This is a gold mine of cannabis growing laboratory research

jammie said:

wow- love reading tech articles while i'm stoned. can anyone tell me which bulbs produce photosynthetic photon flux densities of ∼1500 μmol m−2s−1?? may have to contact the authors

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All the measurements were carried out on five upper undamaged, fully expanded and healthy leaves of each plant with the help of a closed portable photosynthesis system (Model LI-6400; LI-COR, Lincoln, Nebraska, USA) equipped with light, temperature, humidity and CO2 controls.

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Different PPFD were provided with the help of an artificial light source (Model LI-6400-02; light emitting silicon diode; LI-COR), fixed on the top of the leaf chamber and were recorded with the help of quantum sensor kept in range of 660-675 nm, mounted at the leaf level.

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Air flow rate (500 mmol s-1) and relative humidity (55 ± 5%) were kept nearly constant throughout the experiment.

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At 20 and 25 oC, WUE (water use efficiency) increased with increase in PPFD up to 2000 μmol m-2s-1 (Fig. 5). On the other hand, WUE increased only up to 1500 μmol m-2s-1 PPFD at 30 oC and decreased thereafter at higher light levels. Temperature higher than 30 oC had an adverse effect on WUE of this species. The maximum WUE was observed at 30 oC and under 1500 μmol m-2s-1 PPFD. Photosynthesis appears to have a greater influence than E (transpiration) over regulating water use efficiency in C. sativa. A highly significant positive correlation was observed between WUE and PN (r = 0.92). Together, high temperature and high PPFD had an adverse effect on the WUE in C. sativa.

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Since steady state photosynthesis is reached within 30–45 min, the leaves were kept for about 45–60 min under each set of light conditions before the observations were recorded.

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The photosynthesis and transpiration characteristics were studied under different light levels (0, 500, 1,000, 1,500, or 2,000 μmol m−2 s−1).

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All these plantlets were kept under similar environmental conditions grown in an indoor cultivation facility housed at Coy-Waller laboratory, University of Mississippi. Light was provided with full spectrum 1,000-W high density discharge (HID) lamps (Sun Systems, CA) hung on the top of plants. A hot air suction fan was attached, and about 1-m distance between plants and bulb was maintained to avoid heating due to HID bulbs. Using an automatic electric timer, artificial day/night cycle was regulated with a 16-h photoperiod. Grow room temperature and relative humidity was kept nearly 25–30°C and 60%, respectively.

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Specifications
Output Range: 0 to 2000 μmol m-2 s-1 at 30°C.
Minimum Fraction Blue: 5% (photon basis).
Typical Fraction Blue: 100 μmol m-2 s-1, 13%; 1000 μmol m-
2 s-1, 10%; 2000 μmol m-2 s-1, 7%.
Red Peak Wavelength: 665 nm ±10 nm at 25°C.
Red Peak Wavelength Temperature Dependence:
+ 0.2 nm/°C, typical.
Red Full Width Half Max (FWHM): ≤ 30 nm at 25°C.
Blue Peak Wavelength: 470 nm ±10 nm at 25°C
Blue Peak Wavelength Temperature Dependence:
+ 0.05 nm/°C, typical.
Blue Full Width Half Max (FWHM): ≤ 40 nm at 25°C.
Output Spatial Uniformity:
Red: Coefficient of variation ≤ 6%; maximum deviation
from mean ≤ 9%, corner to corner, typical.
Blue: Coefficient of variation ≤ 13%; maximum deviation
from mean ≤ 18%, corner-to-corner, typical.
Coefficient of variation ≤ 9%; maximum deviation from
mean ≤ 14%, excluding corners, typical.
Accuracy: 5% of reading at 25°C with a leaf reflectance
R<10%.
Power Consumption At 2000 μmol m-2 s-1: ≤ 8 W.
Operating Temperature Range: 0-50 °C.
Operating RH: 0-100%, non-condensing.
Size: 5.2H 5 5.6W 5 7.3D cm (2.0 5 2.2 5 2.9 in.).
Weight: 0.2 kg (0.44 lb).

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6400-02B Red/Blue LED Light Source . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . $3,100

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LJB said:

The objective of this study was to determine the effect of light intensity, temperature and CO2 conditions on gas and water vapour exchange characteristics of C. sativa L. to establish suitable and efficient environmental conditions for its indoor cultivation.

Photosynthetic response of Cannabis sativa L. to variations in photosynthetic photon flux densities, temperature and CO2 conditions

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.

Key words Cannabis sativa - Photosynthesis - Transpiration - Water use efficiency

http://www.springerlink.com/content/a3527u6018823x43/

full text pdf!!!!!: http://www.springerlink.com/content/a3527u6018823x43/fulltext.pdf

******

Note that this study was conducted at the (public) University of Mississippi, but it appears this document was not published in the United States.

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jammie said:

wow- love reading tech articles while i'm stoned. can anyone tell me which bulbs produce photosynthetic photon flux densities of ∼1500 μmol m−2s−1?? may have to contact the authors

Click to expand...

jammie said:

wow- love reading tech articles while i'm stoned. can anyone tell me which bulbs produce photosynthetic photon flux densities of ∼1500 μmol m−2s−1?? may have to contact the authors

Click to expand...

jammie said:

wow- love reading tech articles while i'm stoned. can anyone tell me which bulbs produce photosynthetic photon flux densities of ∼1500 μmol m−2s−1?? may have to contact the authors

Click to expand...

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.

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All this lead to the designation of the "Einstein" as a unit of irradiance. A whole Einstein is defined as 1 mole of photons. Recall that one mole is 6.02x10^23 atoms (Avogadro's number). The unit used for PAR irrandiance is a millionth of an Einstein per square-meter per second, or 6.02x10^17 photons per square-meter per second, the microEinstein (µE). [4] Note, however, that the Einstein is not an official SI unit of measure [3].

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Another means of measuring light quantity for plant growth involves the understanding that light is always emitted or absorbed in discrete packets called "photons." These packets or photons are the minimum units of energy transactions involving light. For example, if a certain photosynthetic reaction occurs through absorption of one photon of light, then it is sensible to determine how many photons are falling on the plant each second. Also, since only photons in the PAR region of the spectrum are active in creating photosynthesis, it makes sense to limit the count to PAR photons. A lamp could be rated on how many actual tiny photons it is emitting each second. At present no lamp manufacturer does this rating.

Instead, plant biologists and researchers prefer to talk of the flux of photons falling each second on a surface. This is the basis of PPF PAR with PPF standing for Photosynthetic Photon Flux, a process which actually counts the number of photons falling per second on one square meter of surface. Since photons are very small, the count represents a great number of photons per second, but the number does provide a meaningful comparison.

Another measure appropriate for plant growth, called YPF PAR or Yield Photon Flux, takes into account not only the photons but also how effectively they are used by the plant. Since red light (or red photons) are used more effectively to induce a photosynthesis reaction, YPF PAR gives more weight to red photons based on the plant sensitivity curve.

Since photons are very small packets of energy, rather than referring to 1,000,000,000,000,000,000 photons, scientists conventionally use the figure "1.7 micromoles of photons" designated by the symbol "µmol." A µmol stands for 6 x 1017 photons; 1 mole stands for 6 x 1023 photons. Irradiance (or illumination) is therefore measured in watts per square meter or in micromoles (of photons) per square meter per second, abbreviated as µmol.m-2.s-1

The unit "einstein" is sometimes used to refer to one mole per square meter per second. It means that each second a 1 square meter of surface has 6 x 1023 photons falling on it. Irradiance levels for plant growth can therefore be measured in micro-einsteins or in PAR watts/sq. meter.

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Anti said:

This would seem to be the meat of the quotation, for those seeking a quick explanation.

25-30 °C = 77-86 °F

∼1500 μmol m−2s−1 = i have no idea.

quick googling turned up nothing useful. Any chemistry majors in the building? I know that μmol is the symbol for micromole which is one millionth of a mole.

Anybody who understands this care to translate that bit? Thanks.

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Plant height is influenced by the difference (DIF) between day and night temperature. A positive DIF (higher day than night) will produce taller plants. A negative DIF (higher night than day) will produce shorter plants. Plant height can be decreased by lowering the day temperature and also by increasing the night temperature. It can also be decreased by introducing a relatively cooler temperature, or DIP for two hours starting just before sunrise. DIP and DIF affect the length of the stem internodes rather than the number of leaves.

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LJB said:

http://www.allcat.biz/mesurez/anglais/default/news.php

PPF (µmol m-2 s-1) to Lux conversion

PPF (µmol m-2 s-1) conversion to Lux is depending on the type of light. Following tables from AllCat Instruments show conversion factors for most common light types.

Using their table

HPS - 1500 µmol m-2 s-1 = 11426 lumens / square foot
MH - 1500 µmol m-2 s-1 = 9894 lumens / square foot

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These conversion tables are based on the following reference: "Thimijan, Richard W., and Royal D. heins 1982. Photometric, Radiometric, and Quantum Light Units of Measure: A Review of Procedures for Interconversion. HortScience 18:818-822."

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