Nightshade

I find Bittersweet Nightshade (Solanum dulcamara) really lovely, despite its status as a weedy alien that is sometimes invasive.  Bright, violet star-shaped flowers give way to red berries, while leaves touched by bronze add a dignified touch.   It is a shade-tolerant perennial vine plant that you will see growing up fences and out of hedges all over the place once you know it.  

Bittersweet Nightshade has the distinction of being a close relative to several food plants: tomato* (Solanum lycopersicum), potato (Solanum tuberosum) and eggplant (Solanum melongena).  All these plants collectively have the lesser distinction of being poisonous.  You should particularly avoid the green parts and unripe fruit.  (You may already know to avoid eating potatoes that have begun to green-up.  On the other hand, we have pickled and eaten end-of-season green tomatoes without a second thought!)  All these plants produce solanine and dulcamarine (among other active chemicals) which are quite poisonous in moderate doses. The ripe berries are the least poisonous part.  Still, if you see it around it wouldn't hurt to warn you children.  --unless of course they're the sort of children who reflexively challenge authority!  Another plant, the much-more-poisonous Deadly Nightshade is in a different genus in the same family. 

One Bittersweet Nightshade (Solanum dulcamara) in late-spring and summer.

*Here in the Michals-Brown household it's tomato sandwich season: slice tomatoes fresh from the garden onto toasted bread spread with mayo.  Season liberally with salt, pepper and dill weed.  Yum!

Drought and Plant Stress

Another shower, another eight-inch of water that makes no difference, and the drought goes on.  We in Massachusetts have had four continuous months of low rainfall.  In June, at our nearest recording station, less than two inches of rain fell altogether, and only two days brought a quarter-inch or more.  July was as bad or worse, with just over two inches, and no day with even half-an-inch, never reaching more than the top-most inch-or-so of soil.   Three weeks ago the state declared a drought watch; Worcester's reservoirs are down a third or more, Brockton draws increasingly on a desalinization plant on the Taunton River to help preserve the main reservoir of Silver Lake.  Walking raises dust--even crossing the lawn--groundwater recedes, plants are stressed.  

I have watched for some time for signs of drought stress in the trees.  Trees and most shrubs are not yet in obvious trouble, but there are exceptions. 

 European buckthorn, an alien invasive, is wilting even on a drizzly, overcast day.

 Wild grape, Vitus labrusca, wilts in sunshine, but has recovered turgor in the overcast.

 Gray dogwood, Cornus racemosa, a thicket-forming shrub, is wilted all over my little wood.

 Garlic mustard, a prolific alien invasive, is suffering; but its a tough plant and will recover.

 Enchanter's nightshade, Circaea quadrisulcata (above), and especially heart-leaved aster, Aster divericatus (below) are looking poorly.

 The cucumbers in my garden have wilted nearly every day--even when watered
--but they recover out of direct sun. 

 White ash, Fraxinus americana (above), and 

ash-leaved maple, Acer negundo (below), have leaves curling with wilt.

 Of the three paper birches I saw this day, only this one was losing leaves prematurely.

The same stretch of Salisbury Brook in early May above, and mid-July below.

Like all living things, plants are critically dependent on water.  With carbon dioxide from the air, water is a raw material for photosynthesis: the building of sugar molecules (and many other compounds) using the energy in sunlight.  Photosynthesis is a trick that every other creature around you, from mushroom to man,  depends on for life: it is the ultimate source* of all our food and oxygen.  

Of the enormous amount of water consumed by plants, only a tiny fraction is "split" into hydrogen, for making sugar, and "waste" oxygen; most is used to maintain turgor pressure in soft tissues, to expand their cells as they grow, and to transport minerals upwards in the plant.  If you've ever marveled at how soft a football is when deflated, you will understand turgor pressure: just as the pressure of air can turn flabby pigskin into a nearly-rigid football, the pressure of water does the same for plants.  Typical plants first draw water into their roots by maintaining a higher concentration of dissolved substances in their root cells than are present in soil water (osmosis).  From these root cells, water is drawn upward in the tube-like vascular tissue of the stems in a kind of tug-of-war by evaporation of water from leaf cells.  (These tubes--"vessels" in flowering plants and "tracheids" in conifers-- are small enough that the attraction of water molecules for each other causes them to act as if the water were in "strands" that could be pulled upward.)  Plants are forced to lose water at high rates by their need for carbon dioxide from the air: the same pores (stomata) in leaves that allow carbon dioxide to diffuse in and oxygen to diffuse out, also allow water to evaporate from cell surfaces and difuse away.  (The evaporation of water from plant surfaces is called transpiration.)

Bad news for plants begins when water is not entering the roots quite fast enough to replace that evaporating from leaves.  Plants respond to this by closing their stomata: these pores (usually in the undersides of leaves) are flanked by banana-shaped "guard cells" that are spring-loaded to close automatically as their turgor pressure declines.  Since the closing of stomata reduces water loss, you may not see any change in the plant at this point, but the plant is feeling it.  With stomata closed, carbon dioxide  becomes scarce inside the leaf tissue, so photosynthesis declines.  Then a funny thing happens--called photorespiration--yet another fact that argues against living things being "designed".  

In the first step in building a sugar molecule by photosynthesis, an enzyme called ribulose 1,5-bisphosphate carboxylase** ("rubisco" for short) grabs a carbon dioxide molecule.  The rubisco enzyme has a peculiar trait: it has a small tendency to grab oxygen (O2) instead of CO2, probably because the enzyme has a hard time telling these compounds apart.  As long as the stomata are open, there will be a good supply of CO2 inside the leaf, so that photosynthesis usually occurs normally.  But with stomata closed and CO2 scarce, more and more often rubisco will grab oxygen and engage in photorespiration--a sort of "reverse photosynthesis" that is very wasteful of energy and creates nothing good for the plant.  In dry conditions under bright sun, it is possible for a plant to waste by photorespiration much of the sugar it already fixed.  My guess is that many even of those plants that are not visibly wilting are photorespiring*** furiously in the bright sun, and at best marking time until there is enough moisture in the soil to go back to the business of making the food our local ecosystems depend on.

Micrograph of the underside of a fern leaf, showing seven stomata.  Besides the flanking guard cells, some of the choroplasts that do the work of photosynthesis are visible as tiny green hockey pucks.

Source: https://www.flickr.com/photos/epingchris/5152579683

Micrograph of cross-section through a privet leaf shows different cell types (mesophyll) that do photosynthesis, the air spaces in the leaf, the vein that brings water and minerals, and stomata.

Source: http://researchguides.library.vanderbilt.edu/c.php?g=69346&p=809936

*Our understanding of another of way of making food--extracting energy by chemosynthesis from inorganic chemicals such as the hydrogen sulfide (think ocean floor "black smokers") as certain bacteria can--is still evolving.  Some believe chemosynthesis is as important a food source for life as photosynthesis, and it may well have preceded photosynthesis in life's early history.

**Rubisco is fairly slow enzyme and so plant chloroplasts need them in high concentration--making it possibly the most abundant protein on Earth, and responsible for "fixing" more than 100 billion tons of atmospheric carbon dioxide each year.

***A small fraction of plant species have solved this problem.  They have evolved a way of isolating their rubisco from the air and using a powerful added enzyme (PEP carboxylase) to scavenge CO2 even at low atmospheric concentrations to provide rubisco with a high CO2 levels even with stomata closed.  Such plants can do better in dry conditions, and also in dense stands of plants that have drawn down the CO2 concentration in the air around them.  Among these C4 plants are corn and  crabgrass.

The Taming of the American Child

I had just finished doing some yard work today when I spotted them: berries.  Raspberries or blackberries.  LOTS of them, and many were the almost-black of peak ripeness.  I turned over a leaf--green: blackberries, then.  (Raspberry leaves are white underneath, but their berries are just as sweet.)  As I picked all I could carry, I wondered.

A brief survey

1. When did you last pick and eat a wild berry? 
2. When did you last see the moon?  (Did you know the moon was full on Wednesday?) 
3. When did you last pause to listen to birds sing? 
4. When did you last spend half an hour in your garden?  (Do you even have a garden?) 
5. When did you  relax outdoors with a little something to eat or drink? 
6. When did you last walk a mile or more in a wood or a park or another natural place?

I hope you have good answers!  But your children may answer these questions very differently than you do. Yesterday I listened to a radio interview with author Scott Sampson (How To Raise A Wild Child: The Art and Science of Falling In Love With Nature) who cited a statistic that scared me:  
American kids today spend only four to seven minutes a day playing outdoors.

The statistic was new to me, if not the issue--advocating that people get outdoors and experience the natural world was the reason I started this blog.  It also led me to  a few years ago to design and run an after school program designed in part to get city kids outdoors.  Even so, I hadn't imagined the situation was that bad.


Sampson sees two big consequences.  Children grow up impoverished, lacking awareness of the world around them, and are also less healthy (studies have found that spending time in nature reduces stress hormones).  Just as important--perhaps even more so--they will not develop the love of natural environments, the emotional connection, that provides the impetus to save these places.  And of course nature itself is increasingly in danger from human activities ranging from over-fishing to habitat destruction to greenhouse gas emissions.  Our very future might very well depend on the emotional connections we and our children form with the wild outdoors.  

Sampson blames many forces, including the lure of electronics, over-scheduling by busy parents who want kids supervised, and fears of media-soaked parents who see a child outdoors and unsupervised as a target in a dangerous world.  

Their parents largely grew up differently.  It was commonplace in my neighborhood to be told to shut off the TV and GO OUTDOORS.  We would be left to our own devices without supervision for hours at a time--for whole days in summer.  Was this dangerous?  Perhaps.  But not nearly as dangerous as we have come to assume today, after a generation of seeing kidnapped children's faces on milk cartons. 

Of course, some neighborhoods really aren't safe, and these present special challenges.  And the issue is, in general, not on the radar screens of less-affluent, or those from an ethnic minority.  But it needs to be.

Sampson's  solution for those of us who care about this?  Start small and manageable: get your kids outside for half an hour three times a week.  

Go to wild places--they don't need to be wilderness.  Engage.  Notice things--the clouds, the weather, trees, bugs.  Wonder about things: asking questions is much more important than answering questions. 


So much depends on adult attitudes that children absorb.  Are bugs yucky, or cool?  Are grass-stained knees a disaster, or something to accommodate with "play clothes?"  Does a skinned knee call for major first aid, or just some antiseptic and a bandaid?  Do you avoid rain or cold like the plague, or do you simply dress differently? 


Plant yards and cities with native plants.  Native plants attract native insects, birds, and other animals.  And don't manicure everything, for goodness' sake!


In school, space needs to be made for recess, or other outdoor time.  Though time is short in the era of standardized testing, freedom to burn a little energy might pay dividends in greater attention during regular learning.  


It may take a generation or longer to get back to a society in which "free range" parenting isn't a crime, and where boredom can be viewed as a creative force (a bored child might be forced to entertain herself!), but it is vital we do so.