Cactus Hides From the Sun

overhead view of green cactus with small white buds with dry dirt

Biological Strategy

Mescal buttons

AskNature Team

Image: antefixus21 / Flickr / CC BY NC ND - Creative Commons Attribution + Noncommercial + NoDerivatives

Protect From Loss of Liquids

Water is essential to life. Liquids, mostly water, make up 70 to 90% of all living systems, and the loss of even a small percentage can mean the difference between life and death. Living systems must maintain a proper liquid balance, which is especially difficult in dry conditions. To do so, they must control the movement of liquids across their boundaries. Living systems do this using structures or waterproof materials to prevent or slow liquid movement. For example, when humans receive a cut, they must limit blood loss. Scattered throughout the bloodstream are lens-shaped structures that serve to plug the wound.

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Modify Position

Many resources that living systems require for survival and reproduction constantly change in quantity, quality, and location. The same is true of the threats that face living systems. As a result, living systems have strategies to maintain access to shifting resources and to avoid changing threats by adjusting their location or orientation. Some living systems modify their position by moving from one location to another. For those that can’t change location, such as trees, they modify position by shifting in place. An example of an organism that does both is the chameleon. This creature can move from place to place to find food or escape predators. But it also can stay in one place and rotate its eyes to provide a 360-degree view so that it can hunt without frightening its prey.

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Flowering Plants

Clade Angiosperms (“receptacle seed”): Dandelions, oaks, grasses, cacti, apples

With 416 families containing some 300,000 known species, angiosperms are the most diverse group of plants, and they can be found around the globe in a wide variety of habitats. They are characterized by seeds that grow enclosed in ovaries, which are enclosed in flowers. The floral organs then develop into fruits of myriad kinds and dimensions, from simple seed casings on maples to elaborate fleshy growths like papayas. The oldest flower known from fossils, Montsechia vidalii, appeared during the Jurassic Period 130 million years ago. They are the primary food source for herbivorous animals, which in turn makes them the indirect food source for carnivores as well.

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The shoot of the mescal cactus adapts to seasonal water availability via dehydration-induced shrinking below the desert floor, and hydration-induced swelling to reemerge after rainfall.

Image: Frank Vincentz / Wikimedia Commons /

Image: MyName (Hans B.) / Wikimedia Commons /

''Lophophora williamsii'', own collection

Image: Kauderwelsch / Wikimedia Commons /

“He refers to the impressive of the mescal cactus Lophophora williamsii, which converts the dehydration-induced shrinking during the beginning of the dry season to reduce the shoot length and submerge below the desert floor. After just one seasonal rainfall the hydrating shoot reemerges by pushing the photosynthesizing apex out of its soil cover into the light and open air.” (Bar-Cohen 2006:489)

Here’s another species:
“We investigated how the ‘living rock’ cactus Ariocarpus fissuratus, like other low-growing desert plants, can endure potentially lethal high temperatures at the soil surface. Specifically, we examined how shoot descent by root contraction in the presence or absence of soil rocks influences shoot temperatures and transpiration…Plants embedded in rocky soil survived an extreme heat episode, unlike plants in sandy soil, though rocks did not moderate low temperatures. Root contraction occurred regardless of season and soil moisture. Xylem conduits (wide-band tracheids) formed a compressible lattice that decreased root length as rays enlarged the root base radially. Plant position in the soil did not affect transpiration…Contractile roots pulled plants of A. fissuratus into the soil at rates of 6 – 30 mm [per year]. Maintaining shoots level with the soil surface kept plant temperatures below the high lethal temperature and improved survivorship in soil shaded by surface rocks.” (Garrett et al. 2010:1951)