Golden Protector

I’ve always planted marigolds among my garden. I’ve heard these orange beauties have protective properties against herbivores. Is it true?

Hmm. Most researchers have found properties released from marigold roots inhibit bacteria, fungi, and/or nematodes (although this is extremely variable, depending upon the part of the plant used, how the marigolds are grown, and the pest species tested).

Most interesting sidetrack from my search… some research shows inhibition of Plasmodium, the microscopic organism that causes malaria (1).

Thanks to Charlie O’Shields of DoodleWash for the #WorldWatercolorMonth inspiration.

1. Pankaj Gupta & Neeru Vasudeva (2010) In vitro antiplasmodial and antimicrobial potential of Tagetes erecta roots, Pharmaceutical Biology, 48:11, 1218-1223

A Poinsettia by any other name… the cuetlaxochitl

Politics was different in the early 1800s. You didn’t even have to run for office to be elected. Joel Poinsett’s friends nominated him to the South Carolina House of Representatives, and he won. By that time, he’d already completed years of travel through Europe, Russia, the Middle East, and South America where he’d met with foreign ministers, consuls, an empress, and many other political figures.

Within a few years, Poinsett became a U.S. congressman and then the first foreign minister in Mexico. That’s where he saw that plant that would later carry his name. He sent cuttings back to his greenhouses in Charleston and introduced the United States to a beautiful Mexican plant. Unfortunately, Poinsett got in a bit of trouble over his political views in Mexico (the word “poinsettismo” was coined as a result of his intrusive meddling) and was recalled from his post. Poinsett went on to cofound the National Institute for the Promotion of Science and the Useful Arts, later known as the Smithsonian Institution.(1)

Of course, the Poinsettia was well-known in Mexico long before Joel Poinsett. The plant is called cuetlaxochitl (pronounce), and grows as a shrub in Mexico City. The blood-red bracts are symbolic of sacrifices and creation.(2)

1. To learn more about Joel Poinsett, read “Joel R. Poinsett: Versatile American” by J. F. Rippy
2. Lots of interesting information about Poinsettias can be found at http://extension.illinois.edu/poinsettia/

The Corpse Flower Opens – and Stinks!

Many flowers use insects to transfer pollen from one plant to another. Some flowers attract bees or butterflies. The corpse flower, though, uses carrion beetles and flesh flies. What attracts these pollinators? The color of decaying flesh, putrid scents, and the warm temperature of a freshly dead body. Lovely.

While we humans tend to focus on color, beetles and flies who pollinate the corpse flower may be more attracted to the scent and temperature. Angioy et al. (2004) showed that certain insects have the abilities to “see” temperatures and are attracted to heat. The heat generated by the spadix of the flower is unusual in the plant kingdom. Not many plants expend tons of energy to warm up to around 100 degrees Fahrenheit. Those few that do are called “thermogenic plants.” It’s generally accepted that the heat increases the range of the odors (Barthlott et al. 2009), which is true of course. But wouldn’t all plants benefit by increasing scent ranges? Yet this mechanism is found in plants that only mimic carcasses to attract pollinators – plants like the skunk cabbage and voodoo lily.

While most flowers give their pollinators a reward of some kind (think nectar), the corpse flower seems to just take, take, take. The plant mimics carrion, where pollinators normally lay their eggs, yet gives the pollinators no food or reward. Or could it?

I personally found it interesting that the spathe of the corpse flower closed back up after it bloomed. It’s probably protecting the developing fruit. Yet the fruit takes 6-9 months to mature. At the Chicago Botanic Garden, the spathe of their corpse flower wilted after about 3 months, exposing yet unripe fruit. Could the flower serve as protection for the developing carrion beetles? Is there any food supply for those youngsters when they hatch? Or is it just a dead end (pun intended)?

FYI: while other arums smell like corpses too (my personal favorite is the “pig-butt arum”), some species of Amorphophallus smell like bananas or carrots.

1. Angioy AM et al. 2004. Function of the heater: the dead horse arum revisited. Proceedings of the Royal Society Biological Sciences. 271(3) S13-15.
2. Barthlott W et al. 2009. A torch in the rain forest: thermogenesis of the Titan arum (Amorphophallus titanium). Plant Biology 11. 499-505.

The Corpse Flower, a Botanical Marvel

It’s rare to see a corpse flower bloom. If you ever have the opportunity, take it… especially if you get to visit Sumatra. Lucky for me, a corpse flower (Amorphophallus titanium) blossomed in the greenhouse next to my office last weekend at NC State University (https://cals.ncsu.edu/corpse-flower-at-nc-state/).

It took the corpse flower, dubbed Lupin, 13 years to save up enough energy to bloom.  It’ll probably be another five years before it does so again. So corpse flowers are rather special. Actually, fewer than 200 cultivars have been recorded since 1889. But now’s your opportunity. For some yet unknown reason, a bunch are flowering at once (1).

Lupin grew six feet tall in under two months! That tall, purple-grey phallic structure is called a spadix. At its base are about 700 vibrant orange and purple female flowers and thousands of male flowers (2). When the one giant petal (actually a bract known as a spathe) opens, the spadix releases a stench to attract carrion beetles and flies who pollinate all those female flowers.

So actually, the corpse flower isn’t a flower at all. It’s over a thousand flowers wrapped into one giant, stinky, gorgeous inflorescence.

1. http://www.sciencealert.com/no-one-really-knows-why-but-america-s-corpse-flowers-are-all-blooming-at-once
2. Gandawijaja, D, S. Idris, R. Nasution. 1983. Amorphophallus titanium Becc.: a Historical Review and Some Recent Observations. Ann. Bot. 51:269-278.

Ahh chooo! Pine Pollen and Climate Change

 

The bane of many a Southerner’s existence is springtime pollen. All that yellow dust swirling on the breeze and coating your car, that’s pine tree sperm.

The male cones of a Loblolly Pine (Pinus taeda) look like a bunch of tiny bananas growing from twig tips. If you’re thinking, “wait, that’s not a cone,” the woody cone we use to hot glue decorative wreaths or smear with peanut butter for DIY bird feeders is the female cone. Its spirals of woody shingles (or bracts) protect the tree’s eggs and, after fertilization, the developing pine embryos inside.

Male cones are much smaller and shorter lived. They release pollen for a couple of weeks each spring. And it’s a LOT of pollen: 3-5 pounds per tree. Why so much? Pines transfer pollen from male to female cones by wind. It’s not a very efficient system. More pollen increases the chance of fertilization.

With Climate Change, pollen’s gonna get worse. Ladeau and Clark (2006) found that pines growing in an elevated CO2 environment produce more pollen cones, and more pollen, at younger ages.

p.s. If you ever wondered what a pine pollen grain looks like, it’s a microscopic Mickey Mouse logo!

Ladeau SL, Clark JS. 2006. Pollen production by Pinus taeda growing in elevated atmospheric CO2. Functional Ecology. 20(3) 541-547.

Of Leaves & Worms

Every autumn, vibrant leaves float down from the tree tops to stitch a patchwork quilt resting on the forest floor.

Over time, leaves are broken down by fungi, bacteria and other detrivores (organisms that eat dead stuff) like earthworms. The superpower of the earthworm (Lumbricus terrestris) is its ability to compost vegetation and return vital nutrients to the soil.

Charles Darwin was fascinated by earthworms, conducting wonderful experiments to determine how much soil they moved and whether worms preferred to collect leaves from the broad end or pointed end. Worms pull leaves into their burrows (narrow end first) to plug the opening and protect themselves from ‘early birds’.

In much of North America, earthworms were killed off in the last ice age (~10,000 years ago). The worms you see now in Michigan, Maine and Minnesota are all invaders. Sounds great, right? More nutrients in the soil? Unfortunately, the northern hardwood forest ecosystem is adapted to a thicker leaf litter layer and slower release of nutrients. So now, the introduction of the earthworm changes which seeds can germinate (and which trees will continue to survive), nutrient run-off, and which animals live in the new, de-littered forest. (1)

If you’re interested in appreciating the awesome recycling power of the worm, check out a delightful little book by Amy Stewart – “The Earth Moved: On the Remarkable Achievements of Earthworms”.

Want to read more specifics about leaf-earthworm experiments? Natural History Magazine has an entertaining write-up.

1. Hale CM et al. 2008. Exotic earthworm effects on hardword forest floor, nutrient availability and native plants a mesochosm study. Oecologia. 155:509-518.

Wildflower Stories – the Hercules of Plants

Cow Parsnip (Heracleum maximum) has a fascinating relationship with war, GMOs and sunscreen.

The plant’s scientific name probably points to its size – it’s taller than me (but that’s not saying much). It takes two years to grow that big. If you’re going to put that much time into growing, you’ll want to make sure nobody eats you; which leads us to the other possible reason for Cow Parsnip’s scientific name. Some claim Hercules used this plant medicinally.

Many plants contain chemicals to protect them from predators. This plant makes “furocoumarin”. In humans, furocoumarin combines with sunlight to cause a rash. This is where war comes in. During World War II, military organizations recruited plant and insect experts to investigate the defensive (or offensive) properties of these chemicals. Mustard Gas is similar in its blistering effect to furocoumarin.

Most plant predators, though, are not humans; they’re insects. As you can imagine, Cow Parsnip is very effective at deterring insect herbivores. So, the genes that will ultimately produce furocoumarin are prized. If you could insert those genes into another plant (how GMOs are made), the same protection will occur.

Beware the inevitable evolutionary “arms race” that results though. A few insects can eat Cow Parsnip, either due to mutations that let them break down the furocoumarins or behavioral shifts (like eating that plant only at night or when rolled in one of the plant’s leaves. Remember, the chemical has to be combined with sunlight to produce an effect.

And we get to sunscreens. A related chemical was used as a “tanning accelerator” up until 1996. Unfortunately, it caused rashes (“sun poisoning”), skin loss and even cancer. Turns out, furocoumarins can mutate DNA.

Cow Parsnip belongs to the Carrot family of plants. They tend to have hollow stems and flowers in “umbels” (like umbrellas). Some relatives are frequently on our dinner table (carrots, celery, parsley, dill, etc.); some, like hemlock (not hemlock), are deadly.