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14 C-Translocation in Kalanchoe pinnata at two Different Stages of Development

MARÍA LUISA MAYORAL and ERNESTO MEDINA
Journal of Experimental Botany
Vol. 36, No. 170 (September 1985), pp. 1405-1413
Published by: Oxford University Press
Stable URL: http://www.jstor.org/stable/23691386
Page Count: 9
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14
          C-Translocation in Kalanchoe pinnata at two Different Stages of Development
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Abstract

Translocation of 14C-compounds from mature leaves was measured in plants of Kalanchoe pinnata to determine the interaction between plant age and CAM phase when CO2 is taken up. Mature leaves of 4 and 12 month old plants were fed with 14CO2 either during CAM phase 1 (midnight) or at the beginning of CAM phase 4 (early afternoon). Export of 14C activity from source leaves, and distribution of 14C activity in soluble and insoluble compounds was measured both in source leaves and sink organs. In 4 month old plants 4 d were needed to export 76% of total 14C activity incorporated during CAM phase 1, while leaves labelled at the beginning of CAM phase 4 exported 44% of total 14C activity after 4 h, and 80% after 24 h. In both cases the major fraction of total radioactivity translocated was found in the roots in the form of neutral sugars. Differences in translocation patterns are due to distribution of 14C in the source leaves, 96% of 14C taken up during CAM phase 1 is found in the insoluble fraction at the end of the subsequent phase 3, while 93% of total radioactivity taken up at the beginning of phase 4 is found in the soluble fraction at the end of this phase. In 12 month old plants labelled during phase 1 very little translocation could be detected at the end of phase 3, while only 20% of total radioactivity was translocated from leaves labelled during phase 4 and measured 4 h later. 14C activity in the older leaves had a similar distribution in soluble and insoluble fractions as the one determined in the younger plants. Ability to translocate carbon compounds from source leaves during phase 3 was shown by loading mature leaves at dawn with 14C-sucrose. Here again, mature leaves of younger plants showed faster translocation of radioactivity than those of older plants.

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