Effects of Auxins on Plants

Research Project

Submitted to the Council of the College of Education

at Salahaddin University-Shaqlawa in Partial Fulfillment of the

Requirements for the Degree of B.Sc.in biology

By:

Enas A. Aziz

Supervised by:

Mohammed O. Hamadameen Barznji

Erbil, KURDISTAN

2021

I

SUPERVISOR DECLARATION

This research project has been written under my supervision and has been

submitted for the award of the degree of BSc. in Biology with my approval as a

supervisor.

Signature:

Name: Assist. Lecturer. Mohammed O. Hamadameen Barznji

Supervisor

Date: 28/4/2021

I confirm that all the requirements have been fulfilled.

Signature:

Name: Sherko M. Abdulrahman

Head of the Department of Biology

Date: 28/4/2021

I confirm that all the requirements have been fulfilled.

II

ACKNOWLEDGEMENTS

First and foremost, I have to Thank to my God and my parents for their support

and thank my sisters and brothers for giving me strength and helped me a lot in

finalizing this project within the limited time frame and Great thanks to my friends for

their support.

I would like to express my special thanks of gratitude to my supervisor

(Mohammed O. Hamadameen Barznji) ‏who gave me the opportunity to do this

wonderful project on the topic (Effects of Auxins on Plants) ‏which also helped me in

doing a lot of Research and i came to know about so many new things I am really

thankful to them. and help throughout the period of my study.

I am so happy to gratitude to SalahaddenUniversity-Erbil, and special thanks are ‏

to Dean of College of Education-Shaqlawa and Head and Staff of biology

department for giving me an opportunity to complete this study.

DEDICATION

This work is dedicated to: My dear parents

My dear sisters and brothers

III

SUMMARY

Some chemicals occurring naturally within plant tissues, have a regulatory, rather

than a nutritional role in growth and development. These compounds, which are

generally active at very low concentrations, are known as plant hormones (or plant

growth substances). It is a Greek word meaning “to stimulate” or “to set in motion. They

regulate plants germination, growth, reproduction as well as both biotic and abiotic

stress responses under different environmental conditions. plant hormones are produced

in meristems, leaves, and developing fruits. The concentration of the hormones can vary

between different plant tissues, developmental stages and environmental conditions.

Plant hormones are usually divided into five main groups namely;auxins, cytokinins,

gibberellins, ethylene, and abscisic acid. Here, we review what is known on effects of

auxins on plants. auxin indole-3-acetic acid was discovered in the 1930s, there’s four

types of auxin (Indole-3-acetic acid (IAA), indole-3-butyric acid (IBA), 4-chloroindole-

3-acetic acid (4-Cl-IAA) and phenylacetic acid (PAA) Auxin is important because of its

potent impact on cell division, cell growth, and differentiation, auxin is very commonly

used for artificially controlling plant growth. And‏ level of auxin is different between

plants. IAA is synthesized from tryptophan or indole primarily in leaf primordia and

young leaves, and in developing seeds. IAA hormone in plants plays an important role in

cell division, proliferation, and differentiation, vascular tissue alteration, responses to

light and gravity, The biosynthesis and transport of auxin and its signaling play a crucial

role in controlling root growth. Auxin controls many aspects of fruit development,

including fruit set and growth, ripening and abscission.

IV

CONTENTS

SUPERVISOR DECLARATION ............................................................................................. I

ACKNOWLEDGEMENTS ................................................................................................... II

SUMMARY ...................................................................................................................... III

INTRODUCTION ............................................................................................................... 1

REVIEW OF LITERATURE .................................................................................................. 3

2.1 Definition of auxin hormone ............................................................................... 3

2.2 Why is it so important to study auxin? ................................................................ 3

2.3 How was auxin discovered? ................................................................................ 4

2.4 Are auxin levels the same in all plant cells? ........................................................ 4

2.5 Is auxin specific to plant growth? ........................................................................ 5

2.6 Effect of auxins on plants .................................................................................... 5

2.7 Effect of auxin on tropisms ................................................................................. 6

2.8 Effect of auxin on wall expansion ........................................................................ 7

2.9 Effect of auxin on root growth ............................................................................ 8

2.10 Effect of auxin on fruit ........................................................................................ 8

REFERENCES .................................................................................................................. 11

ەتــــــــپوخ ‌أ ...........................................................................................................................

1

INTRODUCTION

The term “hormone” was initially used about 100 years ago in medicine for a

stimulatory factor. It is a Greek word meaning “to stimulate” or “to set in motion. Plant

hormones are defined as a group of endogenous organic substances which influence

various physiological and developmental processes in plants at low concentrations. A

number of biological processes in plants are affected by internal and external stimuli

through the involvement of plant hormones. Plant hormones can occur at different

morphological and cytological locations, and their actions may be observed at their sites

of production, or they may get translocated to some distant target tissues to evoke a

response. Generally, plant hormones are produced in meristems, leaves, and developing

fruits. Different plant hormones can cause opposite effects on a particular developmental

process at varying concentrations. Antagonistic and synergistic interactions among

various plant hormones further add to the complexity of hormonal actions in higher

plants. Different hormones are able to influence the biosynthesis of some other

hormones or may interfere with their signalling mechanisms. A hormone can evoke

different responses in different tissues or at different times of development in the same

tissue. Different tissues require varying amounts of hormones of specific kinds for their

development. Such differences are referred to as differences in sensitivity (Bhatla,

2018).

Plant hormones are small organic molecules that naturally occurring in

plants at very low concentrations. They regulate plants germination, growth,

reproduction as well as both biotic and abiotic stress responses under different

environmental conditions. These molecules show diverse chemical properties and

unique chemical structures with wide polarity range and poor photo-thermal

stability (Wang et al., 2017, Porfírio et al., 2016, Miransari and Smith, 2014). The

concentration of the hormones can vary between different plant tissues,

developmental stages and environmental conditions (Chini et al., 2007). There are

several recognized classes of plant growth substance. Until relatively recently only

five groups were recognized namely auxins, cytokinins, gibberellins, ethylene and

abscisic acid (George et al., 2008, Isoda et al., 2020). Auxins and cytokinins are by

far the most important for regulating growth and morphogenesis in plant tissue

and organ cultures, in these classes, synthetic regulators have been discovered with

a biological activity, which equals or exceeds that of the equivalent natural growth

substances (George et al., 2008). Gibberellins (GAs) are particularly important for

2

adaptation because their metabolism depends on external conditions, and their

functions are widespread along the plant’s life cycle (Hedden and Thomas, 2012).

Apart from being widely known for promoting plant growth via cell expansion and

division, they are also instrumental in the response to different environmental

stimuli such as gravity, light or temperature (Hernández-García et al., 2020). Their

roles in development include the differentiation of pollen in angiosperms, male

organ formation in ferns (Tanaka et al., 2014).

Ethylene the growth and development of plants under varied environmental

conditions determine agricultural production. The growth, development, and

senescence of plant’s organs can influence crop production by modulating

photosynthesis, nutrient remobilization efficiency, and harvest index (Iqbal et al.,

2012). Abscisic acid plants adapt to tolerate stress through production of specific

hormones that are produced at very low concentrations. One of the classical and

well-studied phytohormones is abscisic acid (ABA), the importance of which is

highlighted by its various roles in development such as seed dormancy,

germination and floral induction, and stress responses such as drought, salinity,

and pathogen infection (Alazem and Lin, 2017). Sites of biosynthesis IAA is

synthesized from tryptophan or indole primarily in leaf primordia and young

leaves, and in developing seeds, sites of biosynthesis CK is through the biochemical

modification of adenine. It occurs in root tips and developing seeds, sites of

biosynthesis GAs are synthesized from glyceraldehyde-3-phosphate,

via isopentenyl diphosphate, in young tissues of the shoot and developing

seed. Their biosynthesis starts in the chloroplast and subsequently involves

membrane and cytoplasmic steps, sites of synthesis Ethylene is synthesized by

most tissues in response to stress. In particular, it is synthesized in tissues

undergoing senescence or ripening and Sites of synthesis ABA is synthesized

fromglyceraldehyde-3-phosphate via isopentenyl diphosphate and carotenoids

in roots and mature leaves, particularly in response to water stress. Seeds are also

rich in ABA which may be imported from the leaves or synthesized in situ (Davies,

2010).

Aim of study There are very few knowledge and information about this topic very few

people know about it. It has a very important role for growth and development and

division of plant we wanted to give some information to people and be acknowledged

for ourselves.

3

REVIEW OF LITERATURE

2.1 Definition of auxin hormone

Auxin (indole 3-acetic acid, IAA) is a small molecule plant hormone derived from

the amino acid tryptophan that controls virtually all aspects of plant life. And as such is

a determining factor in the acquisition of the final shape of plants (Weijers and Wagner,

2016). A particularity of auxin is that it is actively transported across cells and tissues by

specialized, plasma membrane (PM)-localized, influx and efflux carriers. The combined

activity of these transporters allows the generation of auxin gradients, as well

as auxin maxima and minima that are critical for organ patterning and differential

growth during tropic responses (i.e. growth of the plants toward or away (Finet and

Jaillais, 2012). The combination of each auxin concentration in a given cell induces

specific transcriptional programs that can have a wide range of outputs, including cell

differentiation into various cell types and activation or inhibition of elongation growth

(Kepinski and Leyser, 2005). The plant hormone auxin controls diverse aspects of plant

growth and development by regulating the fundamental cellular processes of

expansion, division, and differentiation. One of auxins most striking effects is to rapidly

mediate changes in cell expansion. Indeed, this property was the basis of the bioassay

leading to the chemical discovery of auxin (Du et al., 2020). The word auxin has a

Greek origin auxein means to enlarge or to grow (George et al., 2008, Du et al., 2020).

In organised tissues, auxins are involved in the establishment and maintenance of

polarity and in whole plants their most marked effect is the maintenance of apical

dominance and mediation of tropisms (George et al., 2008). Chemical structure of four

endogenous auxins. Indole-3-acetic acid (IAA), indole-3-butyric acid (IBA), 4-

chloroindole-3-acetic acid (4-Cl-IAA) and phenylacetic acid (PAA), (Simon and

Petrášek, 2011).

2.2 Why is it so important to study auxin?

Because of its potent impact on cell division, cell growth, and differentiation,

auxin is very commonly used for artificially controlling plant growth. The most common

use of auxin in our daily life is in growing plants from cuttings. Gardeners often use a

powder to stimulate root proliferation; this is essentially auxin at low concentration. As

ever, the dose makes the poison and, at high concentrations, synthetic auxins like 2,4-D

are used as herbicides to which dicotyledonous plants are much more sensitive than

4

monocotyledonous plants. An infamous example is “Agent Orange” used for defoliation

during the Vietnam War.As auxin induces cell division at physiological concentrations,

it can be used in a balanced cocktail with another growth regulator, cytokinin, to

promote cell proliferation in cell culture or in vitro propagation. This knowledge

allowed, for instance, the emergence of low cost orchids and virus-free potatoes.Detailed

knowledge of the mechanism of action of auxin has recently also led to powerful new

technology in non-plant laboratories. The ability of IAA to rapidly and efficiently induce

the degradation of Aux/IAA proteins without the requirement of plant-specific

components other than TIR1 led animal and yeast biologists to import this system to

rapidly and conditionally target the degradation of other proteins when coupled to a

small domain of an Aux/IAA protein (Nishimura et al., 2009).

2.3 How was auxin discovered?

IAA was isolated from maize by during the 1930s, but its existence had been

hypothesized several decades earlier. For example Charles and Francis Darwin

hypothesized the existence of a mobile signal that promotes elongation of grass

coleoptiles. In simple and elegant experiments, father and son showed that coleoptiles

bend to the light source when illuminated from one direction. Other scientists, including

Boyen-Jensen, Paal, and Went, independently used the same experimental system to

show that the bending was promoted by a mobile signal that was hydrophilic in nature,

and this signal was finally identified as IAA (Abel and Theologis, 2010).

2.4 Are auxin levels the same in all plant cells?

No, you do not find the same amount of auxin in all the tissues of a plant. In fact,

the uneven auxin distribution is a key factor for proper development. IAA

concentrations can differ by an order of magnitude between shoot and root and appear

highest in meristems located at the tip of the roots and the shoots. Even though many

cell types seem able to produce auxin (Ljung et al., 2005). Even though many cell types

seem able to produce auxin, the capacity in young leaves is comparatively high. This

freshly made auxin is then transported from source organs (such as young leaves) to sink

organs (such as meristems) where auxin accumulates. In those organs, levels of auxin

differ between cell types (Petersson et al., 2009). In those organs, levels of auxin differ

between cell types This heterogeneity in auxin levels is due to directional auxin

transport mediated by specific families of influx (Aux/LAX proteins) or efflux (PIN

5

proteins) regulators located on polar domains in the cell membrane The precise

positioning of these auxin channels orient auxin flux and create heterogeneity for IAA

distribution (Petrášek and Friml, 2009).

2.5 Is auxin specific to plant growth?

While auxin is a key regulator of plant development, IAA and genes involved in

its biosynthesis are also found in a wide range of different bacteria or fungi. While auxin

can impact gene expression in some bacteria, it does not seem to be used as a growth

signal there, but rather as a signal to communicate with plants in an ecological context

(Koul et al., 2015). Furthermore, IAA biosynthesis is used by some pathogenic bacteria

to hijack plant development (for example, the crown galls induced by Afro bacterium

timesavers) in a range of plant species. Thus, the question becomes whether all plant

species respond to auxin. There is no clear answer to this question yet, even though the

presence of auxin and auxin response have been reported in algae (De Smet et al., 2011).

Without genomic, genetic, and biochemical investigations, it is not possible to tell if

such responses are based on conserved mechanisms. However, auxin response is clearly

ubiquitous in all flowering plant species investigated, with Arabidopsis, maize, and rice

being focal species. Recently, it has been found that a very similar auxin response

pathway operates in the earliest diverging land plants, the liverworts and mosses. Rather

strikingly, while the moss Physcomitrella patens still has some degree of genomic

complexity in its NAP (Lavy et al., 2016). the liverwort Marchantiapolymorpha appears

to have a nearly minimal set of NAP components. Thus, auxin response has an ancient

history but critical questions remain unanswered as to the origin of auxin response and

how different sets of genes have become auxin-dependent during plant evolution. So far,

only orthologs of auxin signalling that are not part of the NAP have been found in algae

and nothing is known about the emergence and evolution of the NAP components.

Hopefully, the steady release of genome or transcriptome, sequences thanks to new

sequencing technologies will help to answer these questions (Kato et al., 2015).

2.6 Effect of auxins on plants

Generally, IAA hormone in plants plays an important role in cell division,

proliferation, and differentiation, vascular tissue alteration, responses to light and

gravity, general root and shoot architecture, seed and tuber germination, organ

differentiation, peak predominance, ethylene syn- thesis, vegetative growth processes,

6

fruit development and aging (Ahemad and Kibret, 2014). Auxin is also effective in the

growth and seed development of oilseed crops, sub- sequently increasing the production

of oils from seeds. Among different plant hormones that play a role in regulating

reproductive plant growth, auxins trigger flower and fruit development programs that are

closely related to flower and fruit development (Brcko et al., 2012).

1. Cell enlargement - auxin stimulates cell enlargement and stem growth

2. Cell division - auxin stimulates cell division in the cambium and, in combination with

cytokinin, in tissue culture

3. Vascular tissue differentiation - auxin stimulates differentiation of phloem and xylem

4. Root initiation - auxin stimulates root initiation on stem cuttings, and also the

development of branch roots and the differentiation of roots in tissue culture

5. Tropistic responses - auxin mediates the tropistic (bending) response of shoots and

roots to gravity and light

6. Apical dominance - the auxin supply from the apical bud represses the growth of

lateral buds

7. Leaf senescence - auxin delays leaf senescence.

8. Leaf and fruit abscission - auxin may inhibit or promote (via ethylene) 9. Leaf and

fruit abscission depending on the timing and position of the source.

10. Fruit setting and growth - auxin induces these processes in some fruit

Assimilate partitioning - assimilate movement is enhanced towards an auxin source

possibly by an effect on phloem transport

Fruit ripening - auxin delays ripening

Flowering - auxin promotes flowering in Bromeliads

Growth of flower parts - stimulated by auxin (Davies, 2010).

2.7 Effect of auxin on tropisms

Differential growth of plants in response to the changes in the light and gravity

vectors requires a complex signal transduction cascade. Although many of the details of

the mechanisms by which these differential growth responses are induced are as yet

unknown, auxin has been implicated in both gravitropism and phototropism.

Specifically, the re- distribution of auxin across gravity or light- stimulated tissues has

been detected and shown to be required for this process. The approaches by which auxin

has been implicated in tropisms include isolation of mutants altered in auxin transport or

response with altered gravitropic or phototropic response, identification of auxin

gradients with radio- labeled auxin and auxin-inducible gene reporter systems, and by

7

use of inhibitors of auxin transport that block gravitropism and phototropism. One

important difference between light and gravity-induced auxin gradients has been

reported. During gravitropic bending in maize coleoptiles, lateral translocation of IAA

has been reported to occur along the length of the coleoptile, whereas during

phototropism, lateral auxin movement occurred only at the coleoptile tip (Muday, 2001).

2.8 Effect of auxin on wall expansion

Plant cells are surrounded by cell walls, which are dynamic structures displaying a

strictly regulated balance between rigidity and flexibility. Walls are fairly rigid to

provide support and protection, but also extensible, Water accumulation in the vacuole

induces high turgor pressure, which drives plant cell growth. This strong tensile stress

presses against the plasma membrane, leading to the stretching of the cell wall

polysaccharides. The wall needs to be moderately rigid to oppose this turgor pressure, to

avoid breaking. However, the wall also has to adapt its composition by modifying and

constantly adding polysaccharides to allow cell extension (Cosgrove, 2018). Cell wall

expansion and overall cell growth is regulated via several factors, including plant

hormones. Among them, auxin plays a vital role in controlling plant growth and

development via promotion of cell division (proliferation), growth (expansion,

elongation) and differentiation (Velasquez et al., 2016). Enlargement of the cell occurs

prior to cell division, however, no changes are observed in the vacuole size at this stage.

On the other hand, cell expansion includes vacuole extension and is defined as a turgor-

driven increase in cell size, which is controlled by the cell wall capacity to extend. Cell

expansion is related to an increased ploidy level (endoreduplication), cellular

vacuolization and differentiation(Perrot-Rechenmann, 2010). Auxin activates the

expression of cell wall-related genes and stimulates the synthesis of proton pumps,

which leads to apoplast acidification (Cosgrove, 1993). Auxin also activates plasma

membrane (PM) H+-ATPases through upregulating the phosphorylation of the

penultimate of threonine of PM H+-ATPases, leading to apoplast acidification (Ren and

Gray, 2015). In an acidic environment, wall-loosening proteins are active and cause wall

enlargement. The changes in the wall trigger the cell to activate calcium channels, which

pump calcium into the wall and increase the pH, causing growth cessation. Finally,

auxin acts on the cytoskeleton (AFs and cMTs) through RHO OF PLANTS (ROP)

GUANOSINE-5′-TRIPHOSPHATASES (GTPases) and promotes trafficking of vesicles

containing new cell wall material (Gu et al., 2004).

8

2.9 Effect of auxin on root growth

Roots are considered to be a vital organ system of plants due to their involvement

in water and nutrient acquisition, anchorage, propagation, storage functions, secondary

metabolite synthesis and accumulation. They are also a major site of interaction with

mycorrhizae, nitrogen-fixing organisms and diverse pests and pathogens. In recent

years, plant root system has emerged as a central focus of research in many laboratories

across the world. The growing interest in root biology has emanated from the challenges

faced for increased demand for crop production, shrinking land resources, adverse soil

and environmental conditions (De Smet et al., 2012). To address these future concerns,

research efforts towards production of a vigorous and more efficient root system are

much warranted. This goal can be achieved by under- standing the underlying

mechanism and complexities involved in root development .Root growth and

differentiation in plants has been inextricably linked with plant hormones. Auxin is one

of the most investigated classes of plant hormones known. It is involved virtually in

every aspect of plant growth and development such as, embryogenesis, organogenesis,

tissue patterning and tropisms (Davies, 2010). Indole-3-acetic acid (IAA) is the primary

auxin present in most of the plants and is responsible for root system architecture and

various stages of root development (Lewis et al., 2011). Indole-3-butyric acid (IBA) is

another minor endogenous auxin that efficiently promotes adventitious root

development and is commonly used in horticultural practices. The paradigm shift from

classical to new molecular genetic approaches in the study of the develop- mental

plasticity of roots, strongly suggests a pivotal role of auxin in primary root (PR), lateral

root (LR) and root hair (RH) development (Benfey et al., 2010). Root development in

plants, culminates through auxin biosynthesis, transport, and its signalling. The sites of

auxin biosynthesis create a source, transport generates a gradient or local accumulation

and finally the perception or response affects root development. Other phytohormones,

such as cytokinin (CK), brassinosteroids (BR), ethylene, abscisic acid (ABA), gib-

berellins (GA), jasmonic acid (JA), polyamines (PA) and strigolactones (SL) also

integrate into these three important processes to trigger cascades of events leading to

root development (Saini et al., 2013).

2.10 Effect of auxin on fruit

Auxin controls many aspects of fruit development, including fruit set and growth,

ripening and abscission. However, the mechanisms by which auxin regulates these

processes are still poorly understood. While it is generally agreed that precise spatial and

9

temporal control of auxin distribution and signaling are required for fruit development,

the dynamics of auxin biosynthesis and the mechanisms for its transport to different fruit

tissues are mostly unknown (Pattison et al., 2014). Such genetic and physiological data

has led to a model of fruit initiation whereby a transient increase in auxin levels in the

ovary afterfertilisationactivates auxin signalling and modulates the expression of

downstream target genes to promote fruit growth (De Jong et al., 2009). Auxin is also

believed to promote continued fruit expansion though much less is known about auxin

regulation of cell division and enlargement following fruit set. In the majority of

angiosperm species, the formation of seeds is intimately linked with fruit growth and

development. Concentrations of indole-3-acetic acid (IAA), the main endogenous auxin,

are higher in the seeds than the other fruit tissues in a diverse range of species

(Devoghalaere et al., 2012). Although high auxin levels in seed tissues are associated

with the development of the embryo and endosperm, it has been suggested that the seeds

are a source of auxin that diffuses, or is transported to, other fruit tissues where it

promotes growth by cell division and expansion. Final fruit size is largely determined by

seed number, and in some cases it has been shown that a peak in auxin concentration.

Coincides with an increased rate of cell elongation, and that both are absent in seedless

fruit. Auxin activity during the different stages of fruit development is regulated via its

biosynthesis, metabolism and transport. However, until recently there has been a

remarkable lack of information about the auxin biosynthesis pathway in the fruit and

the molecular basis for establishing local auxin maxima and gradients in fruit tissues

(Tiwari et al., 2013).

10

CONCLUSION

1. During the last ten years, our understanding of auxin metabolism and its role

during plant growth and development has greatly improved. Nonetheless, there are still

many gaps in our knowledge and we lack a deep understanding of these metabolic

process. The great challenge will be to integrate knowledge about auxin metabolism into

the regulatory networks that act on different developmental processes operating in

plants, and to understand how these processes work in different plant species under

normal and stress conditions.

2. Auxin is very important Because of its potent impact on cell division, cell

growth, and differentiation, auxin is very commonly used for artificially controlling

plant growth. The most common use of auxin in our daily life is in growing plants from

cuttings. Gardeners often use a powder to stimulate root proliferation.

11

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‌أ

تەــــــــپوخ

‏بە‏ ‏پێویستیان ‏داڕوودەدان، ‏ڕووەک ‏شانەی ‏لەناو ‏سروشتی ‏بەشێوەیەکی ‏کە ‏کیمیایی ‏ماددەی هەندێک

‏لە‏ ‏گشتی ‏شێوەیەکی ‏بە ‏ئاوێتانە ‏گەشەسەندندا.ئەم ‏و ‏گەشەکردن ‏لە ‏خۆراکی ‏ڕۆڵی ‏نەک ‏هەیە رێکخستن

‏ ‏ماددەکانی ‏یان ‏) ‏ڕووەکی ‏هۆرمۆنی ‏بە ‏، ‏چالاکن ‏کەمدا ‏زۆر ‏.‏چڕبوونەوەیەکی ‏ناسراون ‏ڕووەک‏( گەشەی

‏رێکخستنی‏ ‏بە ‏هەڵدەستن ‏دابن". ‏جوڵەدا ‏لە ‏ئەوەی ‏"بۆ ‏یان ‏" ‏"هاندان ‏واتای ‏بە ‏یۆنانییە ‏وشەیەکی هۆرمۆن

ڕووەکەکان‏لەرووی‏چەکەرەکردن‏و‏گەشە‏و‏دووبارە‏بەرهەمهێنانەوە‏و‏وەڵامی‏سترێسی‏بایۆلۆجی‏و‏زیندەوەران‏

مێریستم‏و‏گەڵا‏و‏گەشەکردنی‏‏‏هۆرمۆنەکانی‏ڕووەک‏بەرهەمدێت‏لەلە‏ژێر‏باری‏ژینگەیی‏جیاوازدا‏دەدەنەوە.‏

‏باری‏ ‏بەهۆی‏قۆناغی‏گەشەو ‏، میوە.خەستی‏هۆرمۆنەکان‏دەکرێت‏جیاوازبێت‏لەنێوان‏شانەی‏ڕووەکی‏جیاواز

‏پ ‏بۆ ‏کراون ‏دابەش ‏زۆری ‏بە ‏ڕووەک ‏هۆرمۆنەکانی ‏ئەمانەن؛ئۆکسینس،‏ژینگەیی. ‏کە ‏سەرەکی ‏گروپی ێنج

‏پێداچونەوە‏دەکەین‏بەو‏شتەی‏زانراوە‏لەسەر‏کاریگەری‏ سیتۆکین،‏گیبێرلین،‏ئەسیلین،‏و‏ترشی‏ئەبسکی.‏لێرەدا

‏ئیندۆل ‏.ترشی ‏ڕووەکەکان ‏لەسەر ‏ئۆکسینەکان ‏IAAئەستێیک‏)-3-ەکانی ‏ساڵی ‏لە ‏چوار‏‏1930(, دۆزرایەوە.

‏ ‏ئەمانەن ‏هەیەکە ‏ئۆکسین ‏ئیندۆلجۆری ‏)-3-:ترشی ‏ئیندولIAAئەستێیک ‏)-3-(، ‏IBAبوترییک ،)4-

‏)-3-کلۆرۆئیندۆل ‏ئەستێیک ‏)Cl-IAA-4ترشی ‏ترش ‏فینیلەستیک ‏و )PAA‏بەهۆی‏ ‏گرینگە ‏ئۆکسین ،)

کاریگەریی‏بەهێز‏لەسەر‏دابەشبوونی‏خانە،‏گەشەی‏خانە،‏و‏جیاکاری،‏ئۆکسین‏بە‏شێوەیەکی‏زۆر‏زۆر‏بە‏کار‏

نی‏دەستکردی‏گەشەی‏ڕووەک.‏وە‏ئاستەکانی‏ئۆکسین‏جیاوازە‏لە‏نێوان‏رووەکەکان‏.‏لە‏دەهێنرێت‏بۆ‏کۆنترۆڵکرد

‏ ‏تۆوە‏‏IAAڕووەکدا ‏ولە ‏گەنج ‏گەڵای ‏و ‏سەرەتایی ‏گەڵای ‏لە ‏سەرەکی ‏شێوەیەکی ‏بە ‏یان ‏تریپتۆپهان لە

‏هۆرمۆنی‏ ‏دروست‏دەبێت. ‏‏IAAپەرەسەندووەکان ‏دابەشبوونی‏خانە ‏ڕۆڵێکی‏گرنگ‏دەبینێت‏لە ‏ڕووەکدا و‏لە

‏،‏ ‏ڕاکێشان ‏و ‏ڕووناکی ‏بۆ ‏وەڵامدانەوە ‏لە ‏بەرپرسە ‏وە ‏ڤاسکولەر، ‏شانەی ‏گۆڕینی ‏، ‏جیاکاری ‏و زۆربوون

بایۆسینتازم‏و‏گواستنەوەی‏ئۆکسین‏و‏ئاماژەکردنی‏ڕۆڵێکی‏گرنگ‏لە‏کۆنترۆڵکردنی‏گەشەی‏ڕەگدا‏دەگێڕێت.وە‏

میوە‏و‏گەشە.‏ئۆکسین‏کۆنترۆڵی‏چەندین‏لایەنی‏گەشەکردنی‏میوە‏دەکات،‏لەوانە‏دانانی

‏

کاریگەری ئۆکسینەکان لەسەر ڕووەکەکان

ەرچوونەد ەیژۆپر

یکانیەستیداوێپ ەل کێشەب کەو ،ەکراو یجۆلیۆبا یشەب ەب شەشکیپ

یجۆلیۆبا یزانست ەل سیۆرۆکالەب ەیبروانام ینانێستهەدەب

:ناوی‏قوتابی

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:‏یرشتەرپەبە‏س

یرزنجەب نیمدمح مرع مدمحی. م.

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