Botany Photo of the Day

It's been a while since I took a botany course, but let's see if I can get a few.

Most of the plants have small leaves, and I know that some desert plants, even though they aren't succulents, look like them because they develop thick leaves. I suspect this is an adaptation to the desert, where there is lots of sun almost every day that could suck moisture out of the plant. By reducing surface to mass ratio, the plants can retain more water by exposing less of themselves to evaporation.

Similarly, most desert plants I've encountered have tough exteriors, not in that they have a rough texture, but that they are thick, strong, and opaque (unlike the thin leaves of tropical plants where I live).

Speaking of exteriors, though, the classic desert plant, the cactus, does have some extra exterior properties. Most cacti have spins to keep animals from cracking them open to drink the moisture stored in their leaves.

Of the flowers in the picture, all are red. I don't know if this might mean something, but thinking back on all the desert plants I've ever seen, I don't recall any having blue flowers, for example.

I can't think of any more right now. Maybe others can help.

What looks like a cactus in the far right of the photo is actually a species of Euphorbia, I believe.

Matt you are right the cactus thing in the far right is a euphorbia. I'm not sure which one though the euphorbia genus is huge. The plant in the middle of the photo is a Euphorbia also, probably Euphorbia milii aka crown of thorns.

I wish i could grow all the plants in this picture in my backyard, but its too cold where i live.

Here's my contribution to this desert adaptation exercise: the blue tint to some of the plants is probably due to a layer of wax that prevents moisture loss.

You're right about the Euphorbia milii, William. I suppose another task would be to see if someone can identify all of the plants in the photograph to genus - though I think there are fewer than a handful.

To summarize the desert adaptations mentioned so far:

1) reduction of leaves to prevent water loss
2) succulent strategy, whether it be in leaf tissue or stem tissue, to increase water storage
3) development of physical barriers to herbivory to discourage water loss either by direct ingestion or secondary damage
4) waxy cuticle to prevent water loss

Those are 4 of the 5 I was thinking of. Anyone else?

Gordon, I'm not certain about the flower colour. You're general observations about the colour of desert flowers is accurate (although I do have a blue-coloured desert flower photograph in the queue).

its a wonderful picture

On a different topic, if you appreciate the Invasive Species Weblog as much as I do, head on over there and give Jennifer a thank-you for four years of educating about this critical conservation issue.

On flower color: I wonder if the most common pollinators in the desert are hummingbirds, who can see red well. Insects supposedly are more attracted to yellow and blue flowers (and also those with ultraviolet markings) as they cannot see in the red range.

In terms of desert adaptations, spines are also effective radiators. Spines (modified leaves) and thorns (modified branches) have intimate contact (at least initially) with the plant's vasculature. Most of the succulent euphorbias (including the ones pictured--Euphorbia coerulescens? and E. millii) have thorns, not spines. Such long, thin extensions that protrude into the surrounding air act much like the fins of a radiator. (see http://www.californiadesert.gov/plants.php). Indeed, the very ribs and tubercles of cacti and similarly adapted plants have some heat exchanging value themselves.

Armature also provides shade, and particularly when densely produced, considerable insulation (from increased boundary layer resistance).

Succulence is a well recognized adaption to water thriftiness, but there is a continuum of drought adaptability in succulents, from the merely fleshy to the entirely succulent. Here we see the blue, terete-leafed Senecio mandraliscae, pictured lower right, which has a moderate ability to withstand drought. The arborescent aloes (Aloe bainesii?) have reservoirs of water in both leaves and stems (the leaves, the more expendable). Tubercled cacti and ribbed-stemmed euphorbias and barrel and tree cacti, have the ability to inflate their stems accordian-like when water is available.

To Ginny's question: All of the tubular red flowers pictured (Aloes) are predominantly bird pollinated, but since they are African plants, we can rule out hummingbirds. I wonder whether Euphorbia millii is also bird pollinated. Insects are evidently not signalled as strongly by the colour red as are birds (they can see it, but don't always associate it with food), but the crown of thorns' flowers don't look particularly bird adapted. (see http://www.pubmedcentral.nih.gov/articlerender.fcgi?artid=521733).

What a great garden, and what a superb picture.

How about photosynthetic stems? This goes hand-in-hand with reduction of leaf surface...

Getting back to the picture itself - This is so beautiful. The light seems sourceless - did you use some kind of reflector, or was it just surreal by itself?

Justine - sure, I agree.

I was also thinking along the lines of compact shapes and forms reducing air movement around the photosynthetic tissue, i.e., creating a still-air zone against dessicating winds. It's probably the weakest of the five adaptations I was thinking of.

Chris - it was the best light I had on the entire trip (or at least when I had camera in hand), so it was nearly surreal - but entirely real. You did have to be looking for it, though.

that pictire is amazing im definately printing it out. it is so pretty.but is that a real desert cause im doin a project on deserts. write back cause i want to talk to u about the picture

Hi Brittany, this is a cultivated desert garden, so all of the plants in it were purposefully placed (and it is growing in the middle of a city!)

This is not of much reference to this picture, but could somebody please explain how the waxy surface on cacti prevent water loss?
Thankyou

This is a beautiful picture...and I am amazed that it is grown in the city. I cannot tell in this photo but if any have hair on their leaves it would also be helpful in preventing waterloss by decreasing winds over the evaporative surfaces.

One adaptation I see that has only been somewhat brushed over is the red pigmentation at the tips of some leaves. I would guess that it is indicative of anthocyanins or other accessory pigments that help reduce genetic damage caused by ultraviolet radiation, as well as acting as a slight fungicide, among other benefits.