Daily Account #4- Botany Greenhouse, UW
we got to spend class touring three stations in the biology/botany greenhouse on campus today. I LEARNED SO MUCH ABOUT PLANTS, it was wonderful.
the first station i was at was tasting miracle berries and learning about chilis with professor tewksbury. miracle berries (Synsepalum dulcificum) are a fascinating fruit that, when eaten, block one's sour and bitter receptors (in your taste buds)- making otherwise sour and bitter things taste sweet. we tried this by eating lemon slices- which tasted like tantalizing lemonade to me. we also tried thinking about why it does this- since the berries are bird dispersed (hence the red color), and have no immediate gains from having this effect on humans. the point was emphasized that plants use chemistry to communicate, mask certain things about themselves, and trick life around them. i don't think there is a consensus on why the berries do this... we also decided it might be to mask bad chemicals (such as tannin or chemicals that prevent against pests, etc.) while tasting good to others.
we also talked about chilis. why are they hot? and is heat a taste? i hadn't thought about it before, but heat is caused by a pain-sensing neuron (the same as is activated when you touch a burner), not taste buds. these neurons tell your brain that tissue damage is occurring where you feel the heat (as it would be if you touched a burner), but this isn't actually true.
the active component of chilis is called capsaicin, which isn't actually inside the seeds but coats them like a thin layer of oil. it helps stop fungal growth. we were looking at a curious type of chili in which some trees have hot peppers and some don't (also known as chili russian roulette). we learned that birds don't taste the heat, though all mammals do (including snails)- but birds evolved long before chilis, so why do some trees not have capsaicin? the prevailing thought is that there is some cost to producing capsaicin, so for some trees, the costs must outweigh the benefits to being pungent.
i noticed that i was salivating a lot more after eating the chili than before- why does that happen?
at the next station, we heard several different stories from doug. the first was regarding the largest seed on the planet, which weighs 26 pounds in the greenhouse but can weigh up to 60. it is a palm tree that grows to be 100 feet tall. the seed cannot float, nor is it marine dispersed or generally mobile, BUT you can pack a lot of nutrients in it. so it falls right under the mother tree, but it can produce a 30 foot shoot that tunnels underground and starts the tree further away.
the leaves of the tree are produced at a fibonacci angle, and doug showed us that when it rains, the water is funneled straight towards the roots.
the next plant he talked about was Monstera deliciosa, and is a native. it seeds on the forest floor, germinates, and then actually grows toward the darkness (is skototropic). but later switches to becoming phototropic. the leaves had a beautiful holed-out pattern in them, which i guessed correctly to be mimicking catepillar feasting. this discourages butterflies from laying their eggs there. doug also said that the fruit right now would be painful to eat, but that when it sheds it has a delicious pineapple-like fruit- hence the name "deliciosa."
he talked about a few more plants (Dischidia, Eichhornia, Nymphaea) before we moved onto the desert room with susan.
the first plant we talked about was Welwitschia, which comes from the Namibian desert and gets only 25mm of rain per year. this heat has selected for reflective leaves. the plant is also dioecious, meaning that individual plants are either male or female. it is a gymnosperm, or a cone-bearing plant that produces pollen but not flowers (same taxa as douglas fir). it can live to be 2,000 years old! susan also illustrated the point that the plant doesn't "like" living in Namibia under those harsh conditions, it just couldn't compete anywhere else- so doug watered and cared for it like any other plant, and it grew to be enormous relative to other Welwitschia.
she also talked about how leaves have stomates (or pores) that open to let in CO2 to make sugars, but the trade-off is in losing water when the stomates are open (through transpiration). the Peperomia plant in the desert room, however, retains its water by doing photosynthesis inside the leaves through leaf "windows" that let in light.
we then walked over to a much damper room and learned about some carnivorous plants and peat bogs. the latter are usually characterized by sphagnum moss. bogs tend to be acidic and low in nutrients, thus plants that thrive in that environment tend to be carnivorous- where they can eat bugs for nutrients that they can't get from the soil.
we also saw examples of epiphytes, and i learned that this is just a term for plants that "piggy-backs" onto other plants for some benefit, usually to get access to more light. this includes mosses and lichen, as well as the plant we saw- Platycerium.
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