Metabolic process of the 14C-sugars on the translocation pathways of cucumber plants

Abstract

Studies on the metabolic process of photoassimilates and enhancement of sugar accumulation into fruit are important in fruit crop production. The metabolic process of the 14C-photoassimilates in cucumber plants was analyzed with respect to the vascular system. At 4 h after the start of 14CO 2 feeding, the 14C-photoassimilates synthesized in a selected leaf on the main shoot were translocated to the vascular bundles of the internode just below the 14CO 2-fed leaf. The radioactivity of 14C-stachyose was as high as that of 14C-sucrose in the vascular bundles of petiole and internode just below the 14CO 2-fed leaf as well as in the midrib, while the radioactivity of 14C-stachyose was lower than that of 14C-sucrose in the mesophyll. The 14C-photoassimilates appeared to have been translocated without any metabolic change in the translocation pathways between the petiole and internode just below the 14CO 2-fed leaf, because the ratio of 14C-stachyose radioactivity in the two parts was similar. At 8 h after the start of 14CO 2 feeding, the 14C-photoassimilates were translocated to the fruit. In the vascular bundles of the peduncle, the ratios of the radioactivity of 14C-stachyose and 14C-raffinose were lower, and the ratio of the radioactivity of 14C-sucrose was higher, than that at the petiole and internode just below the 14CO 2-fed leaf at 8 h after the start of 14CO 2 feeding. Therefore, it seemed that 14C-stachyose and 14C-raffinose were hydrolyzed to 14C-sucrose in the peduncle.