Floral Mucilage

Spend enough time around various Bromeliads and you will undoubtedly notice that some species have a rather gooey inflorescence. Indeed, floral mucilage is a well documented phenomenon within this family, with something like 30 species known to exhibit this trait. It is an odd thing to experience to say the least.

The goo takes on an interesting consistency. It reminds me a bit of finding frog spawn as a kid. Their brightly colored flowers erupt from this gooey coating upon maturity and the seeds of some species actually develop within the slimy coating. Needless to say, the presence of mucilage in these genera has generated some attention. Why do these plants do this?

floral mucilage.JPG

Some have suggested that it is a type of reward for visiting pollinators. Analysis of the goo revealed that it is 99% water and 1% carbohydrate matrix with no detectable sugars or any other biologically useful compounds. As such, it probably doesn't do much in the way of attracting or rewarding flower visitors. Another hypothesis is that it could offer antimicrobial properties. Bromeliads are most often found in warm, humid climates where fungi and bacteria can really do a number. Again, no antimicrobial compounds were discovered nor did the mucilage show any sort of growth inhibition when placed in bacterial cultures.

It is far more likely that the mucilage offers protection from hungry herbivores. Flowers are everything to a flowering plant. They are, after all, the sexual organs. They take a lot of energy to produce and are often brightly colored, making them prime targets for a meal. Anything that protects the flowers during development would be a boon for any species. Indeed, it appears that the mucilage acts as a physical barrier, protecting the developing flowers and seeds. One study found that flowers protected by mucilage received significantly less damage from weevils than those without mucilage.

The mucilage could also provide another benefit to Bromeliads. Because these plants rely on water stored in the middle of their rosette (the tank, as it is sometimes called), some species may also gain a nutritional benefit as well. Bromeliad flowers emerge from this central tank so anything that gets stuck in the mucilage may eventually end up decomposing in the water. Since nutrients are absorbed along with the water, this could be an added meal for the plant. To date, this has not been confirmed. More work is needed before we can say for sure.

Photo Credit: [1] [2]

Further Reading: [1] [2] [3] [4]

 

Is it a pine? Is it an apple? It's neither!

Pineapples - the fruit that is neither a pine nor an apple. In reality, pineapples are a type of bromeliad. The genus to which they belong, Ananas, is comprised of something like 7 different species, all of which are native to Central and South America. Considering we rarely encounter these plants outside of a grocery store, it is no wonder then that many are surprised to realize how pineapples grow.

The fruit itself is not the entire plant. It is made up of many fruits that fuse together after flowering. The flowers themselves are quite lovely and originate from the center of the hexagonal units that make up the tough rind. The whole inflorescence arises from the center of a large rosette of leaves. Only when you see the entire plant does the bromeliad affinity become apparent. Like all other bromeliads, pineapples undergo vegetative reproduction as well. Small offshoots called "pups" arise from the base of the plant and the axils of the leaves. These can take root and grow into clones of the parent plant.

In the wild, pineapples require pollination to set seed. This is undesirable in cultivation because pollination means lots of seeds that consumers don't want to contend with. Because of this, pineapples are gassed with ethylene, the simplest of plant hormones. Ethylene causes the fruits to artificially ripen without being pollinated. In this way, no ovules mature into seeds.

The dirty little secret about pineapple farming is that it is done at great environmental cost. The dominant producer of pineapples is Costa Rica. Because of the humid, tropical climate, insects and fungi flourish. In order to ensure that production is maximized, pineapple farmers dump thousands of gallons of pesticides and herbicides onto their crops. These farms are largely void of all other lifeforms save for endless hectares of pineapples. This, however, is not a story unique to pineapple farming. The same could be said for all other forms of monoculture farming.

Photo Credits: Fractalux, H. Zell, and hiyori13 - Wikimedia Commons

Further Reading:

http://www.kew.org/science-conservation/plants-fungi/ananas-comosus-pineapple

http://www.theguardian.com/business/2010/oct/02/truth-about-pineapple-production

Carnivorous Bromeliads

Brocchinia reducta

Brocchinia reducta

I would like to introduce you to quite possibly the strangest members of the Bromeliad family - those of the genus Brocchinia. Aside from the odd appearance and habits of this particular group, researchers have learned quite a bit about the Bromeliad family as a whole from studying this group. From their origins to their impressive radiation, Brocchinia offers us a window into the history of this charismatic family.

Brocchinia are considered sister to all other bromeliads. They were the first genus to diverge some 70 million years ago. Their center of origin can be traced back to the Guayana Shield, a region in the northeast corner of what is now South America. The earliest members of this group were likely terrestrial plants growing in nutrient poor areas. Surprisingly, the epiphytic nature of many bromeliad species we know and love today evolved more recently.

Brocchinia reducta

Brocchinia reducta

Since this time, Brocchinia has undergone an impressive adaptive radiation. Because they have remained specialists on nutrient poor soils, much of this radiation has to do with the evolution of nutrient acquisiton. Like its cousins, Brocchinia utilize a "tank" formed by their tightly clasped leaves.

Interestingly, at least two species of Brocchinia, (B. reducta and B. hechtioides) have taken this to the extreme and have adopted a carnivorous lifestyle. Their tall, columnar growth form coupled with slick, waxy leaves means insects can't keep a foothold and fall down into the tank. The plants sweeten the deal by luring them in with sweet secretions.

Pflanze-auf-roraima8.jpg

Whether or not this was a case of true carnivory was highly debated until 2005 when a group of researchers analyzed the chemical makeup of the liquid inside the tank. They discovered that they plant was secreting an enzyme called phosphatase, which actively digest hapless insects that fall in. A true carnivore indeed!

Others have even more peculiar evolutionary adaptations for nutrient acquisition. B. tatei, for example, was discovered to house nitrogen-fixing cyanobacteria within its tank. Another species, B. acuminata, produces hallow chambers at the base of its leaves that house ant colonies. The ants pay rent via their nutrient-rich waste and voracious defense of their bromeliad home.

Brocchinnia acuminata

Brocchinnia acuminata

In total, this group is quite amazing. The amount of information we have been able to glean from studying Brocchinia has allowed us to shine a light on the whole bromeliad family. As we have also seen, the species within this group have quite the evolutionary history to tell in their own way. Brocchinia serves as a reminder to researchers blind to organismal study. We shouldn't have to study ecology at the expense of individual organisms. There is plenty to learn from both avenues of research.

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

Further Reading: [1] [2]