Original, traditional and truly American

Native from North America, the Saguaro cactus can only be found in the Sonoran Desert (US states of Arizona and California and Northwestern Mexico). The peculiarity of such plant is part of the imaginary of the native tribes since ancient times. Many legends have been build-up around the cactus; many of those legends confer special gifts or divine powers to these plants. Its shape and size (which can grow over 20 meters tall) makes a superb view along the desert landscapes, and this was probably the reason why natives believe that the Saguaro cacti were reincarnations of the spirits of Native American warriors, standing in the desert as guardians of their people with arms upwards, supplicating for water and light to the Creator.

Seri People in Sonora Desert, Mexico (Photo: Graciela Iturbide, 1979)

As in a desert whatever you find is a gift from heavens, the Saguaro has been venerated for generations and used as a source of food and shelter for the natives, especially by the Tohono O’odham and the Mexican Seri people, as well as for other inhabitants of the desert. The fruits are an important food source not only for the people but also for birds, whereas the plant itself is used by some species for nesting. The needles were used for sewing, and other parts of the plant were used to build shelters or to produce tools.

A - Parabuteo unicinctus (Photo: Walter Meayers Edwards); B - Micrathene whitneyi (Photo: Bruce D. Taubert); C - Zenaida asiatica; D - Bubo virginianus (Photo: Jim Zipp)

But the real magic happens during the quiet night, when pollination takes place. Any guess on who’s starring this time? Bats! Just take a look at the flowers – white, open, big and on the top of that, it releases a sweet smell of nectar during the night. 

Bat pollination of Saguaro flowers by Leptonycteris yerbabuenae
(Photos by: Merlin Tuttle / Bat Conservation International)  

However during the day the cacti flowers keep opened, so other animals can pollinate when bats are asleep – after all, nothing forbids them to do the job, even though the main pollinator is the lesser long-nosed bat (Leptonycteris yerbabuenae). Unfortunately these bats are threatened and considered Vulnerable according to IUCN, especially due to habitat destruction.

Day pollinators

We have to admit cacti flowers are absolutely gorgeous. More than the natural gorgeousness, they are a botanically interesting case to study. Caryophyllales’ members tend to be odd and have their own peculiarities, and so does Cactaceae, having an immense (botanically speaking, we actually say infinite) number of petaloid tepals. No, not petals – they are not real petals, Caryophyllales lack petals and this is probably one of the reasons why so many different trends arose in this group. They had to find a way to attract pollinators even though they did not have petals to do it! What a task… But they went over it and they reinvented petals with the genetic sources they had. Phenotypically, my dear Cactaceae, I must admit I love what you invented – isn’t Nature truly an artist?

Photo source: Flickr (J Rindrr)

Well-behaved plants live in wild Borneo

Probably the most interesting group of plants for the majority of people are the carnivorous plants because of their behaviour with insects. Wait, because of the insects’ behaviour with these plants! Well, in any case we must all agree that carnivorous plants were a wild invention of Nature. 

Different growth stages of pitchers in the QBG carnivorous plants glasshouse

My opinion about them became even wilder when I found an old article about a Bornean pitcher plant (Nepenthes bicalcarata), which relationship with insects is absolutely unexpected for a carnivorous plant. So first, let me remind you some aspects about the biology of these plants: pitcher plants are known by getting nutrients from insects as a supplement. Their strategy is to attract insects using a trap, a modified leaf (the pitcher), which is full of enzymes and digestive liquid where the nutrients can be absorbed. 

In Nepenthaceae, the leaves are differentiated into pitchers and the petioles are the photosynthetic part of the plant, having the function of the leaf but not being a true leaf

The insects are attracted by the extra-floral nectaries and often fell in, drowning in the fluid. However this particular species, Nepenthes bicalcarata, nests ants (Camponotus schmitzi) in their swollen and hollow tendrils. Strangely, these ants forage on the inner side of the pitcher, crawling over the slippery walls without difficulty and even swimming in the pitcher fluid to forage and feed on the insect prey’s of pitchers. So, what is the advantage for the plant on having other insects eating the food that they get alone by using their own pitchers? The ants only collect large prey insects – all the other small insects are digested and absorbed by the plant. Big preys take long time to digest, and this would end up on putrefaction and rotten pitchers, which is obviously something not very healthy for a pitcher plant to have. So these pitcher plants get rid of the large preys by offering them to their friends - ants. “Wow!” – I can hear you guys whisper. No worries, I whispered the same – these plants are really something!

Picture of Nepenthes calcarata sourced from the magical internet. It is possible to see the nests that the plant produces in the tendrils, as well as the "horns" that are very characteristic of this species

Even though this is all undoubtedly very interesting, the flowers of Nepenthes do also tell a story. Nepenthaceae, as all the members of Caryophyllales order have no petals, so their perianth has only one single whorl made out of sepals. The flowers are also easily recognizable by being dioecious (meaning that sexes are separated in different flowers, male and female) and tetramerous. Of course that a carnivorous plant also needs insects for pollination, so they do produce a lot of nectar to attract a lot of insects. Some will end up in the pitcher-insect-hell, but others will end up licking the sepals which are fully loaded with sweet nectar. It’s a matter of luck for insects I suppose.

Typical inflorescence of Nepenthes, a racemose with paired tetramerous flowers, each one subtended by one bract

Another very interesting fact about the Nepenthes are the male flowers, which have all the stamens (ranging usually from 4 to 24 in number) fused together in a structure which botanists decided to call “synandrium” (syn meaning fused and andrium referring to the male part).