|
|
RESEARCH: PHOTOBIOLOGY /
LIGHT QUALITY |
|
|
PHOTOBIOLOGY
Tracy Dougher completed her Ph.D. in 1999 on “The effect of
blue light and temperature on leaf expansion, stem elongation, and
growth.” She is now an Assistant Professor at Montana State University.
We now know that the
blue light fraction of sunlight (30%) is too high for optimum leaf
expansion and growth. The optimal level of blue light for both
monocots and dicots is about 6% of the photosynthetic photon flux,
regardless of the total PPF intensity. In subsequent yield
optimization studies we demonstrated that lettuce productivity can be
increased by increasing the PPF level up to almost full sunlight, if
CO2 is elevated and all other environmental parameters are
optimized.
|
CLICK ON THE TITLES TO VIEW ABSTRACTS:
|
 |
|
-
Toward an
Understanding of Blue Light Effects on
Diverse Species: Implications
for Advanced Life-Support Systems
Tracy Dougher and B. Bugbee
International
Conf. on Environmental Systems (ICES)
Jul.
1999; Denver, CO
|
ABSTRACT The use of
more energy efficient lamps for controlled environment agriculture has
led to less blue light (0-6%) available for plant growth than sunlight
(30%). In some species, this reduction in blue light has introduced
serious plant abnormalities, increased plant height, or altered plant
architecture. In order to understand the effects of blue light on
plant productivity and carbon partitioning, we filtered lamps to
attain a continuous response curve. We attained five UVA/blue light
fractions (0, 2, 6, 12, and 26%) with equivalent phytochrome
photoequilibrium and tested two photosynthetic photon fluxes (200,
500) on wheat, soybean, and lettuce. Lettuce was most sensitive to
changes in blue light, wheat was least sensitive. The blue light
response curve of lettuce suggests that 6% blue is necessary for best
growth. However, the blue response of lettuce appears to also depend
on other wavelengths. Lettuce and soybean stem elongation was
excessive at 0 and 2% blue, but was within field height from 6 to 26%
blue. Excessive stem elongation caused an increase in carbon
partitioning to the stems at the expense of the leaves. Lettuce leaf
area increased 8-fold from 0 to 6% blue but was relatively constant
above 6% blue. Increasing blue light from 0 to 26% decreased soybean
leaf area only 12% but had no effect on specific leaf area.
|
|
|
|
ABSTRACT
Light
quality affects not only growth, but also plant morphology (shape).
Nowhere is this more important than in the horticulture and
floriculture industry where plant morphology determines commercial
value.
Current
lighting technology for controlled environments depends on efficient
lighting sources. These lamps are often lacking in blue wavelengths.
We found that blue light effects on plant growth are species dependent
with effects ranging from no effect seen in wheat to gross
morphological changes as in lettuce.
Although researchers believe that sunlight is the best light source
for growth, more desirable canopy structure can be obtained by
filtering some sunlight wavelengths. We are currently investigating
the interaction of different wavelengths and their effects on plant
morphology.
|
|
-
Substituting for Sunlight: Photosynthesis, Photobiology, and Electric
Lights
Bruce Bugbee
Presentation:
Agronomy Society of America
Nov.
10-14, 2002; Indianapolis, IN
|
|
|
|
|
