Distribution of non-structural carbohydrates in the vegetative organs of upland rice

Abstract

Rice is one of the main foods consumed by half of the world’s population. The rice crop requires plenty of water, but upland rice is cultivated in a non-flooded environment, although its productivity is lower than that of lowland rice. Rice grains mostly consist of starch, which is synthesized from the non-structural carbohydrates imported from the vegetative organs. The long-term storage of carbohydrates plays a remarkable role in maintaining the supply of photoassimilates during grain filling if photosynthesis does not meet energy demand. Therefore, the dynamics of non-structural carbohydrates is central to the productivity of rice crops. The present study aimed to determine the non-structural carbohydrate content and soluble carbohydrate profiles in different vegetative organs of upland rice of the genotype BRS Esmeralda. The content was determined at the end of vegetative development. The identification and quantification of carbohydrates were performed by high-performance anion-exchange chromatography with pulsed amperometric detection. Fully expanded leaf blades, expanding leaf blades, and expanding stems exhibited the soluble carbohydrate content of 59.7, 53.3, and 52.3 mg g–1 DM, respectively. The stem was found to be the main organ for the long-term storage of non-structural carbohydrates, wherein the starch content was 36.1 mg g–1 DM. It also contained soluble carbohydrates such as glucose, fructose, and sucrose. The non-structural carbohydrates were found in low amounts in the roots, showing that this organ does not store long-term carbohydrates.