Nucleotides of Sugarcane: Increased Nucleotide Content of Leaves as a Function of Nutritional Stress

Abstract

Nucleotide analyses were conducted with sugarcane subjected to decreasing levels of nitrate, phophorus, potassium, and calcium over a period of 16 weeks in sand culture. In each instance of nutritional stress, abnormally high levels of sucrose appeared in leaf tissues. This study was motivated by the theory that abnormal nutritional status might induce added nucleotide synthesis, with the concurrent formation of sucrose precursors. Lyophilized leaf samples were extracted with trichloroacetic acid, and nucleotide preparations were analyzed by anion exchange plus paper chromatography. Total nucleotide content was higher in each of the near deficient plant sources as compared with those receiving adequate nutrient supply. Nucleotide increase was greatest among low-calcium and low-nitrate treatments, and least increase was found in low-potassium samples. Increased nucleotides of low nitrate and phosphorus samples were removed from anion-exchange resins by pH 2.9 formic acid-sodium formate elution. Low-Ca induced nucleotides were retained at pH 2.9, but were removed from resin columns by 6 N formic acid. Nucleotide preparations from nitrate- and phosphorus-treated plants contained high levels of reducing sugar, inorganic phosphorus, and organic phosphorus. More than fivefold increases of organic phosphorus were obtained in both treatments. Low-potassium and low-calcium treatments induced high sucrose without accumulating high organic phosphorus. The nucleosides adenosine and cytidine were present in all samples. Guanosine was found in nitrate-, phosphorus-, and potassium-deficient plants only. The possibility is discussed that an azaguaninelike endogenous antimetabolite is formed as a consequence of nutritional stress, accounting in part for growth retardation and abnormally high nucleotide content.