The effect of auxin application and cutting position on the rooting of stem cuttings of four common ornamental shrubs in green spaces

Dissertation for M.Sc. degree

Trend: green space, ornamental plants in the landscape

Auxin application and cutting position on the rooting of stem cuttings

Four shrubs A common ornamental in the green space

By: Hossein Ramezani

Abstract

In order to investigate the effect of different concentrations of indole butyric acid (IBA) (zero, 1000, 2000 and 4000 mg per liter) and cutting position (end, middle and bottom) on rooting. Stem cuttings of Bougainvillea spectabilis, Hibiscus syriacus, Callistemon viminalis and Lantana camara L. researches were conducted in the form of four separate factorial experimental designs based on a completely random design in a greenhouse in Lamard city in 1392-93. The results of this research showed that in the stem cuttings of all four ornamental species, with the increase in the concentration of IBA hormone, the rooting characteristics, including the percentage of rooting, the number and length of roots, and their wet and dry weight, increased, although in the highest concentration of IBA (4000 mg/liter) compared to the concentration of 2000 mg/liter, in most cases, the increase in rooting characteristics was not significant. Regarding the length of the shoots obtained from the buds on the cuttings, the treatment with a concentration of 4000 milligram per liter of IBA led to a decrease in their length. In all four studied species, regardless of the use of auxin, the highest percentage of rooting, root number, root length, fresh and dry weight of roots, and the length of shoots on the cuttings were obtained in the lower cuttings, which had a larger diameter and were more woody. After the lower cuttings, the middle cuttings had the highest amount of rooting, and in all four species, the end cuttings had the lowest amount of rooting. In the study of the mutual influence of IBA concentration and cutting position, the results showed that in all four species, the highest rooting rate and rooting characteristics were obtained in the treatment of the lower cuttings with a concentration of 4000 mg/liter of IBA.

Key words: rooting, stem cutting, auxin, paper flower, tree marshmallow, salt glass, Shah Pansand tree

Chapter One

Introduction

1-1- Preface

Generally, plants reproduce in two ways, sexual and asexual. Each of these two methods has special advantages and limitations. For several reasons, most trees and shrubs are propagated by asexual methods such as cuttings, branch grafting, bud grafting, laying, and micropropagation. Among the asexual methods of propagation by cuttings, it is one of the easiest methods and has several advantages, including preserving the genetic characteristics of the plant, requiring a smaller number of mother plants, being cheap, quick and simple, and not requiring special techniques or special equipment for transplanting or micropropagation (Hartmann et al., 1997). There are many differences in the rooting ability of cuttings among plant species and cultivars. Stem cuttings of some species are rooted easily, while in some species and cultivars, rooting is not done easily and optimization of the conditions for rooting is necessary. In most plant species, careful selection of cuttings from the mother plant, management of cuttings and control of environmental conditions during the rooting process will be decisive factors in success or failure (Hartmann et al., 1997). In general, choosing the type of cuttings, preparing the cuttings at the right time, the appropriate temperature and humidity of the cuttings rooting environment, using the right planting medium, performing some treatments before or after preparing the cuttings, using plant growth regulating substances and finding the optimal concentration of these substances are among the most important factors that should be considered to increase the rooting of the cuttings (Davis and Haissing, 1990, Hartmann et al., 1997 &). Regarding the selection of cuttings from mother plants, it has been seen that there are great differences in rooting ability between different parts of the shoot from which the cuttings are prepared (Davis and Haissing, 1990).Usually cuttings are divided into three groups of end, middle and bottom cuttings based on their position on the stem, among them, the bottom cuttings are thicker and the end cuttings are thinner. In many plant species, the position of the cutting is one of the important variable factors that is closely related to the rooting ability (Leakey and Mohammed, 1985). In addition, it has been seen that the effect of the position of the cutting is dependent on the type of species because in some cases, the lower and middle cuttings had better rooting, while in some other plants, the end cuttings had more rooting (Hartmann et al., 1997).

Another influential factor in the rooting of stem cuttings is the use of growth regulators. Among these substances, auxins have a special place in such a way that the discovery of the natural auxin indole acetic acid [1] (IAA) and synthetic types of auxin such as indole butyric acid [2] (IBA) and naphthalene acetic acid [3] (NAA) caused a huge change in the growth of plants by stimulating the rooting of cuttings (Hartmann et al., 1997). The purpose of treating cuttings with auxin is to increase the percentage of rooting, accelerate the initiation of roots, increase the number of roots and uniformity of rooting (Al-Barazi and Schwabe, 1982).  In most woody plants, in the comparative application of the same amounts of IBA and NAA, the use of IBA has obtained better results, although in some cases the results have been the opposite. In addition, in some cases, the use of a mixture of IBA and NAA has a greater effect on rooting than the use of each of these two alone (Davis and Haissing, 1990; Hartmann et al., 1997). In order to determine the best type of auxin and its optimal concentration in the rooting of stem cuttings of a specific plant species, it is necessary to design and implement experiments. It is necessary to mention that in most cases, the use of artificial auxins in high and more than optimal concentrations can prevent the growth and development of buds on the cuttings and have a negative effect on rooting (Hartmann et al., 1997). It is involved in the sexual reproduction in the tweed stages, such as in plants, in the reduction division of chromosomes (meiosis). In this way, the seed or embryo (embryo) is created from the growth of a cell that is obtained from the union of the male gamete (pollen) and the female gamete (egg cell). Therefore, the resulting plants have a new genetic structure. In asexual reproduction, a complete plant is produced from a cell, tissue, organ or organs of the mother plant. In this reproduction, direct cell division (mitosis) is involved, which usually repeats the genetic structure of the parent plant completely in the progeny (Khoshkhovi et al., 2015). In horticulture, many plants are propagated by asexual methods, because in this way the desirable and desired characteristics of the plant can be stabilized (Gardener, 1968). Among the methods of vegetative propagation, the use of cuttings is one of the most important methods of adding treasured ornamental shrubs, broad-leaved and narrow-leaved evergreens (Khoshkhoi et al., 2016). rtl;">Cutting is a part of the stem, leaf or root that is separated from the mother plant and placed in suitable conditions for rooting (Khoshkhoi et al., 2015). One of the appropriate and important methods of plant propagation is the use of cuttings. Through cuttings, a large number of new plants can be produced from a limited number of mother plants. Propagation of plants by cuttings is a simple, cheap and fast method, and the plants produced in this way are more uniform, and the production of plants by cuttings requires less space. The plants that are produced as seeds have many differences. In propagation by rooting the cuttings, the genetic properties of the mother plants remain unchanged, and if certain traits are desired, the same properties can be obtained in new plants by increasing them through cuttings. The types of cuttings are:

1-2-1- Root cutting [5]

Plants such as silk flower or red raspberry that have the ability to produce buds on their roots and produce leaves, as well as plants that have fleshy roots (such as Begonia Tekme) can be Added with root cuttings.