LEAVES: FORM & FUNCTION

LEAVES: FORM & FUNCTION

• Fonksiyon• External Anatomy

• Internal Anatomy ????• Absisyon

• Transpirasyon• Specialized Leaves

The Plant Body: Leaves

• Fonksiyon– Güneş enerjisi ve CO2

toplayıcısı– Bazı bitkilerde belirli fonk.

İçin özelleşmiş (modifiye)– Transpirasyon

Dış Anatomi• blade veya lamina

• marjin

• Vein (vascular bundles)

• petiole

• stipule

EXTERNAL ANATOMY

Filotaksi – gövdede yaprak dizilimi

Yaprak çeşitleri: Simple, compound, peltate ve perfoliate

• Simple leaf = bölünmemiş lamina, petiol tabanında tek axillary bud

• Compound leaf = leaflet (yaprakçık) halinde, leafletlarda axillary bud yok sadece compund yaprak tabanında bulunur

– pinnat-compound leaves: yaprakçıklar çiftli ve merkezi rachis üzerinde (gül)

– palmat-compound leaves: yaprakçıklar petiolün sonunda aynı noktadan çıkar (at kestanesi)

• Peltate leaves = petiol blade ortasından bağlanır

• Perfoliate leaves = sessile leave (yapışık yaprak) stemi çevreler

Leaf types – Pinnately & Palmately Compound Leaves

Peltate & Perfoliate Leaves

MayappleYellow Wort

Venation (Damarlanma) = yaprakta venlerin dağılımı

• Netted-venation = bir veya birkaç dominant midvein vardır aralarda daha ince ağsı damarlar bulunur (dicotlar) – Pinnately-veined leaves = midrib denen ana damar, burdan

orjinlenen secondary veinler – Palmately-veined leaves = veinler blade tabanından ayrılır (maple).

• Paralel venation = monocots (grasses, cereal grains); venler birbirine paralel

• Dikotomus venation = midrib veya büyük venler yok; benzer ebatta cok sayıda ven çatal oluşturarak tabandan iki farklı yöne gider, fan şekilli yaprak

Venation Types

Netted or Reticulate Venation

Absisyon

Abscission

Auxin (Oksin, IAA) Etilen (C2H4) absisyona etkisi??

IAA

C2H4

• Etilenin etkileri - yaşlanma

- cellulase gibi duvarı inhibe eden enzimlerde artış - Hücrelerde şişme ve parçalanma

- yapraktaki oksin miltarı azalma

Abscission program1. Mobilizasyon

2. Cork oluşumu

3. Detachment (Ayrılma)

1. MobilizationÖnemli materyalleri ana gövdeye transport eder

– Proteins– Chlorophyll– Starch– DNA

aa

enzymes

Proteins, DNA, starch, etc

aa, glucose

signal+

+

2. Cork formation – Absisyon zonu altında:

• Absisyon zonunun altındaki parenkimatik hücreler cell wall’da suberin ve lignin miktarını artırır (protective cork)

3. Detachment – abscission zone:

• Parenkima hücreleri bazi cell wall enzimleri salgılar (glucanases and pectinases); self digest

• Hücler su alır şişer

TRANSPIRATION• Plants must supply water to all their

tissues. It moves from the roots up the stem to the leaves by capillary action.

• The evaporation of water vapor from plant surfaces is called transpiration.

• Stoma neden var

• Stomanın açılıp kapanması transpirasyonu düzenler

• Az Su, düşük sıcaklık, ışık ; kapalı

• gündüz açık gece kapalı

• guard cells

Stomatal control

GUARD CELLS AND PLANT HOMEOSTASIS

• kidney-shaped with thick inner walls and thin outer walls.

• When they become full of water (turgid) the unevenness of the walls causes them to bow outward and the stomate opens.

• When they lose water they become less turgid and the stomate closes.

• Guard cells gainand lose water byosmosis.

Stomatal guard cells• Environmental factors are sensed by

guard cells– Light intensity, temperature, relative

humidity, intercellular CO2 concentration

• Integrated into well defined responses– Ion uptake in guard cell – Biosynthesis of organic molecules in guard

cells• This alters the water potential in the guard cells • Water enders them • Swell up 40-100%

Plants and water

• Bitkiler dehidrasyondan uzak durmak ister

• water conservation X CO2 assimilation

– Bazı yapılar su dengesinde önemli– 1: iyi gelişmiş root– to get water from soil– 2: suya direnç götermeyen taşıma– xylem– 3: leaf cuticle – reduces evaporation

– 4: stomata – controls water loss and CO2 uptake

– 5: guard cells – control stomata.

Habitatlara göre bitkiler

Mesophytes: plants adapted to a habitat with adequate water

Xerophytes: plants adapted to a dry habitat

Halophytes: plants adapted to a salty habitat

Hydrophytes: plants adapted to a freshwater habitat

Hydrophyte:Nemli ortam

Xerophytes

• Sunken stoma

• Hair, air current

• Waxy cuticle waterproof

• Rolled leaf

• Daha az stoma

• Küçük yaprak

• İyi kök sistemi

Adaptation How it works Example

thick cuticle stops uncontrolled evaporation through leaf cells

small leaf surface area

less surface area for evaporation

conifer needles, cactus spines

low stomata density

smaller surface area for diffusion

sunken stomata maintains humid air around stomata

marram grass, cacti

stomatal hairs (trichores)

maintains humid air around stomata

marram grass, couch grass

rolled leaves maintains humid air around stomata

marram grass,

extensive roots maximise water uptake cacti

Left and right Epidermis of the cactus Rhipsalis dissimilis. Left: View of the epidermis surface. The crater-shaped depressions with a guard cell each at their base can be seen.Right: X-section through the epidermis & underlying tissues. The guard cells are countersunk, the cuticle is thickened. These are classic xerophyte adaptations.

Transverse Section Through Leaf of Xerophytic Plant

.

Specialized or Modified Leaves

• In pine trees, the leaves are adapted to living in a dry environment too.

• Water is locked up as ice during significant portions of the year and therefore not available to the plant; pine leaves possess

– sunken stomata,

– thick cuticles

– needle-like leaves

– hypodermis, which is an extra cells just underneath the epidermis –

Cotyledons or “seed leaves”

Çinlenen tohumun ürettiği ilk yaprakBol miktarda besin (endospermden gelir)

Tendrils

Garden Pea

Tendrils – yaprağın blade kısmı indirgenmiş, sarılma özelliği

Figure 11.8 (1)Böcek kapan

• nitrojen• Enzim• turgor

Cotyledons or “seed leaves”

Leaves as Colorful Bracts