TRANSLOCATION OF C¹⁴ IN TOBACCO AT DIFFERENT STAGES OF DEVELOPMENT FOLLOWING ASSIMILATION OF C¹⁴O₂ BY A SINGLE LEAF

Abstract

Single leaves of tobacco plants at four different stages of development were allowed to carry on photosynthesis in C14O2 for 30 to 50 minutes followed by photosynthesis in air. The total elapsed time from the beginning of assimilation was [Formula: see text] hours. Redistribution of C14 was determined in: I, a young plant with eight leaves; II, an older plant with 19 leaves; III, a mature flowering plant with 29 leaves; IV, a mature seed plant with 35 leaves. The leaf treated with C14O2 in each of the four plants was number seven, counting from the bottom. This leaf was only half expanded in the youngest plant but fully expanded in the other three plants.The treated leaf of the youngest plant translocated 22% of the total C14 fixed, twice as much as the treated leaves of the other three plants. The large amount of translocation in the youngest plant occurred from a leaf that contained 28% of its ethanol-soluble fraction as sugar phosphates and only 25% as sucrose. The treated leaves of the older plants that translocated half as much radioactivity had less C14 in sugar phosphates and more C14 in sucrose. For example, the treated leaf of the seed plant contained 13% of its soluble C14 in sugar phosphates and 70% in sucrose.Sucrose and some hexose was recovered from the stems and roots of all plants. Amino acids were recovered from both stem and root of the youngest plant but not from these parts of the three older plants. Since 80 to 100% of the C14 in the stems was recovered as sucrose it is concluded that this sugar is the main form in which carbon is translocated in tobacco. Although sugar phosphates and organic acids were found in the treated leaves of all plants they were not detected in stems or roots and were apparently not translocated.All plants translocated C14 to leaves both below and above the treated leaf. Two factors influenced the destination of C14. One was the anatomical connection among leaves, and the second was the stage of development of any particular leaf. Although C14 was translocated to leaves at nodes bearing flowers no C14 was translocated to these flowers or to developing or mature seeds in any of these plants.

Carbon Assimilation and Translocation in Soybean Leaves at Different Stages of Development

“…3) adjusted for the increased SLW) following LPI 4.1 may have resulted from the decline in translocation rate in the absence of any apparent decline in SPS activity. Our results are in agreement with those of Shiroya et al (19) who observed decreasing translocation rates and an increased sucrose pool size in older tobacco leaves. Evidence exists for a storage pool of sucrose in leaves that is not directly accessible to translocation (6).…”

Photosynthesis in Artificial Communities of Cotton Plants in Relation to Leaf Area I. Experiments with Progressive Defoliation of Mature Plants

“…This conclusion is supported by the results of translocation studies with many plants in which lower, shaded, old leaves have been found not to import assimilates from upper, younger leaves (Belikov 1958;Shiroya et al 1961;Thrower 1962;Hartt, Kortschak, and Burr 1964). Thus, if the lower, shaded leaves are to survive for any length of time, their respiration rate must be greatly reduced.…”

Comparison of Upward and Downward Translocation of 14C From a Single Leaf of Sunflower

“…There is evidence to support the idea that sucrose is the main form in which carbon compounds are translocated in plants (1,7,8,9). Swanson (10) showed that the ratio of labeled hexoses to labeled sucrose decreased with increasing distance from the fed leaf after assimilation of 14CO-.…”

“…Seventy ,uc of 14CO.) were generated and introduced into the chamber as previously described (7). The whole planit was placed under illumination of 30,000 lux for 30 min to allowv the fed leaf to fix 14CO.…”