transportation in plants

the movement of substances absorbed or synthesised by one part of a plant to another part.

conducting system/vascular system

Xylem + Phloem form the conducting system in plants.

Xylem

a tissue that forms a tubular passage for the movement of water and minerals from the roots to the aerial parts of the plant.

tracheids

elongated dead cells with tapering ends. its edges are thickened and it has lateral pores.

use of tracheids

it provides mechanical strength and conducts water upwards.

vessels

Tube-like structures with 2 openings that are placed one on top of the other to create long channels.

use of vessels

Provides mechanical support and conduct water upwards like tracheids.

xylem/ wood parenchyma

small, thick-walled living cells that store food and help conduct water and minerals.

xylem sclerenchyma/ wood parenchyma

thick walled, long, narrow cells with tapering ends. only provides mechanical support.

Phloem

transports food manufactured by the leaves to the rest of the plant.

sieve tubes

cylindrical cells that are devoid of a nucleus. the are found in vertical rows. their end walls are called sieve plates and they are perforated.

use of sieve tubes

through its sieve plates, food material passes from cell to cell.

companion cells

thin walled, elongated cells found attached to sieve tubes.

Phloem parenchyma

thin walled cells that store food.

Phloem fibres

dead, elongated cells that provide mechanical support to the plant.

difference in xylem and phloem: energy

xylem's conduction does not require expenditure of energy, unlike phloem.

transport of food / translocation of solutes

plants create glucose for food, which is stored as starch. this starch is transported as a sucrose solution, and this transport of starch as sucrose is called translocation of solutes.

root hair

it is a long extension of the epidermal cell of a root.

cell sap in root hair

it has more solutes than the surrounding water, which promotes absorption of water.

how does root hair improve absorption of water?

1. it provides a larger surface area 2. root hairs contain a higher concentration of cell sap than the soil water. 3. cell membrane is semi permeable, so it does not allow larger molecules to enter, so only the water is absorbed.

osmosis

the movement of water molecules from its region of higher concentration of water through a semi-permeable membrane to its lower concentration.

diffusion

movement of molecules from higher to lower concentration.

active transport

movement of mineral molecules from lower to higher concentration using energy.

Ascent of sap

water is absorbed by the root hairs by osmosis. it moves into the inner cells of the plant by cell-to-cell diffusion to reach the central xylem.

Root pressure

Pressure develops in the roots due to the constant inflow of water by cell-to-cell osmosis. As a result of the pressure, water enters the xylem cells and pushes the plant sap upwards.

transpiration

the loss of excess water as water vapour from the aerial parts of the plants.

transpirational pull

due to transpiration, a suction force is developed in the xylem, which cause the water to be pulled up by the roots to the stem to the leaves.

capillary force

when the xylem vessels are empty, the water molecules are pulled up because of water's tendency of its molecules sticking together.

factors that affect the rate of transpiration

sunlight, temperature, humidity, wind

use of transpiration

it keeps the plant cool, and it helps maintain the concentration of cell sap by evaporating some of the solvent. the water is evaporated out, preventing dilution of sap.

uses of water in plants

a. to cool the plant b. the water in the plant is used to transport substances in a solution form from one part of the plant to the other. c. it is required to produce food during photosynthesis.

Macro nutrients

nitrogen, phosphorus, potassium

nitrogen

main constituent of proteins. without it, leaves will yellow and cereal grains will wrinkle.

phosphorus

constituent of cell membrane and certain proteins. without it, germination will be delayed and purple and yellow spots will appear on the leaves.

potassium

involved in opening and closing of stomata. poor growth rate with reduced rate of transpiration.

Micro nutrients

iron, manganese, zinc

iron

constituent of some proteins. yellowing of leaves

manganese

constituent of some enzymes. yellowing of leaves with grey spots.

zinc

constituent of plant hormones. deshaped, yellowing leaves with stunted plant growth.