Behavior of carbohydrates within peanut plant

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Abstract
To analyze the behavior of carbohydrates in the peanut plant (Arachis hypogea L.), changes in the sugar and starch contents were characterized in various parts of the plant throughout the growth stages and over the diurnal cycle. At the earlier growth stages, the contents of crude starch, fructose, and glucose in leaves, petioles, and stems remarkable decreased due to the rapid growth of the vegetative organs and formation of pods, while at the pod-enlarging stage, they remained at constantly high levels, suggesting that not all of the reserve pools of carbohydrates are utilized for seed formation. Compared with other sugars, a remarkably lower sucrose content remained in the leaves throughout the growth stages and over the diurnal cycles. However, the ratio of the content of sucrose to other sugars in each organ increased with the increase of the distance from leaves to roots. During the growth period and the diurnal cycle, the changes in the fructose content in leaves were similar to those of the sucrose content in stems. Furthermore, the fructose content in expanding leaves, fully expanded leaves, and petioles, respectively showed the most significant peak at 17:00 in the diurnal cycles. During constant darkness, the fructose content in expanding leaves and the sucrose content in stems continued to display the pattern of a diurnal cycle, while the fructose and glucose contents in fully expanded leaves decreased slightly. The predominant sugar in the gynophore sap was inositol, followed by fructose and glucose, while the sucrose content was lower. This composition of sugars in the sap was consistent with that of the leaves, but different from that of fruits in which sucrose was the main sugar. These results suggest that the exported form of photoassimilates from the leaves may be fructose, and not sucrose; that sucrose may be synthesized in the stems, roots, and pods; and that inositol may play an important role in the growth of the peanut plant.