Plant Hormones and Structures.

Photosynthesis

The process by which plants and algae synthesize food from sunlight.

Producers

Organisms

Chloroplasts

Organelles in leaves where light energy is transferred during photosynthesis.

Photosynthesis equation

light + carbon dioxide + water → glucose + oxygen.

Temperature effect on photosynthesis

The rate of photosynthesis increases with temperature until enzymes denature.

Light Intensity effect on photosynthesis

Higher light intensity generally increases the rate of photosynthesis.

Carbon dioxide concentration effect on photosynthesis

Increased carbon dioxide concentration raises the rate of photosynthesis.

Limiting factor

An environmental condition that restricts the increase in the rate of photosynthesis.

Pondweed experiment setup

Pondweed is placed in a test tube with water

Distance measurement in photosynthesis experiment

The distance the oxygen bubble moves in the capillary tube is measured to calculate volume.

Variables in photosynthesis experiment

Factors such as temperature

Light intensity variation

Changing the distance of the lamp from the plant to alter light intensity.

Enzymes

Proteins that catalyze reactions

Denature

The process by which enzymes lose their functional shape due to high temperatures.

Graph with One Limiting Factor

A graph that has one line leveling off

Graph with Two Limiting Factors

A graph that represents two limiting factors in two experiments

Light Intensity

Measured in lux

Inverse Proportion

A relationship where one factor increases while another decreases

Inverse Square Law

The principle stating that light intensity is inversely proportional to the square of the distance from the light source.

Light Intensity Formula

Light intensity is proportional to 1/distance squared.

Temperature as Limiting Factor

A condition where temperature limits the rate of photosynthesis while other factors remain constant.

Graph of Distance vs. Gas Volume

A graph plotting distance from the lamp on the x-axis and change in gas volume on the y-axis.

Root hair cells

Specialised to take up water by osmosis and mineral ions by active transport from the soil as they are found in the tips of roots.

Xylem cells

Specialised to transport water and mineral ions up the plant from the roots to the shoots.

Phloem cells

Specialised to carry the products of photosynthesis (food) to all parts of the plants.

Transpiration

The loss of water vapour from the leaves and stems of the plant.

Stomata

Pores on the leaf surfaces that allow water to evaporate and gases to be exchanged.

Guard cells

Cells that close and open stomata

What structures do the cell walls of phloem cells form when they break down?

Sieve plates

Are phloem cells alive or dead?

Alive

What supplies the energy needed for phloem cells to be alive?

Mitochondria of the companion cells

What substance do phloem cells transport around the plant?

Sucrose

Companion cells

Cells that supply energy to phloem cells via mitochondria.

Translocation

The movement of food substances (such as sucrose) made in the leaves up or down the phloem.

How is sucrose transported in the plant?

From the sources to the sinks via the pholem tubes

Continuous transpiration stream

The result of water molecules being pulled up through the xylem as some leave the plant.

What is the function of stomata in leaves?

Stomata allow gas exchange and can close to minimize water loss or open to increase evaporation and transpiration.

What is the color of chlorophyll and why is it significant?

Chlorophyll is green

Why are leaves thin?

Leaves are thin to minimize the distance for carbon dioxide to enter and oxygen to diffuse out during photosynthesis.

What is the advantage of a large surface area in leaves?

A large surface area allows the leaf to absorb more light at once

Root hair cell adaptations

Have a large surface area due to root hairs

The large permanent vacuole affects the speed of movement of water from the soil to the cell

Mitochondria to provide energy from respiration for the active transport of mineral ions into the root hair cell

Xylem adaptations

Xylem tube made of dead xylem cells that have become hollow and are joined end-to-end to form a continuous tube.

Lignin is deposited in spirals which helps the cells withstand the pressure from the movement of water

Increase in temperature

The molecules move faster

Relative humidity

If the relative humidity is high

Increased air movement

If more air is moving away from the leaf due to it being blown away

Increase in light intensity

This leads to an increased rate of photosynthesis

Potometer

A potometer is used to measure the uptake of water by the plant

Distance travelled by bubble

The distance travelled by a bubble in a potometer measures how far the bubble moves in a set time

Leaf shape and size

Many desert plants do not have leaves

Waxy cuticle

Many leaves have a waxy cuticle on top

Adaptation of stomata

Stomata can be opened when carbon dioxide is needed for photosynthesis

Plant hormones

Plants need hormones to coordinate and control growth and they are needed for tropisms.

Gaseous exchange

Gaseous exchange occurs when stomata open to allow carbon dioxide in and water vapor out.

Concentration gradient

A concentration gradient is the difference in concentration of a substance between two areas

Transpiration rate

The rate of transpiration increases with higher temperatures and light intensity.

Environmental adaptations

Many plants have specific adaptations to survive in extreme environments

Phototropism

The response of plants to light

Gravitropism

The response of plants to gravity.

Auxin

A growth hormone that moves to the shaded side of a plant shoot to stimulate growth.

Positive Phototropism

Most plants show this as they grow towards the light source.

Negative Gravitropism

Most shoots show this as they grow away from gravity.

Positive Gravitropism

Most roots show this as they grow towards gravity.

Weed Killers

Herbicides containing auxin that affect broad-leaved plants by causing rapid cell growth

Rooting Powders

Powders containing auxin used to promote root growth in plant cuttings.

Gibberellins

Hormones used in germination

Breaking Seed Dormancy

The process by which gibberellins allow seed germination to occur.

Increasing Yields

The effect of gibberellins that allows fruits to grow heavier and larger.

Faster Flowering

The effect of gibberellins that encourages flowering plants to flower more quickly.

Ethene

A hormone that controls fruit ripening and is used in the food industry.

Controlling Cell Division

The process stimulated by ethene that results in fruit ripening.

Fruit Ripening

The process that occurs when fruit is exposed to ethene and warmer temperatures.

Petri Dish Experiment

An experiment to investigate the effect of gravity on newly germinated seedlings.

Auxin Distribution

When auxin is distributed equally on both sides of a plant

Light Levels

The reason shoots grow away from the ground