Effect of α‐Naphthaleneacetic Acid on Dichotomous Branching of Isolated Roots of Pinus silvestris (A Preliminary Report)

Abstract

As has been shown in an earlier paper (Slankis 1948). dichotomous branching may be produced in isolated pine roots by addition of exndates of mycorrhi/al fungi (e.g. species of Boletus) to tbe nutritive solution. Similar branching of pine roots occurs in nature, according to the investigations of Melin (1923) and others, in connection witb the formation of mycorrhiza. Further investigations (Slankis 1949) indicated tbat ^-indoleacetic acid might be one of the components of the fungous exudates which cause this hninclnng. [3-indoleacetic acid which is known to have a marked effect on root formation (Thimann 1948). produced in isolated pine roots not only a rich development of short roots hnt also dicholomous brancbing of the last roots formed. The question now arises: Do other substances of tbe so called «auxins" which have a strong inflnence on root-formation (Thimann I.e.) produce a similar branching? Up till now experiments have heen made only with a-naphthaleneacetic acid which, as is generally known (Zimmerman and Wilcoxon 19:^5, Zimmerman and Hitchcock 1935 and others), can produce a rich formation of adventitious roots, as well as enhance the branching of the root system.Five-months old pine roots were used in the experiments. The seeds had been collected from Uddheden (Varmland, Sweden), ahout 110 m altitude. The method of preparing tbe root cultures has previously been descri!>ed (Slankis 1948 a, p. 278). The nutrient sohiti(m contained the following organic and inorganic suhstances per litre redistilled water: 71,95 mg Ca(NO:(),,-4H2O, 20,47 mg MgSO,.7H,0, 10 mg KHoPO,, 1,66 mg FeCI^GHoO (according [40]

Auxin transport inhibitors act through ethylene to regulate dichotomous branching of lateral root meristems in pine

“…Not all mycorrhizal fungi produce auxins, and several nonmycorrhizal species associated with the roots of forest trees do produce auxin. Moreover, auxins induce the proliferation of lateral roots, a phenomenon that is not characteristic of ectomycorrhizas (Slankis, 1950(Slankis, , 1973Wilson & Field, 1984 ;Torrey, 1986). Sensitive measurements of IAA in roots indicated that levels were generally lower in mycorrhizal roots than in control roots Lomax et al, 1995), and a study comparing the response of pine roots to fungal strains producing different amounts of auxin found no relationship between auxin production and root morphology .…”

“…αNAA induces lateral root formation Slankis (1950) reported that treatment of P. sylvestris root cultures with the synthetic auxin αNAA, at concentrations of c. 8-13 µM, induced extensive lateral root formation and dichotomous branching of some of these lateral roots. We confirmed that treatment of axenic root cultures of P. sylvestris with 10 µM αNAA induced profile lateral root formation within 4 wk (Fig.…”

“…For example, Slankis and others observed that the treatment of cultured pine roots with fungal extracts, or with naturally occurring and synthetic auxins, induced occasional dichotomous branching of lateral roots that resembled ectomycorrhizal morphology (Slankis, 1948(Slankis, , 1950Ulrich, 1962 ;Slankis, 1973). On the basis of these experiments, as ' auxin theory ' for ectomycorrhiza formation was proposed (Slankis, 1973 ;Gogala, 1991 ;Smith & Read, 1997), according to which the auxins produced by symbiotic fungi are responsible for the changes in root morphology that are characteristic of ectomycorrhizas.…”

The auxin transport inhibitor 2,3,5‐triiodobenzoic acid (TIBA) inhibits the stimulation of in vitro lateral root formation and the colonization of the tap‐root cortex of Norway spruce (Picea abies) seedlings by the ectomycorrhizal fungus Laccaria bicolor

“…Slankis (1950Slankis ( , 1973) applied exogenous IAA, or culture filtrates of two ectomycorrhizal fungi, Suillus luteus and Suillus variegatus, to excised Pinus sylvestris roots. He observed a stimulation of root branching and formation of dichotomous lateral roots, lacking root hairs and morphologically similar to ectomycorrhizas.…”

Mycorrhizal fungi of white oak

“…Work is beiag conducted upon mycorrhizal fungi that are antagonistic to other soil organisms (Manka, 1960;Santoro and Casida, 1962); and upon the production of auxins by mycorrhizal fungi along with the effect of these auxins upon the morphology of the root system (Slankis, 1950(Slankis, , 1960Ulrich, 1960aUlrich, , 1960b)« Recently a new classification scheme for ectotrophic mycorrhizae has been devised based upon morphological and anatomical characteristics (Dominik, 1959).…”