the transport of substances in plants

The Transport of Substances in Plants

Bio Form 5 Chapter 1 Transport by AHM 2

Transport organic substances

from leaves to storage organs (roots,

buds)

Transport water and mineral salts absorbed in the roots, up the stem to

the leaves


-Xylem vessels-Tracheids-Parenchyma-Fibres ( a type of sclerenchyma)

-sieve tube-Companion cell-Parenchyma-fibres


Translocation• The transport of dissolved organic solutes

(sugar sucrose, amino acids, metabolites) in the phloem

• Important for plant’s survival & enables organic substances eg sucrose to be stored or converted to other sugar

• Translocated downward from leaves to storage organs ( roots, growing region and buds)


Translocation – from SOURCE (leaf cell to SINK (root cell)


Transpiration• Loss of water vapour from a living plant

due to evaporation• Take place through stomata & lenticels• Importance of transpiration :

– helps in the absorption & transport of water and mineral ions from the roots to other parts of the shoots


Transpiration

• Transpiration stream = the continuous stream of flowing water from the roots to the leaves


The Process of TranspirationRoots xylem vessels leaves (mesophyll cells) - Surface of mesophyll

cells are covered by a thin layer of water

- Air space is saturated with water vapour as the Sun heat the external surface

- [H20 vapour] in atmosp. Is lower than water vapour in air space water evaporates from leaves

- The loss of water make the mesophyll hypertonic as compared to an adjacent cell

- Water from adjacent cell diffuse

- Create transpirational pull


The External Conditions that affects the rate of transpiration

Light intesityTemperature

Relative

Humidity

Air movement


The Movement of Water from soil leaves

• Movement of water through the roots• Water enter from soil to roots

cells through osmosis [cytoplasm of root hair cells are hypertonic compared to the surrounding soil water]

• the cell hypertonic compared to adjacent cells

• water diffuse into adjancent cells

• Water move inwards to cortex• Cortex = cytoplasm, vacuole,

cell wall of parenchyma cells =until endodermis


- Via cell wall is blocked by Casparian strip at endodermis (impermeable to water)


• Root pressure = results in the upward push of water & mineral ions into the xylem of the stem

• The gradient of water concentration that exists across the cortex creates a pushing force that results the inflow of water into the xylem


• Small plants = the root pressure can push water all the way up to stem and hydathodes @ edges of leaves GUTTATION

• Occurs on cool humid mornings


The Movement of Water from soil leaves

• Movement of water through the stem- Adhesive and cohesive

properties of water molecules

- Xylem are long, narrow & hollow column of water and creates capillarity / capillary action

- Water molecule adhere to one another = cohesive force

- Water molecule adhere to the xylem vessels = adhesive forces

- Due to hydrogen bonding


The Movement of Water from soil leaves• Movement of water from LEAVES to ATMOSPHERE

- Transpirational pull =

force due to the water cohesive properties that draw water from the xylem of the leaves and stems and eventually from the xylem in the roots

Root pressure, the adhesive and cohesive properties of water (capillary action) and the transpirational pull contribute to the movement of water from roots to the leaves


The Regulation of transpiration by the stomata

the transport of substances in plants

Education

water bio form

buds transport water

absorption transport

inflow of water

layer of water

leaves bio form

roots bio form

adjacent cell water