Botany Lab of the Month, Superbowl Edition

In 2016, the International Year of Pulses, we’ll be writing a lot about pulses (dried beans and peas), and we’ll also tackle the huge and diverse legume family more broadly. This weekend Katherine kicks things off with February’s Botany Lab of the Month: beans and chickpeas for your Superbowl bean dip and hummus.

The species name of Cicer arietinum means "ram's head."

The species name of Cicer arietinum means “ram’s head.”

Beans are a bit like football: a boring and homogeneous mass of protein, unless you know where to look and what to look for. In this lab, we’ll make the smashing of beans into bean dip or hummus much more interesting by taking a close look at some whole beans before you reduce them to paste. The directions are very detailed, but this whole lab can be completed in the time it takes to explain the onside kick.

Of course, if you have only pre-mashed refried beans in your pantry, it’s too late. Then again, if you are using canned refried beans for your recipe, you are probably not living in the moment or sweating the details right now. That’s OK. Go watch the game and let us know when someone scores.

1. For this Botany Lab of the Month, you can start with soaked dried beans, home cooked beans, or even whole canned beans if that’s what you’ve got. Uncooked soaked dried beans are definitely the best choice. You can even set a few aside and watch them become seedlings.

2. The first thing to consider about beans is that they are seeds and thus came out of a fruit – in this case a legume “pod.” Bean-dip beans (Phaseolus vulgaris, e.g. white, kidney, pinto, black) develop within a regular edible green bean and are harvested when the pod is fully mature. Chickpeas (Cicer arietinum = garbanzo beans) come in small inedible hairy pods that resemble one-seeded edamame or peanut shells. Each individual seed is tightly enclosed by a seed coat (the testa), which often slides off when beans are soaked or cooked.

Close up of Phaseolus beans showing parts we often overlook

Close up of Phaseolus beans showing parts we often overlook. Click to enlarge.

The same image, with parts labeled. Click to enlarge.

The same image, with parts labeled. Click to enlarge.

3. Look for evidence of the fruit connection right on the outside of the bean seed. Before harvest, a bean seed is attached to the inside of its fruit by a short little stalk (funiculus, or “slender rope”) through which it draws water, sugar, and nutrients. The same word is used for our umbilical cord (funiculus umbilicalis). Once the bean seed is mature, it becomes dry and separates from the fruit wall, but it carries a pale scar like a belly-button where its funiculus was attached. That scar is called a hilum, and it’s an obvious feature. In black-eyed peas, for example, the hilum stands out as a white scar in the middle of a black splotch. On the chickpea, the hilum is surrounded by a ridge so that it looks like one giant nostril under a beaky nose. Fun fact: Cam Newton won the Hilum Trophy in 2010.

Close up view of a chickpea flashing its hilum. Click to enlarge.

Close up view of a chickpea flashing its hilum. Click to enlarge.

4. Several very interesting anatomical features appear when you look even more closely at a bean seed’s parts. On an ordinary Phaseolus type bean, the hilum sits in the center of the curved side of the seed. Extending from one end of the hilum is a narrow ridge, which may be easiest to see from the side. That ridge is the embryonic plant’s root (called a radicle) pressing out against the seed coat like overly tight clothing. When the seed germinates, the radicle will emerge from the seed coat, grow downward to anchor the seedling, and start drawing up water for rapid growth. The radicle of the chickpea is extremely obvious: it’s in the beaky nose of the seed overhanging the hilum.

5. Between the hilum and the radicle ridge is a tiny structure you may not be able to see: the micropyle (“tiny hole”). That’s where a pollen tube entered the seed (at that point still an “ovule”) and deposited its sperm. It may also be an entry point for water in some plant species, kicking off the process of germination. Finally, radicles generally emerge through the seed coat by way of the micropyle, which is usually found near the radicle tip. So if you can find the radicle in a seed, it will often guide you to the elusive micropyle. The micropyle is much more easily seen on Phaseolus beans than on chickpeas.

6. On the opposite side of the bean hilum is a pair of bumps called the strophiole. Allegedly, its Latin roots mean “little wreath,” which suggests that whoever named this structure was looking at some other species, and definitely not beans. Anyhow, in beans, there is some evidence that water enters the seed through the strophiole as well as through the micropyle (Smykal et al 2014).

7. Finally, running between the strophiole and the end of the seed is an elongated pleat or groove called the raphe. The raphe is a mark in the seed coat showing where, during development, the seed rested up against its funiculus (that umbilical-cord-like structure).

8. Oddly enough, the rest of the bean seed is much simpler than its outside. To get inside, first pull off the testa (seed coat). By the way, some hummus recipes suggest that you strip all your chickpeas of their coats (chefs usually call them hulls or skins) to make an elegant spread. If you mash by hand, it is nice not to have those tough testas scattered around in the hummus. If you plan to puree your beans or chickpeas, then it’s probably not worth the trouble.

9. Without the seed coat, you have a naked embryo. The radicle should be obvious now as a short thick curved root lying right where you expect it. On a chickpea, it’s in the nose. On a Phaseolus bean it runs halfway along the inside of the curve.

Chickpea embryo, with close-up showing the shoot tip (plumule) and its young leaves. Click to enlarge.

Chickpea embryo, with close-up showing the shoot tip (plumule) and its young leaves. Click to enlarge.

10. Now separate the two large lobes making up the bulk of the embryo. They are smooth in a bean and a little dimply in a chickpea. Those halves are the cotyledons, which store resources for the developing seedling. In beans, they are drawn out of the seed coat and carried above ground by part of the stem (the hypocotyl), where they become the first photosynthetic green leaves. In chickpea, they stay below ground while the rest of the seedling draws upon their stores for growth.

11. When you spread the cotyledons you will break one of them off, but you will still see that they were attached to each other near the top of the radicle and below a tiny little tuft of new leaves. The radicle grows out to become a root, and the tuft, or plumule, grows out to become the shoot.

12. Extra credit: If you do have soaked but uncooked beans, spread them in a shallow dish on wet paper towels to sprout. The seeds should not be submerged, but the water should pool around them on the paper towel. Keep the dish lightly covered (with a translucent plastic container lid, for example) and don’t let the seeds dry out. Change the water once a day so it doesn’t start to smell funny. You will see the root emerge first, followed by the shoot, which will turn green in the light, straighten up, and unfurl its young leaves.

From here you can continue with your favorite bean dip or hummus recipe or you can just go back to the game. I myself am a baseball fan, counting the days until spring training. Keep your eyes out for a peanut post.

Reference:

Smýkal, P., Vernoud, V., Blair, M. W., Soukup, A., & Thompson, R. D. (2014). The role of the testa during development and in establishment of dormancy of the legume seed. Frontiers in Plant Science, 5, 351. http://doi.org/10.3389/fpls.2014.00351

Shout out to my friend and partner in teaching 3 long lab sections in a day, Kay H, who taught me just how funny beans can be.

Botany Lab of the Month (Oscars edition): potatoes

This month we introduce a new feature to the Botanist in the Kitchen: Botany Lab of the Month, where you can explore plant structures while you cook. In our inaugural edition, Katherine explains why she would like to add her nominee, Solanum tuberosum, to the list of white guys vying for Best Supporting Actor.

In one of this year’s biggest and best movies, Matt Damon was saved by a potato, and suddenly botanists everywhere had their very own action hero. It’s not like we nearly broke Twitter, but when the trailer came out, with Damon proclaiming his fearsome botany powers, my feed exploded with photos of all kinds of people from all over the world tagged #Iamabotanist. The hashtag had emerged a year earlier as a call to arms for a scrappy band of plant scientists on a mission to reclaim the name Botanist and defend dwindling patches of territory still held within university curricula. Dr. Chris Martine of Bucknell University, a plant science education hero himself, inspired the movement, and it was growing pretty steadily on its own. Then came the trailer for The Martian, with Matt Damon as Mark Watney, botanizing the shit out of impossible circumstances and lending some impressive muscle to the cause. The botanical community erupted with joyous optimism, and the hashtag campaign was unstoppable. Could The Martian make plants seem cool to a broader public? Early anecdotes suggest it’s possible, and Dr. Martine is naming a newly described plant species (a close potato relative) for Astronaut Mark Watney.

In the film, that potato – or actually box of potatoes – was among the rations sent by NASA to comfort the crew on Thanksgiving during a very long mission to Mars. After an accident, when the rest of the crew leaves him for dead, Watney has to generate calories as fast as he can. It’s a beautiful moment in the movie when he finds the potatoes. In a strange and scary world, Mark has found a box of old friends. They are the only living creatures on the planet besides Mark (and his own microbes), and they are fitting companions: earthy, comforting, resourceful, and perpetually underestimated. At this point in the movie, though, the feature he values most is their eyes. Continue reading

Winter mint

This is our second of our two contributions to Advent Botany 2015. All the essays are great!

An early image of candy canes. From Wikipedia

An early image of candy canes. From Wikipedia

The candy cane, that red- and white-striped hard candy imbued with peppermint oil, is a signature confection of the winter holidays. Peppermint has a long history of cultivation and both medicinal and culinary use. Infusions of the plant or its extract have been used for so many hundreds of years throughout Europe, North Africa and Western Asia that the early history of peppermint candies, including cane-shaped ones, is murky. Fortunately, the biology behind peppermint’s famous aroma is better known than the story of how it came to be a Christmas staple. Continue reading

Sugar

This is our first of two contributions to Advent Botany 2015.

Sugar plums dance, sugar cookies disappear from Santa’s plate, and candied fruit cake gets passed around and around. Crystals of sugar twinkle in the Christmas lights, like scintillas of sunshine on the darkest day of the year. Katherine and Jeanne explore the many plant sources of sugar.

Even at a chemical level, there is something magical and awe-inspiring about sugar. Plants – those silent, gentle creatures – have the power to harness air and water and the fleeting light energy of a giant fireball 93 million miles away to forge sugar, among the most versatile compounds on earth, and a fuel used by essentially all living organisms.

Sugar naturally occurs in various chemical forms, all arising from fundamental 3-carbon components made inside the cells of green photosynthetic tissue. In plant cells, these components are exported from the chloroplasts into the cytoplasm, where they are exposed to a series of enzymes that remodel them into versions of glucose and fructose (both 6-carbon monosaccharides). One molecule of glucose and one of fructose are then joined to form sucrose (a 12-carbon disaccharide). See figure 1.

Sugars: glu, fru, and sucrose

Figure 1.

Sucrose is what we generally use as table sugar, and it is the form of sugar that a plant loads into its veins and transports throughout its body to be stored or used by growing tissues. When the sucrose reaches other organs, it may be broken back down into glucose and fructose, converted to other sugars, or combined into larger storage or structural molecules, depending on its use in that particular plant part and species. Since we extract sugar from various parts and species, the kind of sugar we harvest from a plant, and how much processing is required, obviously reflects the plant’s own use of the sugar. Continue reading

Throwback Thursday Thanksgiving feast

We’ve got several posts in the pipeline – and this year we are contributing to Advent Botany – but meanwhile, we bring you posts from the past to nerd-up your kitchen as you cook. Don’t forget, nothing deflects from an awkward personal revelation or a heated political conversation like a well-placed observation about plant morphology.

We wish you a happy, healthy Thanksgiving!

Continue reading

How giant pumpkins got so big: A Q&A with Jessica Savage

Biologist Jessica Savage answers a few of our questions about her research on the physiology behind giant pumpkin size.

In October 2014, a giant pumpkin grown by Beni Meier of Switzerland tipped the scales at 1056 kilograms (2323 pounds) and set a new world record for the heaviest pumpkin ever weighed. Modern competitive pumpkin growers have been imposing very strong selection on pumpkin size for decades. Pumpkin fruit size keeps climbing, and old records are broken every year or two (Savage et al. 2015).

Beni Meier with his 2014 record-winning 2323-pound pumpkin, presumably a specimen of the Atlantic Giant variety of Cucurbita maxima. Photo from here.

Continue reading

Triple threat watermelon

Will seedless watermelons make us superhuman or turn our children into giants?  Hardly, but they do give home cooks the power to count chromosomes without a microscope.   Just a knife or a hard thunk on the sidewalk are enough to get a watermelon to spill its genetic guts.

If you were reading a Hearst Corporation newspaper in late 1937, you might have thought humanity would eventually be swallowed up by giant carnivorous plants, unwittingly unleashed by uncontrolled biotechnology.  The San Francisco Examiner reported on November 21st of that year that the discovery of an “elixir of growth,” meant that “…science may at last have a grip on the steering wheel of evolution, and be able to produce at will almost any kind of species…”  including “…a plague of man-eating ones.”  In 1937 Americans had much more important things to worry about, just as we do now.  Still, that discovery may in fact have threatened one cherished aspect of the American way of life by triggering the slow demise of late summer state fair watermelon seed spitting contests.  It doubtlessly paved the way for seedless watermelons, and in 2014 the total harvest of seedless watermelons on American farms – nearly 700 thousand tons – outweighed the seeded watermelon harvest more than 13 to 1 (USDA National Watermelon Report). A similar pattern is emerging this year.  Is there no stopping the attack of the seedless watermelons?

Image from microfilm of an actual page in the San Francisco Examiner, published Sunday November 21, 1937. Found in the Media and Microtext Center of Stanford University Libraries.

CLICK to read. Image from microfilm of an actual page in the San Francisco Examiner, published Sunday November 21, 1937. Found in the Media and Microtext Center of Stanford University Libraries.

And more important, how is it even possible to get seedless fruit from an annual plant?  From a plant whose only mode of reproduction is through those very seeds?  From a plant that cannot make suckers as bananas do and cannot be perpetuated endlessly through grafts like fruit trees and vines?   Such is the challenge posed every single year by watermelons, but thanks to the “elixir of growth” discovered by Albert Blakeslee and subsequent work by Hitoshi Kihara, one of the most prominent agricultural geneticists of the 20th century, the world has an elegant solution. Breeders continually improve the varieties available, and consumer demand keeps growing, yet seedless watermelon production methods have remained essentially unchanged for three quarters of a century. Continue reading

The new apples: an explosion of crisp pink honey sweet snow white candy crunch

What’s in a name?  An apple with an old fashioned name could taste as sweet, but it might not sell.  The most sought after branded varieties reveal what people look for in an apple: sweet and crunchy and bright white inside.  Do the fruits live up to their names?  Are Honeycrisp apples crunchier than others?  Do Arctics actually stay white?  We zoom in on the cells to find out.

Some of you will remember the era when the Superbowl halftime show repeatedly featured Up With People.  That was around the time when Granny Smiths arrived in our supermarkets and finally gave Americans a third apple, a tart and crunchy alternative to red and golden delicious.  Those were simple days.  Continue reading

Taking advantage of convergent terpene evolution in the kitchen

The Cooks Illustrated recipe masters recently added nutmeg and orange zest to a pepper-crusted steak to replace two flavorful terpenes, pinene and limonene, lost from black pepper when simmered in oil. In doing so they take advantage of convergent evolution of terpenoids, the most diverse group of chemical products produced by plants. Nutmeg and orange zest, though, were hardly their only options.

The terpene swap

Black pepper (Piper nigrum) growing in Cambodia (photo by L. Osnas)

Black pepper growing (photo by L. Osnas)

To develop satisfying crunch, the Cooks Illustrated recipe for pepper-crusted beef tenderloin requires a prodigious quantity of coarsely ground black pepper (Piper nigrum; family Piperaceae). If applied to the meat raw, however, in the recipe authors’ view, this heap of pepper generates an unwelcome amount of spicy heat. To mellow it, the recipe authors recommend simmering the pepper in oil and straining it out of the oil before adding it to the dry rub. The hot oil draws out the alkaloid piperine, which makes black pepper taste hot, from the cracked black pepper fruits (peppercorns).

Nutmeg seed showing brown seed coat folded within the ruminate endosperm

Nutmeg seed

To their dismay, however, the recipe authors discovered that the hot oil also removes flavorful compounds from the cracked pepper, in particular the terpenes pinene and limonene. To rectify this flavor problem, the recipe authors added pinene-rich nutmeg (Myristica fragrans; Myristicaceae) and limonene-rich orange (Citrus x sinensis; Rutaceae) zest to the dry rub, along with the simmered black pepper. In doing so they take advantage of widespread and diverse array of terpenoids in the plant kingdom. Continue reading

Rapunzel

The rapunzel plant (Campanula rapunculus; Campanulaceae). Photo from Wikipedia.

The rapunzel plant (Campanula rapunculus; Campanulaceae). Photo from Wikipedia.

I never suspected that I’d learn something about edible botany by indulging my 3-year-old’s princess obsession, but I have. According to the Brothers Grimm, Princess Rapunzel is named after the cultivated  vegetable of the same name, growing in a witch’s garden. The wording of the story suggested to me that the Grimms’ contemporaries would be familiar with the plant as a vegetable, that it wasn’t a fantastical invented thing. Apparently rapunzel was a popular vegetable in the Grimm’s Europe. Continue reading