2c. Plant Transport Key words

Cambium

Stem cells (undifferentiated) found in a ring around the inside of a stem that can divide and differentiate into new xylem and phloem.

Cortex

Cells that make up the main tissue in the root. Often used to store food (e.g. starch).

Epidermis (upper/lower)

The out layer of cells around the leaf that surround the other tissues. (may also secrete the waxy cuticle) Don't contain chloroplasts.

Flaccid

Where the cell membrane pulls away from the cell wall due to a loss of pressure within the cell (loss of water).

Guard cell

Pairs of cells that surround the stoma and can change shape to open or close the stoma.

Humidity

A measure of the amount of water vapour in the air.

Meristem tissue

Undifferentiated cells/ stem cells.

Palisade mesophyll

The layer of regular/ rectangle shaped cells near the top of a leaf that contain the most chloroplasts for absorbing light energy for photosynthesis.

Phloem

Vessels that carry sugars (sucrose) and other substances either up or down the stem to/from the leaves and roots depending on where the products are made/ needed.

Pith

Cells found in the stem of a plant. May be used to store food/ provide support.

Potometer

A piece of apparatus used to measure the rate of water uptake by a plant.

Root hair

Specialised cell found on the epidermis of the root that is adapted for water and mineral absorption.

Spongy Mesophyll

The layer of irregular shaped cells (under the palisade layer) that creates air spaces for gas exchanges within the leaf. Has fewer chloroplasts than the palisade layer.

Stoma/stomata

The opening(s)/ holes found mainly in the bottom of the leaf where gas exchange occurs with the air by diffusion. Water vapour is also lost from the leaves via diffusion.

Translocation

The movement of organic compounds in the phloem (like sucrose) from where they are made, e.g. in the leaf, to where they are needed/ used e.g. the roots.

Transpiration

The loss of water from the leaf of a plant by evaporation and then diffusion of the water vapour through the stomata.

Transpiration stream

The flow of water from the roots to the leaves through the xylem. It is pulled up by the loss of water in transpiration.

Turgid

When a plant cell's vacuole is full of water and the cell surface membrane is pushed firmly against the cell wall. The cell will be firm.

Vascular bundle

The combined bundle of xylem, phloem and cambium.

Waxy Cuticle

Waterproof layer secreted by the (upper) epidermis cells to reduce water loss.

Wilt

When plant cells lose their turgidity the leaves will become floppy.

Xylem

Waterproof (dead) vessels (tubes) that carry water and minerals up the stem to the leaves from the roots.