Translocation of ¹⁴C-assimilates from Leaves of Strawberry Plants in Vegetative Stage as Affected by Leaf Age and Leaf Position

Abstract

In the vegetative strawberry plants with a single leaf retained per plant and fed with ¹⁴CO₂, the current export of ¹⁴C-assimilates was small from the half- and just fully-unfolded leaves, but it increased from the expanded old leaves, reaching about 45% from the 40-day-old leaves. The percentage export of about 45 from the old expanded leaves and the change in percentage export with the leaf age were little affected by the position of leaves on the stem and the extent of new apical growth.
On the contrary, the distribution pattern of ¹⁴C-assimilates varied much with the position of leaves and depending on relative capacities of sinks. When the leaves differing in age but on the same position on the stem were fed, the percentages distribution to the roots and new apical growth were minimal and maximal from the 10-day-old leaves, respectively, although the number of apical developing leaves was greatest in the plants fed to the 40-day-old leaves.
In the intact plants with 7 leaves, in which L 7 was the uppermost and just fully-unfolded leaf at feeding, the percentages export from the expanded leaves, L 1 to 5, were also 40 to 50. The percentage distribution to the new apical growth was greater from upper leaves, ranging from 40 from L 1 to 85 from L 7, and the reverse was true for the roots, ranging from 75 from L 1 to 29 from L 7. The phyllotaxis of 2/5 did not affect the distribution pattern perhaps because the anastomosis developed well in the crown.
Although nothing but a case study, in the plant set upright and irradiated from just above, the contribution rate to the total production of photoassimilates was greatest for L 5 with the percentage value of 25 followed by 21 for L 6, although the photosynthetic capacity (measured with detached leaves under the uniform conditions) differed little between L 1 to L 5 and somewhat lower in L 6 and 7, while the leaf area was greatest in L 5 and 6. The extent of mutual shading was also estimated with the ratios of the photosynthetic rates of leaves in situ on the plant to those of detached leaves, and it was shown to be about 20% in the 3 upper leaves, while it increased in lower leaves, reaching 67% in L 1.