Science 7
Unit 3
Living Things: Protista-Plantae
Name: ______________________________
Date: ______________ Period: __________
Leaves: Characteristics of Seed Plants
The leaves are the main food making part of the plant.
Review: Leaves capture energy from the ________________. Inside the plant cells is an organelle called a chloroplast;
inside the chloroplast is a green pigment called ___________________________________. Through a process called
_____________________________________, the plant uses ____________________ and ___________________
______________________ and the sun’s energy to make __________________________ and
____________________________. Excess food is stored as ________________________ in the plant cells, either in
the leaves or in the roots and stems.
Water for photosynthesis gets to the leaves by the roots and xylem. The carbon dioxide comes straight into the leaf from
the air around it; oxygen also leaves the leaf directly to the air. The underside of the leaf has small openings or pores
called stomata (singular-stoma). These open and close to control when gases enter and leave the leaf. The stomata is
surrounded by two curved crescent shape guard cells.
The outer layer of the leaf is called the epidermis. This layer is both above and below the leaf and protects it
from drying out. The top of the leaf has an additional single celled layer of a waxy substance called a
________________________ to also help in water retention.
Transpiration also occurs from the surface of the leaf through the stomata; this is the process where water
evaporates from the leaf. In jungles of the tropics, so much water transpires during the day that storm clouds
form from them and it rains almost every day.
The middle layer of a leaf is called mesophyll and contains chlorophyll; it is here that photosynthesis occurs.
There are also vascular bundles of xylem and phloem in the veins of the leaf. Every cell of every leaf must
have a ready supply of water and nutrients for photosynthesis and a way to get the food made in the chlorophyll
to the rest of the plant.
1. What major role do leaves play in a plant? _________________________________________
2. How do they do this? __________________________________________________________
Look at the structure of a leaf pictured above. Match the leaf part with its function.
Leaf Part
Function
_______ 3. cuticle
a. carries water from the roots to the leaves
_______ 4. xylem
b. waxy, waterproof coating that covers a leaf’s upper surface
_______ 5. phloem
c. spaces between these cells store oxygen and carbon dioxide
_______ 6. stomata
d. contain lots of chloroplasts as the sun shines most there
_______ 7. epidermis
e. tiny pores that open and close to let air and water in and out
_______ 8. vein
f. carries food from the leaves to the rest of the plant
_______ 9. guard cells
g. contains the vascular bundle of xylem and phloem
_______ 10. palisade mesophyll
h. controls the opening and closing of stoma
_______ 11. spongy mesophyll
i. outer layer of cells on top and bottom of leaf
12. The process by which water vapor evaporates from a plant’s leaves is called ________________________.
13. On very hot days, the stomata often
OPEN or CLOSE to keep the plant from losing water.
Leaf shapes vary from plant to plant and their morphology is used to identify the plant. More on this later.