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Gardening Articles for week ending 24th February 2018

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Written by Wally Richards.

LIGHT

There are two sources of light; sunlight and man made artificial light, normally these days from electricity using Incandescent light bulbs, Halogen, fluorescent and more recent, LED lighting
(Which according to them that know has a blue light spectrum band/frequency which overtime can cause cataracts and blindness.) see https://opto.ca/health-library/blue-light-is-there-risk-of-harm
Plants can grow in artificial light dependent on the spectrum such as a combination of cool white fluorescent with a Incandescent light bulb (which are harder to find these days) or Grolux Tubes.
Plants need light to preform photosynthesis by which green plants and certain other organisms use the energy of light to convert carbon dioxide and water into the simple sugar glucose. In so doing, photosynthesis provides the basic energy source for virtually all organisms.
Oxygenic photosynthesis functions as a counterbalance to respiration; it takes in the carbon dioxide produced by all breathing organisms and reintroduces oxygen into the atmosphere.
So here we have two of the most important aspects of plants, they need/use light (sunlight) to produce carbohydrates (sugars) to grow and produce food for most living species and also convert CO2 into oxygen for all breathing creatures on land or in the sea.
Imagine what would happen if we did not have sunlight? Our food sources and our oxygen would disappear and then goodbye world.
Readers of my articles over the last few years have noted that I am very concerned about the amount of sunlight that our plants are getting and the affects this is having.
(Stunted growth, larger leaves, no flower buds, no flowers, no nectar in flowers, predominately one sex only flowers, few or none of opposite sex, crops lacking taste, low sugars, smaller fruit)
Plants want sunlight but UV hampers their ability to photosynthesis. There are three types of UV, UVA, UVB and UVC.
Sunlight spectrum is from 400-700 nm and is termed Photosymthetically Active Radiation (PAR). This light is in the blue (400-500 nm) and red (600-700 nm) spectrum.
When we look at a plant and see green, it is because the chlorophyll molecules in the plant absorb blue and red light and reflect other colors, resulting in the green color we see.
Through experimentation, it has been determined that red light has a stronger impact on the rate of photosynthesis than the same intensity of blue light.
UV spectrum's are UVA 400 nm - 320 nm : UVB 320 nm - 290 nm : UVC 290 nm - 100 nm
UVA rays, which account for 95 percent of radiation that reaches the earth's surface; clouds and hazy only reduce UVA a little.
UVB is rays reaching the surface can be reduced by 70 to 90% on a really overcast day. But on a partial cloudy day they can be increased by 40% from reflection and refraction.
Hazy skies from aerosols or pollution increases UV levels that reach the surface.
The intensity of light is important for maximizing the rate of photosynthesis. The optimal light level for photosynthesis is 10,000 lux.
Lux is a unit for measuring light intensity. Low light intensity lowers the rate of photosynthesis. However, after reaching an intensity of 10,000 lux, there is no increase in the rate.
The rate of photosynthesis may in fact be lowered as chlorophyll is bleached from the chloroplast and the plant’s stomas are closed to slow down water lost through respiration.
Another aspect is radiation passing through clouds heats the earth's surface but the clouds prevent that heat from dissipating into the atmosphere.
Example of this is in winter; if its a cloudy sky at night little chance of a frost but if a clear sky heat escapes and a frost settles.
Hopefully I have made my case; Plants are receiving much less than the ideal (10,000 lux) of sunlight, UVA and UVB are reducing the plant's ability to convert the lessor light to carbohydrates.
Plants are not growing as they used to do in the past. (And the skies are very different to those of my young years)
Examples of insufficient light levels include male flowers on cubits such as pumpkins and zucchini, corn crops that are stunted, farmers complaining that their grass has not sufficient goodness for the stock and have to supplementary feed.
I grow snake beans which need lots of sunlight to flower and they have not flowered this season or last but the years before they did and hence I had long beans to harvest..
This week I received an article that talked about Sun Dimming or Global Dimming so I looked it up on the net.
Global dimming is the gradual reduction in the amount of global direct irradiance at the Earth's surface that was observed for several decades after the start of systematic measurements in the 1950s.
The effect varies by location, but worldwide it has been estimated to be of the order of a 4% reduction over the three decades from 1960–1990.
Global dimming is thought to have been caused by an increase in particulates such as sulfate aerosols in the atmosphere due to human action. (Geoengineering) Most patents taken out in regards to Geoengineering state sun or Global dimming!
The idea presumably is to reduce global warming by reducing sun light reaching the Earth's surface.
In fact the reverse applies as it traps more heat and thus increases more evaporation which increases more cloud cover, then later resulting in the crazy weather patterns we now are having including downpours and extreme flooding.
More heating of oceans resulting in hurricanes.
Independent research in Israel and the Netherlands in the late 1980s showed an apparent reduction in the amount of sunlight, despite widespread evidence that the climate was becoming hotter.
The rate of dimming varies around the world but is on average estimated at around 2–3% per decade.
At that rate is have lost a total of between 10 to 13% of the sunlight since 1990. (4% then).
I also found another aspect to this as some say that the sun is actually turning off and that this completes a Biblical prophecy see http://www.cuttingedge.org/news/n1998.cfm also see (Matthew 24:29)
Now if that info on the web site has an element of truth in it and the sun is dimming down to turn off point and if there are aerosols causing less direct sunlight; for this to continue unabated its going to make not only gardening difficult/impossible but also life as we know it as dead as the Dodo.
A very serious matter and it puts the CO2 aspect into a not very important prospective.
There are a number of people that think the CO2 thing is just a distraction and money making play for the super rich 1% anyway.
Changes in our climate maybe a natural cycle or as a result of Geoengineering; maybe a combination of the two things.
One thing is for sure is; whenever mankind tries to fiddle with Nature the outcome is never good......
Powdery mildew; to change the subject is starting to appear on susceptible plants which as it spreads will finish them off for the season.
I have found that a spray of Super Neem Tree Oil with Raingard added wipes out the white powdery residue and makes the leaf greener again.
That allows the plant to continue getting energy from the sun and maybe allows a few pumpkins to reach full maturity or similar with some other crops.