Photo by Linda De Volder licensed under CC BY-NC-ND 2.0

While perusing the internet the other day, I scrolled past an image of what looked like the physical manifestation of the sun emoji on my phone. The bright yellow flash was so striking that it caused me to pause and scroll back to the source. I was pleasantly surprised to see that the sun-like object belonged to something botanical. I was even more surprised to find out that it was produced by a unique cousin of the banana called the golden lotus banana (Musella lasiocarpa).

The golden lotus banana is an oddball in many ways. For starters, it has a confusing taxonomic history. For many years, this odd plant has bounced back and forth between what was originally the only two genera in the banana family (Musaceae). Indeed, it has many outward characteristics that could firmly land it in either the genus Musa or the genus Ensete. Still, this plant is strange enough that numerous taxonomists have taken their own stab at narrowing down its correct placement. It wasn’t until DNA analyses revealed it to be so distinct from either of these genera that it warranted its own unique taxonomic placement. Thus, the monotypic genus Musella was born.

Photo by FarOutFlora licensed under CC BY-NC-ND 2.0

The plant itself is well known and widely cultivated throughout its home range in the Yunnan province of China. In fact, the golden lotus banana is so widely cultivated in this region as food for both humans and cattle alike, that experts couldn’t quite figure out if there were any wild populations left. It wasn’t until relatively recently that some wild populations were found. Sadly, these populations are under threat of being completely extirpated as much of the conifer-oak forests it calls home have been highly fragmented and degraded due to human activities. At least its popularity in cultivation means this species is not likely to go completely extinct any time soon.

The golden lotus banana is rather interesting in form. When you look for pictures of this species around the web, you are likely to pull up images of a stubby, nearly leafless stalk tipped with the bright yellow bracts that look like the rays of a cartoonish sun. Apparently, plants can lose many of their leaves in cultivation around the time the inflorescence matures, giving the impression that it never had any to begin with. Of course, the plant does produce typical banana-like leaves for most of the year. As mentioned, the amazing inflorescence is borne at the tip of what looks like a small, woody trunk, but in reality is actually the fused petioles of their leaves. All members of the banana family are, after all, overgrown herbs, not trees.

As is typical with this family, the flowers don’t all ripen at once. Instead, they begin at the base and gradually ripen over time, revealing consecutive whirls of tubular flowers surrounded by bright yellow bracts, though a variant population that produces red bracts was recently described as well. Interestingly, the golden lotus banana differs from its banana cousins in that its flowers are not pollinated by bats or birds. Instead, bees and wasps comprise the bulk of floral visitors, at least among cultivated populations. The first flowers to mature are male flowers that produce a small amount of nectar and copious amounts of pollen. Only the flowers near the base of the inflorescence are female and they produce a lot more nectar than the male flowers.

Research has shown that bees are far more likely to visit female over male flowers and their visits to female flowers last much longer. This is likely due to the differences in nectar production, but the end result is that by encouraging bees to spend less time on male flowers and more time on female flowers, each plant greatly increases the chances that pollen of unrelated individuals will end up on the stigma. After pollination, tiny fruits are formed, however, from what I have read they are largely inedible to humans. Once the fruits ripen and seeds are dispersed, the flowering stalk dies back and is replace by a fresh new growth stalk from the underground rhizome.

The next time you find yourself at a botanical garden with a decent tropical plant collection, keep an eye out for the golden lotus banana. Outside of China, this species has gained some popularity among specialist plant growers and you just might be lucky to stumble across one in the process of blooming.

Further Reading: [1] [2] [3]

Photo by endolith licensed under CC BY-SA 2.0

Bananas are one of the most popular fruits in the world. Love them or hate them, most of us know what they look like. Despite their global presence, few stop to think about where these fruits come from. That is a shame because bananas are fascinating plants for many reasons but now we can add blue fluorescence to that list.

Before we dive into the intriguing phenomenon of fluorescence in bananas, I think it is worth talking about the plants that produce them in a little more detail. Bananas belong to the genus Musa, which is located in its own family - Musaceae. Take a step back and look at a banana plant and it won't take long to realize they are distant relatives of the gingers. There are at least 68 recognized species of banana in the world and many more cultivated varieties. Despite their pan-tropical distribution, the genus Musa is native only to parts of the Indo-Malesian, Asian, and Australian tropics.

Photo by Forest & Kim Starr licensed under CC BY 3.0

Banana plants vary in height from species to species. At the smaller end of the spectrum you have species like the diminutive Musa velutina, which maxes out at about 2 meters (6 ft.) in height. On the taller side of things, there are species such as the monstrous Musa ingens, which can reach heights of 20 meters (66ft.)! Despite their arborescent appearance, bananas are not trees at all. They do not produce any wood. Instead, what looks like a tree trunk is actually the fused petioles of their leaves. Bananas are essentially giant herbs with the aforementioned M. ingens holding the world record for largest herb in the world.

When it comes time to flower, a long spike emerges from the main growing tip. This spike gradually elongates, revealing long, beautiful, tubular flowers arranged in whorls. For many banana species, bats are the main pollinators, however, a variety of insects will visit as well. In the wild, fruits appear following pollination, a trait that has been bred out of their cultivated relatives, which produce fruits without needing pollination. The fruits of a banana are actually a type a berry that dehisce like a capsule upon ripening, revealing delicious pulp chock full of hard seeds. Not all bananas turn yellow upon ripening. In fact, some are pink!

For many fruits, the act of ripening often coincides with a change in color. This is a way for the plant to signal to seed dispersers that the fruits, and the seeds inside, are ready. As many of us know, many bananas start off green and gradually ripen to a bright yellow. This process involves a gradual breakdown of the chlorophyll within the banana skin. As the chlorophyll within the skin of a banana breaks down, it leaves behind a handful of byproducts. It turns out, some of these byproducts fluoresce blue under UV light.

Amazingly, the fluorescent properties of bananas was only recently discovered. Researchers studying chlorophyll breakdown in the skins of various fruits identified some intriguing compounds in the skins of ripe Cavendish bananas. When viewed under UV light, these compounds gave off a luminescent blue hue. Further investigation revealed that as bananas ripen, their fluorescent properties grow more and more intense.

There could be a couple reasons why this happens. First, it could simply be happenstance. Perhaps these fluorescent compounds are simply a curious byproduct of chlorophyll breakdown and serve no function for the plant whatsoever. However, bananas seem to be a special case. The way in which chlorophyll in the skin of a banana breaks down is quite different than the process of chlorophyll breakdown in other plants. What's more, the abundance of these compounds in the banana skin seems to suggest that the fluorescence does indeed have a function - seed dispersal.

Researchers now believe that the fluorescent properties of some ripe bananas serves as an additional signal to potential seed dispersers that the time is right for harvest. Many animals including birds and some mammals can see well into the UV spectrum and it is likely that the blue fluorescence of these bananas is a means of attracting such animals. Additionally, researchers also found that banana leaves fluoresce in a similar way, perhaps to sweeten the attractive display of the ripening fruits.

To date, little follow up has been done on fluorescence in bananas. It is likely that far more banana species exhibit this trait. Certainly more work is needed before we can say for sure what role, if any, these compounds play in the lives of wild bananas. Until then, this could be a fun trait to investigate in the comfort of your own home. Grab a black light and see if your bananas glow blue!

Photo Credits: [1] [2] [3] [4]