A Mid-Night Horror Story

Imagine you’re walking around in the forest at night and suddenly you find a pile of thin bones, you look up and you see a tree with dangling sickles and bats flying over… Creepy, uh? Well, maybe if you look a little bit closer the bones are not real bones, they are fallen branches and there are no sickles, they are just the fruits of this bat-pollinated tree – but that was scary enough! Today’s story is about the “Midnight Horror”!

The midnight horror tree, Oroxylum indicum, is a very popular tree in Southeast Asia due to their weird appearance, but despite of this, there is no reason to fear it - in fact most of the plant is used for medicinal purposes (leaves, seeds, bark and roots).

Oroxylum indicum. On the left side: the tree with hanging fruits; on the right side: the flowers.

Oroxylum indicum belongs to the Bignoniaceae family, a family with tropical distribution, belonging to the problematic Lamiales order. Lamiales encomprises some closely related and big families such as Lamiaceae, Acanthaceae, Oleaceae, Gesneriaceae, Scrophulariaceae, Plantaginaceae, Verbenaceae… The relationships between these families are not well understood and in many cases the morphological characters are not strong enough to determine the families’ delimitation, especially floral morphology. The typical Lamiales flowers have a well developed and basally fused calyx, a monosymmetric bilabiate corolla (upper and lower lips) and a superior bicarpellate ovary.

*Wow, botanists’ sophisticated dialect alert!*

Ok, ok… It is easier if I show some pictures, but what I want to show you here are the fluctuations on the number of stamens.

Typical Lamiales flowers. On the left: Lamiaceae, upper lip formed by 2 fused petals and lower lip formed by 3 fused petals; Dashed line representing the monosymmetric corolla. On the right side: Orobanchaceae, upper and lower lips fused forming the corolla tube; the calyx is fused on the base. 

In Lamiales the androecium varies from one to five stamens, including reductions of stamens into staminodes (sterile stamens) which are not well understood. This character is highly variable, and in my opinion is due to the current evolution of the group. This means that the characters for families’ circumscription are not well established yet, giving this morphological fluctuation as a consequence.

However, Bignoniaceae, has some characters restricted to the family, which makes it easy to spot in the field. The flowers in this family are very big, colourful and showy – hard not to see. They usually also have big nectarines in the base of the flower, releasing a strong and sweet fragrance – no wonder they are pollinated by big animals such as bats! Usually they have 4 fertile stamens and 1 unfertile stamen (staminode), but this species in particular has 5 fertile stamens and no staminodes. I have also found Bignoniaceae flowers with more variation, but as I explained before, I believe the presence or absence of staminodes is possibly related with a transitional evolutionary state. The stigma (the female part which receives the pollen) is usually wet and relatively broad.

Typical Bignoniaceae flower with 2 pairs of stamens (long and short) and one staminode

 The essential vegetative character of the Lamiales is the simple-opposite leaves, but luckily Bignoniaceae has compound opposite leaves, and this makes our lives easier! Bignoniaceae are usually represented by trees, shrubs and are also well represented in tropical America by climbers, having the terminal leaflet differentiated into a tendril.

So don’t forget, whenever you see a tree or climber with big showy flowers with the petals fused into a tube, check for the leaves, if they are compound, you probably found a Bignoniaceae! In the case of the midnight horror tree, they have big white or whitish flowers, blooming and releasing a sweet scent at night – all perfect characters for efficient bat pollination.

Viola’s love story

Some of you might already know that my favourite flowers are probably Viola’s, however I never did any work or wrote anything about them – to be honest I don’t even know why they are my favourites. Personally, they do have a special meaning to me as Viola riviniana was the first plant I identified alone using a flora – this is a mark in a botanist’s life!

Viola riviniana

Viola’s have the cutest flowers on earth, and although this is a very personal opinion, many people had similat thoughts. Many of us know Viola’s as ornamental flowers – in fact their beauty also attracted gardeners since early 19^th century. Many varieties of pansies (hybrids between Viola tricolor with other Viola species) were produced since then and today we have countless cultivars of the original pansy, but I do prefer the wild Viola tricolor. There is nothing like having wild Viola’s “staring” at us – they are lovely! To start with, I have to say that the Portuguese common name for Viola is “amor-perfeito”, meaning “perfect love”, but it is not only a Portuguese thing to think that Viola’s are so deeply related with love… Or is it a Portuguese thing to give attention to Viola’s love clues?

They are also famous by their sweet odor, especially Viola odorata, which is used in perfume industry. Not happy with being beautiful and fragrant they are also full of goodness! The entire plant is edible, and in Europe, violets are used to make popular spring salads. They also have being used with medicinal purposes in many cultures and for the most variable reasons since ancient times. Europeans, Asians and also Native Americans used to produce traditional medicines with Viola’s leaves and flowers. Homer said once that Athenians used Viola tricolor to temper the anger, but it is also used with many other medicinal purposes, including pain relief and heart problems. It is clear for me – it is used to cure love diseases! And in fact, Ancient Greeks considered the violet a symbol of fertility and love, using them in love potions... Can't be a coincidence.

Viola’s are mainly pollinated by bees, and this is easy to understand by looking at the flower features. The colors are mainly purple, but also yellow and white; the lines in the petals act as landing lines, indicating to the pollinator where the nectar can be found. One of the most characteristic features of Viola flowers is the presence of the spur – a structure that produces and stores the nectar. The pollinator must follow the landing lines to find the nectar in the spur, and by doing so, the pollen gets attached to its body – pollination succeeds again! The leaves of Viola are usually heart-shaped (how adorable is that?!), at least in the base of the plant.

 To finish with, I just want to make a small art reference I found about these loving flowers. Viola’s also inspired many artists (no wonder!), but I won’t bother you with a list of famous classic pieces. I just want to share this last curiosity about “Shakespeare in Love”, have you ever seen this film? It tells a fiction story of Shakespeare while writing his famous “Romeo and Juliet”, inspired by his muse, a woman named Viola – coincidence? In any case, if roses are for some the flowers of passion for some, violas are surely synonyms of pure & sincere love after this post.

Marcgravia: the MacGyver of the flowers

"Oh I've heard about you! You're the guy who does the whatchamacallits, you know, MacGyverisms; turns one thing into another?"

Do you remember the American TV series MacGyver? The other day, by chance I found a very interesting paper published recently in Science explaining an amazing co-evolutionary event in a tropical plant, Marcgravia. After reading it, I automatically thought: Marcgravia is the MacGyver of pollination! Turns one thing into another… Want to know why?

Marcgravia is a plant genus belonging to its own hidden family, Marcgraviaceae, only found in the New World Tropics (Central and South America). The group is relatively small and the flowers not well studied. However, their inflorescences are pretty extravagant. The inflorescences consist on upside-down umbels with several flowers hanging down. The flowers have 4 or 5 petals fused together (characteristic of Ericales clade, where they belong to) and the number of stamens is highly variable and showy. Not a very exciting description, right? Yep, that’s because the excitement of these flowers remain on the bracts and bracteoles – and now you are asking: “What are those?”. Bracts and bracteoles (small bracts) are leaf-like structures associated with the inflorescences (bracts) and individual flowers (bracteoles). Bracts and bracteoles are sometimes associated with the protection of the flower, but in many cases they don’t have any particular function, so some plants might lack them. In Marcgravia we can find both structures and both of them have a good reason to exist. 

The bracteoles of Marcgravia are a piece of art! They were modified into big and exuberant pitcher-shaped nectaries, imagine big nectaries full of yummy nectar… Lucky pollinators! Oh yeah, and who pollinates these amazing flowers? Any guess? Well… It actually depends, but such big structures with large quantities of nectar are definitely not pollinated by invertebrates… They are pollinated by big animals, mainly humming birds and bats. Actually, the reason why I wanted to tell you this story is because of the amazing co-evolution of pollination between Marcgravia evenia and bats. Just like MacGyver, using common things to make complex gadgets, Marcgravia evenia also made quite a gadget with their bracts. How? By turning a boring leaf-like structure with apparently no use (the bract) into an echo-location device! 

The inflorescence bracts of Marcgravia evenia developed into a dish-like structure, guiding the bats in the forest into the inflorescences! The shape of the bract produces a strong and easily recognizable echo by the bats, making it easier for the bats to find the inflorescences. Once they find the inflorescence, they feed on the nectar inside the pitcher-like nectaries (the modified bracteoles); the hanging flowers (with numerous stamens which are full of pollen ready to be released) are strategically positioned, leaving the bat’s back full of pollen and this is how pollination happens in this species. Actually, this system is highly efficient, since the bats take only half of the time to find flowers with these bracts in comparison to other flowers without them. 

So Marcgravia is for me like MacGyver, turning things with no apparent use into very usefull ones: bracteoles into pitcher-shaped nectaries and bracts into echo-location devices… Isn’t Nature absolutely amazing?

The Sacred Bodhi Tree

During my visits to the Buddhist temples in Chiang Mai, I realized that there is a sacred tree at the entrance of these temples. This tree is usually surrounded by a short wall with Buddha statues around it – this is Ficus religiosa, the sacred fig. This is a very important tree in Buddhist culture since it was under a Ficus religiosa where Buddha attained enlightenment while meditating.

The original plant was in India, and cuttings were taken from it and transplanted to other places across the Buddhist world at the time to keep the sacred tree safe. One of the cuttings was taken to Sri Lanka, and it is the only surviving member of the original plant. With more than 2500 years old (!!!) this is the oldest living angiosperm on record! The most impressive thing is that the Ficus religiosa found at the entrance of the temples all around the world (including Thailand), are all clones of the original tree in Sri Lanka (in Mahabodhi Temple) that grew from cuttings of the mother plant and are thus all genetically identical!

Now, back to botany… Ficus belongs to the Moraceae family – the figs. As some of you might already know, this family is very widely dispersed in the tropics and the presence of white sap is one of the field characters recurrently used to identify the family. But the flowers and the fruits are the most characteristic and weird features, with a very specific pollination syndrome. To begin with, figs are not fruits – they are false fruits, multiple fruits (tricky!). So the fig is actually a group of very small aggregated fruits, enclosed in a structure that we call syconium (the fig). The syconium is also the inflorescence, and encloses all the male and female flowers. The apex of the syconium has a hole (ostiole) from where the specialized pollinator comes into the inflorescence; the pollinators of Ficus are usually very small wasps. As I mentioned, these plants are known for having very strange flowers, and in China they are also known as the fruits without flowers, since you can never see the flowers as they are enclosed in the syconium. The truth is also that figs have usually 3 types of flower in the same inflorescence – male flowers are found surrounding the ostiole and two types of female flowers are found in the inner part of the syconium, type one has long styles and type two has short styles. The pollination is carried out by wasps that visit the syconium to lay their eggs and they lay their eggs in the short styled female flowers.

The most interesting thing about this pollination syndrome is the very close co-evolutionary relationship between species of figs and wasps. Most of the time one wasp is specialized on the pollination of one single species of fig. A good example for this is that in Hawaii, where around 60 species were introduced, but only 4 wasps were introduced, so only four species of figs are pollinated to produce viable seeds.

An introduction to flowers

Flowers are plants’ devices for reproduction, the sexual organs of angiosperms (the flowering plants) and since very early times have kept the attention of humans. Their incredible diversity is probably the most distinctive feature for the identification of plants, having a special importance for botanists. However, not only botanists (or pollinators) have been attracted to flowers – they have a constant presence in our society having different meanings and we heard about them in history, traditional medicine, religion, and even artists from all fields have been inspired by their beauty.

To understand flowers’ morphology is to understand plants’ evolution and co-evolution with their pollinators. Maybe some of you are not interested on the evolution or morphology of flowers, but plants are everywhere, and by giving attention to these beings you will probably find out some surprising things. Although plants are still and silent, they have other ways to communicate with us – we just need to understand how they do it!

My aim with these stories is to explain the floral morphology, development and evolution by using a language understandable to all interested. This might be a nice way for you to get to know better the organization of structures in the flower itself.

On this first post, I will explain a little bit about the floral morphology and the basic floral characters – it will be easier for you to understand the stories and you can always take a look at this first post to remember what the structures are.

Flowers are formed by fertile and unfertile parts. The unfertile parts are usually to protect the fertile ones (sepals, the green and outermost parts of the flower), or to attract the pollinators (petals, which are usually showy and colourful). The fertile parts are in the center of the flower and consist on the male and female parts. The stamens (male organs), are formed by the filament and the anthers (the structures that produce the pollen grains). The female parts are the carpels and are always found in the center of the flower, surrounded by all the other floral structures. Carpels are formed by the ovary (the organ that bears the ovules and that, once fertilized will originate the fruit), the style and the stigma (the structure that receives the pollen grains, which are guided to the ovary to fertilize the ovules). As plants don’t move they have to pollinators (like animals or wind), to take the pollen to the stigma, this is called pollination.

Flowers are not this simple, but this will help you on understanding the basics of the flower morphology. Some flowers have extra structures, others lack structures, and others have modified structures, having a totally different appearance. I will talk about them later, on each story, as different flower have different structures for the most different reasons…