Jumping Cacti Can't Jump

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When I first heard of the dreaded "jumping cactus" I was more than a little curious. I had just moved to the West and had no experience with cacti in the wild. My relationship with this group of spiny plants had, up until that point, been limited to some unfortunate encounters trying to grow them on a windowsill at home. I had gotten quite used to using duct tape to remove their spines from my hands. Needless to say, the thought of a cactus "jumping" was a bit intriguing if not a little nerve-racking. 

The cactus in question here is commonly referred to as the jumping cholla. Scientifically speaking it seems less scary calling it Cylindropuntia fulgida. At the time of my first introduction I was much more botanically naive. Having witnessed first hand fluid movements of a sensitive plant (Mimosa pudica), or the lightening fast snap of a Venus fly trap (Dionea muscipula), a jumping cactus didn't seem too outlandish of an idea. 

In reality, jumping cholla do not jump. The common names comes from the fact that the individual stem segments of the plant are only weakly attached. The slightest touch will detach them. This gives unfortunate hikers the idea that the plant has physically jumped out and attacked. Needless to say, cholla are a spiny lot and each spine is covered in backward pointing barbs, which make removing them a painful experience. As a result, they not only fall off the plant readily, they grab on for a ride. 

A ride is exactly what they are looking for. Whereas plants like burdock (Arctium sp.) or tick trefoils (Desmodium sp.) have barbed seed capsules to facilitate seed dispersal, jumping cholla utilize this strategy as a form of vegetative reproduction. Stem segments that stick to the hair or into the skin of passing mammals can be carried quite a distance before they are successfully dislodged. If the cholla is lucky, this will happen in spot that is favorable for growth and thus a new plant can begin. 

The result of this is a rather quick lifestyle for this cactus. Stands of cholla can be relatively short lived. There is a lot of competition for light and space in mature cholla stands and being able to get as far away from that congestion is very beneficial in the long run. This mobile form of vegetative reproduction has worked quite well for the jumping cholla, much to the displeasure of anyone that has come into contact with this plant. As such, an entire mythos has developed around Cylindropuntia fulgida

Photo Credit: meligrosa (https://www.flickr.com/photos/meligrosa/8396656703/)

Further Reading:

http://www.jstor.org/stable/10.1086/425665?seq=1#page_scan_tab_contents

Blowout Penstemon

While living and working in Wyoming, I had the chance to meet so many amazing plant species. Many of these were quite unique to the high desert environments where we were assigned. Countless hours were spent searching large swaths of land rarely visited by humans. One species of plant managed to elude me during my time in that beautiful part of the country. The plant is incredibly rare and thus a focus of federal protection and restoration efforts. 

Based on first impressions, blowout penstemon (Penstemon haydenii) may look like any other penstemon. The similarities stop there and indeed, this is one of the most unique species of penstemon I have ever heard of. Originally it was only known from a few locations in the Sand Hills of Nebraska. Recently, a few populations were discovered in Wyoming but it is by no means common. 

As its common name suggests, P. haydenii is a specialist of blowouts. These depressions in the sand are caused by blustering winds that carve out and remove all vegetation. Most plants cannot survive in these conditions. There is very little water, the sands are constantly shifting, and as the wind kicks up sand at high speeds, the abrasive force can actually cut down frail vegetation. This is where P. haydenii excels. 

It has a thick, waxy cuticle covering its stem and leaves that protect it from this sandblasting effect as well as drought. The seeds of these species are dispersed by wind and have extreme longevity in the soil. They can remain dormant for decades until the right conditions are present for them to germinate. P. haydenii seeds need at least 2 weeks of steady moisture and lots of abrasion from sand in order to break dormancy. Research has shown that these conditions are only ever present one out of every 8 to 10 years. As a result, P. haydenii has a debilitatingly small recruitment window. 

This rarity has placed it on the endangered species list. Ironically, the very regulations that were put into place to control range degradation by cattle ranchers may have caused serious declines in this species. It was once common practice to over-graze the land where P. haydenii is found and as a result, vegetation became sparse. This increased the likelihood of blowout formation, which favored P. haydenii. Fire suppression is another threat. Regular fires help kill back vegetation that would otherwise outcompete P. haydenii

With droughts on the increase and human activities expanding into areas where the few remaining populations of P. haydenii occur, the future of this strange little endemic is uncertain. There has been a lot of effort to save and restore this species numbers but it is by no means the end of the story. Only time will tell...

Photo Credit: Vernon Jenewein Vljenewein

Further Reading:
http://plants.usda.gov/core/profile?symbol=peha12

http://ecos.fws.gov/speciesProfile/profile/speciesProfile.action?spcode=Q2EX

A Strange Gymnosperm From Africa

What you are looking at here is not just a pile of discarded leaves. It is indeed a living plant. Would you believe me if I told you that it is a distant relative of pines, spruces, larches and firs? It's true! This right here is Welwitschia mirabilis, a representative of an ancient lineage of gymnosperm!

Welwitschia is endemic to the Namib Desert of Africa. It is hard to picture any plant living in such a dry area. In some years it never even rains. Welwitschia persists despite this fact. It tends to grow in watercourses and outcrops, thus enabling it to gather what precious little rain does fall. It has a deep taproot suggesting that it relies heavily on ground water. The leaves of Welwitschia also have high amounts of stomata on both surfaces enabling it to absorb water directly from the fog that regularly blows through when colder air currents mix with hot air from the desert.

For a long time it was believed that Welwitschia represented true neoteny, which is the retention of juvenile characteristics into adulthood. It was thought that Welwitschia was nothing more than a sexually mature seedling with exaggerated cotyledons. This idea was later abandoned when Martens showed that Welwitschia do develop further than the seedling stage. What really happens is the apical bud, which is responsible for vertical growth in plants, dies quite early on in development. In essence, Welwitschia has lost its "head."

I was not kidding when I said that Welwitschia is a gymnosperm. Once sexual maturity is reached, cones are produced. Individual plants are either male or female and unlike many of its relatives, Welwitschia is not wind pollenated. Instead it relies on insects to transfer pollen from male cones to female cones.

Probably the most remarkable aspect of Welwitschia ecology is its longevity. Individual plants can live well over 1000 years. Some individuals are estimated at around 2000 years old! In such a harsh desert environment, persistence is the key to survival for Welwitschia.

Photo Credit: Petr Kosina

Further Reading:
http://www.jstor.org/discover/10.2307/2442386…

http://www.plantzafrica.com/plantwxyz/welwitschia.htm

Sandfood

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Pholisma is yet another amazing genus of parasitic plants. Endemic to the southwestern United States and Mexico, these peculiar members of the borage family tap into the roots of a variety of plant species. They do not photosynthesize and therefore obtain all the nutrients they need from their hosts. Oddly enough, researchers have found that most of their water needs are met by absorbing dew through the stomata on their highly reduced, scale-like leaves. Water is then stored in their highly succulent stems. Throughout their limited range, Pholisma are critically imperiled. Development and agriculture have already eliminated many populations. To add insult to injury, the dunes in which most extant populations are found are owned by the BLM and are open to heavy off-road ATV traffic, which will likely push them to the brink of extinction if nothing is done to limit such recreational use. Unless people speak up about protecting these plants and their habitats, they could disappear for good.

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Photo Credits: [1] [2] [3]

Further Reading: [1] [2]