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Another Take On The Term “Rewilding”?

In the previous post, we explored the concept of crop “rewilding” as it pertains to genetically resurrecting “wild” plant genes by reintroducing or by re-activating them in some modern crop plants.

One of the main justifications for doing so is to develop new crop plants to help feed and clothe the Earth’s growing human population, especially since we may be soon running out of food (see As Global Population Grows, Is The Earth Reaching The ‘End Of Plenty’?, for instance).

With all of this freshly in mind, I was interested to discover a couple of recent stories (Refs. 1 & 2 below) that are sort of about crop “rewilding”.

But, in these cases, genetic engineering is NOT involved.

Instead of the resurrection of plant genes, these stories are about the resurrection of so-called “lost crops”. That is, native or traditional crop plants that may have been displaced by modern crop plants, such as GMO crops.

African Super Veggies

The idea of using indigenous crop plants as a basis for African agricultural development is not new.

In the 1990s, the US National Research Council (NRC) in Washington DC convened a panel to examine the potential of Africa’s ‘lost crops’, including grains, fruits and vegetables. Chaired by renowned agricultural researcher Norman Borlaug, the panel concluded that native plants held tremendous potential for improving food security and nutritional intake across Africa, and should be a greater focus for researchers.” (From Ref. 1 below)

It may have taken twenty years, but “Scientists in Africa and elsewhere are now ramping up studies of indigenous vegetables to tap their health benefits and improve them through breeding experiments. The hope is that such efforts can make traditional varieties even more popular with farmers and consumers.” (from Ref. 1 below)

Asiatic Cotton Versus GMO Cotton

The authors concluded that under rain-fed conditions, the benefits traditionally associated with growing Bt American cotton are not necessarily realised. They recommend that a range of factors – including yields and profits but also irrigation and alternative cotton varieties – should be taken into account when planning strategies to improve cotton farming in India.” (from: Oxford University News)


1. Cernansky, R. (2015) “The rise of Africa’s super vegetables”. Nature, Vol. 522, pp. 146-148. (Full Text)

2. Romeu-Dalmau, C., et al. (2015) “Asiatic cotton can generate similar economic benefits to Bt cotton under rainfed conditions.” Nature Plants, Article Number 15072. (Abstract)

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A Blast From The Past?

Is it just me, or does there seem to be a lot about the so-called “rewilding” of crop plants in the news lately? (Please see here, for example.)

I think I first heard the term “rewilding” about 20 years ago in a Biology Department seminar at Montana State University. In this case, the term “rewilding” was used in the context of conservation biology.

Simply put, rewilding, as a means of ecological restoration, has to do with reintroducing apex predators or keystone species into an environment. (Think wolf reintroduction into Yellowstone National Park, for example.)

But the recently-newsworthy “rewilding” of crop plants refers to something quite different. Instead of physically reintroducing “wild” species into “domesticated” ecosystems, crop plant rewilding has to do with genetically reintroducing “wild” genes back into the “domesticated” genomes of crop plants.

Of course, this can be done via traditional plant breeding techniques such as crossing a crop plant species with a wild relative.

But the main reason for the recent increased interest in the rewilding of crop plants is the emergence of new plant breeding techniques (NBTs) that are more precise and much faster than traditional “introgression” plant breeding.

“Introgression breeding is the standard method used to introduce genes and traits from wild plants into domesticated crops. This method uses an initial cross between the crop and the wild relative of interest followed by repeated backcrossing to the domesticated crop to erase as much genetic material from the wild relative as possible while keeping the trait of interest. Molecular markers can be used to track the trait of interest through the crosses, a process called ‘marker-assisted breeding’. However, introgression breeding is time consuming and technically challenging when more than one gene is being selected for, and it is often difficult to get rid of closely linked undesired genes.” (from Ref. 1 below)

Some of these new plant breeding techniques rely on powerful new ways to edit DNA (more about this later on).

Some of these NBTs involve methods of genetic engineering that allow for “rewilding” in such a way that the final crop can’t be distinguished from a crop bred by traditional means. Therefore, some scientists see a natural place for ‘rewilded’ plants in organic farming.

Because no “foreign” genes (from another species) are present in genetically-engineered, rewilded crop plants, will that render these GMO’s more socially acceptable?

More on this fascinating topic to come….


1. Andersen, M. M., et al. (2015) “Feasibility of new breeding techniques for organic farming.” Trends in Plant Science, http://dx.doi.org/10.1016/j.tplants.2015.04.011. (Full Text)

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The “Inside” Story?

An article in Science magazine (see Ref. 1 below) reports evidence supporting the hypothesis that leaf-dwelling, nitrogen-fixing bacteria may provide host plants with significant amounts of nitrogen.

In the past, we briefly explored the microbial phyllosphere, that is, the microbes – including nitrogen-fixing cyanobacteria – that dwell on the surfaces of plant leaves.

However, the bacteria in today’s story don’t dwell ON the leaves, but INSIDE the leaves.

Yes, there are bacteria (and fungi) that actually live in the spaces between the plant cells, inside the leaves. These microbes are collectively known as endophytes (as opposed to the surface-dwelling “epiphytes”).

And there is no question that most plants – even cultivated crop plants – likely serve as hosts for some endophytes.

The BIG question is: Do these endophytes affect the physiology (function) of the host plants? And, if so, how?

Presumably, the endophytes benefit, at least, from the solar-powered donut factory (i.e., photosynthesis) provided by the leaves. If the endophytes use some of the carbs (sugars) made by the plants, they are somewhat of a drain on the plant’s resources.

Then, another good question is: Why do the plants put up with these microbial “moochers”?

The likely answer is that the plants are somehow benefiting from these microbial endophytes. And, indeed, there are lots of studies showing that plants with certain endophytes may grow better (and may even survive harsh conditions better) compared to plants without these endophytes.

If this is true, then what are these microbial endophytes doing that benefits the host plant?

In other words.…

How Do Endophytes Work?

Despite all the studies showing that endophytes can improve plant growth (and may even be responsible for plant survival in extreme physical environments), precise reasons to explain HOW such endophytes do this have remained elusive.

At least a partial answer to this fundamental question may be provided by results reported in this Science magazine article (Ref. 1 below).

According to this article, at a recent scientific meeting, two separate researchers – Prof. Sharon Doty and Prof. A. Carolin Frank – presented evidence supporting the notion that that some leaf-dwelling bacterial endophytes can convert atmospheric nitrogen gas (N2) into a more biologically usable form (NH4+), which is then used by the host plants.

These results provide evidence that one reason that some bacterial endophytes benefit their hosts is by providing the plant with a source of nitrogen. Plants are often deficient in this essential mineral nutrient, especially in nutrient-poor soils.

Simply put, some of the bacteria living inside plant leaves may actually be fertilizing the plant with nitrogen.

However, this is a controversial hypothesis, and it has met with skepticism from some in the scientific community.

“That’s a radical notion, because nitrogen fixation is generally thought to happen primarily in bacteria-rich nodules on the roots of legumes and a few other plants, and not in the treetops. “We are completely fighting dogma,” says Doty, a plant microbiologist at the University of Washington, Seattle.” (from Ref. 1 below)

One reason for this skepticism is that the bacterial enzyme (nitrogenase) that converts N2 into NH4+ is significantly inhibited by oxygen gas (O2), which, of course, is quite abundant in photosynthesizing leaves.

Despite such objections some scientists “…are now cautiously embracing the idea. “There’s a change in attitude, not from skepticism to believing but from skepticism to cautious questioning,” says Gerald Tuskan, a plant geneticist at Oak Ridge National Laboratory in Tennessee. Tuskan and his colleagues have isolated about 3000 microbes from poplar, many of which are equipped with nitrogenase. Some sequester themselves in biofilms with oxygen-limited compartments, where nitrogenase could function even in the leaf’s oxygen-rich environment.” (from Ref. 1 below)

Why is this important?

Frank and Doty suspect that nitrogen-fixing leaf bacteria may be widespread, and, if transferred to crops, could help boost yields on marginal soil.” (from Ref. 1 below)

“Other plant biologists, although far from convinced, are paying attention. “If there’s an unrecognized set of nitrogen fixers in a wide number of [tree] species, that’s a big deal,” says Douglas Cook, a plant and microbial biologist at UC Davis.” (from Ref. 1 below)


1. Pennisi, E. (2015) “Leaf bacteria fertilize leaves, researchers claim.” Science, Vol. 348, pp. 844-845. (Abstract).

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You Talkin’ To Me?

Dodder (genus Cuscuta) is an example of a parasitic plant. That is, it derives some or all of its nutritional requirements from another living plant.

In a previous post, we saw how dodder seedlings may “sniff out” their victims.

But dodder seedlings may do much more than use volatile chemicals to find their plant hosts. Dodder may also “genetically communicate” with its host plant using small bits of RNA, specifically mRNA.

A paper published in the journal Science (see Ref. 1 below) has provided evidence that “When dodder attacks a host plant, it opens up a conduit through which messenger [RNAs] and perhaps other regulatory RNAs are exchanged between parasite and host. Because a single dodder plant can attack multiple hosts, such exchanges may underlie instances of genes transferring between species.” (from Editor’s Summary Ref. 1 below).

You can read a brief report regarding these findings HERE and watch a video below (thanks to Virginia Tech for both).

This is not the first report of small bits of RNA acting as a potential means of communication within an organism and between different organisms.

The ability of messenger RNAs (mRNAs) to move long distances in plants is well known. This mobility is thought to be controlled by the specific interactions between mRNAs and proteins that produce complexes capable of traversing plasmodesmatal pores into the phloem stream where they can be carried throughout the plant. Our understanding of this process has been limited by challenges in tracking specific mRNAs. In this issue of Nature Plants Thieme et al. [Ref. 2 below] describe a substantial step forward in characterizing mRNA mobility, revealing patterns of movement that suggest a broad scope and sophisticated regulation.” (from Ref. 3 below)

Of course, the main question about all of this is that, if small bits of RNA serve as a “language” among plants (and also among plants and fungi), then what are these organisms actually saying to each other?

There is some evidence that pathogenic fungi may use small bits of RNA to compromise the immune system of host plants (see for example small things considered).

It’s not unreasonable to expect that parasitic plants such as dodder use RNA trafficking to their advantage. For example, “…it is interesting to speculate whether RNAs from the parasite could be used as pathogenic factors in establishing and maintaining host connections.” (from Ref. 4 below).

Perhaps the greatest implication of all of this mobile RNA has to do with horizontal gene transfer.

As noted by the authors of Ref. 1 below:
This widespread exchange of mRNA raises the possibility of horizontal gene transfer (HGT). Given what appears to be a constant exchange of mRNA between Cuscuta and its hosts, the relative prevalence of cases of HGT involving Cuscuta is not surprising. Although most documented cases of HGT in parasitic plants suggest a mechanism involving direct transfer of DNA, at least one case of HGT into a parasitic plant (Striga hermonthica) exhibits evidence of an RNA intermediate in the mechanism.


1. Kim, G., et al. (2014) “Genomic-scale exchange of mRNA between a parasitic plant and its hosts.” Science, Vol. 345, pp. 808-811. (Abstract).

2. Thieme, C. J. , et al. (2015) “Endogenous Arabidopsis messenger RNAs transported to distant tissues.” Nature Plants, Article number: 15025 (Abstract).

3. Westwood, J. H. (2015) “RNA transport: Delivering the message.” Nature Plants, Article number: 15038.

4. LeBlanc, M., G. Kim and J. H. Westwood (2012) “RNA trafficking in parasitic plant systems.” Frontiers in Plant Science, Vol. 3, p. 203. (Full Text).

Parasitic Plant Time lapse – Virginia Tech from VirginiaTech on Vimeo.

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Dandelions Redux

Dandelions – Much Maligned.

Yes, it’s that time of year again in the upper left-hand corner of the USA when the dandelions are making themselves highly visible (by flowering). This prompted me to to consolidate and update a couple of previous dandelion-related posts.

A lot of people are pissed off by dandelions. Few plants generate such annoyance among suburban homeowners with immaculate lawnscapes as the common dandelion (in North America, they are most likely Taraxacum officinale).

What Do Suburban Lawns and the Vietnam War Have in Common?

Answer: The herbicide 2,4-D.

You may be familiar with this herbicide as an active ingredient in “Weed ‘n Feed®”, “Weed B Gon MAX®”, Turf Builder® With Weed Control”, etc..

During the Vietnam War, it was an active ingredient in Agent Orange.

On lawns it’s used to kill the dandelions, but NOT the grass. (Find out how it does this below).

In the Vietnam War the U.S. military used it to defoliate the trees (so that they could more easily spot the Viet Cong) and to kill crops (some of which were used as the enemy’s food source).

You’re likely familiar with the term “Agent Orange” because of the controversy regarding the tragic health problems it caused to U. S. soldiers. (For current info re. this issue see here).

The serious health issues to both Americans and Vietnamese caused by Agent Orange are due to contaminants called dioxins produced during its chemical synthesis. (For more info on this see 2,4-D and dioxins and also here.)

How Does 2,4-D Kill Dandelions…?

First produced in the 1940’s, the herbicide 2,4-D is one of many so-called phenoxy herbicides. These herbicides all are both structural and functional analogs of the plant hormone auxin, more precisely, indole-3-acetic acid (IAA). Such synthetic auxins as 2,4-D are not only structurally similar to IAA, but they are also biologically active as auxins in most plants. Although they both look and act like auxins, plants can not metabolize these phenoxy herbicides as they can with IAA, the natural auxin. This turns out to be the key to why phenoxy herbicides such as 2,4 D are able to kill some plants.

Auxin-based herbicides are referred to as “selective” herbicides because they kill so-called “broadleaf” plants (a.k.a., dicots) but not grasses, for example. (Hence, that’s why they’re such popular herbicides with both growers of lawns as well as of wheatfields.)

But how exactly does spraying 2,4-D on susceptible plants kill them?

This turns out to be very poorly understood, and it’s also the subject of much misinformation. For example, I’ve heard people say that such herbicides kill the plant because ” it grows itself to death”, and I’ve read that 2,4-D “…simply confuses the plant to death”.


At the present time nobody really knows precisely how the auxin-like herbicides kill susceptible plants. As with most effects of plant hormones, it probably has a lot to do with the plant species in question.

However, recent findings have provided important clues. And these clues support the idea that plant death may occur as a result of a combination of factors.

Here’s a summary of the story:

First off, one of the well-know effects of excess amounts of auxin on dicots is to cause them to overproduce the plant hormone ethylene. For example, in 1969, Mary Hallaway and Daphne J. Osborne first showed that ethylene is a factor in defoliation caused by 2,4-D.

Because plants can’t break down 2,4-D, it’s action persists. This action includes the excess production of ethylene, which may result in a number of plant responses, including epinasty and senescence.

Another effect of excess ethylene production in response to 2,4-D is to stimulate the production of yet another plant hormone, abscisic acid (ABA). The effects of ABA on the plant may contribute to eventual plant death. (For an illustration of the complex effects of auxin-based herbicides on plants, see Figure 1 in Ref. 1 below.)

…and why doesn’t 2,4, D Kill the Grass? (and You?)

Perhaps the simplest explanation for both questions has to do with sensitivity to the plant hormone auxin.

In general, grasses are much less sensitive to synthetic auxin herbicides than are dicots. That is, a much higher threshold level of auxin-based herbicide is required to elicit physiological responses in grasses versus the so-called “broadleaf” plants. So, at the doses used to kill dandelions, for example, grasses are largely unaffected. (Higher doses of 2,4-D may kill the grass, too, however.) Grasses may be more resistant to such herbicides because of differences in leaf morphology, translocation of the herbicide inside the plant, and the ability to metabolize (breakdown) synthetic auxins.

Aside from the toxic contaminant dioxin, 2,4-D has no physiological effects on animals at hormonal levels, that is, at the concentrations that affect plants. (Indeed, there is no reputable evidence that any of the five main plant hormones affects animals.)

Is Sex Necessary? – For The Common Dandelion, Apparently Not

Despite efforts to eradicate them using chemical warfare, the dandelions exhibit a remarkable ability to proliferate.

They do so likely because they produce seeds asexually, that is, without the complications of sexual reproduction, such as pollination.

This is because most dandelions reproduce by a process called apomixis.

Unlike other forms of asexual reproduction in plants such as vegetative plant propagation via cuttings, apomixis is asexual reproduction via seeds.

In the case of most dandelions (i.e., Taraxacum officinale), the embryo in the seed forms without meiosis, thus the offsping are genetically identical to the parent.

Hence, most, if not all, of the dandelions in your neighborhood may be clones.

What are the benefits of apomixis?

Well, despite the lack of the evolutionary benefits of sexual reproduction (lack of diversity), apomixis allows for the “mass production” of seeds, which appears to be an effective strategy for dandelion propagation.

By rapidly producing cloned offspring, sex is certainly not necessary for the common dandelion.

Dandelions – Highly Underrated?

Perhaps to the chagrin of suburban “lawnscapers” who spend so much time and effort and money in eradicating dandelions, did you know that dandelions are actually commercially cultivated in many places in the United States? Vineland, New Jersey, may indeed be the “dandelion capital of the world”. See here and here for why.

Also, did you know that dandelions can be a significant source of latex for the manufacture of tires (or tyres, if you’re outside the USA or Canada)?

It’s true! See here and here, for just two links.

Yes, and because of this, dandelions are plants of interest to biotechnologists in the USA, Germany, and the Netherlands.

So, despite the fact that millions of pounds of herbicides are used every year to kill them in lawns throughout the USA, dandelions can be used for food and as herbs, to make wine (“mellow yellow”), and even to make tires (or tyres).

And, There’s More!

If you’d like more information about these plants that are seemingly ubiquitous this time of year because of their bright yellow flowers, here are some online resources:

  • Dandelions in folklore, in literature, and much more can be found here and here.


1. Grossmann, K. (2007) “Auxin Herbicide Action: Lifting the Veil Step by Step”, Plant Signaling & Behavior 2:421-423. (PDF)

2. Grossmann, K. (2010) “Auxin herbicides: current status of mechanism and mode of action.” Pest Management Science, Vol. 66, pp. 113–120, (Abstract)

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Flowers That Change Color Over The Course Of A Day

Are transgenic plants a curse or a blessing?

Many people in the industrialized countries believe the former, despite ample scientific evidence to the contrary.

But I really don’t want to get into this thorny issue here, mainly because it’s been so well discussed elsewhere. (Please see, for example, Ref. 1 below.)

I would, however, like to tell you about some recent examples of genetically-engineered plants that may lead to greater social acceptance of plant GMO’s – starting with Petunia Circadia.

How would you like to grow plants with flowers that change color continuously throughout the day, from pink to blue and back again?

Well, the folks at Revolution Bioengineering are genetically modifying common petunias to do just that.

Here’s a YouTube video summarizing their story:

How do they do it? A good explanation can be found at: the science of color changing flowers.

For More Information: A list of stories about Revolution Bioengineering

If you’d like to grow some color-changing petunias, here’s your chance to help make it so:

Currently, Revolution Bioengineering is seeking financial support at INDIEGOGO, and you can see their latest updates here.


1. Raven, Peter H. (2014) “Transgenic Plants and the Natural World: Curse or Blessing?” (Full Text)

HowPlantsWork © 2008-2015 All Rights Reserved.

P1000980Where Does The Daffodil Flower’s “Trumpet” Come From?

An answer to this question can be found in a 2013 report published in The Plant Journal (please see Ref. 1 below). The full text of this article is now available online (thanks to the Wiley Online Library), and I’ve read it (so that you don’t have to). Here’s my take on this story:

Maybe we should we should start by taking a closer look at the flower of the daffodil.

Starting from the outside working in, the six petals are actually “tepals”, which are a kind of developmental combination of sepals and petals.

Next up is the famous trumpet-shaped part of the daffodil flower called the corona (“crown”) that is the main subject of this blog post.

The central part of the daffodil flower consists of the six stamens that encircle the carpel (gynoecium). In the photo above, you can barely see the anthers (produce pollen) of the stamens, and also you can only see the top of the carpel called the stigma (receives pollen).

When And How Is A Daffodil Flower Made?

You maybe surprised to find out that a miniature version of the daffodil flower actually develops not in the spring just before it blooms, but at the end of the previous growth season. Thus, a floral bud is fully formed, and over-winters, within the dormant bulb.

This means that plant scientists investigating daffodil flower formation (see Ref. 1 below) have to dissect out flower buds from the developing bulbs. Whew! (Thank goodness for grad students: nearly the ultimate in cheap labor. Ultimate = undergrads!)

Anyway, as a result of such efforts, Waters, et al. (Ref. 1 below) discovered that the daffodil corona forms relatively late in the flower-development program.

As described in a previous post, the flower-development program can be described like a play with several acts.

In the first act, the plant genetically shifts from a vegetative state to a flowering state.

In the second stage, which I call “arranging the chairs”, the spatial arrangement of the flower is determined.

In the third act, which I call “seating the guests”, the different flower parts (in this case, tepals, stamens and carpel) are seated in their appropriate “chairs”.

In daffodils (and perhaps other species within the Amaryllis plant family that have trumpet-shaped flowers) there apparently is an additional fourth act.

In this final act of daffodil flower development, new “chairs” are provided and arranged in a circle between the rings of the tepals and the stamens. These “late” guests are then seated.

The question was: to which of the four basic flower parts (sepals, petals, stamens, carpels) are these “late” guests most related? Turns out they are genetically related to stamens.

But, of course, an obvious question is: How does the daffodil make something that looks like petals by starting with the genetic “blueprints” for stamens?

The honest answer is we simply don’t know at the present time. It should be mentioned, however, that some of the results of Ref. 1 show that there is a late burst of coronal growth in the spring, so a great deal of elaboration of the “stamen” program is happening to result in a petal-like structure. This and other evidence suggest that petal-like structures “…can be produced by different genetic pathways even within the same flower.” (from Ref 1 below)

Why Do Daffodils Have Trumpet-Shaped Flowers?

Most explanations from botanists involve attracting pollinators. But who pollinates domesticated daffodils? Mostly likely, it’s people!

Most of the showy daffodils that we see in the spring in parks and around homes and businesses are a product of plant breeding, i.e., artificial selection, not natural selection. (You can read more about this here.)

That is, such daffodil flowers are a product of what has looked good to humans (daffodil breeders especially), not insects. Indeed, most of the domesticated daffodils that we see in the spring may not be especially attractive to bees, and thus the daffodils may not even be pollinated (unless the bees are desperate).

What about the origin and evolution of trumpet-shaped flowers (before humans got involved)?

No one can be absolutely certain of an answer, but the long narrow corona of the genus Narcissus may have evolved to accommodate pollination by bees over butterflies or moths, which can’t easily enter the tall narrow corona to access the pollen. (from Ref. 2 below)

In Summary:

If all of the above was a bit much, it might help to listen to a brief (4 min) audio clip about the daffodil’s mysterious trumpet courtesy of The Science Show on Australian Broadcasting Corporation’s RadioNational.

OK, if you’ve listened to this audio clip, then you’ve heard that the “trumpet” or “corona” of the daffodil flower is probably not an extension of the petals, as previously thought, but is a distinct organ – sharing genetic identity with stamens.

If you haven’t listened (and even if you have), you can read brief summaries of Ref. 1 (below) here and here.


1. Waters, M. T., A. M. M. Tiley, E. M. Kramer, A. W. Meerow, J. A. Langdale, and R. W. Scotland (2013) “The corona of the daffodil Narcissus bulbocodium shares stamen-like identity and is distinct from the orthodox floral whorls.” The Plant Journal, Vol. 74, pp. 615-625. (Full Text)

2. Graham, S. W. and S. C. H. Barrett (2004) “Phylogenetic reconstruction of the evolution of styler polymorphisms in Narcissus (Amaryllidaceae).” American Journal of Botany, Vol. 91, pp. 1007–1021. (PDF)

Question: Doesn’t the scientific study of flower development ruin people’s appreciation of the aesthetic beauty of flowers?

Answer: Here’s the best answer to this question that I know of, provided by Nobel Laureate (Physics, 1965) Prof. Richard Feynman:

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Are Plants Smarter Than Smartphones?

We’re back for Round 2 of the iPhone vs. plant rematch: Which is more intelligent, an iPhone 6 or a plant?

If you missed Rematch, Round 1, here it is. (I think the iPhone 6 clearly took the first round.)

By the way, this contest mainly has to do with the question of which is better at sensing its environment, an iPhone 6 or a plant?

As previously mentioned, intelligence is often defined as an entity’s ability to adapt to a new environment or to changes in the current environment. So, here we’re using complexity and versatility of environmental sensing as a measure of relative intelligence.

They’ve Got The Touch

This second round has to do with “touch ID”.

This is not “touch” as it relates to feeling or stimulation, but “touch” as it relates to identity.

Thus, we’re NOT talking about “touch-sensitive” plants, for instance, such as the Venus flytrap or Mimosa.

Instead, we’re talking about surface-to-surface contact as a means for specific identification. (Think fingerprints, for example.)

Such “touch ID” is useful for security reasons, such as for determining friend versus foe. In a biological context, it’s also a way to determine self from non-self at the cellular level, especially in regard to innate immunity.

I think that most people would expect that plants would possess much more complex and versatile environmental surface-to-surface sensors for recognizing “friend” versus “foe”, or self from non-self, than a smartphone, even the iPhone 6.

But let’s take a look at what the iPhone 6 can do in this regard before we award Round 2 of this rematch to the plants.

iPhone Fingerprint Recognition

The iPhone 6 Touch ID is a security technology that this smartphone uses to identify a unique individual via fingerprint recognition.

“Touch ID is Apple’s biometric fingerprint authentication technology. A capacitive ring activates the scanner on contact which then takes a high-resolution picture of your fingerprint. That fingerprint is then converted into a mathematical formula, encrypted, and carried over a hardware channel to a secure enclave on the Apple A7 chipset. If the fingerprint is recognized, a “yes” token is released. If it’s not, a “no” token is released.” (from: imore.com)

Briefly put, the iPhone “Touch ID” works by first taking a picture of a finger’s surface and then comparing it to previously-taken pictures of the owner’s (“self”) fingerprints. So, in reality, it’s just comparing two-dimensional digital images. There’s no actual mechanical surface-to-surface contact involved in unlocking the iPhone, such as with a key in a lock.

The “lock and key” analogy does, however, apply for how “touch ID” works in plants, albeit at the molecular level rather than at the mechanical level. And it’s most likely to occur in 3-D rather than in 2-D.

But – you may indeed be wondering – why would plants need something like “touch ID”?

Self/Non-Self Perception In Plants

This is a big old complex subject, with many facets, so I don’t want to wade in too deep here. Let me just briefly tell you about four examples of why “touch ID” is very important in the life of plants.

  • 1. Self-Incompatibility – About one half of all flowering plant species are “self-infertile” (a.k.a., “self-incompatible”), that is, the flowers of such plants are able to distinguish between self and non-self pollen (hint: proteins on the pollen surface may play a role), and they reject their own pollen.

    Why would a plant do this?

    Such self-incompatibility (SI) promotes outcrossing, which typically increases genetic diversity. (And this is a very good thing, evolutionarily speaking.)

  • 2. Disease Resistance – In a previous post, I asked the question Do plants have an immune system?. Briefly, the answer is yes, plants have a rudimentary immune system, but it’s much less complex compared to the mammalian immune system, for instance.

    One of the things that plant and animal immune system’s have in common, however, is that they have cellular receptors that can detect foreign substances occurring only in microorganisms and that, when activated, trigger defensive reactions.

  • 3. Symbiosis – I think most plant scientists would agree that plants were able to colonize the land thanks to symbiotic partnerships with certain soil-dwelling fungi, which we call mycorrhizae. And many plants are able to thrive in nitrogen-poor soils thanks to nitrogen fixation resulting from a symbiosis with specific soil bacteria.

    But in order to form such symbiotic partnerships with such “friendly” microorganisms, plants must first turn off their defensive responses. That is, they need to be able to distinguish between “friend” and “foe” when it comes to bacteria and fungi.

  • 4. Kin Recognition – “Several lines of experimental evidence suggest that roots have ways to discriminate non-related roots, kin, and—importantly—that they can sense self/non-self roots to avoid intra-plant competition.” (from Ref 2. below)

    These are four examples of different sorts of “touch ID” in plants. From this, I think it’s clear that plants are much, much more sophisticated than an iPhone 6 at answering the question: “Who Are You?*

    Bottom Line: The winner, and still champ, at environmental sensing and response is the plant. Thus, plants are more intelligent than even the iPhone 6. (But don’t stop trying Apple.)

    *Look for more information about HOW plants answer the question “Who Are You?” in future posts.


    1. Sanabria, N. M., J.-C. Huang and I. A. Dubery (2010) “Self/nonself perception in plants in innate immunity and defense.” Self Nonself, Vol. 1, pp. 40-54. (Full Text)

    2. Depuydt, S. (2014) “Arguments for and against self and non-self root recognition in plants.” Frontiers in Plant Science, Vol. 5, p.614. (Full Text)

    HowPlantsWork © 2008-2015 All Rights Reserved.

  • Which Is More “Intelligent”?

    A few years ago, when the iPhone 4 was first introduced by Steve Jobs, I mused on Which is more intelligent? An iPhone or a plant?

    Over the course five successive posts, we explored most of the iPhone’s different sensors and compared analogous environmental sensors in plants.

    And, in the end, what did I conclude? (Please see here for the answer.)

    Well, currently Apple is up to the iPhone 6.

    Is the iPhone 6 more “intelligent” than the “garden variety” plant?

    To borrow from a previous post…

    Intelligence is often defined as an entity’s ability to adapt to a new environment or to changes in the current environment.

    Intelligence is not a term commonly used when plants are discussed. However, I believe that this is an omission based not on a true assessment of the ability of plants to compute complex aspects of their environment, but solely a reflection of a sessile lifestyle.” (from Ref. 1 below)

    If the new iPhone is better at sensing its environment than a typical plant, then does it follow that the iPhone 6 is more “intelligent” than the average plant?

    So, of course, the critical question: Is the iPhone 6 better than plants at environmental sensing?

    According to the Apple website, the new iPhone 6 has the following sensors:

    Three-axis gyro, Accelerometer, Proximity sensor, Ambient light sensor, Barometer, Touch ID

    The first four of these sensors were featured on the iPhone 4, so I’ve already compared them to analogous sensors in plants in a previous series of posts.

    But there are two new sensors on the iPhone 6 – the Touch ID and the Barometer.

    So, I guess that means it’s time for a….REMATCH!

    Let’s first take a look at the barometer…

    Plants Under Pressure

    Apple added a barometric (atmospheric) pressure sensor to provide the iPhone 6 with relative altitude data to help the device more rapidly acquire a GPS lock by delivering altitude coordinates to the required latitude and longitude GPS equation (see here for example). The iPhone 6 barometer may also be useful for weather forecasting (see here, for example), with some caveats.

    The iPhone 6 uses a Bosch BMP280 absolute barometric pressure sensor. This type of electronic pressure sensor uses a force collector (such a diaphragm or piston) to measure strain (or deflection) due to applied force (pressure) over an area. (Specifically, the iPhone 6 pressure sensor is a piezoresistive pressure sensor.)

    How accurate is the iPhone barometer? “…absolute accuracy of +-1 hPa and relative accuracy for pressure changes of +-.1 hPa (normal sea level pressure is roughly 1013 hPa). To give you a better idea of the accuracy of this barometer, the average decrease in pressure with height near sea level is 1 hPa per 8 meters (26 ft).” (from Cliff Mass Weather Blog)

    So, the iPhone 6 atmospheric pressure sensor is highly accurate and responds to pressure changes nearly instantaneously.

    Do plants have environmental sensors comparable to the iPhone’s ability to sense changes in barometric pressure?

    Despite the existence of the so-called “barometer bush” (Leucophyllum frutescens), I could find no credible evidence that plants have the ability to sense changes in barometric pressure.

    The first places on plants I might look, however, are the stomatal guard cells. This is because they are known to be sensitive to, and respond to, changes in the relative humidity (which may be the “secret” behind the “barometer bush”.)

    This is not to say that plants don’t respond to significant changes in barometric pressure. They do (see Ref. 2 below, and literature cited therein). Many of these responses are most likely related to changes in atmospheric CO2 and O2 partial pressures such as occur with plants growing at high altitudes versus sea level, for example. (This is somewhat analogous to how your body adapts to breathing in the mountains at high altitudes.)

    Atmospheric pressure also may affect the rate of transpiration in plants as well as levels of the gaseous plant hormone ethylene (see Ref. 3 below, for example).

    Bottom Line: It looks like the iPhone 6 wins this round because it has the ability to sense subtle changes in atmospheric pressure, and plants apparently do not possess such sensitive barometers.

    Next-Time: The match continues with round two – Touch ID.


    1. Trewavas, A. (2003) “Aspects of Plant Intelligence” Annals of Botany, Vol. 92, pp. 1-20. (Full Text)

    2. Paul, A.-L., et al. (2004) “Hypobaric Biology: Arabidopsis Gene Expression at Low Atmospheric Pressure.” Plant Physiology, Vol. 134, pp. 215-223. (Full Text)

    3. He, C., et al. (2003) “Effect of hypobaric conditions on ethylene evolution and growth of lettuce and wheat.” Journal of Plant Physiology, Vol. 160, pp. 1341–1350. (Abstract)

    HowPlantsWork © 2008-2015 All Rights Reserved.

    Plants – Food Versus Fuel

    A recently published report has pounded another nail in the biofuels coffin.

    This report, published by the World Resources Institute provides evidence that governments have made a mistake by supporting the large-scale conversion of plants into fuel.

    Turning plant matter into liquid fuel or electricity is so inefficient that the approach is unlikely ever to supply a substantial fraction of global energy demand, the report found. It added that continuing to pursue this strategy — which has already led to billions of dollars of investment — is likely to use up vast tracts of fertile land that could be devoted to helping feed the world’s growing population.” (from Ref. 1 below)

    I’ve always been a skeptic of industrial-scale cultivation of plants for bioenergy (see here, for example.)

    Please Note: This does NOT mean I’m against recycling used vegetable oil to make biodiesel, for example, or the conversion of waste biomass into ethanol.

    But is spending tens of millions of dollars on biofuels-related plant research to facilitate the conversion of natural grasslands, and even croplands, to grow plants to be harvested and then be chemically converted into fuel for cars, jets and ships a misguided policy?

    After reading this report you may indeed think so.

    To read a summary of this report – or to download a free copy of the report itself (PDF) – please click on the link in Ref. 2 below.

    News Update: The U.S. Is Pumping So Much Oil It’s Running Out of Places to Stash It.

    Research Update: On a cheerier note, at least some “biofuels” federal grants are being used to fund basic research on the nature of plant cell walls. (Please see here, for example.)


    1. Justin Gillis (January 28, 2015) “New Report Urges Western Governments to Reconsider Reliance on Biofuels”, New York Times.

    2. Tim Searchinger and Ralph Heimlich (January 2015) “Avoiding Bioenergy Competition for Food Crops and Land”, World Resources Institute.

    HowPlantsWork © 2008-2015 All Rights Reserved.

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