biologia plantarum

Biologia plantarum 44:517-521, 2001 | DOI: 10.1023/A:1013778201203

Apoplastic Transport of ¹⁴C-Photosynthates Measured under Drought and Nitrogen Supply

V.I. Chikov¹, N.Y. Avvakumova¹, G.G. Bakirova¹, L.A. Belova¹, L.M. Zaripova¹

¹ Institute of Biochemistry and Biophysics, Kazan Scientific Centre of Russia Academy of Science, Kazan, Russia

Using water infiltration of the plant and individual shoots with the subsequent intercellular liquid extraction by the pressure chamber, dynamics of the movement ¹⁴C-photosynthates from cell to apoplast, and ¹⁴C distribution among photosynthetic products in mesophyll cells and apoplast were studied. The relative quantity of ¹⁴C-photosynthetes in leaf apoplast depended on growing conditions; drought increased, and nitrate supply decreased it. When the middle leaves absorbed ¹⁴CO₂, photosynthates moving down in stem phloem appeared in intercellular space, where they were transported up by transpiration stream. ¹⁴C-photosynthates entering to the apex and young leaves were utilized a accumulated, and photosynthates transported to the mature leaves were reloaded into the phloem and reexported. Thus, photosynthates circulated through the plant and were redistributed to the plant organs according to their transpiration. In leaf apoplast photosynthetic sucrose was partly hydrolyzed to glucose and fructose. This increased under high nitrogen supply. The result indicate that apoplast sucrose hydrolysis is the basic cause of the reduction of photosynthate flux from leaves when the nitrate concentration in soil increases.

Keywords: assimilate transport; bean; flax; hexoses; Linum usitatissium; Phaseolus vulgaris; photosynthate utilization; sucrose

Subjects: apoplastic and symplastic transport of ¹⁴C photosynthates; bean; flax; Linum usitatissimum; nitrate supply, photosynthesis; Phaseolus vulgaris; photosynthates, apoplastic and symplastic transport

Published: December 1, 2001  Show citation