Which Is More Intelligent? An iPhone Or A Plant?

Is the New iPhone More Aware of Its Environment Than a Typical Flowering Plant?

Today I was watching a bit of Steve Jobs’ recent WWDC keynote address introducing the newest iPhone. (Click on image below to view part of his presentation.)

About half way through his talk, Steve enumerates the sensors (see the list above) built into the iPhone 4 to provide information about the world around it. Very impressive.

But as an inveterate plant physiologist, I began to ponder whether the new iPhone was actually more “aware” of its environment than a typical flowering plant.

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 4 is more “intelligent” than the average plant?

So, of course, the critical question: Is the iPhone 4 better than plants at environmental sensing?

To try to answer this question, I’ll briefly compare each iPhone sensor to the equivalent (if there is one) in plants. Let’s use the list above and work from the bottom up.

Ambient Light and Proximity Sensors

Hidden behind the translucent dark glass above and to the left of the iPhone’s earpiece are two different kinds of sensors, the ambient light sensor and the proximity sensors.

These sensors help improve battery life. For example, under low light conditions, the ambient light sensor signals the iPhone’s software to dim the screen. When the phone is placed against your head during a call, the proximity sensor deactivates the touch sensitivity and illumination of the iPhone’s screen.

How do they work?

Both of these tiny photodetectors are able to convert light energy into electrical energy. The ambient light sensor is basically a light meter, that is, it contains a photodiode that produces more electrical energy the brighter the light.

The proximity sensor is more complicated, however. The iPhone uses a reflective photoelectric sensor, thus it contains both a light emitter and a receiver. The light reflected from an object is used for the sensor detection. A near-infared beam is sent from the emitter. When this near-infared beam is reflected off an iPhone user’s head several inches from the sensor, the receiver detects the reflected beam, and the sensor then signals the iPhone’s software to shut down the display.

OK, but what about plants?

Ambient Light Sensors – Plants can also detect and respond to changes in light intensity. For example, inside leaf cells, chloroplasts may reorient in response to changing light conditions, as I’ve mentioned in a previous post. Another example is that leaf stomatal conductance usually increases with increasing light intensity.

Plants use so-called photoreceptors to perceive the light in such cases. These include phototropins, phytochromes and cryptochromes.

Unlike the iPhone photodetectors above, these plant photoreceptors don’t convert light energy into electrical energy. Instead, light absorption actually causes a conformational change in the photoreceptors. These shifts in their 3D structures, in turn, result in a changes in their relative biological activities.

The nature of these activities is too complex to describe here, but suffice it to say that they may elicit dramatic changes in enzyme activity, membrane transport, and gene regulation within the plant cells.

Life_In_The_Shade.jpgProximity Sensors – Plants may use both photoreceptors, chemical sensors, or both, to gauge their relative proximity to other plants and to respond accordingly.

For instance, many plants apparently use phytochrome to measure changes in light quality that result from light reflected from the leaves of adjacent plants.

This phenomenon is called shade avoidance. Plants may respond by increasing their stem elongation, for example.

Plants also produce and detect volatile chemical signals such ethylene and methyl salicylate. Although evidence is not definitive regarding this, it is likely that plants may also use chemical signals to do proximity sensing.

To Be Continued: Compass, Accelerometer, & Gyroscope


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

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