Chapter 4: Organising Plants and Animals II Flashcards
define epidermal
the name given to cells that make up the epidermis or outer layer of the organism
what do the epidermal tissues do?
- secrete a waxy substance that waterproofs the surface of the leaf
- protects the leaf
define palisade mesophyll
the upper layer of the mesophyll tissue in plant leaves made up of closely packed cells that contain many chloroplasts for photosynthesis
define spongy mesophyll
the lower layer of mesophyll tissue in plant leaves that contains some chloroplasts and many large air spaces to give a big surface area for the exchange of gases
what does xylem transport?
- water
- dissolved mineral ions from the roots up to the leaves
what does the phloem transport?
-dissolved food from the leaves around the plant
what is meristem tissue made up of?
rapidly dividing plant cells that grow and differentiate into all cell types needed
what do the roots, stem and leaves form in the plant?
an organ system
define translocation
the movement of sugars from the leaves to the rest of the plant through the phloem
are mature xylem cells dead or alive?
dead
what is the main difference between the xylem and the phloem?
phloem transports food (sugar) and xylem transport water
why is transport so important? (food)
- cells need sugar for respiration and providing materials for growth
- mineral ions are needed for the production of proteins and other molecules
why is transport so important? (water)
- plants need water for photosynthesis
- water is the main method of support, to make plants turgor
what is stomata?
small openings all over the leaf surface
define guard cells
surround the stomata in the leaves of plants and control their opening and closing
Describe the role of stomata in a plant
- carbon dioxide from the atmosphere diffuses into the air spaces and then into the cells down a concentration gradient
- oxygen produced by photosynthesis is removed form the leaf by diffusion into the surrounding air
define transpiration
the loss of water vapour from the leaves of plants through the stomata when they are opened to allow gas exchange for photosynthesis
what is the transpiration stream?
As water is evaporated through the surface of the leaves, more water is pulled from the xylem to take its place.
what factors increase the rate of photosynthesis or stomatal opening?
- temperature
- humidity
- air flow
- light intensity
in what conditions are transpiration more rapid?
- hot
- dry
- windy
- bright
what happens to a plant that loses water faster than it is replaced?
- plant may wilt to reduce the surface area available for water loss by evaporation
- stomata close
