Letting it go

This 4th of July weekend has been a sad one. We’re already grieving for all the things we can’t do because of COVID-19 and mourning for Black victims of police violence. 

Black Lives Matter protest in Times Square on June 7-photo

Anthony Quintano

The holiday adds the overdue realization for me that not all Americans can be proud and happy on Independence Day. Uncritical endorsement of the Declaration of Independence and the founding fathers feels hollow this year. On top of that, there’s the new information that particulates and metals from fireworks damage the environment. 

Polluting the Black Hills on July 3rd-photo National Park Service

It seems an old era is ending. We might be starting a new one that entails further loss of comforting illusions. Let’s hope it also brings gains in equity for the whole community.

    In this setting, I admired the local oak trees’ response to heavy thunderstorms. 

Oaks let branches go in storms

In the last few days, humid weather (and increased energy in the atmosphere because of climate change?) produced high winds and tropical downpours. The rain was very welcome after weeks of drought, but a number of trees lost branches large and small.

    We were lucky that no major limbs came down on our house or cars, as happened elsewhere in the neighborhood. But lawns and sidewalks showed the fallout in smaller branches broken off from maples and oaks, the most common trees on local streets.

Branch from a Norway maple

    I can’t tell whether these tree parts were torn off by the heavy winds, previously weakened by chewing animals or insects, or jettisoned by the trees. Oaks are prone to a phenomenon that arborists call summer branch drop, in which limbs of 4 inches in diameter or more suddenly fall to the ground. What I’m seeing is branches of less than an inch in diameter but well furnished with leaves and side twigs.

    Trees do engage in a self-pruning process called cladoptosis, or shedding of branches, in response to senescence or drought. In plant senescence, a shoot that isn't producing enough sugars to support itself and a root of equivalent size may be cast off.

     The tree “decides” to drop this under-productive part and direct resources to more successful areas. The same can happen to roots that aren’t taking in their share of water and minerals from the soil. This process of abcission is currently understood as directed by a hormone cascade that triggers the death of the cells that attach the unwanted part to the body of the plant.

The same process in an aloe leaf?

    Imagine if the human body could decide to rid itself of diseased or painful parts and go on to develop useful and beautiful replacements! Plant stem cells are located in shoot and root tips and the lining of trunks and stems. These stem cells are pluripotent and totipotent, i.e. they can regenerate freely throughout the plant’s lifetime and can form any kind of plant cell.

    Right now I wish I could drop unwanted and outdated schemata just as easily and grow some new ones better suited for an uncertain future.

I won't be posting next week while I deal with a deadline at work. See you on two weeks!