13.4.4  Vegetative propagation

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Table 13.3

Plant propagation in its various forms often benefits from CO2 enrichment. Root development of cuttings may be stimulated (Table 13.3), a possible outcome of improved plant water relations during root initiation. Increased accumulation of starch for both species listed in Table 13.3 implies dual effects of CO2 enrichment. Transpirational losses from cuttings would be lower due to partial stomatal closure, while photosynthesis would be stimulated due to higher intercellular CO2 concentration. Number, length and dry weight of roots were also improved by CO2 enrichment (Table 13.3) and transplanting success will increase accordingly. Promotion of rooting in cuttings of forest tree species is especially benefical to survival in new plantations.

CO2 depletion by in vitro plant cultures (such as tissue culture and micro-propagation) is commonly due to meagre gas exchange with outside air. This leads to dependence upon the carbohydrates in the medium as a carbon source. CO2 enrichment during in vitro rooting of plantlets can enhance growth during acclimatisation to ambient conditions, while enrichment during acclimatisation can increase survival rates of transplanted plantlets.

Heat therapy has been used for virus elimination in a range of horticultural species. This procedure requires exposure of candidate plants to high temperature (up to 40°C) for many weeks, and plant survival is low. CO2 enrichment during heat therapy has, however, proven beneficial to both plant survival and production of virus-free propagules. As well as presenting Rubisco with a higher partial pressure of CO2, net fixation is further enhanced by suppression of photorespiration which would otherwise be greatly accelerated by high temperature at normal ambient CO2 (see Case study 13.2).

 

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