And along with that here's another good point for avoiding UV, at least with COBs or any LEDs that uses encapsulates like most whites. Was watching a webinar that pointed out UV degrades the encapsulate on COBs and LEDs resulting in lumen degradation so you're basically fucking up your COBs. How fast and how much is really product by product. Some companies offerings may be more resistant than another's. Perhaps the lumen decrease will not happen before you upgrade your lights, but if you're using COBs and UV, (
@captainmorgan) I would shield the COBs from the UV if you're planning on keeping your COBs around and want them running at their best. Oh and if your cooling and grow room temps are less than stellar the degradation of the encapsulate will happen faster in the presence of UV. So maybe LED and UV aren't all that atm for most of us.
A fact. I totally agree .
And also for ( almost ) eveything else that is made out of Carbon based polymers ..
Few things made out of " plastic materials " are resistant to UV ...
Wiring ,piping ,pots ,electric apparatus encasings ,etc will be deteriorating gradually ,
under the UV radiation ..
http://www.cityplastics.com.au/materials-uv-resistance/
http://plasticmentor.com/97/which-plastic-materials-are-uv-stable/
I've been talking to an led grower that uses some Chinese fixture with a uva channel of leds on a dimmer. He starts hitting the plants with uva at day 40 , ramping up intensity. He is getting some crazy colors and increased trich formation.
View attachment 3536181
Crazy colors : Reds and purples are photosynthetic accessory pigments : anthocyanins & carotenoids
(like the -most likely-
lycopene those leaves have in the pic ).
They serve to absorb and dissipate excess light energy ( from UV quanta ) , or work as
antioxidants ( UV radiation
attacks almost every substance that contains oxygen,including intracellular water and DNA .Oxygen is turned in ions ( " free roots " ) and thus for defence against the free roots ,plants produce antioxidants of every kind ..
Including many of the photosynthetic accessory pigments ,also.
increased trich formation :
(...)
Trichome Types
Trichomes grow in numerous shapes and sizes on many types of plants. The cannabis plant has developed three main types (from NationMaster Encyclopedia):
Bulbous: This type is the smallest (15 to 30 micrometers). From one to four cells make up the ‘foot’ and ‘stalk’, and one to four cells make up the ‘head’ of the gland. Head cells secrete a resin, presumably cannabinoids, and related compounds that accumulate between the head cells and the cuticle. When the gland matures, a nipple-like protrusion may form on the membrane from the pressure of accumulating resin. The bulbous glands are found scattered about the surfaces of the aboveground plant parts.
Capitate-Sessile: The second type of gland is larger (25 to 100 micrometers) and more numerous than the bulbous glands. They are called capitate, which means having a globular-shaped head. On immature plants, the heads lie flush, appearing not to have a stalk and are called capitate sessile. They have a stalk that is one cell high, although it may not be visible beneath the globular head. The head is composed of usually eight, but up to 16 cells, that form a convex rosette. These cells secrete cannabinoids and related compounds that accumulate between the rosette and its outer membrane. This gives it a spherical shape.
Capitate-Stalked: Cannabinoids are most abundant in the capitate-stalked glands, which consists of a tier of secretory disc cells subtending a large non-cellular secretory cavity. During flowering, the capitate glands that appear on the newly formed plant parts take on a third form. Some of the glands are raised to a height of 150 to 500 micrometres when their stalks elongate. These capitate-stalked glands appear during flowering and form their densest cover on the female flower bracts [specialized leaves that cover the seeds]. They are also highly concentrated on the small leaves that accompany the flowers. The male flowers have some stalked glands, but they are smaller and less concentrated than on the female.
Inside the Trichome
THC and other cannabinoids are produced in only one place on the cannabis plant: inside the heads of the trichomes. How it happens: Organelles produced by the plant called Vacuoles – which contain phenols, a chemical compound similar to alcohol , and another type of organelle called plastids – containing hydrocarbons called terpenes , make their way up the trichome stalk and combine inside the secretory cavity into a fibrous mat. This concentrated mat is hit by UV-B light waves, causing the creation of cannabinoids. Since all of the psychoactive ingredients are produced inside the trichome, these tiny resin hairs have long been sought after by hash and oil makers and can be separated from the plant and harvested in a variety of ways .
Potency and Tricomes
Many media outlets and politicians say the ‘potency’ of today’s pot has increased dramatically in the last 30 years, claiming it contains anywhere from 10%-40% THC. Most are dubious claims, as it is quite obvious that a sample of herbal plant material does not consist of nearly half THC, but there is still much debate on the issue of potency classification. One thing is for sure; heavy trichome production does not necessarily mean higher potency, because the resins inside the trichome may or may not contain high levels of THC and other active ingredients. Some speculate that the percentage levels refer to the amount of THC in the oils produced inside the resin glands, but new studies show that cannabinoids other than THC also have distinctive effects on brain functions and cause correspondingly different effects on human cognition and psychiatric symptoms . This makes gauging the ‘potency’ or ‘strength’ of cannabis plants very difficult, as different cannabinoid level combinations may induce different types of " highs " .
UV-B RADIATION EFFECTS ON PHOTOSYNTHESIS, GROWTH and CANNABINOID PRODUCTION OF TWO Cannabis sativa CHEMOTYPES
Abstract
The effects of UV-B radiation on photosynthesis, growth and cannabinoid production of two greenhouse-grown C. sativa chemotypes (drug and fiber) were assessed. Terminal meristems of vegetative and reproductive tissues were irradiated for 40 days at a daily dose of 0, 6.7 or 13.4 kJ m-2 biologically effective UV-B radiation. Infrared gas analysis was used to measure the physiological response of mature leaves, whereas gas-liquid chromatography was used to determine the concentration of cannabinoids in leaf and floral tissue.
There were no significant physiological or morphological differences among UV-B treatments in either drug- or fiber-type plants. The concentration of Δ9-tetrahydrocannabinol (Δ9-THC), but not of other cannabinoids, in both leaf and floral tissues increased with UV-B dose in drug-type plants. None of the cannabinoids in fiber-type plants were affected by UV-B radiation.
The increased levels of Δ9-THC in leaves after irradiation may account for the physiological and morphological tolerance to UV-B radiation in the drug-type plants. However, fiber plants showed no comparable change in the level of cannabidiol (a cannabinoid with UV-B absorptive characteristics similar to Δ9 THC). Thus the contribution of cannabinoids as selective UV-B filters in C. sativa is equivocal.
https://smartgrowtechnologies.com/wp-content/uploads/2015/09/UVB-RADIATION.pdf
Check also chapter 8 here =>
http://faculty.ksu.edu.sa/18856/Articles/The effect of ultraviolet radiation on the accumulation of medicinal compounds in plants.pdf
Google for more .Plenty of articles about UV radiation and Cannabinoid content / profile .
http://link.springer.com/article/10.1007/BF02904200#page-1
http://www.clinchem.org/content/46/11/1846.short
http://www.sciencedirect.com/science/article/pii/S0367326X09000422
https://drugs-forum.com/forum/showthread.php?t=41563
Cheers .
