Behavior of carbon from sucrose and asparagine after introduction to flag leaf of rice plant during ripening

Abstract

¹⁴C-[U] -sucrose and L-¹⁴C-[U]-asparagine were taken up from the tip of the lag leaf at the milking stage of rice plant, which was grown without nitrogen application after lowering, and the behavior of ¹⁴C was studied. The results were as follows.

1.

When 14C- [U] -sucrose was taken up from the tip of the flag leaf, at least 42% of the carbon absorbed was translocated to the ear during the 48 h period after 14C-absorption, which 9 and 7% were respired in the ear and flag leaf, respectively. On the other hand, when L-14C-[U]-asparagine was taken up, at least 47% of the carbon absorbed was translocated to the ear, and 14 and 20% were respired in the ear and flag leaf, respectively.

2.

At 48 h after feeding of the 14C-labeiled compounds, 43% of the carbon from sucrose that was taken up was distributed in sugar and starch, while only 21% of the carbon of asparagine that was taken up was distributed in free and protein amino acids.

Thus, during the translocation of the nitrogen compounds from the leaves to the harvesting organs, the proteins of leaves were decomposed into amino acids in the leaves. The amino acids thus produced were translocated to the harvesting organs, and the proteins were reconstructed there from the free amino acids. During these processes it was considered that an active exchange of carbon skeletons of amino acids took place.

Key Words:

• amino acids
• ¹⁴C-asparagine
• ¹⁴C-sucrose
• respiration
• translocation