C3 - Structure and distribution of vascular tissue

What is the function of vascular tissue?

transports materials around the body

Where are xylem and phloem found?

adjacent to each other in vascular bundles

xylem (2)

tissue in plants, conducting water and dissolved mineral ions upwards

phloem (2)

plant tissue containing sieve tube elements and companion cells, translocating sucrose and amino acids from the leaves to the rest of the plant

Describe the structure within a root (2)

xylem is central and star-shaped, with phloem between groups of xylem cells

How does the arrangement of phloem and xylem in the root help the plant? (2)

this arrangement resists vertical stresses, anchors the plant in the soil

Outline the key features of a transverse section of a root (7)

epidermis, root hair, cortex, endodermis, pericycle, xylem, phloem

What does the stele include? (3)

xylem, phloem, pericycle

Describe the structure within a stem (3)

vascular bundles are in a ring at the periphery, with xylem towards the centre, phloem towards the outside

How does the arrangement of phloem and xylem in the stem help the plant? (2)

gives flexible support, resists bending

Outline the key features of a transverse section of a stem (6)

epidermis, collenchyma, cortex, fibres, medulla, vascular bundle

What is included in the vascular bundle? (3)

xylem, phloem, fibres

Where is vascular tissue found in leaves? (2)

in the midrib, in a network of veins

How does the positioning of the vascular tissue in leaves help the leaf? (2)

gives flexible strength, resistance to tearing

Outline the key features shown in a section through a leaf (5)

adaxial surface, vascular bundle, collenchyma, compacted parenchyma, abaxial surface

What is the adaxial surface?

faces the central axis of the plant

What is the abaxial surface?

facing away from the central axis of the plant

What are the vessels in xylem? (3)

water-conducting structures in angiosperms, comprising cells fused end-to-end making hollow tubes, with thick and lignified cell walls

How do these vessels form? (6)

lignin builds up in their cell walls, causing the contents to die, leaving the lumen, as the tissue develops the end walls of the cells breakdown, leaving a long hollow tube, allowing water to climb straight up the plant

How is lignin arranged in vessels?

lignin is laid down in a spiral pattern

What are tracheids? (5)

spindle-shaped, water-conducting cells in the xylem of ferns, conifers, and angiosperms

What effect does mosses not having tracheids have? (2)

mosses have no water-conducting tissues, therefore are poorer at transporting water and cannot grow as tall as other plants

What are the functions of the xylem? (2)

transports water and dissolved minerals, provides mechanical strength and support

What are the two types of conducting cells found in xylem?

vessel elements, tracheids

What is the function of the pits in xylem? (3)

allow water through and up the plant, against gravity, by cohesion and adhesion

What are the defining features of dicotyledon?

embryo plant develops with 2 seed leaves

Why is vascular tissue required in a dicotyledon plant?

diffusion alone would be too slow to meet the demands of the plant for the exchange of materials

medulla

inner region of a structure

cortex

outer region of a structure

endodermis

a single layer of cells around the pericycle

What is found in a dicotyledon stem? (3)

parenchyma, collenchyma, sclerenchyma

parenchyma

filler tissue in soft part of plant

collenchyma (2)

extra structural support, especially in areas of new growth

sclerenchyma

main stiff structural support

Why do plants need to transport water? (4)

water for transport of other solutes, cooling via evaporation, photosynthesis, turgidity for maximum sunlight absorption

Why do plants need to transport nitrates? (2)

nitrates to synthesise amino acids, nucleic acids

What else do plants transport? (3)

magnesium, phosphates, calcium

cell sap (2)

solution of ions and sugars, with a lower water potential than soil

soil solution (2)

very dilute solution of mineral ions, with a higher water potential than vacuole

Why does the root hair done have the greatest water uptake?

large surface area increased by root hairs and thin cell walls

What is the fastest pathway for water to move through the root?

apoplast pathway

apoplast pathway (2)

water moves in the cell walls, cellulose fibres in the cell wall are separated by spaces through which water moves

symplast pathway (2)

water moves through the cytoplasm and plasmodesmata, a continual pathway across the root cortex

plasmodesmata

strands of cytoplasm through pits in the cell walls joining adjacent cells

vacuolar pathway

water moves from vacuole to vacuole

endodermis (2)

a single layer of cells around the pericycle and vascular tissue of the root, each cell has an impermeable waterproof barrier in its cell wall

casparian strip (3)

impermeable band of suberin in the cell walls of endodermal cells, blocking the movement of water in the apoplast, so it moves into the cytoplasm

suberin

waxy material found in endodermis cell walls