Doesn't the name "morning glory" sound nice? Sitting here in the middle of a May snowstorm in upstate New York, "morning glory" reminds me of waking up to crisp sunshine bouncing off lush green blades of grass -- slightly moist from the morning dew -- while adorable little bluebirds, perched atop gently waving branches, chirp melodiously in the background. But alas! Names, just like months and seasons, can be deceptive, for morning glories -- a name that refers to plants in the Convolvulaceae family -- can both profoundly please your senses or serve as agents of chaos. In this 3-part series, I will discuss some of these wondrous aspects of morning glories, focusing mainly on their fascinating chemistry that is used across different cultures for foods, medicines, fragrances, colors and as psychoactive drugs!
Let us take a moment to first review why morning glories are named as such and what they really are. Generally speaking, the Convolvulaceae family is referred to as the morning glory family because of the most popular genus in this family -- Ipomoea, also called morning glory. But confusingly, other members of the species like Calystegia and Convolvulus are also sometimes called morning glories, so there is no real consensus there, just like the name "nightshade" for the sister Solanaceae family.
But why are Ipomoeas called morning glories? It is because of their beautiful flowers that bloom in the morning, and sometimes last only a day. Hence, flowers of species such as Ipomoea tricolor, Ipomoea purpurea, Ipomoea nil, Convolvulus tricolor, Calystegia macrostegia etc. are horticulturally very popular, and can be purchased with attractive names such as Heavenly Blue, Blue Enchantment, Flying Saucer, Red Ensign, Wedding Bells etc. After all, who doesn't want Flying Saucers in their front yard?
These beautiful red and blue colors arise due to a class of compounds called anthocyanins, which are present everywhere in flowering plants, primarily in young leaves, fall leaves, flowers and fruit (such as red grapes used for making red wine). The colors of these anthocyanins can change depending on the pH they are in. The Kondo lab at Nagoya University, Japan, has studied Ipomoea tricolor flowers and their color change in great detail. These flowers are fascinating. They are called tricolor because during their development, they change their color from deep red/purple to blue (and I guess they have white already mixed in there). Now this could hypothetically occur if the buds have one type of anthocyanin and another type in open flowers.
However, the Kondo lab found that this change occurs simply due to the pH in the cellular vacuoles (where the anthocyanins are located) going from an acidic pH to an alkaline pH during development.
Interestingly, they also found that growing the flowers in high carbon dioxide environment (which produces carbonic acid and makes the cellular pH more acidic) rapidly changed the blue flowers to purple color. This purple color reverted back when the flowers were returned to normal CO2 air. Something to try in your home garden or window sill (if you live in a box in a city).
Morning glories produce beautiful, colorful flowers. It is for this reason that they have been popular in many cultures around the world as a symbol of love. Morning glories have been grown and bred in Japan since at least the 9th century CE. They are so popular there, that there is also a morning glory festival -- Asagao Matsuri -- dedicated to selling these beautiful flowers!
Morning glories are also popular in China. There is an ancient folk legend of two lovers Chi-Niu -- the daughter of the Sky Emperor and the Queen of Heaven -- who used to weave beautiful sunrises and sunsets, and Chien-Niou, a royal herdsman of the Gods who used to herd their water buffaloes. Both of them got married and forgot to do their jobs, making the Gods angry. Now, it is not unusual for the Gods to get angry -- many Gods around the world are known to get angry. However, in this case, the couple was unnecessarily punished very harshly (a warning would probably have sufficed), and allowed to meet only once a year -- a day they longingly looked forward to. Morning glory flowers, since they bloom only for a day, are considered a symbol of their forbidden love, which too blossomed only once a year.
Other species in the morning glory family also find horticultural uses. For example, Dichondra argentea Silver Falls is used as ground cover or in hanging pots. Nothing biochemically special there, as far as I know, other than they grow really fast and look rather nice.
Another example of species that grow really fast (but not at all look nice) are bindweeds -- one of the most noxious weeds growing in the US. These belong to the genus Convolvulus, and mostly refer to the species Convolvulus arvensis. Bindweeds could also be hedge bindweeds (Calystegia sepium), a closely related genus. These species grow all weedy and such due to their prolific seed production as well as their ability to send roots deep in the ground (sometimes as much as 30 ft!!), their viny habit, and ability to grow from root runners.
A concerning problem in agriculture right now is their increasing tolerance to glyphosate (RoundUp), one the most commonly used weed killers in agricultural settings. It is due to this resistance too that the bindweeds are spreading across the length and breadth of America.
Another species that grows as a vine is Ipomoea alba, also known as moon vine. Its flowers are not very colorful, but this species is very fascinating. In 1990s, a group of MIT researchers found out that people in ancient Mesoamerica used this plant to make vulcanized rubber as far back as 1600 B.C., 3500 years before the process was re-discovered by Charles Goodyear! The researchers found out that this rubber was used for making balls, sandals, rubber bands etc. and had excellent elastic and shock-absorbing properties. Specifically, the Mesoamericans mixed diterpenoid-rich latex from a Euphorbiaceae species called Castilla elastica with the juice of I. alba, which was found to be rich in sulfur-containing compounds. Sulfur is also used in the modern process of vulcanization of rubber from rubber tree Hevea brasilienses, another Euphorbiaceae species. Anyways, the researchers found that addition of the juice substantially altered the latex properties. Without the juice, pure latex balls just shattered, with juice they had altered, bouncy properties.
It is important to note that these balls were used in the ancient Mesoamerican sport of Ulama -- the oldest known sport involving the use of rubber balls. It is thought that the Spanish forbade this game during the Spanish Conquest due to its religious significance, and its popularity thus waned except in specific areas of Mexico and Central America.
But not all morning glories are weeds. There is one morning glory species that stands tall above all else -- Ipomoea batatas or sweet potato, the world's seventh most important vegetable crop. We eat sweet potatoes boiled, fried, baked, mashed, smashed, crushed, powdered, chopped, and diced, primarily because of their huge vitamin A content (and anthocyanin content in purple sweet potatoes). There is a lot to talk about there - more about them in the next post!
Morning glories are also considered among the "Plants of the Gods" for they accumulate potent, psychoactive compound classes like ergot and tropane alkaloids. Some like Ipomoea purga and Convolvulus pluricaulis (shankhapushpi -- literally meaning flower shaped like a conch in Sanskrit) are also used in traditional medicine in India and Mexico. More on them in post 3 in this series. Hold on!