ISHS Acta Horticulturae 300: In Vitro Culture, XXIII IHC
STIMULATION OF THE PHOTOAUTOTROPHY OF IN VITRO PLANTS |
| Author: | G. Reuther |
| Abstract:
The development of photoautotrophy with cultivars of Pelargonium x hortorum, P. peltatum and Vitis vinifera was studied under conditions in vitro. The influence of a sucrose concentration gradient from 20 g·l-1 to zero g·l-1 in agar-based rooting medium on CO2-exchange, heterotrophic and autotrophic carbohydrate metabolism and on growth of the plantlets rooted in vitro was investigated. The light compensation point in plantlets grown on 20 g·l-1 and 10 g·l-1 sucrose medium shifted from higher light intensities to 20 μE·m-2·s-1 in plantlets on 5 g·l-1 and sucrose-free medium. The photosynthetic efficiency at low light conditions (63 μE·m-2·s-1) was highest with sucrose at 5 g·l-1 and 0 g·l-1 compared with the control plants (20 g·l-1 sucrose). The growth rate of the Pelargonium cultivars was greatest on the medium with 10 g·l-1 sucrose, followed by the 5 g·l-1 treatment: both exceeded the control cultures. The cultures on sugar-free medium revealed delayed development. In the range of 20 to 5 g sucrose per liter the Vitis varieties showed an higher shoot growth than on the sugar-free medium. However rooting was not retarded on the sugar 0 variant in both genera. The glucose and fructose content of the shoots and leaves reflected the sucrose supply whereas the starch content correlated more with the photoautotrophic character. In Pelargonium and Vitis cv. 'Riesling' with decreasing sucrose concentrations in the medium the monosaccharide content of plants also decreased. The starch deposition correlated positively with the sucrose supply, but correlated negatively on the sugar-free medium. The carbohydrate content in 0 variant is due to the photosynthetic activity. An albino Pelargonium mutant revealed on 20 g/l sucrose medium no starch deposition. In Vitis cultivar 'Silvaner' the starch content also increased slightly with decreasing sucrose supply. In Pelargonium the ethylene inhibitor AVG stimulated chlorophyll synthesis and starch deposition significantly; the light response curve for CO2-uptake for plantlets was similar to that on the sugar-free medium. The light response curves for CO2-uptake in the presence of the ethylene-promoting substances ACC and PAA was comparable with plants on the control medium (20 g·l-1 sucrose + 0,5 mg·l-1 IAA). Starch deposition | |
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