for past CO2 variability than ice cores and generally show much higher CO2 variations than do the ice cores.

    As long as the recording and / or interpretation of plant data is not corrupted by warmist prejudices this new research could well prove useful.

  31. Ted Swart says:

    Somewhat more scientific than trying to use tree rings as proxies for past temperatures. Nevertheless, overly optimistic in terms of using the leaves to get a handle on past climate. The fact that tree veins behave like fractals should hardly be a surprise. Being able to infer leaf sizes from the veins in leaf fragments may possible prove to be useful in some way — particularly with respect to the fossil record.

  32. michael hart says:

    Good that researchers are at least thinking about these sort of things, but developmental biology is still fiendishly complex. Attributing observations to genetics or environment or both is not a new problem that is going to be resolved any time soon, if ever.

  33. Dave says:

    A proxy accurate to 0.001 degrees C I’m sure…

  34. Jim Strom says:

    Good work and admirable theorizing, but I suspect it’s early times for this line of thought. In particular, there are likely quite a few confounding factors. For example, it is common to find mature leaves of widely varying sizes on the same plant, and to find nearby plants of the same species producing leaves of varying sizes when growing in different conditions, for example, in sun vs. shade. Effects such as this could lead to mistaken conclusions about historical climate–if, say, the small leaves in a given area tended to decay before they became fossilized.

  35. jack morrow says:

    Just another way to get taxpayer grants. Like someone mentioned , nothing new here ,cactus plants are a good example how plants cope with dry conditions. These “new scientists” must sit around all day trying to come up with a new way to keep their jobs. We’ve got lots of Kudzu here in the Southern states with big leaves that they could pick and study and maybe get rid of some of the plants–no everyone knows you can’t kill kudzu.

  36. Andrew Greenfield says:

    OT but is true that Heartland will not be holding any more ICCC conferences? (Its sad, but there is probably no need anymore for skeptic conferences as majorities everywhere are onto the scam and are skeptical and growing every year Ie a none issue). Anyway why doesnt WUWT organize a last one next year to put the final nail in the coffin of AGW LOL

  37. wsbriggs says:

    Watch the next few weeks, they’ll suddenly discover that the world was a drier/wetter/hotter/colder place than they thought. Pick the change that most supports, “It’s worse than we thought.”

  38. cbrtxus says:

    That’s all very interesting. How much did that project cost us? Considering the fact that the United States cannot balance its budget, is this research the sort of thing that we should be throwing money at? My mom used to tell me that we save money a penny at a time. Of course today with government, that would have to be a hundred thousand dollars at a time.

  39. Chris B says:

    Another opportunity to fabricate a Hockey stick? Were there deciduous trees in Yamal?

  40. Bill H says:

    This is your life line…Oh I’m sorry… I thought that was your palm….

    Climate is science reduced to gypsy liberal arts…….. or was it that way all along?

  41. Bill H says:

    Ally E. says:
    May 24, 2012 at 1:19 am

    This is brilliant. It will be fascinating to apply this to fossils. One of those “But of course!” moments when once stated, it makes perfect sense. I look forward to reading what discoveries can be found on this basis.
    —————————————————————

    let me gaze into my crystal ball…..

  42. Bill H says:

    I wonder if anyone told these folks that a plant will respond to its current environment and conditions at the time it formed? as with all plant life…. just wondering….

  43. Latitude says:

    “”The research also points to a new explanation for why leaf vein evolution allowed flowering plants to take over tens of millions of years ago from earlier evolved groups, such as cycads, conifers and ferns””.
    ===============================================
    because Co2 levels went from limiting to not limiting
    ================================================
    “”flowering plants can achieve much higher photosynthetic rates than earlier evolved groups,””
    ===============================================
    they need carbon
    ============================================
    “”but it doesn’t explain why smaller leaves are found in cool, dry places too, Sack noted.”””
    =====================================
    so you proved nothing, wasted time and money

    …publish or perish

  44. D.R. Williams says:

    Was a time when “predict” referred to something that had not yet happened. Perhaps the team needs an etymologist?

  45. Owen in GA says:

    Well, this is nice. It looks as though we have a way to determine the moisture part of the plant growth equation now. Of course I didn’t see much quantification of the effect, so there is no calibration that says major vein density X equals soil moisture level Y. If we really want to take microclimatic effects out of the treemometer equations we will need a pile of fossilized leaves from the tree to be piled neatly in undisturbed chronological order underneath it. Then we can correct ring width for corresponding moisture limiting factors and finally construct the perfect hockey stick that won’t break during slapshots. (partial /sarc – I can’t help myself)

    I guess what I am saying is this is interesting, but since the above scenario is improbable since most leaves that fall under the tree will simply decompose and the fact that most of the cores are from very long lived conifers (not covered by this study), this doesn’t do anything for the “climate debates”. As John Marshall stated well above, the leaves that fossilize tend to be well away from the tree that produced them anyway. We could say that the region around whatever ancient lake collected these leaves into these fossil caches had an average climate based on a large statistical sampling of leaves in any given layer. Microclimatic effects could still dominate though as it is possible that all the leaves came from the same copse of trees that just happened to drop their leaves into the same stream to be carried to the lake. In fact, it could be the only stand of trees for a hundred miles or more that happens to be in an area that gets just a little more rain due to geography. So, it is interesting but not really a boon or bane for the team.

  46. Paul Marko says:

    I grabed my ‘Trees and Shrubs of New Mexico’ by Jack L. Carter and noticed we had everything from gymnosperms, oaks, cactus and a multitude of broadleaf species including canyon grapes.
    Now, what was that climate again?

  47. Pamela Gray says:

    One would have to be careful not to interpret the oasis environment in which the leaf fossil was found as being representative of the surrounding desert. GISS warms up the Arctic by making this mistake in reverse.

  48. juanslayton says:

    gopal panicker: at the extreme we have cacti with no leaves

    I read somewhere that cactus spines are modified leaves.

  49. ChE says:

    “The previous century is known for exciting discoveries in physics and molecular biology, but this century belongs to plant biology.”

    Cue the beer garden scene from “Cabaret”.

  50. Paul Mackey says:

    It’s not that plants evolve and change over time is it?

  51. wws says:

    Reading through, here’s what the research comes down to: leaves growing in areas with high water availability don’t need to bother with water transport so much, so their veins are streamlined and relatively far apart.

    Leaves growing in dry areas need to put great effort into their water transport support systems, so the veins are densely packed and in great numbers.

    Streamlined, low demand water transport systems allow for relatively large leaves. Densely packed, high demand water transport requires smaller leaf size to be effective.

    Nice model, but come on – pretty bleedin’ obvious. Form follows function.

    and I predict any climate hindcasting that comes from this rather simple observation is going to have a very high bogosity content.

  52. Kevin Kilty says:

    The water must be replaced through the leaf veins, which pull up water through the stem and root from the soil. This drives a tension in the leaf vein “xylem pipes,” and if the soil becomes too dry, air can be sucked into the pipes, causing blockage.

    OK, stop right here. I know our main focus around these parts is climate, but, if fluid in the plant structure were under any reasonable amount of tension, then plants could not stand rigidly and vapor bubbles would form in the network of capillaries. Moreover, how could plants move water from the soil to a height over 10 meters or so, since that would involve a tension greater than one atmosphere?

  53. Mr Lynn says:

    I haven’t read the paper, but fail to see the problem some commenters have with this study. Finding mathematical ways of describing the relationships between leaf size and vein growth seems a legitimate pursuit, and certainly paleontologists are always interested in new clues toward reconstructing (“predicting” is the wrong word) ancient climatic conditions, whether micro, local, or regional. Obviously one would not rely solely on leaf structure.

    Certainly some of the academic press releases Anthony posts here deserve a bit of ridicule (e.g. the street-lamp insect one), but not this one, I think.

    /Mr Lynn

  54. theduke says:

    Forgive my cynicism but how long before the next study using leaf samples proves that the MWP didn’t happen?

    I wonder if leaf samples from that era even exist?

    “Dr. Sack: Dr. Mann on line 2.”

  55. ferd berple says:

    The paper ignores that there are 3 forms of photosynthesis employed by plants, depending on the conditions they are adapted to. C3, C4, and CAM

    It is believed that C4 and CAM evolved later than C3, as they are better suited to low CO2 environments and for most of the past 600 million years CO2 was much higher than at present. C3 works best in high CO2 environments (most plants are C3) which may explain why adding CO2 to greenhouses improves plant production.

    If climate science is correct, then the ice ages are a result of low CO2 and adding CO2 to the atmosphere is helping to prevent global cooling as we had 60 years ago and thus helping prevent the next ice age.

    Adding CO2 to the atmosphere is clearly increasing plant growth, and all the farmers of the world should be paying $$ to everyone filling up at the gas pumps these days, in recognition for all the free fertilizer we are providing them.

  56. Jaye Bass says:

    Think L systems

  57. This is all very nice and I am sure will prove useful in its paleo applications. It would seem that not only have we always known many of these things and just needed to get the scaling business properly accounted for but it is very much like structural geology. The rule of thumb goes the minor structures mirror the major structures. Once again we see then nature has used sensible scaling techniques to conserve all kinds of things. We must be careful however, not to over play the idea. Like fractals, wonderful, useful tool, that needs to be applied with common sense.

  58. Bill Tuttle says:

    Why had these trends escaped notice until now?

    Because none of them though to ask a gardener.

  59. Don Keiller says:

    So what’s new here?
    Stomatal density has a well characterised inverse relationship with CO2 concentration and has been used to estimate (not “predict”!) past CO2 levels.
    E.g.
    McElwain, J.C., Mayle, F.E. and Beerling, D.J. 2002. Stomatal evidence for a decline in atmospheric CO2 concentration during the Younger Dryas stadial: a comparison with Antarctic ice core records. Journal of Quaternary Science 17: 21-29.
    Wagner, F., Bohncke, S.J.P., Dilcher, D.L., Kurschner, W.M., van Geel, B. and Visscher, H. 1999. Century-scale shifts in early Holocene atmospheric CO2 concentration. Science 284: 1971-1973.

  60. kirse says:

    Brilliant. :)

  61. Tenuk says:

    This could be a useful tool to help understand past global climate if fossil leaves are common enough and cover large geographic spreads. However, I’m not sure this is the case and wrong assumption about climate could easily be made – just like happens with the thermometer record.

  62. theduke says:

    I’m with levelgaze. Why do scientists have to torture the language so? How does one “predict” the past? You can “uncover” the past or “develop an understanding” of it or perhaps “discover” climatological conditions in the past but you can’t “predict’ the past.

    The truth is that they really can’t predict the climate (or weather, if you will) three months out, and yet they use words to create the impression that they are some kind of modern soothsayers.

  63. DJ says:

    Goody. Another way of using trees to make hockey sticks.

    Now, we’ll be able to tell from this season’s maple leaf what the climate was like last year. Better yet, any portion of any leaf, from any portion of the tree (healthy or not, shaded or sunny, under the canopy or top of the canopy). No more fears of “cherry picked” data.

    What I do see is a terrific advancement for software developers to incorporate a new algorithm into the fractals for animation. Software for fur, wind and water have made tremendous strides towards realism, now another jump for plants. But hindcasting climate??

    I see weeds in their theory.

  64. JDN says:

    This being a Nature article, we should immediately try to falsify it. Don’t you people remember all the other science-like Nature articles that turned out to make assumptions that were entirely too generous. My bet is that plants do what they like and don’t actually adhere to rigid laws.

  65. John F. Hultquist says:

    And this explains the co-location of wine-grapes (large leaves) and olives (small leaves) in a dry-summer sub-tropical climate (aka a Mediterranean climate) . . .
    Oh, wait! I’ll have to get back to you on this.

  66. Luther Wu says:

    Lonnie E. Schubert says:
    May 24, 2012 at 5:24 am

    My thoughts (observations and emotions) are like the comments above. Mixed–excited, yet cautious and skeptical.
    ____________________
    I found myself with the same set of reactions.
    The state of modern “science” has turned me into a cynic.

  67. Greg R. says:

    This just seems – silly. It is like advertising a non-stop flight from San Diego to Hawaii and thinking it novel! All I can say is “DUH!”

    OF COURSE the major veins in smaller leaves are packed closer together… the leaf is smaller! …And to think that we (the US taxpayer) paid for this study.

    I bet – just maybe – that if these researchers looked hard enough, they would “discover” that the “major veins” in an african spiny mouse are packed closer together than those same “major veins” in an african elephant – yet they both inhabit the exact same biome and neither are indicative of the savannah’s climate – present, past, or future.

  68. hagendl says:

    Developmentally based scaling of leaf venation architecture explains global ecological patterns Lawren Sack et al. Nature Communications 3, #837 doi:10.1038/ncomms1835

    I thought science was based on validating hypotheses. How can this hindcasting model be validated?

  69. Olen says:

    The strength of the mathematical linkage of leaf veins with leaf size across diverse species raises the question of cause.

    Their enthusiasm is obvious but, maybe they should run this by a couple of mathematicians.
    They should not wander into unknown territory without proper support.

  70. Ged says:

    Different species of plants have different leaf shapes and leaf vein patterns. Are they assuming that plants followed the same principles throughout all time for vein patterns, when they don’t between species?

    I am flabbergasted. It’s cool research, but being derailed by climate silliness.

  71. ozspeaksup says:

    yeah, and then theres plenty of evidence seeds from the same plant grown with variations in soil fertilizer and water all have HUGE differences.
    too much calcium iron or not enough makes a massive difference,
    and then
    ages past had les carbon so plants would have struggled bet that gets bypassed, this seems another carbon furphy in the making..
    an adelaide news did a story on nature mag today.
    called it the respected? journal, I had a big laugh/

  72. smilesooner says:

    As well as others, I am not sure how original or surprising this finding is. I recently read a fascinating book on the underlying law governing many such patterns in life.

    “Design in Nature: How the Constructal Law Governs Evolution in Biology, Physics, Technology, and Social Organization” by Adrian Bejan and J. Peder Zane is the book. The first author is an engineer, specializing in thermodynamics, and has written a number of more technical books. This was my first introduction to the ideas, which seem obvious in retrospect. Essentially, life and even existence, is all about flow. This law is why we see so many of the same patterns in nature – riverbeds, branches of trees, root systems, city streets etc. I would highly recommend the book.

    Interestingly, Bejan stresses that human beings are part of nature – an idea that will resonate with a lot of people here. We are not some mysterious plague visited upon the universe – we belong here as much as any other feature of nature. Humanity’s design efforts are all part of the design of nature. But Bejan believes design comes from physical laws – not a grand designer, to be clear.

  73. jorgekafkazar says:

    wsbriggs says: “Watch the next few weeks, they’ll suddenly discover that the world was a drier/wetter/hotter/colder place than they thought. Pick the change that most supports, “It’s worse than we thought.””

    And unprecedented, too. Not to mention robust.

  74. agfosterjr says:

    While such a discovery may seem insignificant to the non-scientist and trivial to the non-biologist, it must be quite a windfall to botanists who study leaves for a living. Congratulations!

    Analogously we all share the same circulatory system, with named major arteries and veins, while capillary count depends on muscle mass. –AGF

  75. tadchem says:

    It struck me that they are still locked in on “using computer simulations.”
    The obvious relationship they are overlooking is that the variation of vein density with water availability and the variation of leaf area with water availability are the same.
    This suggests that the total number of veins per leaf is set when the leaf is formed, and remains unchanging as the leaf grows. The availability of water merely controls the final size to which the leaf can grow.
    This is an easy hypothesis to test *experimentally*, by controlling the water availability for specific individual plants of a selection of species over consecutive years. Greenhouse-grown trees would be good – simply measure the average area of a leaf for each tree and vary the water regiment from year to year.
    If you want to you could also determine the vein density distribution for the leaves at the same time.

  76. Zeke says:

    Certainly Dr. Sack is making an important contribution to the subject of evolutionary ecology and paleo climatology. To support these important scientific endeavors, it would be quite simple to dig up all the high BTU coal in Illinois, and provide Dr. Sack and his undergraduates all the fossil leaf fragments they could possibly want.

    We’ll make sure they get just a little fragment of each leaf, and plenty of brand new computers to model the rest of the leaf structure with, to their heart’s content.

    Boxes of fossilized leaves in all states of preservation could be delivered to his door daily, and Illinois could again enjoy a real economy with energy, jobs, and industry, instead of drying up and blowing away.

  77. “We encourage anyone to grab a big and a small leaf from trees on the street and see for yourself that the major veins are larger and spaced further apart in the larger leaf.”

    Right. And both leaves are from the exact same environment, with the same temperature, humidity and so forth. There might be some useful environmental information in leaf structures, but teasing out that information presumably suffers from all the same challenges as dendro. Namely, all the other factors (besides temperature) that affect plant growth: precipitation, soil condition, predation, humidity, nutrients, age of the particular plant, etc. Also, it will be necessary to carefully select appropriate species consistently across time to be able to say anything about the differential growth rates across time.

    Anyway, some interesting observations about vein structure and lots of good science that can be done purely on the basis of structural biology. Less clear whether this can be applied with rigor to past climate, and particularly to past temperature reconstructions.

  78. Eyal Porat says:

    Isn’t “prediction of past climate” an oximoron?

  79. Crispin in Waterloo says:

    @Stephen Wilde

    Plant stomata are already a better proxy for past CO2 variability than ice cores and generally show much higher CO2 variations than do the ice cores.

    As long as the recording and / or interpretation of plant data is not corrupted by warmist prejudices this new research could well prove useful.
    ++++++++++++++

    I am with you on that one. What would be great is to use veins and pores to calculate the CO2 and the local temperature and rainfall estimate. There may be very interesting in and out-of-sync relationships over time.

  80. Latitude says:

    Mr Lynn says:
    May 24, 2012 at 7:20 am
    Certainly some of the academic press releases Anthony posts here deserve a bit of ridicule (e.g. the street-lamp insect one), but not this one, I think
    =======================================
    They found nothing……

    “This would certainly be an advantage when leaves are in hot, dry environments, but it doesn’t explain why smaller leaves are found in cool, dry places too, Sack noted.”

  81. George E. Smith; says:

    “”””” Using leaf veins to hindcast climate

    Posted on May 24, 2012by Anthony Watts

    Leaf lamina. The leaf architecture probably arose multiple times in the plant lineage (Photo credit: Wikipedia)

    From the University of California – Los Angeles

    Hacking code of leaf vein architecture solves mysteries, allows predictions of past climate

    UCLA life scientists have discovered new laws that determine the construction of leaf vein systems as leaves grow and evolve. These easy-to-apply mathematical rules can now be used to better predict the climates of the past using the fossil record. “””””

    Why not just read a history book; that will tell you what the past was, so you don’t have to PREdict it.
    HEY !! it’s the FUTURE that we need to predict.

  82. Gary Swift says:

    Interesting. So, since the leaf vein pattern responds to precipitation, where tree rings respond to many things, perhaps you could use the leaves to remove the moisture noise from the treemometer temperature + moisture record?

  83. Billy says:

    Do academics ever go outdoors? I see no uniformity in plant leaves. A lush, well grown large leafed plant can found a short distance from a dried up little runt plant. Variations in soil type, nutrients, water, temperature and sun exposure are everywhere. It appears to me that there is a wide variation in leaves every year.

  84. phlogiston says:

    The team discovered predictable relationships that hold across different leaves throughout the globe. Larger leaves had their major veins spaced further apart according to a clear mathematical equation, regardless of other variations in their structure (like cell size and surface hairiness) or physiological activities (like photosynthesis and respiration), Sack said.

    This suggests quite simple genetic control of leaf structure, based on a scaling function – how much growth happens between the veins. So all leaves have a similar number of veins, the difference in size is just a difference in inflation between the veins. For instance, draw a leaf, veins and all, on the surface of an inflated balloon. Then blow it up some more, and you will get the structure of a big leaf. This kind of inflation is quite a common way of changing size in organisms, there is one gene somewhere determining this inflation.

  85. thelastdemocrat says:

    Please give ideas for science-fair projects. The study apparently says you can predict overall leaf size by a fragment. Also, you could predict something about the plant’s environment – although this is not clear – along a riverbed or creekbed, you would have more well-watered plants in a zone that was relatively dry.

    How could leaf vein density be easily measured by schoolkids? Could you scan a leaf, and blow up a region to be easily measured by a ruler, or an e-ruler? You could have kids gather a few leaves, scan them, enter them in computer, blow up a region of th eleaf, measure vein length in the portion of leaf, then determine/”predict” which fragment came from which leaf. Or maybe guess which came from reliably dry or wet terrain?

    Sounds OK? Any other ideas?

  86. Steve Tabor says:

    Aside from the various factors affecting leaf condition that have been mentioned in these comments (water use, sunny or shady side, mineral availability, humidity, etc. — not just temperature), there is always a problem in geohistory with transport and location of deposition. For a long time the Carboniferous was thought of as “The Age of Swamps”, simply because the rocks where it was first studied were swamp rocks with coal and swamp plants and amphibians. But how much of the land surface was swamps and how much was something else? 10%, 1%, 1/10,000 of 1%? All we know is that the lowland areas were great for deposition. It was subsequently found that large glaciers also existed at the same time as the swamps, as is the condition today.

    And of course entire landscapes have been eroded away, more and more the farther back you go. We see only a small part of what existed in geologic history.

    In deposition, the non-swamp, non-marine, non-lakebed and non-river plain areas are underrepresented. High mountains and hill country are hardly ever represented in the fossil record. How far have the leaves been transported, and where did they come from? Hard to know. So how do we relate the leaf characteristics to whatever micro- or regional climate they are expected to represent? And what can we then say about any ecosystem that may have been upstream or upwind, or how many different ecosystems (all climate-dependent) there actually were at the time? At present there are something like seventeen in our state of California, thirteen in Arizona, seven (?) in Virginia.

    What interests me about this and other similar blogs is the quality of the skepticism that commenters bring to these types of allegations and proposals. Commenters seem to have a well-honed set of bull**** detectors, a very encouraging thing. Anthony should be proud. The presenters of the study should be reading this so they’ll know how to design their experiments, or if their experiments are even feasible.

  87. Mark says:

    ferd berple says:

    The paper ignores that there are 3 forms of photosynthesis employed by plants, depending on the conditions they are adapted to. C3, C4, and CAM

    It is believed that C4 and CAM evolved later than C3, as they are better suited to low CO2 environments and for most of the past 600 million years CO2 was much higher than at present. C3 works best in high CO2 environments (most plants are C3) which may explain why adding CO2 to greenhouses improves plant production.

    It would be interesting to know how these processes differ at the genetic level and if the differences are in chloroplast or nuclear DNA.
    Apparently there are plants which are C3/CAM or C4/CAM. Is a C3/C4 or C3/C4/CAM plant possible? (Especially considering that polyploidy is fairly common in plants.)

  88. This article gives the best credibility to tea leaf reading. I was told that the accuracy in tarot cards reading has increased by 30%. On the other hand, my reliable crystal ball says: they have found another way, to keep the propaganda on the front pages; with another stupidity / I hope is not on the taxpayer’s expense…? Connecting the big / small constant climatic changes with the phony GLOBAL warming, is the mother of all lies. If it wasn’t demand for bullshine – they wouldn’t have being producing it. I.e. demand for bullshine controls the supply = blame yourself suckers!!!

  89. Ally E. says:

    There are a few above who responded much as I did along the “This is brilliant” line. I’m glad I’m not alone. :)

    I’m not assuming that this mob are pushing the CAGW idea, they could actually be after information. IF they come the “It’s worse than we thought” line THEN I will dismiss them as just after funding. Until then, this is something interesting.

    Not all science is bunkum and some scientists are looking to see what’s there to refute the nonsense. I’m not ready to slam them yet.

  90. George Steiner says:

    Chicken entrails are even better.

  91. Mr Lynn says:

    Latitude says:
    May 24, 2012 at 10:43 am

    They found nothing……

    “This would certainly be an advantage when leaves are in hot, dry environments, but it doesn’t explain why smaller leaves are found in cool, dry places too, Sack noted.”

    The point of research is not to answer all questions, but to raise new ones.

    /Mr Lynn

  92. G. Karst says:

    Gary Swift says:
    May 24, 2012 at 11:07 am

    Interesting. So, since the leaf vein pattern responds to precipitation, where tree rings respond to many things, perhaps you could use the leaves to remove the moisture noise from the treemometer temperature + moisture record?

    I agree, the more linked data that can be measured from the same tree, should allow for a better proxy. ie tree ring + stomata count + leaf development should provide better calibration of any proxy calculation, correcting for variables to the same tree. Let not throw babies out with the dirty bathwater. GK

  93. jack morrow says:

    Ally E says:
    Sorry Ally-nothing brilliant anywhere in this report.

  94. Caleb says:

    Sick trees have smaller leaves.

  95. On one tree, different branches have leaves with different veins. Some are exposed to the eastern sunlight – others on the top of the trees – not all leaves are on the outside branches – they all have different veins on. If you go from one branch to another side of the tree; was any GLOBAL warming, or GLOBAL cooling in those few minutes…? Must have being, if they say so. Or can they recognize if the fertilized leaf was from inside or outside branch?

    If the next tree has better mulch, or roots closer to the gully, to get more moisture, than the tree 10feet away’ they have different texture veins. See what kind of educators are brainwashing the kids in universities = cloning more idiots of themselves…

  96. Sleepalot says:

    Perhaps those guys ought to visit Kew Gardens, where trees from around the world are grown side by side.

  97. Don Keiller says:

    @Mark there are certainly “facultative” CAM plants, like Mesembryanthenum crystallinum (iceplant) which starts off as C3, but if you dehydrate or water with salt water will convert to CAM.
    (I did some research on them way back). Many desert plants are CAM, but will produce short-lived C3 leaves in the brief periods it rains.
    There are also C3/C4 intermediates.

  98. anengineer says:

    Temperature predictions are based on the assumption that leaves are smaller at higher temperature. Bet there are other factors, like the availability of moisture, that also influence this. just like tree rings.

  99. Tim Clark says:

    So, is the vein length preresponsive to dry conditions or post? As a plant physiologist, let me state:
    bigger leaves are a result of better growing conditions, not an indicator of plant adaptability. i say bullshit on the suppositions in this study.

  100. TonyG says:

    Veins are spaced farther apart on larger leaves? Any gardener would know that. I never gave it a second thought until reading this.

    But what can you actually know from leaf size? I’m looking at one of my squash plants, and it has some leaves nearly 9″ across, and some only 4″ across – and they’re all fully grown leaves.

    I feel like I’m missing something.

  101. Tom Harley says:

    Not forgetting one of Australia’s most widely spread plant families with few leaves, the Acacias, which mostly have flattened stems called phyllodes. They exist in every different climate locality. Then the Eucalypts and Corymbia’s, where juvenile leaves are much larger than adult leaves. Finally Bonsai plants, naturally or artificially, have leaves much smaller, yet flowers are unchanged in size. Nothing to do with climate, even less with temperature.

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