Nanomechanical oscillations…

This week one of our Facebook group members posted a link to a 2013 paper entitled “Love thy neighbour: facilitation through an alternative signalling modality in plants”. The premise in the paper is that plants are capable of acoustic communication and the experiment purported to demonstrate this. (I strongly encourage you to download the article from the link above so you can read it for yourself.)

chilisBriefly, chile seeds (Capsicum annuum) were placed into petri dishes, covered to ensure darkness, and then the dishes were placed in a circle. In the middle of the circle was either an empty acrylic box covered in black plastic (the control), an acrylic box covered in black plastic containing an adult basil plant (Ocimum basilicum) called the masked treatment, or an adult basil plant without a box (the open treatment). Seeds were watered and inspected daily for germination and the petri dishes were randomly rearranged.

According to the authors, “the presence of basil positively enhanced germination rates of chilli seeds, validating the claims of many gardeners who recognise the beneficial effect of basil on the growth of chilli plants.” Their reasoning is that the open and masked treatments induced more seed germination than the control. And since there was little difference between the masked and open treatments, they claim that the phenomenon is due to some signal other than light or gas (since the black plastic-covered acrylic container would prevent this).

How does this work? Well, according to the authors, this is evidence that acoustic signals are “generated in plants by biochemical processes within the cell, where nanomechanical oscillations of various components in the cytoskeleton can produce a spectrum of vibrations.” Never mind that the experimental design and methodology was laden with opportunities for experimental error. In particular, opening the petri dishes to water and count germinated seeds every day is deeply flawed. The easiest and least error-prone method would be to have the petri dishes sealed with parafilm to prevent water loss and inspected ONLY after the experiment was over. That is the standard method for testing for germination rates. Moreover, opening the dishes to count and water seeds every day really screws up the “covered to ensure darkness” part. In fact, chile seeds germinate better with light – which is what they got every day when they were opened. Was each dish exposed to light for exactly the same time every day? Exposure to light converts the seeds’ phytochrome to what’s called the active form, and phytochrome plays a crucial role in seed germination. The longer the light exposure, the more phytochrome is converted.

Now, plant scientists would know these things when they were designing their experiments. But as neither of the authors have degrees in plant sciences, it’s understandable. What’s not understandable is how this article got through peer-review. Unless none of the reviewers were plant scientists, either.

For those of you that belong to a university journal club or some other science discussion group, I think this would be a great article to discuss.

Harvesting, Curing and Storing Sweet Potatoes (A Visiting Professor feature)

Submitted by Ray Eckhart

Introduction
Sweet potatoes (Ipomoea batatas) are warm-season plants in the morning glory family (Convulvulaceae). The part we eat is the fleshy storage root of the plant, which is a little different than the regular Irish, or white, potato (Solanum tuberosum), a plant in the family Solanaceae. In that case, the part we eat is a fleshy underground stem of the plant, called a tuber.

Although sweet potato roots continue to grow until frost kills the vines, an extremely hard frost can cause damage to the ones near the surface. Chilling injury also results when soil temperatures drop to 50°F or lower, and this can result in internal decay in storage. The greatest danger from delayed digging is the risk of cold, wet soil encouraging decay. So the best time to dig is around the time of first frost in your area, or shortly thereafter. The vines can be clipped approximately 5 days before digging to improve skin-set or reduce the incidence of skinning the roots during harvest. To avoid exceptionally large sweet potatoes, a few hills should be dug in advance of the anticipated harvest date to determine the size of the sweet potato roots.

Puerto RicoFreshly dug sweet potato ‘Puerto Rico’

You can cook newly dug sweet potatoes right away, but their flavor, color and storage quality is greatly improved by curing at warm temperatures immediately after harvest. It is during the curing process that starch is converted to sugar.

Cure sweet potatoes by holding them for about 10 days at 80-85°F and high relative humidity (85-90 percent). Commercial producers have temperature and humidity controlled housing to guarantee good results, but for the home grower, they can be cured near a furnace or heat source to provide the necessary warmth. If the temperature near your furnace is between 65-75°F, the curing period should last 2-3 weeks. To maintain the required high humidity (85-90 percent relative humidity), stack storage crates or boxes and cover them with paper or heavy cloth.

CuringSweet potatoes curing

Once the sweet potatoes are cured, move them to a dark location where a temperature of about 55-60°F can be maintained, like an unheated basement, or root cellar. Sweet potatoes are subject to chilling injury, so don’t refrigerate them. Outdoor pits are not recommended for storage because the dampness encourages decay. Good results can be obtained by wrapping cured sweet potatoes in newspaper and storing them in a cool closet. Sweet potatoes can also be stored in sand.

Ornamental Sweet Potatoes
Have you ever wondered what, if any, is the difference between the ornamental sweet potato vines grown as a season-long ground cover, or, as “spillers” in container arrangements, and the vegetable we grow as food? The answer is – not much. They are just different cultivars of the same plant species, Ipomoea batatas. The ones we grow for food are selected and bred to produce large, uniform, good tasting roots, high in nutrients for eating, whereas the ones we grow ornamentally are selected for the striking shapes and colors of their leaves. Plant breeders introduce new variations every year. If you dig up the earth around your ornamental vines, you’ll find the same fleshy roots (different colors, perhaps) as the familiar ones we grow, or buy, for food. So, can you eat them? Well, technically, yes – but there’s no guarantee how they’ll taste. Most ornamental varieties are pretty bland. However, if you dig, cure, and store them as above, it’s possible they can stay viable until spring, when you can try to continue their growth for another season.

PropagationPropagating new plants (called slips) the following spring

References:
http://waynesword.palomar.edu/ww0804.htm
http://urbanext.illinois.edu/bulbs/bulbbasics.cfm
http://content.ces.ncsu.edu/ornamental-sweetpotatoes-for-the-home-landscape.pdf

Ray Eckhart is a former Penn State Extension Educator and avid home vegetable grower, with a weakness, bordering on obsession, for home grown tomatoes.

Infographic with a BIG grain of salt

Infographics can be great: They’re bright colorful ways to make sometimes complex concepts visual and easy to understand. Sadly, “easy to understand” does not necessarily equal “accurate” and they can also be extremely misleading.

Take this beautifully made image from National Geographic. It is an older image — first posted back in 2011, but it makes the rounds on social media from time to time, and popped up in my facebook newsfeed a couple days ago.

Look at it! Oh no! We’re loosing all of our vegetable genetic diversity!

Or not. First, it is comparing apples to oranges. This image looks a commercially available varieties in 1903 and compares it to the number of varieties in one specific center for preserving genetic diversity. What happens if we compare the same metric? If you look at the number of varieties in the National Seed Storage Laboratory, that was founded in 1958… so in 1903, at the top of the graph, the number for all these vegetables would be… zero. If you look at the present day, the current umbrella organization for all the US government funded efforts to preserve genetic diversity of crop plants is GRIN, (Germplasm Resources Information Network)  and if I do a quick search through that database using the keyword “tomato” I get… 9281 results. That is a pretty overwhelming improvement over 79 in 1983.

And what about commercially available varieties? To use tomato as an example again, in 1903, they found 408 varieties offered commercially. I just added up the varieties listed by just ONE seed company, Baker Creek Seeds, currently lists 287 different varieties of tomatoes. That is just ONE company. I have no doubt that if I added up all the varieties that are offered for sale in the giant pile of seed catalogs I get every spring it would be FAR more than the 408 on offer in 1903.

So… are we losing genetic diversity in our crop plants? Probably. There are lots of traditional varieties and land races that were never available commercially that have do doubt been lost, but to be honest, I think we’ve done a pretty good job at preserving the diversity. And certainly the USDA’s system of gene banks is an incredibly well run, impressive thing that deserves high praise indeed, for not merely preserving vast amounts of important genetic diversity but also working hard to characterize it and make it available to researchers and breeders so it can actually be put to work in the development of new and improved selections to try and feed the world.

So despite how colorful and easy to understand this infographic is, you don’t need to freak out about a massive loss of genetic diversity in our vegetable crops. Save that freaking out for all the wild species that have gone extinct or are about to go extinct thanks to habitat destruction and climate change world wide…

Today in Cucurbit News…

Cucumbers are one of the most widely-grown vegetables in the world.  Baker Creek Heirloom Seeds (a great place to buy unusual and international veggie seeds) lists 51 varieties from North America, Southeast Asia, China, India, Mexico, and Europe.  Dark green ones seem to be in the minority – yellow, white, orange and red skins in shapes round to elongated dominate.

Cukes traditionally have a few nutrients including some Vitamin A from carotenoids and beta carotene, but have never had the reputation as nutritional power house. Watery and gas-inducing, yes.

Researchers with the USDA have recently released a cucumber high in beta carotene.  No "frankencuke" this; all the crossing was done by traditionally breeding methods (including bees and self-pollination).  Lots and lots of crosses with a warty, round-ish chinese cuke (Cucumis sativus var. xishuangbannanesis) and some standard pickling cukes has resulted in a stable cultivar that has the smoother skin and proper proportions of marketable pickling cucumbers (there are lots of marketing standards associated with most fruits and veggies).  But the big news is the orange interior, specifically the endocarp (the jelly-like stuff around the seeds) and the mesocarp (the fleshy part that is the whole point). It’s orange because it’s full of beta carotene  (mesocarp is 2.7 micrograms per gram of fresh fruit compared to 0.02 micrograms per gram with a traditional white-fleshed variety.  Even more impressive is the jump in endocarp beta carotene – from 0.16 micrograms per gram to 7.5 micrograms per gram).  I don’t believe the USDA is going to release this particular line directly to the public, rather they’re offering the genetics (two recessive genes control the beta carotene content) to other breeders.  This means other breeders can use it in their own breeding program to bring more nutritional value to their specific lines, at which point varieties will become available to growers/gardeners. Orange tzatziki!!!

from Staub, J.E., P.W. Simon, and H.E. Cuevas.  2011. USDA, ARS EOM 402-10 High β-Carotene Cucumber. HortScience 46:1426-1427.

(Linked, but my guess it won’t work if you don’t have a HortScience subscription or institutional access, sorry) 

A word about GMOs from our visiting GP

I gave a talk to a group of gardeners last year about vegetable and community gardening.  There was a wide variety of gardening experience represented, but one statement from a seasoned gardener bothered me a bit.  And I think my response bothered him a bit too.  I haven’t thought much about it until recently, when a high school English teacher I know told me a student expressed similar ideas in her class.  The erroneous idea from my audience member was this: our tomatoes are being poisoned with ‘germetically modinified’…something something.  The arguments have lost me beyond that (because there aren’t any).  And really, there hasn’t been much talk about sex on this blog recently, so that should be remedied too.  Therefore, I would like to take the platform offered by the Garden Professors to talk about plant breeding.

 

 

Fig. 1: Jaune flammee, which has at least one gene from at least one of its parents that causes the fruit to have very little lycopene.

Conventional” breeding is when a plant breeder selects parents and offspring and tests them for desirable characteristics (traits).  It works the same way as breeding works in nature, except that we humans have a goal we’re working toward.  Firm, 5-oz, disease-resistant, crack-resistant tomatoes, for example.  In nature, the offspring that survive and reproduce the best in a given environment are ‘blindly’ selected and tend to stick around (Darwin, 1859).  Male (sperm) cells are transferred to female (egg) cells by a plant breeder, or a bee, or the wind, or a beetle, or a fly or bird or bat or moth (etc.).  The sperm and egg fuse to form an embryo, which grows to become what we’d call a plant.  In both natural and artificial selection of tomatoes, no non-tomato DNA has been added, and no tomato DNA has been removed.  By the classical definition of ‘genetic modification’, there has been none.  I suppose this paragraph was only incidentally about sex, and probably a disappointment to some.  Sorry.

Fig. 2.  Tainan, a tiny heirloom

The confusion of the issue may lie with the Flavr Savr tomato.  This was developed (yes, genetically modified) in the mid-90’s to resist softening during ripening.  It has a couple bits of manufactured DNA in it to make this possible.  The Flavr Savr is no longer grown or sold in the marketplace (that was SO 1990’s), and to my knowledge, no other transgenic tomatoes are either.

 

Fig. 3.  Rutgers, historically much-cultivated and like all other tomatoes we can buy, bred conventionally.

Confusion may also lie with the plant hormone ethylene.  Ethylene is made from incomplete combustion of fossil fuels, but it’s also made by plants.  Keep your bananas away from your carnations, right?  Bananas make ethylene gas, which causes carnations and snapdragons to senesce (die).  Tomatoes make ethylene as they ripen.  If you harvest tomatoes a bit early, but not too early, they are hard enough to ship but will still turn red later.  If you expose these pre-ripened tomatoes to ethylene gas, they will ripen more quickly and uniformly.  That’s what happens to a lot of the tomatoes in our stores.  They are not genetically modified, they are treated with a plant hormone.  That’s not unusual at all.  Ethylene is used to ripen bananas, and to help make cucumber seeds (by eliminating male flowers from female parents).  It’s used in growing ornamental plants quite a bit too (but not as much as many other hormones, and especially hormone inhibitors).

So please, if you are someone who tells anybody who will listen that the tomatoes in the store are GMOs, stop it.  They’re not.

The Hottest Thing in…Veg!

Vegetable transplants and herbs were a bright spot last year (and the one previous) for most retail growers and independent garden centers.  Seed and transplant companies have taken note – saw lots of veg and herbs at the normally-ornamental trade shows.  As always, some good ideas, some a bit far-fetched…

Pelleted lettuce seed (much easier to handle) mixes for the grower to create patio-size planters. Not bad! Snipping a few leaves will be fine, but if you eat salad more than once a month, you’re gonna need a bigger pot.

Basil and Swiss Chard plugs (seedlings), grown by Rakers Acres in Michigan, and shipped to greenhouse growers for “bumping up” to bigger pots to sell.

Saw lots of garden center marketing ideas such as this one from Burpee. Unfortunately, I have a very strong aversion to the word “fixins.”

Oh just stop it. An onion, in a pot. What the heck are you supposed to do with that?!

Animal, Vegetable, Irritable

I’m a big Barbara Kingsolver fan. Just finished “Prodigal Summer” – her tall, lanky, introverted, 40-something forest ranger-heroine encounters handsome, mysterious, much younger guy in the woods; sparks fly, etc.  Rowr!  Ahem.

I really enjoyed “Animal, Vegetable, Miracle” when it came out a couple of years ago. It was the perfect dead-of-winter read as she captured flawlessly the itch to grow things, the scent of thawing soil, the joys of mud, the overwhelming greenness of spring, the mess of canning tomatoes. I was only slightly annoyed at the quiet pace and perfectness of her home life;  as a normal working stiff I don’t have time to bake my own bread daily, or make fresh mozzarella every time we have pizza for dinner (darn this time-consuming, bill-paying job).

But I was totally mesmerized by the cover art – her daughter’s cupped hands filled with the most beautiful shelled beans in the world. The huge maroon and white Christmas Limas shined like leguminous jewels.  Now THAT I can do.

So, Dr. Miss Smartypants here devoted an entire row to them this spring – about twenty feet with plants spaced on one-foot centers and a 20’ x 6’ span of netting for them to scramble up. The second 20’ row was planted with red and green yard-long beans (see my previous post about how fabulous they are).   Both rows received the same amount of irrigation (a little), weeding (some), and zero additional fertilizer except the pre-plant amendment of chicken poop (of which we have a lot).  

Summer wore on, life got busier. The yard-long beans just kept coming despite drought, stinkbugs and 3’ tall lambsquarters.  I’d poke around wistfully in the Christmas Lima vines – there were a few green pods buried amongst copious foliage. I do know these kinds of beans do better in hotter, drier climates, but it’s been pretty much that kind of summer here.

The pods finally, FINALLY filled out a bit and turned dry and brown – ready to pick!! I filled most of a five-gallon bucket and sat down with a beer to shell them (OSHA requirement).  

Behold, my bounty!

 

Total yield: one mess of beans. Two if used as soup components. Yes, they’re listed with Slow Food USA’s Ark of Taste.  Yes, they are indeed beautiful and will probably be totally delicious whenever I get the nerve up to cook them.

It’s just… I’m not sure how to put this… but a family of four would BLOODY WELL STARVE if they devoted much of their garden to these lovelies. I don’t know whether to eat them, frame them, or string them onto a necklace.

p.s. still getting yard-longs by the handful…

Maybe the handful was all Barbara got, too

The Approach Graft

Seeing as this blog is called “The Garden Professors” it has been far too long since we’ve given you a lecture on a useful practice for your garden, so this week I thought I’d give you a little how-to demonstration on something called approach grafting.  Approach grafting is a technique that you could use to graft a tomato to a tomato (good if you want to use a disease resistant root with a non-disease resistant top — common in heirloom tomatoes), a tomato stem to a potato root (just a fun project), or an eggplant root to a tomato shoot (good for wet locations).

So here we go.  First, you need two plants that are about the same size, and you need to plant them in the same container as demonstrated below with a potato and tomato.  You will also need to strip off lower leaves as they may get in the way of the graft.


Above we have a young potato and tomato plant to be grafted.


In the above picture the potato and tomato plant have been planted in the same container and their lower leaves have been stripped off.

After the two plants are in the same container a small slice is made on each plant at the same height.  This slice will be, ideally, just a little bit deeper than the cambium into the center of the stem (you’ll be able to see the plants pith — in the center of the cut — it’s tough to see in the image here).


In the above picture the stem of both the tomato and potato are cut so that they can be joined together.

After making the required cuts on both plants the cuts are pushed together and wrapped.  We used parafilm to wrap this graft, but saranwrap, or even an elastic band would also work.


In the above picture the cuts are being joined.


Here the cuts are wrapped.

The next step is to wait until the graft “takes”.  This could take 3-5 weeks.  After a good strong union is formed the top of the potato and the bottom of the tomato plants are cut off.  Wait a few days to make sure everything’s working properly and plant the result in your garden.

Veggie garden safety

A few months ago I posted a caution about using old pressure-treated timbers for vegetable gardens (see my Sept. 23 posting).  I now routinely get questions about alternatives to these arsenic-laden materials, especially new treated lumber.  What’s in the new wood that makes it rot resistant, and is it dangerous?

Rather than arsenic, new pressure-treated lumber has copper as its active ingredient.  Though it also will leach out of the wood, there is not a human health hazard associated with its uptake by plants or animals.  You probably get more copper leaching into the water carried through your plumbing (assuming you have copper, and not lead, pipes).

What about plastic timbers?  Though I’ve not seen any literature about leachates from plastic lumber, I’ve seen some older plastic timbers that haven’t aged well – they can warp and twist.  I would avoid those made of rubber, because decomposing rubber produces leachates that are quite hazardous (see September 30 for a discussion on rubber mulches).

Of course, there are many other materials one could use to corral their veggies – concrete blocks, stone, natural wood, etc.  Do you have a favorite?  Post a comment to let us know!

Veggie gardening science – whaddya know?

I just had a long conversation with Michele Owens (of Garden Rant fame) about vegetable gardening.  This isn’t one of my strong areas, either professionally or personally (I do have containers of herbs, but that’s as far as it goes).  But what piqued my curiosity was her revelation that the vegetable gardening is just as full of myths and misinformation as my field of ornamental landscaping.

I’ve ventured into the realm of vegetable garden science now and then, especially in reference to having soil tests done before planting edibles (good!), the use of CCA-treated timbers (bad!), and companion planting (silly!).  Beyond that I haven’t given the topic much thought.

          

(You know who loves you know who!)

So, readers, what gardening practices out there need to be screened through the sieve of science?  Jeff and I have both written about many practices and products, but as you know our expertise is more on the ornamental side.

(Forgive my short blog today.  I’ve had some kind of chest crud since last Friday and I’m still wiped out.)