COBS,monos and lenses..

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Journal Physiology and Molecular Biology of Plants
Publisher Springer India
ISSN 0971-5894 (Print) 0974-0430 (Online)
Issue Volume 14, Number 4 / October, 2008
Category Research Article
DOI 10.1007/s12298-008-0027-x
Pages 299-306
Subject Collection Biomedical and Life Sciences
SpringerLink Date Thursday, February 26, 2009

Suman Chandra1 , Hemant Lata1, Ikhlas A. Khan1, 2 and Mahmoud A. Elsohly1, 3

(1) National Center for Natural Product Research, School of Pharmacy, University of Mississippi, Oxford, MS-38677, USA
(2) Department of Pharmacognosy, University of Mississippi, MS-38677 Oxford, USA
(3) Department of Pharmaceutics, School of Pharmacy, University of Mississippi, University, Oxford, MS 38677, USA

Published online: 26 February 2009

Abstract Effect of different photosynthetic photon flux densities (0, 500, 1000, 1500 and 2000 μmol m−2s−1), temperatures (20, 25, 30, 35 and 40 °C) and CO2 concentrations (250, 350, 450, 550, 650 and 750 μmol mol−1) on gas and water vapour exchange characteristics of Cannabis sativa L. were studied to determine the suitable and efficient environmental conditions for its indoor mass cultivation for pharmaceutical uses. The rate of photosynthesis (PN) and water use efficiency (WUE) of Cannabis sativa increased with photosynthetic photon flux densities (PPFD) at the lower temperatures (20–25 °C). At 30 °C, PN and WUE increased only up to 1500 μmol m−2s−1 PPFD and decreased at higher light levels. The maximum rate of photosynthesis (PN max) was observed at 30 °C and under 1500 μmol m−2s−1 PPFD. The rate of transpiration (E) responded positively to increased PPFD and temperature up to the highest levels tested (2000 μmol m−2s−1 and 40 °C). Similar to E, leaf stomatal conductance (gs) also increased with PPFD irrespective of temperature. However, gs increased with temperature up to 30 °C only. Temperature above 30 °C had an adverse effect on gs in this species. Overall, high temperature and high PPFD showed an adverse effect on PN and WUE. A continuous decrease in intercellular CO2 concentration (Ci) and therefore, in the ratio of intercellular CO2 to ambient CO2 concentration (Ci/Ca) was observed with the increase in temperature and PPFD. However, the decrease was less pronounced at light intensities above 1500 μmol m−2s−1. In view of these results, temperature and light optima for photosynthesis was concluded to be at 25–30 °C and ∼1500 μmol m−2s−1 respectively. Furthermore, plants were also exposed to different concentrations of CO2 (250, 350, 450, 550, 650 and 750 μmol mol−1) under optimum PPFD and temperature conditions to assess their photosynthetic response. Rate of photosynthesis, WUE and Ci decreased by 50 %, 53 % and 10 % respectively, and Ci/Ca, E and gs increased by 25 %, 7 % and 3 % respectively when measurements were made at 250 μmol mol-1 as compared to ambient CO2 (350 μmol mol−1) level. Elevated CO2 concentration (750 μmol mol−1) suppressed E and gs ∼ 29% and 42% respectively, and stimulated PN, WUE and Ci by 50 %, 111 % and 115 % respectively as compared to ambient CO2 concentration. The study reveals that this species can be efficiently cultivated in the range of 25 to 30 °C and ∼1500 μmol m−2s−1 PPFD. Furthermore, higher PN, WUE and nearly constant Ci/Ca ratio under elevated CO2 concentrations in C. sativa, reflects its potential for better survival, growth and productivity in drier and CO2 rich environment.

heckler73 said:

https://en.wikipedia.org/wiki/Caustic_(optics)

I believe you are making a thinly technical argument there. If the sun can burn a piece of wood with a converging lens, it is increasing the transmitted intensity, by definition.
However, in this particular context, I don't know if these manufacturers are really putting much thought into the designs. They may just be buying whatever is on sale from the Zhong Guo ACTION MAO crew, and tossing it in there.

http://www.newport.com/Optics-Formulas/144956/1033/content.aspx

Click to expand...

I was talking about total light emitted, irrespective of any specific measurement at distance.

The difference is roughly ten percent.

Tighter beams throw the light further and of course affect irradiance levels at distance, but the tradeoff is less cross lighting.

ttystikk said:

I was talking about total light emitted, irrespective of any specific measurement at distance.

The difference is roughly ten percent.

Click to expand...

There will always be at least a 4% loss by QED. In reality, glass with a refractive index of ~1.5 (borosilicate crown glass) will lose ~7.8% (i.e. 0.96^2).
How to increase transmission? Use a lower value of refractive index.
I'm not aware of anything solid below 1.45; water is 1.33
It is important to note reflectors change the physics; however, it is mostly an amplification (if using high-reflectivity materials, properly oriented), and unless one is using a monochromatic light (with really tight bandwidth) there should be no interference patterns, other than fringe effects.

You know, after a couple spliffs, a well-mated reflector and plano-convex lens would exhibit properties of a confocal resonator. Hmmmm.... HMMMMMMMMMMmmmmmmmm

Ah but wait...recombination with the LED or phosphor is also likely.
Yah...never mind. It's going to lose ~8% with wavelength dependence.

Tighter beams throw the light further and of course affect irradiance levels at distance, but the tradeoff is less cross lighting.

Click to expand...

Well, yes...Energy must be conserved. The point of lensing is to make use of that otherwise lost light, redirecting it with purpose. If one uses the correct lens design, any footprint can be accommodated. If one wishes to get really spectacular, make them tunable; that way there's no need to adjust height, just refocus.

62 days,lookin frosty.