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
Mayapple
Yellow 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
C 2H 4
• Etilenin etkileri
- yaşlanma
- yapraktaki oksin miltarı
azalma
- cellulase gibi duvarı
inhibe eden enzimlerde
artış
- Hücrelerde şişme ve
parçalanma
Abscission program
1. Mobilizasyon
2. Cork oluşumu
3. Detachment (Ayrılma)
1. Mobilization
Önemli materyalleri ana gövdeye transport eder
–
–
–
–
Proteins
Chlorophyll
Starch
DNA
Proteins, DNA,
starch, etc
aa
signal
+
+
enzymes
aa, glucose
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 gain
and lose water by
osmosis.
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
Xerophytes:
plants adapted to a dry habitat
Halophytes:
plants adapted to a salty habitat
water
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
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
conifer needles, cactus
spines
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 yaprak
Bol miktarda besin (endospermden gelir)
Tendrils
Garden Pea
Tendrils – yaprağın blade kısmı
indirgenmiş, sarılma özelliği
Böcek kapan
Figure 11.8 (1)
• nitrojen
• Enzim
• turgor
Cotyledons or “seed leaves”
Leaves as Colorful Bracts