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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)

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