McCree Mokley’s Research And Action Curve

McCree KJ, Ph.D., Professor and Educational Physicist, Department of Soil and Crop Sciences, Texas A&M, who did a wonderful job in plant light radiation applications in the early 1970s, 1972 The article “Functional Spectroscopy, Absorption and Quantum Yield of Crop Photosynthesis” is the most cited article in the field of plant light radiation research. It plays an important role in the development of plant lamp spectroscopy technology. Better study of plant lamp spectrum.

Unfortunately, Dr. Mokley died at Eugene OR on May 12, 2014. His 1972 article became his permanent contribution to plant spectroscopy. An in-depth study of Mokley clearly recognizes that Mokley’s curve cannot A simple understanding, today, we introduce his research results in order to correctly understand the meaning of the curve revealed by Dr. Mockley.

Mokley’s thesis has three themes, and today we only talk about the relative action curves of plants.

Action spectrum: The radiant energy response function of plants relative to photosynthesis for different wavelengths of light. This is also the absorption efficiency function of plant photosynthesis that we have been exploring and studying so far. This function affects the efficiency and energy consumption of light quality.

First, we need to understand how this research is conducted. The following are the conditions for the study.

1.Mean measurement at 22 nm intervals for 22 different plants

2.The photosynthesis rate was tested at the leaves in the controlled chamber, and the PPFD was varied by about 30 to 60 umol/m2s.

3.The light absorption rate is determined by measuring the amount of transmission of the blade sample in the optical cavity.

4.The light source is a cool white fluorescent lamp and an incandescent lamp with a spectral range of 350 nm to 750 nm and a photoperiod of 16 hours.

5.Mokley’s research data is derived from the same outdoor and indoor crops.

6.The experimental changes in carbon dioxide concentration, temperature, ambient light, etc. are small, and the influence on the relative curve is small.

Test plant variety


Planting variety and number

Food crop

Corn  Sorghum  wheat  oat  Small rye  Rice

Oil crop

sunflower Soy peanut

Vegetable crop

lettuce tomato radish Chinese cabbage cucumber


cantaloupe squash

Test Equipment

Device for testing blades

Device for testing optical parameters

Since the test equipment is in the old age, it will not be described in detail.

Mokley has carried out detailed tests on indoor planting and outdoor planting through test instruments. This work is boring and requires a lot of work, and requires long-term research work and painstaking data processing. This boring and repetitive research work is It needs to be done with perseverance. His research work has been affecting the development of plant spectroscopy technology. Almost all researchers in the world are referring to the research results of Mokley. The Japanese trend correction curve is also increased to 61 based on Mokley’s research. The curve of a plant.

Relative action curve: The relative action curve is the relative weight of photosynthesis response to different wavelengths of light.

The graph below is a plot of our data based on Mokley’s research data, which are all plotted using energy response data.

Indoor 22 plant relative action curve

Relative action curve of 8 outdoor plants

Red is outdoor, blue is the average of the room

Compare the Japanese trend correction curve (61 plants) (Note: The Japanese tendency to modify the curve is based on the Japanese literature cited more, while other countries’ research literature cited less, here just to distinguish). The 61 species of plants include 20 species of Mokley’s indoors and 8 species of outdoor, and 7 species of 26 species of woody herbs made by Japanese scientists. No specific plant information is provided.

Japanese tendency correction curve

We can draw a clearer picture of the graphs that are superimposed on the two action curves.

It can be seen from the superposition of the two curves that the results of the study are consistent, but as the data of the plant samples increases, the average value of the data tends to be flat.

The reason why the photon curve of the Mokley curve is not drawn is because the curve of the Japanese tendency is representative and the curve of the photon data has been drawn.

Mokley’s research also provides relative quantum yield curves and absorbance curves, which are not described in detail here.

     Relative quantum yield curve           Relative absorption curve 

Through the data analysis of Mokley, we can draw the following conclusions:

1)The relative action curve is the relative weight of photosynthesis response to light at different wavelengths. It is clear that even if the peak relative effect of the curve is 1, it is only representative that part of the optical radiation is effectively absorbed in photosynthesis.

2)This curve does not represent an indicator of the light radiation required for a particular plant. It can be understood as the importance of certain wavelength regions in photosynthesis, but does not require accurate wavelengths of the actual light of the plant.

3)The Mokley curve is not the ideal light quality of the plant lamp spectrum. Plant lamp simulation Mokley curve is not effective, this is a qualitative expression of the spectrum, many designers in the plant lamp trying to match the Mokley curve contour is purely misunderstood; at present, there is no universal light quality correction curve can directly on the plant lamp spectrum The light quality is weighted.

4)Although the average absorption rate of green light is low, the photosynthesis of green light in plants is still needed. In addition to photosynthesis, the role of green light has other mechanisms, and there is no consistent conclusion.

5)Curves are processed using the average of the data and normalized so that the effects of certain factors are minimized, but not equal to no effect. That is to say, the influence of other factors is not effectively reflected in the curve.

6)The test data of low light quantity does not reflect the difference in the amount of high light.

7)The experimental varieties are still low, and the variety types of plant experiments are too scattered.

8)The light quality of the experimental light source is single, and it cannot reflect the influence of the light quality of the current LED light source on plants.

9)There are no data on the different provenances of the same plant variety.

10)There is no data on the effects of plant growth environments and planting substrates.

Dr. Mokley’s research is based on the conditions and technical environment of that era. His technical research is reflected in the publication of a paper. However, the complexity and hardship of this work is difficult to express, and the research spirit of a scientist The technical wealth has profoundly affected today’s plant lamp spectroscopy technology. While studying his technical data, we realized his scientific spirit, that is, there is no fame and fortune and hard work, and the basic research of photosynthesis needs to be under boring. The hardships and persistence of our technical research require this spirit.

Although I am full of respect for his research, the technology needs to be objective and rigorous. The Mokley curve has guiding significance for the weight correction of the plant light spectrum technology, but it cannot be directly quoted. For the lighting technology, we have a visual effect function. To accurately reflect the visual effect of the human eye on light radiation, but there is no standard definition of the absorption efficiency function of the same plant with the visual effect function of illumination. We still cannot solve the contradiction between plant absorption efficiency and energy consumption. Klee spirit technicians work together.

I am writing this article, I hope that the systematic introduction of Dr. Mokley’s research content is not only to analyze the role curve of Mokley from a technical level, but more importantly to commemorate this ordinary and great scientist Dr. KJ McCREE, let the plant lamp The technicians of spectroscopy remember his contribution to plant spectroscopy and can learn the technical ideas that Dr. Mockley wants to express.

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