Plant Structures Plant Science. Major Plant Parts roots stems leaves buds flowers 2.
Bio presentation (internal structures of leaves)
37
INTERNAL STRUCTURES OF LEAVES A P RESE NTATION BY T A BLE 4
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Transcript of Bio presentation (internal structures of leaves)
INTE
RNAL STR
UCTURES
OF LE
AVES
A P
RE
SE
NT A
TI O
N B
Y T
AB
L E 4
MADE UP OF THE FOLLOWING:
o Upper epidermis: Upper layer of cells. No chloroplasts. Protection.
o Cuticle: Waxy layer water proofing upper leaves.
o Palisade Mesophyll: Tightly packed upper layer of chloroplast containing cells.
o Spongy Mesophyll: Lower layer of chloroplast containing cells. Air spaces around them.
o Lower Epidermis: Lower external layer of cells in leaf.
o Vascular Bundle: Bundle of many vessels (xylem and phloem) for transport.
o Xylem: Living vascular system carrying water & minerals throughout plant.
o Phloem: Living vascular system carrying dissolved sugars and organic compounds throughout plant.
o Guard Cells: Cells surrounding stomata that control rate of gas & water exchange.
o Stomata: Opening between guard cells for gas & water exchange.
INTE
RNAL STR
UCTURE O
F
LEAV
ES
I N G
EN
ER
AL
EPIDERMIS
A layer of thick, tough cells on the top and bottom of leaves. Protect the leaves
Cuticle
1. Produces a waxy layer called cutin, which protects the leaf from dehydration
2. Increases with light intensity
Leaf hairs (Trichomes)
3. Extension of epidermal cells
4. Gives plant leaves or stems distinctive textures
5. Keep insects at bay and secretes toxic or sticky fuilds for protection
CUTICLE AND TRICHOMES
TRICHOMES
MESOPHYLL
Mesophyll cells are specialized for photosynthesis. These cells in the middle of the leaf contain many chloroplasts, the organelles that perform photosynthesis.
o Tightly packed layer of parenchyma cells
o Filled with chloroplasts
o Palisade cells are cylindrical in shape
PALISADE LAYER
o Contains less chlorophyll but photosynthesis still takes place in these layer
o Layer of parenchyma tissues loosely arranged to facilitate movement of gases
SPONGY MESOPHYLL
SPONGY MESOPHYLL
Commonly known as leaf veins.Xylem o Adaxial in position transport
waterPhloemo Abaxial in position transports
nutrients
VASCULAR BUNDLE
XYLEM AND PHLOEM
o Natural openings in leaves that allow transpiration and photosynthesis
STOMATA
o Special epidermal cells that open and close I response to stimuli
o Control the size of the stomata
GUARD CELLS
GUARD CELL AND STOMA
INTE
RNAL STR
UCTURE O
F
LEAV
ES
I N D
I CO
T L
EA
VE
S
EPIDERMIS
o Single layer of cells.o Two parts, lower and upper epidermis.
These are called lower epidermis and upper epidermis respectively.
o Regulates the exchange of gases ( oxygen and carbon dioxide ).
o The cells are barrel shaped and are arranged without intercellular spaces.
o Trichomes serves as protection from water loss.
o Epidermis is covered by cuticle towards outside that protects the leaf from dessication.
o Epidermis shows multicellular hairs and minute pores called stomata.
o Each stoma is surrounded by two specialized kidney shaped cells called the guard cells.
o Stomata are present on both sides and their number is more towards lower epidermis.
o Epidermis gives protection, regulates transpiration and useful for exchange of gas.
LEAF EPIDERMIS (DICOT)
MESOPHYLL
The tissue present between upper and lower epidermis.
PALISADE PARENCHYMA
Below the upper epidermis 1-3 layers of palisade parenchyma is present. It shows elongated columnar cells with small intercellular spaces. As more number of chloroplasts is present, it is mainly useful for assimilation.
SPONGY PARENCHYMA:
Part of the mesophyll towards lower epidermis is called spongy parenchyma. It is 3-5 layered made up of irregular shaped cells with large intercellular spaces. The cells have chloroplasts and their number is less than those of palisade parenchyma. Spongy tissue is primary useful for exchange of gases and secondarily for photosynthesis.
VASCULAR BUNDLE
o Vascular bundles are extended in the mesophyll in the form of veins. These are big at the base of the lamina and small towards margins and apex.
o The vascular bundles are conjoint, collateral and closed. The xylem is present towards upper side (adaxial) and phloem towards lower epidermis.(abaxial).
o The vascular bundle is surrounded by a layer of specialized mesophyll cells called bundle sheath or border parenchyma. The cells are arranged compactly and may or may not contain chloroplasts.
o The bundle sheath cells and grows towards upper and lower sides called bundle sheath extensions. They help in conduction of food materials from mesophyll to the vascular bundles.
DICOT LEAF
INTE
RNAL STR
UCTURE O
F
LEAV
ES
I N M
ON
OC
OT
LE
AV
ES
EPIDERMIS
o On both the sides of the leaf a single layered epidermis is present. The cells are barrel shaped and are arranged compactly without intercellular spaces.
o The epidermis is covered by cuticle outside the epidermis.
o Stomata are found equal in number in both the epidermal layers.
o Trichomes are absent. In some monocots particularly in grasses, some upper epidermal cells are enlarged, specialized and formed into bulged cells and filled with water. These are called bulliform cells or motor cells. These help in rolling and unrolling of leaf.
o The epidermis gives protection to inner tissues, helps in transpiration and exchange of gases.
LEAF EPIDERMIS (MONOCOT)
MESOPHYLL
The tissue present between upper and lower epidermis is called mesophyll.
It may be made up of columnar cells (or) spongy cells. The cells are loosely arranged having intercellular spaces. The cells contain chloroplasts and perform photosynthesis.
VASCULAR BUNDLES
o Several vascular bundles are present in the mesophyll in the form of veins parallelly.
o The vascular bundles are conjoint, collateral and closed. Xylem is present towards upper epidermal side and phloem towards lower epidermal side.
o Each vascular bundle is surrounded by a layer of specialized mesophyll cells called ‘border parenchyma’ or ‘bundle sheath’.
o a. Bundle sheath cells are chlorophyllous (or) non chlorophyllous.
o They show lignosuberised bands on their radial and transverse walls suggesting endodermal nature.
o The tissue present on the upper and lower sides of vascular bundles is called bundle sheath extensions. They give mechanical strength as they are sclerenchymatous.
MONOCOT LEAF
Dicot leaf Monocot leaf1. More stomata towardslower epidermis.2. Bulliform cells areabsent3. Mesophyll isdifferentiated intopalisade and spongytissues.4. Bundle sheathextensions areparenchymatous
1. Stomata are equallydistributed on both thesides of leaf. 2. Bulliform cells arepresent in the upperepidermis.3. Mesophyll isundifferentiated. 4. Bundle sheath extensionsare sclerenchymatous.
COMPARISON
END OF PRESENTATION
