Plant root regeneration as influenced by applied auxins




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We have been performing a great deal of rose propagation with a high success
rate.
One of the areas of our areas of interest was posted to our web site at
http://www.rooting-hormones.com/roseroot.htm

We are pleased to re-print the article below

regards
Joel Kroin

  *************** Hortus USA Corp ***************
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     US Importer of Rhizopon Rooting Hormones
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The following excellent information is an excerpt from an article published
in Publication 520, Acta Horticulturae 189, 1986 Roses. Only the ABSTRACT,
INTRODUCTION and DISCUSSION are posted here.


Root regeneration of rose plants as influenced by applied auxins


H. W. M. Fuchs
Agricultural University, Department of Horticulture
The Netherlands

ABSTRACT

Root regeneration of rose plants was promoted by application of auxin in all
experiments. Indolebutyric-acid (IBA) applied to root segments of Rosa
multiflora 'Kanagawa' increased number of regenerated roots as well as root
length. The best results were obtained with the highest concentrations 11
000 ppm). Addition of sucrose 5% to the solution enhanced the results.
IBA or naphthalene acetic-acid (NAA) applied to roots of dormant 'Motrea' on
rootstock R. canine 'Inermis' promoted root regeneration, while Indole
acetic acid (IAA) showed no promoting effect. Most effective was IBA in a
concentration of 500 ppm.
The promoting effect of IBA on root regenerating of dormant 'Sonia' on
rootstock R. canine 'Inermis' was observed in a range of temperatures from 5
to 25EC. Optimum concentration depended on temperature: at the lowest
temperature the highest IBA concentration was the most effective; at the
higher temperature it was the lower concentration.

INTRODUCTION

A rose crop in the Netherlands often starts with transplanting dormant
material. Survival and good growth of these transplants is only possible
when during the first weeks after transplanting the temperature can be
maintained at about 5EC. This is only possible in a small period in winter.
Problems with survival and bush development may be due to bad root regrowth
(root regeneration). Any treatment that would decrease the time to new root
initiation and increase the number of roots or the elongation rate of the
roots should increase the chances of successful establishment and early
productivity of rose plants. Regrowth of roots is generally known as
root-regenerating potential (RRP) which is defined as the capacity of roots
to elongate or initiate and elongate new lateral roots (Stone et al., 1962).
In woody ornamentals the RRP varies with the species (Struve et al., 1984b),
with scion variety in roses (Lee et al., 1978) and with physiological stages
of the shoot system (Stone et al., 1959; Lathrop et al., 1971; Lee et al.,
1976). Several researchers showed that stimulation of RRP is possible by
auxin treatments (Looney et al., 1968; Lee et al., 1976; Kelly et al., 1983;
Struve et al., 1984b). A review of species studied, method of application,
types and concentration of auxin was recently made by Struve et al. (1984b).
This study was undertaken to determine the effects of types of auxin, auxin
concentration and their interaction with temperature on root regeneration of
rose plants.

DISCUSSION

Auxin enhanced root regeneration in dormant rose roots as was observed ln
several other woody plants (Looney et al., 1968. Lee et al., 1976; Kelly et
al., 1983; Struve et al., 1984b). The best root regeneration in dormant rose
plants occurred after application of IBA, rather than IAA or NAA. This was
also observed in scarlet oak seedlings (Struve et al., 1984a). IAA seemed to
be less effective and NAA only initiated a large number of roots, but these
did not elongate in the same way as those caused by IBA. A similar effect
was observed in seedlings on other plants (Kelly et al., 1983; Struve et
al., 1984a) and also in cuttings with high concentrations of IBA (Hartmann
et al., 1975).
The promoting effect of auxins on dormant rose roots was partly due to an
increased number of newly initiated roots and partly to elongation of these
roots, while in oak seedlings the promoting effect was due primarily to
increased number of regenerated roots rather than to elongation (Struve et
al., 1984a). In other species it varied with the season, in autumn almost
exclusively from elongation of roots, whereas , in spring regeneration
results from both initiation and elongation (Struve et al., 1984a, b). The
promoting effect of sucrose on root regeneration was due partly to an
increase of number and elongation of new roots, but it seemed that
especially elongation is promoted. The reason for this could be the
limitation of available carbohydrates. The need for reserve material for
good root growth and regeneration has been reported for several species
(Richardson, 1958a and 1958b; Blakeley et al., 1972; Rogers et al., 1968;
Lathrop et al., 1971). Another possible mode of action can be the increase
of auxin efficiency (Nanda et al., 1968). Auxin affected root regeneration
in the whole range of temperatures from 5 to 25EC, but optimum concentration
of IBA changed with temperature. The lower the temperature, the higher the
concentration of optimum IBA, hence at high temperatures the optimum
concentration for good root regeneration is lower. This can be due to the
generally known fact that a concentration range of auxin yields an optimum
response curve which changes with temperature. Although according to the
literature cold storage before treatment should unify both root and shoot
growth under forcing conditions (Webb, 1977; Farmer, 1979) in the present
experiment only uniform root development was observed. An explanation could
be that the selection criterion was the root rather than the shoot system.
The application of auxin could have contributed also to this lack of
uniformity because auxin prohibits bud release. Perhaps this prohibition is
for some reason not the same for each plant, however the treatment without
auxin also showed this lack of uniformity. Another possibility is that the
chilling required for good uniformity is different for the root and the
shoot (Lathrop et al., 1971). It should be kept in mind that shoots and
roots in these roses are even genetically different. It can be concluded
that stimulation of root regeneration of dormant rose plants is possible but
further work has to be done on its after-effects on shoot growth and bush
development (cut flower production, renewal canes). Other fields of study
are the different methods of application and the effect of auxin application
on other rose plants that are not dormant (e.g. regeneration of roots after
harvest of the flowers).


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