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Power Efficiency Guide

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Multiplication cycles after the start of propagation (t)

Figure 5. Simulated time courses of total production of harvestable single nodal cuttings (P(n)) and electric energy consumption per propagule (Ep(n), kWh) after many repetitions of multiplication cycles as affected by production method (use of single nodal cuttings (SNC) only vs. use of single nodal cuttings and stock plant bases (SPB) as propagules), and number of repetitive use of the SPB as propagules (i) (after Lok et al, 2002b). The initial number of SNC used as propagules were 400. Multiplication ratios of SNC and SPB were 1.8 and 3.7, respectively. Multiplication cycle was 12 days.

Figure 5. Simulated time courses of total production of harvestable single nodal cuttings (P(n)) and electric energy consumption per propagule (Ep(n), kWh) after many repetitions of multiplication cycles as affected by production method (use of single nodal cuttings (SNC) only vs. use of single nodal cuttings and stock plant bases (SPB) as propagules), and number of repetitive use of the SPB as propagules (i) (after Lok et al, 2002b). The initial number of SNC used as propagules were 400. Multiplication ratios of SNC and SPB were 1.8 and 3.7, respectively. Multiplication cycle was 12 days.

stock plant bases in addition to conventional single nodal cuttings as propagules for vegetative propagation of sweetpotato (Kubota, 2000). Figure 4 shows the simulated results of number of cuttings, total number of stock plants growing in the production system for the successive cutting production, and stock plants bases to be discarded after repeated usage as starting material (propagule) (Kubota, 2000). The graph may look complicated since, in this simulation, stock plants had different subculture duration (10 days) from that of single nodal cuttings (14 days). The stock plant bases were discarded after processing 3 multiplication cycles. Multiplication ratios were 5 for stock plant bases when it was the first or second cycle of repetitious use, or otherwise it was 3 for stock plant bases and nodal cuttings. The simulated results generally agree with the observation by Aitken-Christie and Jones (1987) in terms of enhanced production by using shoot hedges (or stock plant bases) as propagules. Lok et al. (2002a and, b) also predicted the production of single nodal cuttings of sweetpotato as affected by propagation method (use of stock plant bases and nodal cuttings as propagules versus use of only nodal cuttings as propagules) and planting density. Use of stock plant bases, that are eventually discarded, as propagules in a conventional propagation method increased the production of single nodal cuttings 89 to 197 times after 10 multiplication cycles than that using only single nodal cuttings. This is a result of the greater multiplication ratio of stock plant bases than single nodal cuttings (1.8 to 3.7 times) (Figure 5). The number of single nodal cuttings produced after many repetitions of the multiplication cycle was greatest at planting densities of 59-118 m-2, followed by at 236 m-2 and it was the smallest at 473 m-2. Based on such a simulation of production Lok et al. (2002a and b) simulated electric energy consumption per propagule produced. In Lok et al. (2002a), electric consumption per propagule was shown to converge after many repetitions of subcultures and the number of repetitive uses of stock plants did not have significant effects on electric energy consumption (Figure 5). Such analyses of energy and other resource usage in addition to production of explants are important in decision making on selecting propagation method, environmental conditions and other culture conditions. Simulation of important resource usage as well as production will serve as a significant tool for future production planning, scheduling and management of photoautotrophic micropropagation to maximize production efficiency while minimizing use of energy, water, labor and other resources.

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