Postphotosynthetic utilization of labeled assimilates in fiber flax

The distribution of C-14 in various tissues of fiber flax was assayed 1, 17, and 21 days after 30-min assimilation of (CO2)-C-14 by the whole rapidly growing plant. Polymeric photosynthetic products were largely, hydrolyzed in the C-14-donor part of the shoot, and the hydrolysates were transported upward. The content of C-14 in pigments and lipids of the donor leaves (that absorbed (CO2)-C-14) was significantly higher than that in the C-14-acceptor leaves. Additional nitrogen nutrition decreased the labeled sucrose- to-hex ose transport of the assimilates from both C-14-donor and acceptor leaves. C-14 transported to the shoot tip was largely used for the synthesis of poorly soluble proteins (extractable with alkali and Triton X-100) in the acceptor tissues. In the donor part of the shoot, particularly in the bast, cellulose was mainly synthesized from the "new" assimilates.