Nutrition in Plants

Photosynthesis: the fundamental process by which plants manufacture carbohydrates using energy from light

All living things require a source of energy from the environment to stay alive2 Types of Nutrition1. Autotrophic: simple compounds are absorbed and built up into complex substance which may be oxidized (broken down) to release energy2. Heterotrophic: Complex food material is broken down to simple substances during digestion which may be absorbed or oxidized to release energy. 

Plants show autotrophic nutrition and the central process in plant nutrition is PHOTOSYNTHESIS

Raw Materials: carbon dioxide and waterProducts: glucose and oxygenCarbon dioxide is obtained through stomate, Water enters through root hair cellsOxygen diffuses out of stomata into atmosphereEnergy Source: Sunlight absorbed by chlorophyll (contained in chloroplasts)

Carbon Dioxide + Water + Light --> Simple Sugar + Oxygen 

first product of photosynthesis is a sugar- sugar molecules are polymerized (joined together) to produce starch (which can be stored)

Stomata:- opening in the surface of plants which allow gases to pass in or out- guard cells (on either side of the stomata) can change shape to widen or reduce the opening and control gas exchange

Stomata are most common on the underside of leaves

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they let:- water vapour our of the plant- oxygen out of the plant- carbon dioxide in the plant

6C02 + 6H20 + light --> C6H1206 + 602 

Chlorophyll traps light energy and converts it into chemical energy for the formation of carbohydrates and their subsequent storage

Main product of photosynthesis (glucose) is a valuable food- has other uses in plants

CAN BE POLYMERIZED IN TWO DIFFERENT WAYS1. glucose --> starch- used to store food reserves - insoluble so can be stored easily- polymerization is easily reversed (when food is needed)2. glucose --> cellulose- polymerization is not easily reversed- cellulose is a hard substance which is formed in plant cell walls - provides strength and support for the woody parts of plants 

Cells in the green parts of plants contain small structures called chloroplastsPhotosynthesis takes place in the chloroplasts (chlorophyll)- Chloroplasts contain a green substance: chlorophyll- Chlorophyll traps light energyThis energy is used in the reactions which produce glucose from carbon dioxide and water which can be converted into starch (polymerization) and stored.

CHLOROPHYLL DOES NOT ABSORB ALL COLORS OF LIGHT EQUALLY WELLRed or blue light is best for promoting photosynthesis- Leaves look green because chlorophyll absorbs red and blue light but reflects most of the green

1. Dip a leaf into boiling water2. Put the leaf in a boiling tube3. Add ethanol4. Plae it in the water bath until the ethanol is green5. Pour out the ethanol6. Rinse in cold water7. Completely cover the leaf with iodine solution8. Blue/black colour shows that leaf contains starch

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Leaf is placed in boiling water to kill itEthanol gets rid of the chlorophyll in the leafEthanol turned green because of the chlorophyllIodine showed that leaf had starch

Nitrate Ions:- combines with glucose to produce amino acids (which makes proteins)- if nitrates are not present in the soil the growth of the plant is stunted and the stem is very weak + leaves die (AFFECTS GROWTH)

Magnesium:- forms part of the chlorophyll molecule- if magnesium is not present then the plant has yellow leaves and cannot photosynthesis effectively = poor growth

Phosphate:- component of DNA and cell membranes- deficiency symptoms include poor root growth and discolored leaves

Potassium:- must be present for photosynthesis and respiration enzymes to work- lack of potassium = poor flower and fruit growth + discolored leaves

Photosynthesis Rates

Photosynthesis increases with:- increased temperature- increased CO2 concentration- lighter colour - increased light intensity

Photosynthesis

Gas Exchange in Plant Leaves

Products and Chloroplasts

Testing Leaves for Starch

Minerals required by Plants