Portal de Periódicos da CAPES

Distribution of VA mycorrhizal entry points near the root apex: Is there an uninfectible zone at the root tip of leek or clover?

1992; Wiley; Volume: 122; Issue: 3 Linguagem: Inglês

10.1111/j.1469-8137.1992.tb00075.x

1469-8137

Sally E. Smith, Sandy Dickson, N. A. Walker,

Legume Nitrogen Fixing Symbiosis

summary This paper re‐examines the question of the susceptibility of plant roots to infection by vesicular‐arbuscular mycorrhizal fungi, particularly near the root apex. The cumulative distributions of the observed distance between the root apex and the most apical mycorrhizal entry points are compared with expected distributions based on (i) a random distribution of successful encounters between hypha and root and (ii) an uninfectible apical region (of length Z o ). Data for both Allium porrum L. (leek) and Trifolium subterraneum L. (clover) are well fitted by the expected distributions and in the majority of cases (17/31) the best fit is obtained with zero Z o , with 8 additional cases being best fitted by values of Z o of 1 mm or less. Even where the best fits are obtained with values of Z o greater than zero, the distribution using Z o = 0 is still within the confidence limits for the data. These findings indicate that in neither species is there clear evidence for a subapical region that is immune to infection. The fact that there are short uninfected lengths immediately behind the apex is interpreted as representing a delay between an encounter and a detectable infection. Other consistent deviations of the data from the theoretical distributions are discussed. Fitting the distributions yields values for the frequency of infection ( A ). These are compared for the two host plants at different propagule densities. The values for leek are much lower than for clover. In both species there are increases in A with increases in propagule density which are consistent with earlier findings.