Structures of Plants (Chapter 7) Flashcards Preview

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Flashcards in Structures of Plants (Chapter 7) Deck (22)
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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?

Gas exchange


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


Describe the pericycle in stems

Formed from sclerenchyma (a tissue with dead lignified cells for extra strength)

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