There’s a Rainbow in that Dying Cactus

The saguaro pictured above is dying. I was curious about where the colors were coming from. I learned the green color in the photo above is, of course, from chlorophyll; the orange is carotenoids and the purple in the rainbow is betacyanins.

Plants live and die like all living organisms. Some die of old age, but some die when they are young, like this saguaro. A rainbow of colors is revealed as the cactus dies. This is a similar process to what happens to the deciduous tree leaves that change color with the coming of winter, but I wondered what pigments are found in cacti.

The green is chlorophyll, present in the stem for photosynthesis. Photosynthesis is the process which converts light energy into chemical energy that is used to fuel the plant’s activities. As the chlorophyll fades away, the other pigments are revealed.

Associated with the chlorophyll are the yellow to orange carotenoids. As the green chlorophyll degrades, the carotenoids become visible. These pigments act as photoprotective agents as well as additional light-harvesting pigments, enhancing the light collection for photosynthesis.
The nice purplish colors seen here are the betacyanins, reddish to violet betalain pigments. These pigments may act as a screen, protecting the plant tissue, and may also serve an an antioxidant. Fungicidal properties have also been suggested. Betalains are most obvious in the cactus flowers and fruits, such as the yellow-orange betaxanthins and red-violet betacyanins.
So, the rainbow-in-death colors seen in this saguaro are produced by the pigments revealed as the green chlorophyll is reduced.

Book Note: If you’d like to learn about another fascinating Sonoran Desert plant, I wrote Queen of the Night: Night-Blooming Cereus, about the beautiful plants that bloom once a year, all on the same night, usually in July. The blooming is a big deal here in Southern Arizona and something fun and mysterious to learn about. I love to write fun science books (I believe the learning stays when it’s fun), so I wrote Cereus in rhyme. Check it out here.

image of yellow green book cover about the plant Cereus
The Night-Blooming Cereus: An Amazon No. 1 Book!

 

Photo of night-blooming cereus in Tucson AZ
Photo courtesy of ThisisTucson.com

The Marshmallow: Not Merely Fluffy Sugar

In a previous blog, I related a story how even in my early years, I was working to keep wild alligators away from people food with stale, very hard, marshmallows. This occurred on Sanibel Island, FL. 

Have you ever thought about where marshmallows come from? My marshmallow story took place on Sanibel Island, FL, where you can find the marsh mallow growing. Yes, the marsh mallow is a plant. I learned about it while I was working at the “Ding” Darling National Wildlife Refuge. On Sanibel the species is called Kosteletzkya virginica.

Did you think marshmallows were merely fluffy sugar? Well, they’re not. Marshmallows have been around since ancient Egypt. They used the mallow, Althaea officinalis, which grew in salty marshes. The sweet sap was made into a candy that was dedicated to their gods.

The ancient Greeks valued the medicinal properties of the mallow. Many cultures have used mallow to treat wounds, inflammation, toothaches and sore throats.

In the 1800s, the French created a candy for adult consumption, in addition to its previous medicinal uses. The mallow sap was whipped with egg whites and corn syrup into an easily moldable substance and the modern marshmallow was created. The next time you enjoy a marshmallow, think of the plant from which it came:  the mallow growing in salty marshes.

Botanical illustration of the Marsh Mallow Plant

A botanical drawing of the marshmallow plant, featuring the plant as well as close-ups of the flower and seed.

FRANZ EUGEN KOHLER, KOHLERS MEDIZINAL-PFLANZEN

NOTE: Every now and then, I divert from writing about animals to do a bit of plant investigation. To see some of my work on plants, check out The Queen of the Night about the fascinating Night-Blooming Cereus, plants that bloom magnificently only one night per year—and they wait for each other to bloom all at the same time. EAP

book cover for the Night-Blooming Cereus
All about the mysterious plant that blooms only one night per year–all at the same time!