Effects of phosphorus stress on the root morphology and root exudates in different sugar beet genotypes

Phosphorus deficiency was induced in sugar beet plants (Beta Vulgaris L., `var. 14´, `var. 17´ and `var. 20´ with different resistance ability to phosphorus stress), cultured hydroponically and sandily under standardized environmental conditions, by removing phosphorus from the nutrient supply at the seedling stage. Root morphology, H<sup>+</sup> excretion and organic acid in rhizosphere were investigated. The main results were showed as following: the average length of roots and the ratio of root to shoot in all genotypes were increased significantly (p<;0.05), among which, the decreasing range of `var. 14´ was the biggest one; sugar beet root mainly excreted oxalic, lactic, maleic acid and trans-butenedioic acid, among which, the first two kinds of the organic acids were the main ingredient, and the phenomena of the significant increase in the secretion amount of those two kinds acids was only appeared in `var. 20´ with higher resistance to phosphorus stress; phosphorus deficiency stimulated the environment changed in root vicinity of sugar beet, and showed as an increase of the H<sup>+</sup> secretion in all the genotypes used in the experiment, but the increased amount of H<sup>+</sup> were genetic dependent, i.e. `var.20´>;`var.17´>;`var.14´.