NAME: Delania John
DATE:
LAB: #
SKILL: Drawing
TITLE: Dicotyledonous leaves
AIM: To study the internal structures of dicot leaves using the compound microscope.
THEORY: The leaves are often structurally different from other plant organs. The dicot leaf
consists of one or more layers of densely packed parenchyma cells rich in chloroplasts, and a
variety of supporting tissues that allow this thin layer of cells to perform photosynthesis
efficiently. The dense layer of parenchyma is called palisade mesophyll. Its cells are stacked
tightly together, with their long axes perpendicular.to the top surface of the leaf. Each cell is
directly exposed to light at its top end. The bottom end is in contact with a loosely packed layer
of spongy mesophyll, with numerous air spaces between the cells. This airy tissue allows rapid
diffusion of atmospheric gases. The palisade and spongy mesophyll layers are sandwiched
between two transparent layers of epidermis. Veins rise from the vascular bundles of the stem
and enter the leaf through the leaf stalk or petiole. In dicots the veins then branch out in a net-like
pattern to reach all parts of the leaf blade. Each vein contains xylem, which brings in water and
simple minerals, phloem, which carries sugars from the photosynthetic cells to all other live cells
in the plant, and fibres which help to support the otherwise flimsy leaf blade.
MATERIALS:
● Compound microscope
● Slide of typical dicot leaf
● Drawing materials
PROCEDURE:
1. Examine the slide using a microscope.
2. Make a plan drawing of the leaf.
3. Make a detailed annotated drawing of each of the following: An epidermal cell A
palisade mesophyll cell A spongy mesophyll cell.