Percent Survival During Acclimatization Ex Vitro

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Percent survival of calla lily plantlets during the ex vitro acclimatization was 95% in the PAM and 60% in the PMM, and that of China fir was 95% in the PAM-0, 97% in the PAM-1, and 16% in the PMM. The percent survival was about 6 times higher in the PAM"0 and the PAM"1 than in the PMM. The lower percent survival in the PMM was probably due to the malfunction of stomata in leaves (Aitken-Christie et al., 1995) and callus formation at the base of the nodal cuttings. Callus formation has been considered a cause of poor root initiation and limited uptake of nutrient and water (Nguyen, et al., 1999). The higher percent survival in the PAM was probably because the plantlets were already acclimatized and functionally photoautotrophic in vitro (Kozai and Zobayed, 2000). The percent survival of calla lily plantlets transplanted in the farmer's greenhouse without shading (i.e., no acclimatization procedure) was 80%, compared with 95% in the greenhouse with a shading screen. Thus, by further improving the in vitro acclimatization method in the PAM, the ex vitro acclimatization process could be eliminated under moderate weather conditions (Heo and Kozai, 1999). This simplification is one of the advantages of the PAM.

7. PRODUCTION COST OF CALLA LILY PLANTLETS: A CASE STUDY

The investment cost of the module (excluding the culture room) was US$15,180 or CNY126,000 (Chinese Yuan) for the PAM (1 US$ = 8.3 CNY as of 2003), and was 5,807 US$ for the PMM. Since the lifetime of the PAM and PMM was considered to be 10 years, yearly depreciation was 1,518 US$ for the PAM and 581 US$ for the PMM. The yearly production capacity per module of the PAM was about 152,000 plantlets (= 365/18 x 7,500), since one multiplication cycle was 18 days; 15 days for multiplication, 1 day for harvesting and 2 days for cleaning, preparation and transplanting. On the other hand, the yearly production capacity of the PMM was about 52,000 plantlets (= 365/33 x 5,000 x 0.95), since one multiplication cycle was 33 days; 30 days for multiplication, 1 day for harvesting and 2 days for cleaning, preparation and transplanting. Therefore, if the PAM and PMM were operated throughout the year, the yearly depreciation of investment cost per plantlet was 0.010 US$ (= 1,518/152,000) or 1.00 US cent in the PAM, and 0.0112 US$ (= 581/52,000) or 1.12 US cent in the PMM. In other words, the investment cost per plantlet was a little lower in the PAM than in the PMM, as shown in Table 6. The above figures indicate that the investment cost accounted for 18% of the production cost in the PAM and 12% of the production cost in the PMM.

7.1. Production cost per acclimatized plantlet

The production cost per ex vitro acclimatized plantlet from the PAM was 59% of that from the PMM (Table 6). The cost for ex vitro acclimatization in the PAM and the PMM accounted for 50% and 56% of the production cost, respectively. Thus, an increase in percent survival during ex vitro acclimatization significantly decreases the production cost. Of the total costs for ex vitro acclimatization in the PAM, 20% was spent on the construction of the greenhouse, 56% was spent on labor, 19% was spent on supplies such as substrate, electricity, water, fertilizer and pesticide and 5% was spent on other items. On the other hand, in the PMM, 11% was spent on the construction of the greenhouse, 38% was spent on labor, 11% was spent on supplies such as substrate, electricity, water, fertilizer and pesticide and 40% was spent on other items. The lower cost of ex vitro acclimatization in the PAM than in the PMM was mainly due to a higher percentage of survival ex vitro and less labor. The cost for in vitro multiplication, which was equal to that for in vitro rooting, in the PAM was 58% of that in the PMM (Table 6). Labor cost in the PAM was less than half of that in the PMM. This result is consistent with the prediction by Kozai et al. (2000). The reduced labor cost in the PAM significantly reduced the cost for in vitro multiplication and rooting. Electric energy consumption per plantlet during the in vitro multiplication was 27.2 Wh (or 97.9 kJ = 27.2 Wh x 3600 s) in the PAM; 69% for lighting, 24% for cooling, 2% for air pumping and 5% for autoclaving. On the other hand, it was 42.8 Wh in the PMM; 56% for lighting, 21% for cooling, 23% for autoclaving using electricity. Electric energy consumption per plantlet in the PAM, therefore, was 64% of that in the PMM. The lower electricity consumption in the PAM was mainly due to the reduction in multiplication and rooting periods by half, a low electric energy consumption for autoclaving the medium and vessels, and a high percent utilization of light energy by using white reflective sheets. A preliminary experiment showed that PPF was 1.65 times higher on a shelf with the reflective sheets (86±8 ^mol m-2 s-1) than on a shelf without the reflective sheets (52±12 ^mol m-2 s-1) when four fluorescent lamps were turned on. Average air temperature outside the culture room was 18 C during the experiment.

7.2. Cost, labor time and electricity consumption for in vitro multiplication or rooting

The electricity consumption for cooling increases with increasing outside air temperature. Thus, the cooling cost would be increased by 50-60% when outside air temperature was around 35 C (Aitken-Christie et al., 1995).

7.3. Sales price of in vitro and ex vitro acclimatized plantlets

The sales price of calla lily plantlets in vitro was about 7.23 US cents when produced using the PAM, and was 6.02 US cents when produced using the PMM; i.e., the sales price was 20% higher in the PAM than in the PMM because of the higher quality produced by the PAM. The sales price of ex vitro acclimatized plantlets was 18.1 US cents when produced in the PAM, and was 14.5 US cents when produced in the PMM and acclimatized ex vitro; i.e., the sales price was 25% higher in the PAM than in the PMM because of the higher quality produced by the PAM. In this experiment, it was not possible to record the expenses for supervision, administration, sales, transportation of plantlets to farmers, etc., and thus to calculate the profit per plantlet. This is because the personnel doing were doing other jobs concurrently. According to Chu (1992), the supervision cost accounts for 13% of the total production cost in the micropropagation industry. In any case, The PAM could produce higher quality plantlets at a lower cost than the PMM, which shows that the PAM has a commercial advantage over the PMM.

Table 6. A comparison of production cost, labor time and electricity consumption per plantlet of calla lily in the PAM (photoautotrophic micropropagation) and the PMM (photomixotrophic micropropagation) systems.

Cost per ex vitro acclimatized plantlet (US cent)

PAM (A)

PMM (B)

A/B Ratio

Investment cost

1.00 (18%)

1.12 (12%)

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