copyright © 2005 pearson education, inc. publishing as benjamin cummings bitki’de genel...

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings

Bitki’de genel görünüş


• Bitkilerde hayvanlarda olduğu gibi organ, doku, hücre hiyerarşisine sahip

• Root sistem ve shoot sistem

• Üç basic organ; kök (root), gövde, yaprak

Figure 35.2

Reproductive shoot (flower)

Terminal bud

NodeInternode

Terminalbud

Vegetativeshoot

BladePetiole

Stem

Leaf

Taproot

Lateral roots Rootsystem

Shootsystem

Axillarybud


Root (kök)

– Ortama bağlar

– Mineral ve su absorbe eder

– Organik madde depo eder

– Gravitropism

– Absorbsiyon tip (uç) kısma yakın yerde olur (çok sayıda ince türler, yüzey artırır)

– Lateral kök ve emici tüyler aynı mı?

– Kazık ve saçak kök


Embryonic root veya radicle


Tap (kazık) root ve Fibrous (açak) kök

Her iki tipte radicle’den orjin alır


Adventitious Roots:

Radicle’den başka yerde orjin alan kök


Modifiye kök

(a) Prop roots (b) Storage roots (c) “Strangling” aerialroots

(d) Buttress roots (e) Pneumatophores

(f) Photosynthetic roots

(f) Contractileroots


Dış Anatomi

• Root cap (Kök şapkası)

• Hücre bölünme bölgesi

• Uzama bölgesi

• Farklılaşma bölgesi


Root Cap (Kök şapkası)

• Her bir kök ucunda yüksük şeklinde olan hücre grubu

• Mekanik yaralanmaya karşı kök’ü korur

• Golgi mükilaj salgılar ve labirent oluşturur

• Yer çekiminin algısında etkili

– Amyloplastlar (statolit) hücrenin alt kısımlarında gruplaşmış


Hücre bölünme bölgesi

• Apical meristem - gün içinde bir veya iki defa bölünür

• Meristem :

– protoderm (epidermis oluşturur)

– ground meristem (zemin dokuyu verir)

– prokambium (primary phloem ve xylem)


Uzama bölgesiHücreler daha uzun ve geniş


Farklılaşma bölgesi

• epidermal hücrelerin uzantısı olarak emici tüyler oluşur

• Su alımı için yüzey artırıcı

• Kütikül kökte vardır ama emici tüylerde yok


Farklılaşma bölgesi


Lateral kök Pericycle’dan köken alır

Figure 35.14

Cortex

Vascularcylinder

Epidermis

Lateral root

100 m

1 2

3 4

Emerginglateralroot


Root Cap

Bülünme Böl.

Koteks dışına doğru büyüme

Saçaklı (Fibrous) kök, çok sayıda lateral kök oluşumu


Kök nodülü ve Azot fiksasyonu

• Atmosferde serbest azot

• Bakteri (Rhizobium, Clostridium)

• Anabaena, Nostoc

• Mycorrhiza

• Kök nodülü

• Azot fiksasyonu


Mikoriza

• Mantar Bitki ilişkisi

• Ekto ve Endo

• Arbüskül

• Fosfor, şeker


Hetetrof bitkiler• Parazit

• Genelde Fotosentez yok

• Hemiparazit: klorofil var, su minerali konakçıdan alır, stomalı yaprak, kök toprakta değil konakçı epidermisinde

• Holoparazit: klorofil yok, enerji konakçıdan alınan glikoz, yaprak yok yada indirgenmiş,


Hostorium (Emeç) kök

• Parazit

• Kök sisteminde değişim olur

• Ksilem bağlantılı, Fotosentez yapar

• Ksilem ve floem bağlantılı


Uyarılara verilen tepkiler

• Tropism

– Foto-

– Gravi-

– Kemo- (polen tüpü olusumu)

– Tigmo-


Tropism (tropizma)

• Uyarana dogru (+) veya ters (-) yönelim

• Fototropism – en iyi bilinen hareket- ısığa yönelim. Gölgede kalan hücrelerin uzaması veya üremesi. Bükülme (Curving)

• hormone auxin - auxin migrates to the shaded part of the plant and stimulates increased cell growth and elongation on the shaded part of the plant


Fototropism

• Phototropism is the growth of stems of plants toward light - it is probably the best known of the plant tropisms - phototropism is caused by elongation of the cells on the shaded part of the plant - so that entire plant bends or curves toward the light

• This growth pattern is caused by the hormone auxin - auxin migrates to the shaded part of the plant and stimulates increased cell growth and elongation on the shaded part of the plant


Tropisms: cell elongation

• In general, tropisms involve cell elongation or suppression of cell elongation on one side of a plant, causing the plant to grow in a particular direction.


Auxin

Acts by loosening cellulose microfibrils of cell walls

Causes cell expansion


Gravitropism• root will curve to grow downward

• the shoot will curve to grow upward

– Auxin

– Calcium (calcium moves to upper surfaces of shoot cells before the shoot actually curves upward and calcium moves to bottom surfaces of root cells before the root actually curves downward)

– Amyloplast (root cap of roots)


Gravitropism in shoots

• In shoots, auxins are more concentrated on the lower side of the stem, causing the cells there to elongate.


Gravitropism in roots

• In roots, however, auxin concentration on the lower side of the root suppresses cell elongation.

• The upper side of the root continues to grow, causing the roots to bend downward.


Plastids and Gravitropism

How does a root “know” which way is down?Plastids, particularly leucoplasts, in the root cap cell tend to settle on the

bottom side of the cell. This stimulates the release of auxins.


Tigmotropism

• touch or contact with a solid object

• this is most commonly seen in tendrils (modified leaves or stems depending on the species)

• the response can be rapid, a tendril can wrap around a support one or more times in less than an hour


Kirkadian Rhythms

• Gün içinde belirli zamanlarda olan hareket

• some plants open their leaves at dawn and shut them at dusk - some plants may open and shut flowers as the day changes from dawn to dusk

• Photosynthesis, auxin production, and the rate of cell division all have regular daily rhythms

• adjustments of growth, reproduction, and other activities of the organism


Plant Growth Regulator


Plant Growth Regulators

• Biyokimyasal reak. aktive eder

• Plant hormones or plant growth regulators are rather different from animal hormones in chemical structure, mode of synthesis, and function.

• Higher animals possess glands that are part of their endocrine system that are specialized organs for production of hormones

• Plant hormones on the other hand are synthesized in the cells of general organs – the stems, leaves, roots, and flowers


Plant Hormones

• Plant hormones can be divided into two classes:

– Growth promoters: Auxins, Gibberellins, Cytokinins

– Growth inhibitors: Ethylene gas, Abscisic acid


Growth promoters

• Hormones can promote plant growth in two ways:

– Stimulating cell division in meristems to produce new cells.

– Stimulating elongation in cells.


Auxin activity

Auxins stimulate genes in cells associated with plant growth.


Auxin roles

• Auxins carry out multiple roles having to do with plant growth including:

– Tropisms

– Apical dominance

– Growth of adventitious roots

– Fruit growth


Auxin= Indole Acetic Acid (IAA)

1) Functions in phototropism = movement toward light

- Auxin concentrated on dark side

- Induces cell expansion / elongation


Apical dominance

• Auxins are released from the shoot tip. These stimulate cell elongation in the stem, but suppress the lateral buds.

• Cytokinins, produced in the roots, can stimulate lateral buds if the shoot tip is removed.


Auxinapical dominance

Auxins produced by apical meristem

Inhibits growth of lateral branches

If apical meristem damaged, auxin production stopsNo longer inhibits lateral branch growth

lateral buds ---> branches


Adventitious roots

• Adventitious roots are those growing out of places where roots don’t normally grow.

• Auxins stimulate root growth on the end of a houseplant cutting..


Fruit growth

• Developing seeds produce auxins that stimulate growth of the plant ovary into a fruit.

• Removal of seeds from a strawberry prevents the fruit from growing, but add auxin and will grow.

• How could this be used in commercial agriculture?


Gibberellins1) Function in seed germination

- Embryo releases gibberellins

- Causes aleurone layer (in seed coat) to release enzymes (alpha-amylase): break down starch in endosperm to sugars (e.g., maltose)

E.g.,germinatio

nof barley(beerproduction)


Gibberellins

2) Fruit development

Seedless fruit crops (e.g., grapes) may be artificially sprayed with gibberellins - make fruits bigger


Gibberellins

3) Stem growth (elongation, longer internode)

gibberellins added


Functions of Cytokinins

• Promote growth of lateral buds when auxin concentrations are low.

• Promote cell division in meristems.

• Stimulate fruit and seed development.

• Delays senescence of plant parts.


Functions of Ethylene

• Released by fruits and causes the fruits to ripen faster.

• Causes plant parts to age and die (senescence).

• Inhibits stem elongation.


• Which of these methods will make your tomatoes ripen faster and why?

– Putting them on a sunny windowsill.

– Putting them in a paper bag.

WORK

TOGETHER


Functions of Abscisic Acid

• Controls seed and bud dormancy.

• Inhibits gibberellins.

• Promotes senescence in plants.

copyright © 2005 pearson education, inc. publishing as benjamin cummings bitki’de genel...

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