Structure of a Leaf: Photosynthesis Flashcards
What are the Upper and Lower Epidermis?
Upper and Lower Epidermis: They are the two outer layers of the cells, and have few chloroplasts. They are covered in a thin layer of a waxy kind of material called the cuticle, which reduces water loss by evaporation. It acts as a barrier to the entry of pathogens such as bacteria and fungi.
What is the function of the Lower Epidermis?
It contains many holes or pores called stomata or a single pore is called a stoma. The upper epidermis usually contains little to no stomata. The stomata allow carbon dioxide to diffuse into the leaf, to then reach the tissues that photosynthesis. They also allow other things to diffuse out like oxygen and water vapor. A stoma is usually formed between two very specialized cells called guard cells, which can adapt their shape to open and close the stoma.
What is the function of the Upper Epidermis?
The Upper Epidermis: Is relatively transparent, which allows light to pass to chloroplasts in the layer below.
What is the palisade mesophyll?
These are long and narrow cells, each of them contains hundreds of chloroplasts. The palisade mesophyll is close to the sources of light which means that it is the main site of photosynthesis.
What is the Spongy Mesophyll?
Below the palisade layer is the spongy mesophyll made up of spongy cells. They are tissues made up of more rounded, and loosely packed cells, with air spaces between them. They have fewer chloroplasts than the palisade cells but can also photosynthesize. The Spongy Mesophyll form the main gas exchange, absorbing carbon dioxide and releasing water vapor. The airspaces allow these gases to diffuse in and out of the mesophyll.
What is the Xylem?
Water and mineral ions are transported through the vessels in the tissue called the Xylem. Forming a continuous transportation system in the plant.
What is Phloem?
Carries the products of photosynthesis like sugars, are carried away from the mesophyll layer. The Phloem then transports these to other parts of the plants. The veins in the leaf contain both Xylem and Phloem.
