Leaves are the main sites of photosynthesis in plants. Through structures like chloroplasts and the green pigment chlorophyll, leaves are able to convert sunlight, carbon dioxide and water into oxygen and sugars that plants can use as food. Leaves come in different shapes and sizes to help with plant identification. They have specialized tissues like the epidermis, vascular bundles and mesophyll that allow them to perform photosynthesis efficiently.

1. Leaves

3. •Leaves are the powerhouse of plants.
•Leaves are the major site of food production for the
plant.
•Structures within a leaf convert the energy in sunlight
into chemical energy that the plant can use as food.
• Chlorophyll is the molecule in leaves that uses the
energy in sunlight to turn water (H2O) and carbon
dioxide gas (CO2) into sugar and oxygen gas (O2).
This process is called photosynthesis.

4. •Leaves come in many sizes and shapes; they are often
used to help identify plants. Some leaves are flat and
wide; others are spiky and thin.
Plant spines (like cactus spines) are actually
modified leaves.

8. 1. Dermal: also called as the epidermis
• is an outer protective layer of typically polygonal
cells, which helps defend against injury and
invasion by foreign organisms.
• epidermis of the leaf also functions in a more
specialized manner by secreting a waxy substance
that forms a coating, termed the cuticle, on the
surface of the leaf.

9. 2. Vascular:
• which serve as a basic skeletal structure in
addition to functioning in the transport of
materials.
• extend throughout the mesophyll so that the xylem
and phloem are brought into propinquity with leaf
tissues that carry out photosynthesis.
• mesophyll is the mid-section of a leaf, located between the upper
and lower epidermal layers.

10. •Dorsiventral or bifacial: palisade on one side;
spongy on the other
•Isobilateral or isolateral or unifacial:
palisade present on both sides
•Convergent or uniform: mesophyll cell look the
same; no distinct palisade.

11. • Collenchyma a small group of cell found in the
mesophyll section of the leaf.
• collenchyma cells occur in aggregates just
beneath the epidermis and possess thicker
primary cell walls than parenchyma cells.
• the thickness of the walls, however, does exhibit
notable variation.
• main function: of collenchyma cells is to provide
additional support to the plant, especially in
areas of continued growth.

12. 3. Ground:
• comprises the bulk of a plant leaf and is generally
comprised of a variety of cell types, the
predominant of which are parenchyma.
• Often less specialized than other plant cell
types, parenchyma cells are surrounded by
thin, flexible primary walls and execute most of the
plant’s metabolic activities.
• parenchyma cells present in leaves contain
chloroplasts, which are the sites of photosynthesis.

13. • The upper section is termed the palisade
parenchyma and consists chiefly of elongated
columnar parenchyma cells that contain three to
five times the number of chloroplasts as the cells
that comprise the lower layer, known as the spongy
parenchyma.
• cells of the spongy parenchyma are irregularly shaped, allowing
gases to circulate through the numerous air spaces between them
to the palisade parenchyma. The stomata, which are particularly
important for gas exchange, tend to be surrounded by
exceptionally large air spaces.

14. • Usually have bundle sheath (parenchymatous)
• Inconspicuous in C3 plants
• Enlarge d in C4 plants
•Larger Bundles
• lacks sheath or schelerenchymatous sheath

16. The cycle spends ATP as an energy source and consumes NADPH2 as
reducing power for adding high energy electrons to make the sugar. There
are three phases of the cycle. In phase 1 (Carbon Fixation), CO2 is
incorporated into a five-carbon sugar named ribulose bisphosphate (RuBP).
The enzyme which catalyzes this first step is RuBP carboxylase or rubisco. It
is the most abundant protein in chloroplasts and probably the most
abundant protein on Earth. The product of the reaction is a six-carbon
intermediate which immediately splits in half to form two molecules of 3-
phosphoglycerate. In phase 2 ( Reduction), ATP and NADPH2 from the light
reactions are used to convert 3-phosphoglycerate to glyceraldehyde 3-
phosphate, the three-carbon carbohydrate precursor to glucose and other
sugars. In phase 3 (Regeneration), more ATP is used to convert some of the
of the pool of glyceraldehyde 3-phosphate back to RuBP, the acceptor for
CO2, thereby completing the cycle. For every three molecules of CO2 that
enter the cycle, the net output is one molecule of glyceraldehyde 3-
phosphate (G3P). For each G3P synthesized, the cycle spends nine
molecules of ATP and six molecules of NADPH2. The light reactions sustain
the Calvin cycle by regenerating the ATP and NADPH2.