LED Light for plant growth is the future focus and consideration looking at adverse weather conditions were leading to lower supplies of global agriculture production, damaging crops and sending agricultural commodity prices higher.

1. Agriculture/Horticulture
LED Light
For Plant

2. Photosynthetically Active Radiation
(PAR)

3. Identified visible wavelength
• 660nm – drives the engine of the
photosynthesis
• 612nm – Not to promote
photosynthesis, but to match
carotenoids (plant health). Increase
plant’s chlorophyll contents
• 465nm – Proper photomorphogenesis
or plant development
• Sunlight contains 4% ultraviolet
radiation, 52% infrared radiation and
44% visible light

4. Why do plant have photoreceptors?
There are three principle families
of such photoreceptors
1)Red/Far-Red (R/FR) light-
absorbing phytochromes
2)UV-A/blue light-absorbing
cryptochromes
3)Phototropins

5. R:FR Photon ratio

6. Relationship between R:FR and Pfr/P

7. Effect of R:FR Ratio (Zeta,ξ) On Plant
ξ
High R:FR Low R:FR
(Leafy) (Thin & Long)

8. Flowering
• The flowering process is particularly intriguing because, in
most plants, it is precisely synchronized with seasonal
changes. Certain plant species do not flower if the days
are too long; others flower only when daylight lasts longer
than a certain number of hours. This observation suggests
that plants can assess the changing length of the day as
the seasons come and go, a complex and difficult task. To
do so, they must discriminate day from night, measure the
passage of time, and integrate the information. Do plants
possess the means of carrying out such a complex
process? They certainly do. Just as plants measure light
with photoreceptors, they measure time, appropriately,
with a biological clock. And as for the integration of light
and time, we have been able to show, after countless
hours of experimentation, that plants are constantly,
monotonously making and then destroying molecules that
help control flowering. The concentration of those
molecules is the key to a seemingly complex decision.

9. Flowering (Continue)
UVC ultraviolet range which is extremely harmful to plants because it is
200 - 280 nm
highly toxic.
280 - 315 nm Includes harmful UVB ultraviolet light which causes plants colors to fade.
Range of UVA ultraviolet light which is neither harmful nor beneficial to
315 - 380 nm
plant growth.
Start of visible light spectrum. Process of chlorophyll absorption begins.
380 - 400 nm
UV protected plastics ideally block out any light below this range.
This range includes violet, blue, and green bands. Peak absorption by
400 - 520 nm chlorophyll occurs, and a strong influence on photosynthesis. (promotes
vegetative growth)
This range includes the green, yellow, and orange bands and has less
520 - 610 nm
absorption by pigments.
This is the red band. Large amount of absorption by chlorophyll occurs,
610 - 720 nm and most significant influence on photosynthesis. (promotes flowering and
budding)
There is little absorption by chlorophyll here. Flowering and germination is
720 - 1000 nm
influenced. At the high end of the band is infrared, which is heat.
Totally infrared range. All energy absorbed at this point is converted to
1000+ nm
heat.

10. Flowering (Continue)
• The transition to flowering in plants is regulated by
environmental factors such as temperature and light.
Plants grown under dense canopies or at high density
perceive a decrease in the ratio of red to far-red incoming
light. This change in light quality serves as a warning of
competition, triggering a series of responses known
collectively as the 'shade-avoidance syndrome'. During
shade avoidance, stems elongate at the expense of leaf
expansion, and flowering is accelerated. Of the five
phytochromes—a family of red/far-red light
photoreceptors—in Arabidopsis, phytochrome B (phyB)
has the most significant role in shade-avoidance
responses, but the mechanisms by which phyB regulates
flowering in response to altered ratios of red to far-red light
are largely unknown. Here we identify PFT1
(PHYTOCHROME AND FLOWERING TIME 1), a nuclear
protein that acts in a phyB pathway and induces flowering
in response to suboptimal light conditions. PFT1 functions
downstream of phyB to regulate the expression of
FLOWERING LOCUS T (FT), providing evidence for the
existence of a light-quality pathway that regulates
flowering time in plants.

11. Shade Avoidance Syndrome
• Shade avoidance is a set of responses that plants
display when they are subjected to the shade of
another plant. It often includes elongation, altered
flowering time, increased apical dominance and
altered partitioning of resources. This set of
responses is collectively called the shade-
avoidance syndrome (SAS).
• Plants can tell the difference between the shade of
an inanimate object (eg a rock) and the shade of
another plant. In the shade of a plant, is present in
a higher irradiance than red light, as a result of the
absorption of the red light by the pigments involved
in photosynthesis. Phytochrome can be used to
measure the ratio of far-red to red light, and thus to
detect whether the plant is in the shade of another
plant, so it can alter its growth strategy accordingly
(photomorphogenesis). In Arabidopsis,
phytochrome B is the predominant photoreceptor
that regulates SAS.

12. Shade Avoidance Syndrome (Low R:FR)

13. Photoperiod
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16. The Right Duration
• No matter what types of plants you are growing indoors,
you must be sure to always give them a rest. When it's
dark, plants respirate, which is an important part of their
growth process. The balance of rest time to active growth
time affects many biological processes, including the
growth rate, and the setting of buds and fruit.
• Botanists usually divide plants into three categories relating
to their preferred day length: short-day, long-day or day-
neutral. Short-day plants, such as chrysanthemums,
kalanchoe, azaleas and begonias, will thrive on less than
12 hours of light per day. In fact, these plants must usually
go through a series of even shorter days before they will
set buds and flower.
• Long-day plants require at least 14 to 18 hours of light
each day. Most vegetables and garden flowers are long-
day plants, and when they don't receive enough light they
get pale and leggy. Day-neutral plants, including foliage
plants, geraniums, coleus and African violets, are usually
satisfied with 8 to 12 hours of light all year-round.