Flashcards in Structures of Plants (Chapter 7) Deck (22)
What is the epidermis?
A continuous layer on the outside of the plant, one cell thick, that provides protection
What is the epidermis covered with in stems and leaves?
A waterproof waxy cuticle which helps to protect the organ from drying out and from infection
What does the epidermis have in laves?
Stomata, which are pores that allow entry of CO2 for photosynthesis
What does the epidermis have in roots?
Extensions called root hairs to increase the surface area for absorption of water and mineral salts
What is the parenchyma made up of?
Thin-walled cells which are used as packing tissue
Describe 3 characteristics of the cells in the parenchyma
1) they are very metabolically active
2) may be used for storage of foods e.g. starch
3) when they are turgid, they help to support the plant, preventing wilting
What do air spaces in the parenchyma allow?
How are water and mineral salts transported in the parenchyma?
Through the walls and living contents of cells
What does the parenchyma form in roots and stems?
The cortex (outer region of cells)
What does the parenchyma form in stems?
The pith (central region of stems)
What does the parenchyma contain in leaves and what is it modified to form?
- It contains chloroplasts
- It is modified to form palisade and spongy mesophyll
What is the collenchyma?
A modified form of parenchyma with extra cellulose deposited at the corners of cells, providing extra strength
Where is collenchyma in leaves?
In the midrib of leaves
Describe the endodermis
One cell thick and surrounds the vascular tissue (xylem and phloem) in stems and roots
What is the mesophyll made up of?
Specialised parenchyma cells found between the lower and upper epidermis of the leaf
What are the two types of mesophyll?
Spongy and palisade
What do mesophyll cells contain and therefore what are they specilaised for?
They contain chloroplasts ∴ they are specialised for photosynthesis
Where in the leaf are palisade mesophyll cells and why?
Near the upper surface of the leaf where they receive more sunlight ∴ they contain more chloroplasts than spongy mesophyll cells
What does spongy mesophyll contain?
Many large air spaces between cells
What is the pericycle?
A layer of cells just inside the endodermis and next to the vascular tissue
Describe the pericycle in roots
One cell thick and new roots can grow from it