Forced Ventilation Micropropagation Systems and Their Application

Forced ventilation is a method of ventilation which involves the use of mechanical force such as an air pump and an air compressor to flush in a particular gas mixture directly through the culture vessel. With this system, the gaseous composition (CO2, water vapor, etc.) of incoming air and forced ventilation rate and/or air current speed in the culture vessel can be controlled relatively precisely by use of a needle valve, mass flow controller or an air pump with an inverter.4-6

One of the key advantages of photoau-totrophic micropropagation is that it makes it possible to use large culture vessels with minimum risk of microbial contamination. In photoautotrophic micropropagation using a large culture vessel, forced ventilation has several advantages over natural ventilation. The use of larger culture vessels with forced ventilation is expected to reduce labor costs by nearly 50%, as compared with those in conventional micropropagation. By appropriately controlling the gaseous composition, the growth and development of plants can be promoted significantly or controlled properly. Another application of a large culture vessel with a nutrient supply system can also make it possible to measure and control the pH, composition and volume of nutrient solution in the culture vessel.

Fujiwara et al.21 developed a large culture vessel (58 cm long, 28 cm wide and 12 cm high) with a forced ventilation system for enhancing the photoautotrophic growth of strawberry (Fragaria x ananassa Duch.) explants and/or plants during the rooting and acclimatization stages (Fig. 28.6). This was a kind of aseptic microhydroponic system with a nutrient solution control system.

Table 28.4. Effects of sucrose concentration, supporting material and number of air exchanges on increased fresh mass (FM), % dry matter (DM), shoot length (SL), leaf area (LA), number of unfolded leaves (NUFL) and root length (RL) of coffee (C. arabusta) plantlets on day 40 of culture

Treatment code

FM (mg)

DM (%)

SL (mm)

LA (cm2)

NUFL

RL (mm)

SAL

130

19

4.6b

9.7

8.2a

0.0d

SAH

27

23

2.1d

4.5

4.3c

0.0d

SFL

62

31

4.6b

6.1

5.3bc

0.0d

SFH

59

34

3.9bc

5.3

4.6bc

1.7c

FAL

23

15

2.7cd

5.1

4.1c

0.0d

FAH

39

18

3.2bcd

4.5

6.1b

0.0d

FFL

61

18

4.2bc

5.9

5.1bc

11.0b

FFH

277

15

13.0a

13.0

5.1bc

24.1a

LSDp=0.05

1.6

1.5

2.6

Analysis of variance

Sucrose conc.

(A)

*

**

**

NS

NS

**

Supporting material (B)

**

**

**

**

NS

**

Ventilation rate (C)

*

NS

**

**

NS

**

A x B x C

NS

NS

**

NS

**

**

NS, *, **: Nonsignificant or treatment, see Table 28.3.

significant at P=

=0.05* and 0.01*

*, respectively. For symbols

of

Kubota and Kozai22 showed that the net photosynthetic rate and photoautotrophic growth of potato (Solanum tuberosum L.) plants cultured using a large culture vessel with forced ventilation, containing a multicell tray with rock-wool cubes, were significantly greater than those cultured using a conventional (small) culture vessel with natural ventilation.

Heo and Kozai23 developed a forced ventilation micropropagation system with a culture vessel containing a multicell tray widely used for plug seedling production. The cells were filled with sterilized vermiculite or cellulose plugs. The photoautotrophic growth of sweet potato plants cultured with this system was several times greater than the photomixotrophic growth of plants cultured with conventional or small culture vessels containing sugar and with natural ventilation. However, the growth in the culture vessel was not uniform, with larger plants near the air inlet and comparatively small plants near the air outlet.

Zobayed et al.24 developed large culture vessels with air distribution pipes for forced ventilation. The major aim of the system was to provide an air current pattern which enables

Table 28.5. Fresh (FM) and dry mass (DM), and percent rooting of Acacia mangium plants cultured for 28 daysJ4 Means ± SD are shown

Treatment

FM

DM

Cone. Growth (gl"1) regulator

C02 enrichment

No. of air exchanges (h"1)

(|imol m"2s"1)

Substrate

(mg/plantlet)

(mg/plantlet)

rooting

30

Yesz

Yesy

6.7

150

V-CFmix*

222 ± 89

40 ± 21

94

30

No

Yes

6.7

150

V-CF mix

155 ± 21

32 ± 1

81

0

Yes

Yes

6.7

150

V-CF mix

410 ± 145

62 ± 24

100

30

Yes

Yes No

6.7 0.7

150 150

V-CF mix V-CF mix

22 ± 2

82 38

30

No

No

0.7

150

V-CF mix

116W

1 7W

75

0

Yes

No

0.7

150

V-CF mix

110 ± 33

18 ± 4

82

0

No

No

0.7

150

V-CF mix

139 ± 38

20 ± 4

46

(control

No

No

0.7

100

Agar

100w

14w

0

Analysis of variancev

Sucrose conc.

NS

NS

NS

Growth regulator

NS

NS

NS

COj enrichment and number of air exchanges(h"1

**

**

NS

zMedium contained 1 mg I"1 IBA. ycc>2 concentration inside the culture room with or without CO2 enrichment was 1500 or 400 [imol mol"1, respectively. xVermiculite and cellulose fiber mixture. wOnly one replication for treatment with 30 g I"1 sucrose, without growth regulator and no CO2 enrichment, and control treatments. vANOVA (Analysis of variance) was applied for 9 treatments (except for the control treatment). NS, nonsignificant; **, significant at P<0.01.

zMedium contained 1 mg I"1 IBA. ycc>2 concentration inside the culture room with or without CO2 enrichment was 1500 or 400 [imol mol"1, respectively. xVermiculite and cellulose fiber mixture. wOnly one replication for treatment with 30 g I"1 sucrose, without growth regulator and no CO2 enrichment, and control treatments. vANOVA (Analysis of variance) was applied for 9 treatments (except for the control treatment). NS, nonsignificant; **, significant at P<0.01.

Fig. 28.4. Acacia mangium plants on day 28.14,15 S0: Sugar-free medium; CE: CO2 enriched; NE: CO2 non-enriched, GR: presence of growth regulator in the medium; NR: absence of growth regulator; C: control (sugar and growth regulator containing medium, CO2 non-enrichment, airtight vessel).

GR No GR

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