Plants need inorganic nutrients to produce organic compounds such as carbohydrates and proteins. (p.60)
Macronutrients are required in large amounts: carbon, hydrogen, oxygen, nitrogen, potassium, calcium, magnesium, phosphorus, sulphur. (p.60)
Micronutrients are required in small amounts: chlorine, iron, manganese, boron, zinc, copper, nickel, molybdenum. (p.60)
Carbon, hydrogen and oxygen are obtained from air and water; the other nutrients are absorbed as mineral salts from the soil through fertilisation. (p.61)
Nitrogen: gives green colour through chlorophyll; deficiency causes chlorosis of mature leaves and stunted growth. (p.61)
Potassium: maintains turgidity and protein synthesis; deficiency causes yellow leaf edges and premature death. (p.61)
Calcium: component of middle lamella and cell wall; deficiency causes distorted leaves and stunted growth. (p.61)
Magnesium: component of chlorophyll; deficiency causes yellow areas between mature leaf veins and lobed leaves. (p.61)
Phosphorus: forms nucleic acids, ATP and phospholipids; deficiency causes unhealthy roots and dark dull leaves with purple spots. (p.61)
Sulphur: component of some amino acids and vitamins; deficiency causes yellowing of leaves or the whole plant. (p.61)
Chlorine: maintains osmotic pressure and photosynthesis; deficiency causes wilting and lower fruit production. (p.62)
Iron: cofactor in chlorophyll synthesis; deficiency causes yellow young leaves. (p.62)
Manganese: activates photosynthetic enzymes; deficiency causes dark green leaf veins on light green background. (p.62)
Boron: helps calcium uptake and sucrose translocation; deficiency causes death of terminal buds and thick, fragile leaves. (p.62)
Zinc: needed for leaf formation and auxin synthesis; deficiency causes stunted growth and spotted leaves. (p.62)
Copper, nickel and molybdenum are involved in nitrogen metabolism, urea breakdown and nitrogen fixation respectively. (p.62)
A complete Knop culture solution contains calcium nitrate, potassium nitrate, potassium dihydrogen phosphate, magnesium sulphate and iron(III) phosphate in distilled water. (p.63)
Culture solution experiments use controls with missing nutrients to study the role of each nutrient. (p.63)
3.2 Organ for Water and Mineral Salts Uptake
Roots anchor the plant in the soil and absorb water and mineral salts for transport to the stem and leaves. (p.65)
Root structures include the root collar, primary root, lateral root, root hair and root cap. (p.65)
Root hairs are extensions of epidermal cells that increase the total surface area for absorption. (p.66)
Root cap at the root tip protects the root when it passes through soil. (p.66)
The epidermis has thin, permeable walls and root hair cells lack a cuticle; the cortex is loosely arranged for gaseous exchange. (p.66)
The endodermis is one cell thick and has Casparian strips, which allow water and mineral salts to enter the vascular cylinder but block air bubbles. (p.67)
The vascular cylinder contains xylem and phloem surrounded by pericycle, which is involved in secondary growth and lateral root formation. (p.67)
3.3 Diversity in Plant Nutrition
Parasitic plants grow on host plants, penetrate the host stem to the vascular bundles and absorb organic substances, minerals and water; the host becomes malnourished. (p.68)
Examples of parasitic plants include Rafflesia sp. (p.68)
Epiphytic plants live on other plants without harming them, receive more sunlight, make their own food, and absorb nutrients from gaps in the host stem. (p.68)
Examples of epiphytes include Bulbophyllum sp. (orchids) and Asplenium nidus (bird's nest fern). (p.68)
Carnivorous plants photosynthesise, secrete nectar, trap insects in cups and digest them with enzymes to obtain nitrogen. (p.69)
Examples of carnivorous plants include Nepenthes sp. (pitcher plant) and Dionaea muscipula (Venus flytrap). (p.69)