No LED treatment(NL) No LED unit was applied

PPFD in Pulsed LED (PL) was 1/2 compared with in Continuous LED (CL)

a

b

a

b

PLCL

・Introduction

Strawberry(Fragaria × ananassa Duch. ‘Benihoppe’) Spinach(Spinacia oleracea L. ‘Hydroseven’)

0

10

20

30

40

50

60

Yei

ld (

g /

pla

nt)

aa

b

PLCLNL0

10

20

30

40

50

60

70

Yie

ld (

g /

pla

nt)

PLCLNL

b

aa

0

0.01

0.02

0.03

0.04

0.05

0 0.01 0.1 0.4 1 10 100

A /

PP

FD

(m

ol

mo

l-1)

Pulse cycle (ms)

b

a a a a a a

0

0.01

0.02

0.03

0.04

0.05

0.06

0.07

0 0.01 0.1 0.4 1 10 100

A /

PP

FD

(m

ol

mol-1

)

Pulse cycle (ms)

d

a a a a bc

Excessively low solar radiation during cold season

Depression in photosynthesis and crop growth

Decline in crop production

Energy-saving system for supplemental lighting

Pulsed LED irradiation promote light use efficiencies

Pulsed LED irradiation promote the crop growth and yield at the same level of continuous LED irradiation

There is a possibility that pulsed LED irradiation can supplement a required light efficiently for crop growth and electricity consumption

・Energy use efficiencies

No significant difference between PL and CL

Yield was increased

Pulsed LED irradiation can be expected to promote the crop growth and yield at the same level of continuous LED irradiation

Time (s)0

Cur

rent

Turning on

Turning off

Turning on

Turning off

Light use efficiency Light use efficiency

Light use efficiency in PL was about 1.2 times as large as that in CL

Yield

Results & Discussion Results & Discussion

Yield

* Kyushu University **Postdoctoral Research Fellow of the Japan Society for the Promotion of Science, QST Takasaki Advanced Radiation Research Institute, National Institutes, *** NARO Kyushu Okinawa Agricultural Research Center, **** Kankyou Photonics Co., Ltd.

KYUSHU UNIVERSITY

Turning on and off at a high rate

De-exciting steps of P680 and P700 effect of pulsed LED irradiation

Pulsed LED irradiation can be expected to promote the crop growth and yield efficiently under energy saving

0

0.2

0.4

0.6

0.8

LA

(m

2 /

pla

nt)

PLCLNL

a

a

b b

a

b

Dec.

Feb.

0

50

100

150

200

250

300

Pla

nt

Hei

ght

(mm

)

c

a

b

PLCLNL

aa

bb

cc

11/21

12/1

12/12

(PL: duty ratio was 50%, CL: duty ratio was 100%)

Reduction of photosynthetic rate in PL was only 20%

Spinach PL was 2 times as large as CL

Yield was increased

No significant difference between PL and CL

Pulsed LED irradiation can be expected to promote the crop growth and yield at the same level of continuous LED irradiation

・Summary

0

0.2

0.4

0.6

0.8

PLCLNL

aa

b

LA

(cm

2 /

pla

nt)

Duty ratio; 50% Blinking time; 0.1 ms PPFD; solar radiation + 100 μmol m-2 s-1

Duty ratio; 100% Blinking time; 0 ms PPFD; solar radiation + 140 μmol m-2 s-1

No LED (NL)

Treatments

LED unit : (KP-E2-RBB, Kankyou Photonics Co., Ltd.)

No LED unit was applied

Duty ratio; 50% Blinking time; 0.1 ms PPFD; solar radiation + 70 μmol m-2 s-1

Duty ratio; 100% Blinking time; 0 ms PPFD; solar radiation + 200 μmol m-2 s-1

Treatments

No LED unit was applied

No LED (NL)

CL PL

Duty ratio 50%

Strawberry

Spinach

LA was increased No difference in Dec (before

supplemental lighting)

PPFD in PL was 1/2 compared with in CL

Light use efficiency in PL was about 1.4 times as large as that in CL

(PL: duty ratio was 50%, CL: duty ratio was 100%)

Reduction of photosynthetic rate in PL (0.01-1ms) was only 10%

CL PL

Duty ratio 50%

Plant Height No difference Effect of

Far-red light ?

Term Term

Nov.21,2017 -Dec.12,2017

Dec. 2016 - Feb. 2017

PL was increased at same level of CL in Feb (after supplemental lighting)

To make dark period during these steps…

Strawberry PL was 3 times as large as CL

During these steps, light energy is not required

P700+

P680+

Ph

oto

syst

em II

P680+

2H20 4H++O

Higher

Lower En

erg

y o

f e

lect

ron

4 Photons

Cytochrome complex

4 Photons Ph

oto

syst

em I

4e-

P700+

P680+

P700+

2NADP+

+2H+

Pulsed LED irradiation promote energy use efficiencies

Leaf area(LA) and Plant Height LA

Not included in supplemental light

exci

te ex

cite

de-excite

de-excite

P

PF

D

(μmol

m-2

s-1

)

600

400

200

0

P

PF

D

(μmol

m-2

s-1

)

300

200

100

0

E

ner

gy

use

eff

icie

nci

es

(g

kW

h-1

)

1.2

1

0.8

0.6

0.4

0.2

0

0.5

0.4

0.3

0.2

0.1

0