B6 - Plant structures and their functions

Producer

the first organism in a food chain which produces its own food

Photosynthesis

the process in which green plants use sunlight to convert CO2 and water to glucose and oxygen

Chloroplast

green disc containing chlorophyll, makes glucose through photosynthesis

Endothermic

a reaction where the products contain more energy than the reactants, e.g. Photosynthesis because it absorbs light energy

Starch

carbohydrate made by the joining of glucose molecules

Limiting factor

a single factor that when in short supply can limit the rate of photosynthesis

Directly proportional

when the percentage change of a variable occurs with an equal percentage change of another variable, makes a straight line graph

Inversely proportional

where one variable increases at the same rate as another decreases

Inverse square law

where a quantity varies in inverse proportion of the square of the distance from the source of the quantity

Root hair cell

cells in the roots with a large surface area and thin cell walls to increase the rate of osmosis and active transport.

Xylem

transports water and mineral ions up from the roots to the leaves; provide support for the plant via lignin fibres. For transpiration

Lignin

thicken the outer cell walls of the xylem vessels. Is rigid and waterproof to keep the water in the xylem

Xylem vessel

made of dead xylem cells with no top or bottom cell walls to become a long tube for transpiration

Phloem

carry sugars and amino acids made in the leaves to other parts of the plant for use or storage. Materials are dissolved in water. Translocation

Sieve tubes

cells in the phloem arranged in long columns. They have cell walls, a thin layer of cytoplasm but no nucleus. They have sieve plates for liquids and dissolved nutrients to pass through

Companion cells

support the sieve tubes; have dense cytoplasm

Sucrose

the type of sugar found in the phloem of plants

Transpiration

The loss of water vapour from plant leaves due to the movement of water upwards through the plant xylem.

Translocation

occurs in either direction, is the transportation of sugars and amino acids in solution

Diffusion

movement of particles from a high concentration to a lower concentration

Osmosis

the net movement of water across a partially permeable membrane from a dilute to a concentrated solution OR high water pot. to a low water pot.

Active transport

the movement of particles against a concentration gradient, requires energy, uses protein pumps. e.g. uptake of mineral ions

Stomata

small openings on the surface of leaves that allow for gas exchange

Guard cells

can open and close the stomata

Palisade mesophyll

tall, column-shaped cells near the upper surface of a leaf, containing many chloroplasts

Spongy mesophyll

plant tissue in a leaf with loosely packed cells with air pockets for gas exchange

Epidermis

the transparent, outermost layer of the leaf

Waxy cuticle

the waxy layer on the top of the leaf to protect it and stop water evaporating from the top layer

Potometer

a device which measures the rate of water uptake (transpiration)

Xerophyte

a plant adapted to reduce water loss to enable it to survive in dry conditions

Deciduous

a plant that loses its leaves in the winter to conserve energy

Tropism

plant hormone causing growth or turning towards a stimulus

Phototropism

plant hormone responding to light

Geo/gravitropism

plant hormone responding to gravity

Auxin

chemical substance produced at the tip of the stem which stimulates cell elongation

Gibberellin

plant hormone that stimulates seed germination and flower and fruit growth

Ethene

plant hormone that stimulates fruit ripening

Weedkiller

a substance that kills weeds

Germination

the process in which a plant grows form a seed

Parthenocarpy

development of fruit without fertilisation

Rooting powder

contains plant hormones, to speed up the growth of roots

Photoperiodism

the response of an organism to the number of daylight hours in a day