Yes, I've read the thousands of comments, threads, and everything else where people have mentioned these words. Can somebody just tell me, while looking into LED lights, what are the recommended requirements for a plant in regards to PAR, lumens, and lux? Per square meter? Per square feet? I don't care which type of units, I just want the units to make sense. And please, please, please, don't answer if you actually don't know.
...Ok ....
Firstly :
" recommended requirements "
..Recommended by
who ?
A )By the most led growers ?
B ) By NASA ?
C ) By Chuck Norris ?
D) Other ?
Secondly :
"for a plant "
A ) For just a single plant or all the rest of them included ?
B ) A tomato plant ?
C ) Or is it a banana tree ?
D ) Or might be a Cannabis tree,since this is a relative forum ...
For Cannabis L. species ,experiments have shown that it can grow ,with continuous power -stable
irradiation starting from ~100 umol/sec/m^2 and reaching up to 1500 umol/sec/m^2 ,no matter the population of plants.
Although,a dense populated grow site ,might be neededing more irradiation,than the same area with less plants ...
....
Some lads ,dressed in white and holding weird glass tubes say that :
Photosynthetic response of Cannabis sativa L. to variations in photosynthetic photon flux densities, temperature and CO2 conditions
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
http://link.springer.com/article/10.1007/s12298-008-0027-x
Effect of Light Intensity on Photosynthetic Characteristics of High Δ9-THC Yielding Varieties of Cannabis sativa L.
Cannabis sativa L. (Cannabaceae), an annual herb is the natural source of cannabinoids that mainly accumulate in glandular trichomes of the plant. Due to the allogamous (cross fertilization) nature of
Cannabis sativa it is very difficult to maintain the efficacy of selected high THC yielding elite varieties if grown from seeds under field conditions. Thus, the indoor cultivation, under controlled environmental conditions, using vegetative propagation of selected high yielding female clones can be a better alternative for its mass propagation. In the present study, plants of four drug type
Cannabis varieties namely HPM, MX, K2 and W1 were grown indoors, under controlled environmental conditions (25±3°C, 55±5% RH and ˜ 700±24µmol m–2s–1 light at plant canopy level). Gas and water vapor characteristics of these plants were studied at different Photosynthetic Photon Flux Density (PPFD; 000, 500, 1000, 1500 and 2000µmol m–2s–1) for their efficient indoor cultivation. An increasing trend in photosynthesis (PN), transpiration (Tr) and stomatal conductance (gCO2) was observed with increase in PPFD up to 2000µmol m–2s–1 in all the varieties at optimum growth temperature (25±3°C). However, the magnitude of increase and maximum rate of PN (PN max) varied with the varieties. Highest rate of photosynthesis was observed in W1 followed by MX, K2 and HPM. Water Use efficiency (WUE) in W1, MX and HPM increased with light up to highest level tested, whereas, in K2 highest WUE was observed at 1500µmol m–2s–1.
Our results show that this species is able to use high level of PPFD for its PN and therefore, may be cultivated in under bright indoor light (˜1500 to 2000µmol m–2s–1) for better growth and biomass. The strict control of other environmental factors however, should be maintained for a higher yield. Acknowledgment: This work was supported with federal funds from the National Institute of Drug Abuse (NIDA), National Institute of Health (NIH), Department of Health and Human Services, USA, under the contract No. N01DA-7–7746.
https://www.thieme-connect.com/products/ejournals/abstract/10.1055/s-0030-1251773
Cheers,cheers,cheers
