Science Experimentation at Grad Student Prices: Nepenthes bicalcarata

One of the nice things about having absolutely no natural light in the back area of the gallery, and having all of the lights on timers to encourage winter growth patterns and spring blooming, is that it gets DARK back there when the lights go out. While this is horrific if you get turned around and can’t find the front hallway, it’s excellent when conducting experiments with ultraviolet light. A little messing about with the handy violet kaleidoscope laser pointer in the gallery led to some interesting observations.

To begin, the squat little pitcher up top belongs to the famous Asian pitcher plant Nepenthes bicalcarata. N. bicalcarata is one of the only Nepenthes species to have a commonly used nickname in carnivorous plant circles, “bicalc” singular or “bicalcs” plural, and it’s also one of the only Nepenthes species to have a common name in English. That name, “fanged pitcher plant,” refers to the two distinctive sharp “fangs: that run down from where the pitcher meets its lid. Those “fangs” are officially called nectaries, in that they secrete and channel nectar, which leads to the slightly disturbing view of a happy and healthy bicalc being one that’s drooling nectar off these structures like a snake’s fangs dripping venom. These nectaries are both strong and sharp, leading to all sorts of suppositions on how the “fangs” prevent monkeys and birds from removing trapped prey from the pitcher. The reality, however, is that nobody really knows what these structures are for, as well as the comparably eye-catching and risky structures on the equally famous N. inermis, N. edwardsiana, and N. hamata.

As a handy hat-tip to any grad student wanting an interesting subject for their first paper, N. bicalcarata shares with its insectivorous kin an actively ultraviolet-fluorescing band of tissue along the lip of pitchers called the peristome. This is fascinating but not necessarily news: this fluorescence has been known among many completely unrelated genera of carnivorous plant for the last decade, and Nepenthes species such as N. hemsleyana and N. ampullaria that no longer produce digestive enzymes in their pitcher fluid also no longer have UV-fluorescent peristomes. What might be news is that nobody seems to have noted that the nectaries on N. bicalcarata fluoresce as hard and as brightly as the peristome itself.

The real surprise? This is an absolutely horrible photo that will require retaking with an actual photographer, but this is the fluorescence of a juvenile N. bicalcarata pitcher. Interestingly, the pitcher itself fluoresces a bright red along the peristome, but the nectaries, only a little over a millimeter long, fluoresce the same yellow-green as the nectaries on full-sized pitchers.

As to why these nectaries fluoresce, that’s a really good question. Since I don’t have any in the gallery at the moment, I don’t know if N. edwardsiana and N. hamata peristomes fluoresce in the same way, or if they go for different patterns under UV the way Nepenthes species with particularly wide peristomes (such as N. rafflesiana) do. I also don’t know at the moment whether the fluorescence in the nectaries matches that of the peristomes as the pitcher ages and dies, because that requires repeated observations over the months the pitcher may live. However, for an enterprising botany grad student wishing to publish for the first time with a paper that might get to the top of standard newsfeeds, run with this.

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