MORFOGENESIS TUMBUHAN 2013(1).pptx

MORFOGENESISTUMBUHAN

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WHAT IS MORPHOGENESIS …..?

PENDAHULUANDefinisi Morfogenesis:

Morfo berarti bentuk dan genesis berarti asal mulaAsal mula terjadinya suatu bentuk

Beberapa pendapat:

Menurut Strasburger (1978): Morfogenesis adalah proses pembentukan organisme yang dipengaruhi faktor internal (endogen)dan fektor eksternal (exogen).

Menurut Hill (1982) : Morfogenesis adalah proses pertumbuhan dan perkembangan bentuk, diferensiasi suatu organisme.

Strassburger (1978), menyatakan bahwa pengertian morfogenesis ada 2 kelompok, yatu:

1. AUTOMORFOSE Proses pembentukan yang dipengaruhi gen, a.l perkembangan organ generatif Angiospermae , yaitu selama pembentukan bunga yang dilengkapi dengan polen, maka kemudian dapat terbentuk biji, sedangkan yang tidak dilengkapi oleh pembentukan polen, kemudian tidak berbiji.

2. HETEROMORFOSE Proses pembentukan yang dipengaruhi oleh adanya induksi dari luar, a.l oleh adanya cahaya àfotomorfose; adanya air àhidromorfose dan oleh pengaruh panas àtermomorfose.Berdasarkan kedua kelompok ini maka tumbuhnya organisme mengikuti konsep morfogenesis.

MORPHOGENESIS AND DIFFERENTIATION

Morphogenesis- the development of form.

Differentiation- a process by which a relatively unspecialized cell undergoes a progressive change to form a more specialized cell.

INTERNAL ORGANIZATION OF THE PLANT BODY

Tissue- a group of similar cells organized into a structural and functional unit.

Tissue System- a tissue or group of tissues organized into a structural and functional unit; larger units of the plant body.

There are 3 Tissue Systems Ground Vascular Dermal

GROUND TISSUE Parenchyma

Polyhedral to round in shape. Occur throughout the plant body. Photosynthesis, storage, and secretion.

Collenchyma Elongate in shape. Occur beneath the epidermis in young

stems. Support young growing tissues.

Sclerenchyma- fibers and sclereids. Long or stellate in shape. Occur throughout the plant body. Support (strengthen) and storage.

VASCULAR TISSUE Xylem- principal water-

conducting tissue in vascular plants; dead at maturity; lignified.

Tracheary Elements Tracheid- elongate and

tapering; pits, but no perforations; seedless vascular plants, gymnosperms, and some angiosperms.

Vessel element- elongate; pits and perforations; angiosperms.

VASCULAR TISSUE #2 Phloem- principal food-

conducting tissue in vascular plants; living at maturity; not lignified.

Gymnosperm Sieve Elements Sieve cell- elongate & tapering;

with sieve areas. Albuminous cell- elongate &

tapering; delivers substances to sieve cells.

Angiosperm Sieve Elements Sieve-tube element- elongate &

tapering; with a sieve plate. Companion cell- variable; delivers

substances to sieve-tube elements.

DERMAL TISSUE Epidermis- outermost cell layer

of the primary plant body. Variable in shape; guard cells

and trichomes. Outermost layer of plant body. Protective (cuticle and water

loss) and aeration (stomata). Periderm- secondary

protective tissues. Rectangular in shape; cork cells. Beneath the epidermis. Protective and aeration

(lenticels); replaces epidermis.

TAHAP PROSES PERTUMBUHAN

Ada 3 tahap proses pertumbuhan1. Tahap seluler2. Tahap organ3. Tahap individu

TAHAP SELULERPertumbuhan serta perkembangan sel, terdiri dari 4 tahap, yaitu: -Tahap pembelahan sel, -pertambahan plasma,-perpanjangan sel -dan diferensiasi.

Pembelahan sel- Terbatas pada daerah meristem, - Mitosis atau amitosis dan meiosis

Pertambahan plasma, dan perpanjangan sel.Selama sel masih hidup dan dalam pembelahan sel, akan terjadi pertambahan plasma.Salah satu pembuktian adanya pertambahan plasma dapat diukur dari berat kering, atau dengan adanya penambahan volume serta oleh adanya perpanjangan sel.

-Pengukuran pertumbuhan, dari adanya pertambahan protoplasma dapat diukur melalui berat kering (Karena kandungan bahan hidup dari sel adalah: karohidrat, lemak dan protein, sebagai hasil metabolisme).

Pertambahan plasma, dan perpanjangan sel. Bagaimana dengan pengukuran berat kering biji yang sedang berkecambah? Tepatkah mengukur pertambahan protoplas dari berat keringnya?. Pengukuran apakah yang lebih tepat?

DiferensiasiSetelah pembelahan sel, akan terjadi perubahan-perubahan, a.l: pembentukan organel-organel sel seperti mitokondria, kloroplas, yang kemudian akan terjadi pembentukan jaringan-jaringan khusus perubahan ukuran sel ,bentuk dan fungsi sel.

BAGAIMANA HUBUNGAN PERTUMBUHAN DENGAN DIFIRENSIASI :1. Adakah pertumbuhan tanpa diferensiasi ?2. Adakah diferensiasi tanpa pertumbuhan ?

BAGAIMANA HUBUNGAN PERTUMBUHAN DENGAN DIFIRENSIASI :1. Adakah pertumbuhan tanpa diferensiasi ?2. Adakah diferensiasi tanpa pertumbuhan ?

1. Pertumbuhan tanpa diferensiasi:- terbentuknya endosperm biji- terbentuknya kalus

Diferensiasi tanpa pertumbuhan:- Pembentukan sporocarp pada jamur lendir: Pembentukan agregasi myxoamoeba à membentuk pseudoplasmodium à sorus

Proses diferensiasi dapat dipelajari dari:

1. Struktur /Konfigurasi : sel --- jaringan --- diferensiasi.2. Aspek ontogeni: perubahan dari tumbuhan muda ke dewasa.3. Faktor lingkungan : perubahan struktur.4. Faktor fisiologi.

STRUKTUR /KONFIGURASI DIFERENSIASIAda 2 macam diferensiasi :- Diferensiasi external Pembentukan bagian vegetatif yang diteruskan menjadi pembentukan bagian generatif.- Pembentukan bunga dari primordial bunga yang kemudian membentuk pola dengan terbentuknya sepal, stamen dan karpel.- Metagenesis

STRUKTUR /KONFIGURASI DIFERENSIASIAda 2 macam diferensiasi :- Diferensiasi external

- Diferensiasi internal- Mitosis dan meiosis- Pembentukan jaringan (teori Hanstaein).

DIFERENSIASI SECARA ONTOGENISecara umum akan terjadi diferensiasi adalah karena adanya proses ontogeni yang dipengaruhi faktor genetis.

Perkembangan batang :Batang primer yang berkembang dari protoderm, prokambium dan meristem dasar.Pucuk batang, umumnya terdiri atas axis dengan ruas-ruasnya serta primordia daun, yang akan tersusun pada batang dengan sebutan filotaksis.

DIFERENSIASI KARENA LINGKUNGANAdanya perubahan struktur, akibat adanya pengaruh faktor lingkungan seperti cahaya, air, temperatur dan zat kimia.

Sebagai contoh perkecambahan biji kacang hijau, akan cepat apabila dalam keadaan tidak ada cahaya. Biji Bayem harus ada cahaya untuk berkecambah.Temperatur yang cukup tinggi dapat mempengaruhi perubahan fase vegetatif menjadi fase pembentukan organ generatif. Pada musim panas, maka fase pembungan akan cepat terbentuk.

DIFERENSIASI KARENA FISIOLOGIUmumnya proses diferensiasi, akibat adanya proses fisiologi.

Seperti pembentukan akar pada kultur jaringan memerlukan penambahan zat pengatur tumbuh golongan auxin

PEMBENTUKAN/PERKEMBANGAN

BUNGA

The shoot meristem of dicotyledons, which gives rise to the stalk and leaves, is comprised of three layers: L1 (outermost layer, 1 cell thick) L2 (lies beneath L1, 1 cell thick) L3 (inner most layer) L1 & L2 comprise the tunica and divide by anticlinal divisions (perpendicular to layer). L3 cells divide in any plane and make up the corpus.

Cell fate has been determined by generating chimeric tissues. Chimeras are composed of cells of different genetoypes and are made by treatment with radiation or chemicals (colchicine). Periclinal chimeras have one of the three layers marked differently.

In angiosperms, L1 becomes the epidermis while L2 & L3 produce cortex and vascular tissue. Occassionly L1 or L2 cells divide periclinally, invade a new layer and adopt the fate of the new layer (regulative).







GENETIC CONTROL OF FLOWERING Flower formation

Involves a phase change from vegetative growth to reproductive growth

Is triggered by a combination of environmental cues and internal signals

The transition from vegetative growth to floweringIs associated with the switching-on of floral meristem identity genes

Plant biologists have identified several organ identity genes That regulate the development of floral pattern

Figure 35.30a, b

(a) Normal Arabidopsis flower. Arabidopsisnormally has four whorls of flower parts: sepals(Se), petals (Pe), stamens (St), and carpels (Ca).

(b) Abnormal Arabidopsis flower. Reseachers haveidentified several mutations of organ identity genes that cause abnormal flowers to develop.This flower has an extra set of petals in place of stamens and an internal flower where normal plants have carpels.

Ca

St

Pe

Se

Pe

Pe

Se

Pe

Se

The ABC model of flower formation Identifies how floral organ identity genes direct the

formation of the four types of floral organs

Petals

Stamens

CarpelsAB

Sepals

C

C geneactivityB + C

geneactivity

A + Bgene

activity

A geneactivity

(a) A schematic diagram of the ABChypothesis. Studies of plant mutationsreveal that three classes of organ identitygenes are responsible for the spatial patternof floral parts. These genes are designated A,B, and C in this schematic diagram of a floralmeristem in transverse view. These genesregulate expression of other genesresponsible for development of sepals,petals, stamens, and carpels.

(b) Sepals develop from the meristematic region where only A genes are active.

(c) Petals develop where both A and B genes are expressed. Stamens arisewhere B and C genes are active.

(d) Carpels arise where only C genes are expressed.

Figure 35.31a

An understanding of mutants of the organ identity genes

Depicts how this model accounts for floral phenotypes

Figure 35.31b

StamenCarpel

Petal

Sepal

Wild type Mutant lacking A Mutant lacking B Mutant lacking C

(b) Side view of organ identity mutant flowers. Combining the modelshown in part (a) with the rule that if A gene or C gene activity is

missing, the other activity spreads through all four whorls, we can explain thephenotypes of mutants lacking a functional A, B, or C organ identity gene.

Activegenes:Whorls:

A A C C C C AA CCCCCCCC A A C C C C AB B B B B B BB

A A B B A A B B AA A A A

Flower Development Flowers develop from the shoot meristem and

contain the reproductive cells of higher plants. In most plants, environmental controls (day length and temperature) drive the transition from shoot meristem to floral meristem. Complex mechanisms pattern the flower to form the sepals, petals, stamens & carpels. Three classes of genes are involved in basic flower patterning. 1) Organ genes identify different floral organs (much like homeotic selector genes in animals). 2) Cadastral genes set boundaries of organ gene expression. 3) Meristem identity genes convert shoot into floral meristem.




Homeotic genes control organ identity Shoot meristem converts to inflorescence meristem which can form one or more floral meristems.

The floral organ primordia arise from floral meristem by cell differentiation and enlargement. 4 concentric whorls reflect the order within the floral meristem. Sepal (whorl 1) from the outer ring. Petals (whorl 2) from the next ring. Stamens (whorl 3; male reproduction) from the inner ring. Carpels (whorl 4; female reproduction) from the centre.

In Arabidopsis there are 15 separate primordia (4 sepals, 4 petals, 6 stamens and 1 pistil [with 2 carpels]).






Model of gene activity in floral organ development. The floral meristem is divided into three overlappng regions, A, B and C. Region A contains whorls 1 & 2, B contains whorls 2 & 3, and C covers whorls 3 & 4, This combination of a, b and c regulatory functions give each whorl an unique identity. In addition, the aand c regulatory functions must be mutually exclusive such that a prevents c activity and vise versa. A floral meristem region with ... a function only produces sepals, a & b functions produce petals, b & c functions produce stamens and c function only produces carpels. Homeotic mutants eliminate either a, b or c function.




The transition to a floral meristem is under environmental and genetic control Flowering in Arabidopsis is controlled by internal and external factors. The apical meristem generates leaves during the vegetative phase but undergoes a transition to a floral meristem in one of two ways. Determinate transition: the inflorescence meristem becomes the terminal flower. Indeterminate transition: the inflorescence meristem becomes a number of floral meristems (as in Arabidopsis). Leafy and apetala1 are floral meristem identity genes. Mutants in these partially transform flowers into shoots.


13. DESCRIBE HOW THE STUDY OF TOMATOES HAS CONTRIBUTED TO THE UNDERSTANDING OF FLOWER DEVELOPMENT.

Environmental cues (ex: day length) initiate processes that convert shoot meristems to flower meristems

This induction is exemplified by tomato flowers

Mixing mutant and wild-type plants resulted in floral meristems in which the three cell layers did not all arise from the same “parent”

These layers’ sources were traced and it was determined that the number of organs/flowers depended on genes in the L3 cell layer (the innermost)

14. DESCRIBE HOW THE STUDY OF ARABIDOPSIS HAS CONTRIBUTED TO THE UNDERSTANDING OF ORGAN IDENTITY IN PLANTS.

Organ-identity genes determine the type of structure that will grow from a meristem- they are analogous to homeotic genes- they are divided into 3 classes: A, B, and C these 3 genes direct the formation of four types of organs

They appear to be acting like master regulatory genes that control the transcription of other genes directly involved in plant morphogenesis- do Not contain the homeobox sequence

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MORFOGENESIS TUMBUHAN 2013(1).pptx