Advances in Environmental Biology Azalea alexander Ahmad Majd,

Advances in Environmental Biology, 8(22) November 2014, Pages: 389-393
AENSI Journals
Advances in Environmental Biology
ISSN-1995-0756
EISSN-1998-1066
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A study of Anther development in Azalea alexander L.
1Ahmad
1
2
Majd, 1Maryam Mohana, 1Sayeh Jafari, 2Shadi Kiabi, 1Maryam Paivandi
Department of Biology, Faculty of Biological Sciences, North- Tehran Branch, Islamic Azad University, Tehran, Iran.
Department of Biology, Faculty of Biological Sciences, Tonekabon Branch, Islamic Azad University, Tonekabon, Iran.
ARTICLE INFO
Article history:
Received 25 September 2014
Received in revised form
26 October 2014
Accepted 25 November 2014
Available online 31 December 2014
Keywords:
Azalea
alexander
L.,
Anther
development,
microsporogenesis,
pollen grain.
ABSTRACT
Azalea alexander L. is belonging to Ericaceae family. In this study, anther development
and microsporogenesis of Azalea alexander L. were considered. The flowers, in
different developmental stages, were collected, fixed in Formalin -glacial acetic acidalcohol (FAA), stored in 70% ethanol, embedded in paraffin and then, sliced at 7-10 μm
by rotary microtome and Stained by Eozine and hematoxylin. The results indicated that
Anther walls development followed the dicotyledonous type and were tetrasporangiate
with composed of epidermal layer, endothecium layer, middle layers and tapetum layer.
Microspore tetrads are tetrahedral tapetum layer was secretory type. Pollen grains are
tricolporate. The nucleus is divided by the mitosis into two nuclei, small generative and
large vegetative nuclei that's why they are called bi- nucleated pollen grain.
© 2014 AENSI Publisher All rights reserved.
To Cite This Article: Ahmad Majd, Maryam Mohana, Sayeh Jafari, Shadi Kiabi, Maryam Paivandi., A study of Anther development in
Azalea alexander L. Adv. Environ. Biol., 8(22), 389-393, 2014
INTRODUCTION
Azaleas alexander L. are one of the most important of garden plants. The majority of naturally occurring
species are native to the areas in western and central China . Azaleas belong to family of Ericaceae and genus
of Rhododendron.
The genus Rhododendron belongs to tribe Rhodoreae. [1,3].
They require acid soils and protection from the cold and wind. Appropriate soil for this plant is peat and
soil's drainage must be excellent [20].
It's flowers in the different colors are red, violet, white, pink and yellow. Few other everegreen shrubs
produce such a spectacular floral display in March and April. The leaves are deciduous or perennial it is a shrub
and has alternate leaves. It's height reaches 1.5 meter [20].
It has 8 stamens with oblong anther. Often Azaleas are planted near foundations, steps and decks to soften
architectural features [1].
Notably, there is not enough information about anther structure and male gametophyte developmental
stages of Azalea alexander L.. Development of male gametophyte involves a series of occurrences to produce
and release mature pollen grains from anther .
The main aim of this paper was to investigate a detailed study on microsporogenesis of Azalea alexander
L., for improving the knowledge of microsporogenesis developmental events and for evaluating of taxonomic
relationship among Azalea species.
MATERIAL AND METHODS
In this research flowers from natural population were collected at different developmental stages between
8:00 - 9:00 AM, from Chalus in north of Iran.
Flowers were fixed in FAA (Formalin –glacial acetic acid- alcohol). After the fixation process; the samples
were dehydrated during alcohol series (15, 30, 50, 70), and embedded in paraffin after the process of paraffin
saturation in toluene. And sections with a thickness of 7-10 m using a rotary microtome. Staining was carried
out with Eozine and Hematoxylin [23,9].
Corresponding Author: Maryam Mohana, Department of Biology, Faculty of Biological Sciences, North- Tehran Branch,
Islamic Azad University, Tehran, Iran.
E-mail: mohana.maryam@yahoo. com
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Advances in Environmental Biology, 8(22) November 2014, Pages: 389-393
Several sections for each anther developmental stages were investigated with a Zeiss Axiostar plus light
microscope. Many samples were studied before each stage and photomicrographs were made from the most
effective ones.
Result:
Each pollen sac was concluded of peripheral cells forming an undifferentiated walls and a mass of
uniformed cells (archeosporial cells) (fig1A).
Each young anther was consisted of 4 pollen sacs (tetrasporangiate) with connective tissue in the center (Fig
1C).
From the cross section we see that the anther wall consists of layers from outer to inner: epidermis,
endothecium, middle layer and layer of tapetum (Fig. 1D).
Taptum layer Azalea alexander L. was secretory type in this development stage. microspore mother cells
(Microsporocytes), were also detectable (Fig1B).
Microspores and pollen grains are produced from pollen mother cells (Microsporocytes), PMCs within
loculus anthers of the flower. Microsporocytes are recognizable by their large volume, dense cytoplasm, and
conspicuous nuclei. The single cell layer of tapetum surrounding the anther loculus is first recognizable at the
early Microsporocyte stage .
Large volume, dense cytoplasm and one or two large nuclei are evident in the tapetal cells at this point.
Each microspore mother cell undergoes meiosis; during which M.M.C undergo successive type.
Fig. 1: A: Archeospore cells; B:Microspore mother cells(M.M.C) C:Tetrasporangiate anther with connective
tissue (Con) D:Each anther contains four layers: epidermis (Epi), endothecium (End), middle layer
(Mid) and tapetum (Ta) E: Pollen grains in dyad stage F: A dyad cell with callosic wall (C.W)
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Fig. 1G: Terahedral tetrads (Tet) in the anther loculus H: callosic wall in a tetrad cell I: adult anther with
endothecium layer (End) J: endothecium (End) layer are tangentially elongated K: pollen grain with
Exin (Ex) and Intin (In), nucleus (Nu) In early stage of meiosis, Microsporocytes separate with callose
walls; The first nuclear division of meiosis. (meiosis I) is accompanied by cell wall formation
resulting in the formation of two haploid cells in a dyad (fig1 E,F).
After meiosis II numerous tetrads of microspores appear, tetrad shape is tetrahedral and the wall formation
taking place after each stage of meiosis.
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Then the wall surrounding the each microspore cells dissolve and the microspores in the pollen sac are
released.
The mitotic division of the microspore is unequal. Therefore, a darker generative nucleus and a lighter
vegetative nucleus appear. So pollen grains are two-celled at the time of shedding. Exin (Ex) and Intin (In) are
formed in this stage (fig 1K).
when pollen grains become mature, the tapetal cells were degenerated, In meiotic division, the middle
layers cells start a degeneration process. After the tetrads are formed, the inner most of the middle layers begins
to degenerate and all of them become flatted during the free microspore stage and have degenerated completely
at the mature pollen grain stage. Pollen grain is tricolpated.
Discussion:
Results obtained from this research show that Developmental stages of Azalea alexander L. anther wall
followed the dicotyledonous type, which was composed of an epidermal layer, an endothelial layer, one middle
layer and tapetum which is consistent with Davis 1966 and bagheri 2014. The tapetum was secretory that was
similar with the findings of Chehregani et al., [8] and bagheri [2] for Lepidium vesicarium L and Lepidium
sativum L. for Azalea alexander L.. The anther tapetum is the main supplier of nutrients and cell wall
precursors for developing pollen grains [21].
A sharp correlation was observed between division in microspore mother cells (M.M.Cs) and development
of anther`s tapetum. That was reported for other dicotyledonous plant [6,13,10].
The microspores at releasing time are vacuolated and they have peripheral nucleus. The nucleus is then
divided during mitosis into two nuclei, a small generative nucleus, and large vegetative nucleus, hence the name
bi- nucleated pollen grain, which is in accordance with findings of chehregani and jafari [8,16].
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