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RH: relative humidity, NAA: a-naphthaleneacetic acid

RH: relative humidity, NAA: a-naphthaleneacetic acid

Table 3. Growth and development of calla lily (Zantedeschia elliottiana) plantlets during in vitro rooting stage in the PAM (photoautotrophic micropropagation) and PMM (photomixotrophic micropropagation) systems.

Treatment code

Shoot length (mm)

Number of leafy shoots

Leaf area (cm2)

Fresh weight (mg)

Dry weight (mg)

PAM (on day 15)

91.4a

3.7a

12.8a

674a

45a

PMM (on day 15)

51.3cz

3.3a

7.3b

395b

23b

PMM (on day 30)

76.3b

3.4a

9.8b

579ab

36a

zMean separation within columns by LSD test at P <0.01 (n=100).

30 g L1 sucrose 0 g L"1 sucrose (PMM system) (PAM system)

30 g L1 sucrose 0 g L"1 sucrose (PMM system) (PAM system)

Figure 4. Calla lily (Zantedeschia elliottiana) plantlets on day 15 cultured on sugar-containing medium (PMM system, Left) and sugar-free medium (PAM system, Right) (See also Table 3).

The PAM shortened the period of in vitro multiplication as well as rooting by half (from 30 to 15 days), compared with that in the PMM. The greater plantlet growth in the PAM than in the PMM was mainly due to the increased photosynthesis and transpiration under high PPF, high CO2 concentration, enhanced air movement, and low relative humidity in the vessel (Aitken-Christie et al., 1995). Under such environmental conditions, the plantlets generally develop physiologically and morphologically normal stomata. Low relative humidity enhances transpiration, and thus nutrient uptake. The percent loss of in vitro plantlets due to contamination was 0% on day 15 in the PAM, and 5% on day 30 in the PMM (Table 4). Therefore, the monthly production capacity of calla lily plantlets in the PAM is about 3 times (= 30/15 x 67,500/(0.95 x 45,000) higher than that in the PMM (The factor of 0.95 in the above expression comes from the 5% loss of in vitro plantlets in the PMM). Percent rooting in vitro was 98% in the PAM (day 15) and in the PMM (day 30).

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