Allocation of Photosynthate to Individual Tubers of Solanum tuberosum L.: II. RELATIONSHIP BETWEEN GROWTH RATE, CARBOHYDRATE CONCENTRATION AND 14C-PARTITIONING WITHIN TUBERS |
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Authors: | ENGELS, CH. MARSCHNER, H. |
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Abstract: | Potato plants (Solanum tuberosum L.) were grown in water culturein a controlled environment. The growth rates of individualtubers were closely reflected by their 14C-content 20 h after14CO2 had been applied to the aerial parts of the shoot for4 h. The 14C-content of the tuber (sink strength) was significantlycorrelated to the 14C-concentration of the tuber tissue (14Cg1 fr. wt.=sink activity). The sink activity, which differedbetween individual tubers by up to a factor of 10, was alsoclosely related to the conversion rates of 14C into the starchand the remainder as well as to the 14C-content in the ethanolsoluble fraction. This indicates the simultaneous use of photosynthatefor growth and storage in the growing tubers. No preferenceof photosynthate utilization for either of these processes couldbe detected in relation to the sink activity of the tubers.Tubers with high sink activity imported 14C-labelled photosynthateat higher rates although their tissue contained higher concentrationsof reducing sugars and sucrose than the tissue of tubers withlow sink activity. Despite the close relationship between sinkactivity and the rate of starch synthesis (14C-conversion intostarch), no significant correlation was found between sink activityand the actual starch concentration of the tissue. The applicationof zeatin riboside directly onto individual tubers increasedtheir growth rates in comparison to non-treated tubers of thesame plant. The results indicate the importance of both growthand storage processes for the regulation of sink activity inyoung potato tubers. Key words: Potato tuber, 14C-photosynthate partitioning, zeatin riboside application |
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