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Heinemann Senior Science 1 Chapter 2 Plants 2.1 Plant function Questions 1 Phloem, xylem, guard cells. 2 They can convert carbon dioxide and oxygen with sunlight into a food source. 3 The stem holds plant upright. The roots absorb water and dissolved nutrients from the soil and anchor the plant. Leaves capture sunlight for photosynthesis. 4 Yellowing of leaves, stunted growth. 5 Macrominerals: nitrogen, important for leaf growth; phosphorus, promotes root growth and flowering; potassium, increases disease resistance. Trace elements: iron, required by chloroplasts for functioning; copper, required by plant enzymes; zinc, used in the production of the plant hormone auxin. 6 Further questions 1 Spray a small amount of the liquid fertiliser into a flame and observe the colours given off; compare to the known colours of metal salts. 2 3 a carrot b spinach Vegetables do not contain seeds; fruit do. Copyright © Pearson Australia (a division of Pearson Australia Group Pty Ltd) 1 Heinemann Senior Science 1 4 Plants absorb oxygen and carbon dioxide from the air and these react in the presence of sunlight and water to form glucose, a substance that supplies food for the growing plant. 5 A farmer can observe plant growth for signs such as yellowing of leaves, mottling and stunted growth. From the signs, he or she can determine which mineral element is lacking and apply the appropriate fertiliser. 2.2 Seed germination and requirements Questions 1 To germinate seeds under conditions generally seen as unfavourable, for consumers, home gardeners and nurseries to keep up with supply. 2 Water, oxygen, warmth. 3 25–30C 4 Growth is slowed and a food supply is maintained for the following growing season. 5 When a seed absorbs water the seed coat bursts, allowing oxygen into the seed and respiration to start. 6 a [top to bottom] b lateral bud c [top to bottom] root/shoot swollen stem seed coat lateral bud cotyledon old corms roots Further questions 1 The seeds require a period of cold exposure to promote germination; the seeds may be tulips or seeds from a typically cold zone. 2 In a dry container, not humid, and vacuum sealed (no oxygen) to prevent germination and to maintain health. 3 Increased germination. 4 The seed cannot obtain enough oxygen to start respiration for germination to occur. 5 Use a plastic tray or box and place a lamp underneath it to heat the bottom. 6 Provides nutrients for Rhizobia bacteria and neutralises the soil so bacteria aren’t killed. 7 Heat to crack the nuts, as they have very hard protective shells. 8 a leaching Copyright © Pearson Australia (a division of Pearson Australia Group Pty Ltd) 2 Heinemann Senior Science 1 9 b scarification c abrasion Plant A—temperate. Plant B—cold. If plant B was grown in Central Australia cold storage prior to germination would be needed. 2.3 Factors affecting seedling growth Questions 1 Warmth, sunlight, oxygen, carbon dioxide, soil nutrients and water. 2 Competition for resources will limit: 3 space to grow in, resulting in smaller plants and reduced yields water availability, resulting in smaller plants and reduced yields available nutrients, resulting in smaller plants and reduced yields. As seed size increases, seed sowing spacing needs to increase because of competition for resources. 4 Leaf size, shape, plant height, root length. 5 No, the roots establish first, then the stem and leaves. Further questions 1 A fern requires high moisture, humidity and temperate conditions. A eucalypt requires temperate to hot conditions and moderate rainfall. A geranium requires temperate conditions and moderate rainfall. A lily has very high water requirements; conditions can range from cold to hot. 2 The green colour of leaves is actually a mixture of pigments. Chlorophyll usually hides the other pigments; as leaves die, chlorophyll is reabsorbed and the yellow and orange colours become visible. 3 Generally red (650 nm) and blue (400–450 nm). 4 Photosynthetic rate would increase but not indefinitely. Eventually the maximum level of photosynthesis will occur. 5 Sunlight, water, oxygen, carbon dioxide because they are all required for photosynthesis to occur. Copyright © Pearson Australia (a division of Pearson Australia Group Pty Ltd) 3 Heinemann Senior Science 1 2.4 Water requirements of plants Questions 1 A plant that lives under arid conditions with adaptations to overcome heat and irregular or low water. It would be found in arid regions of Australia, e.g. Central Australia. 2 They are aerial roots on mangroves that poke out of mud; they absorb oxygen from air and excrete salt. 3 Spray, drip and flood. 4 Excessive watering problem Description Pooling Collection of water in stagnant ponds can lead to contamination, insect problems and disease Wastage Run-off of water and wastage of our precious resource Erosion Run-off taking topsoil with it and destroying the soil profile Leaching Removal of nutrients from soil profile Waterlogging Raising of the water table and filling of soil pores with water which leads to lack of oxygen for plants 5 Saving time and labour in large agricultural organisations. Further questions 1 Absorption of water by pneumatophores at high tide; absorption of water by pneumatophores from mud at low tide; excretion of salt from salt glands on leaves so that osmosis can stop plant from losing water from cells. 2 Plants that require cold conditions for germination or flowering to occur. 3 The species will decrease in number and perhaps die out. 4 a In waterlogged environments oxygen is limited. The aerial roots allow oxygen to be obtained from the air. 5 b Maintains osmotic balance, stops water from leaving the plant cells. a The roots quickly absorb water after rainfall before the water passes through the soil profile. Copyright © Pearson Australia (a division of Pearson Australia Group Pty Ltd) 4 Heinemann Senior Science 1 b structural 2.5 Asexual reproduction in plants Questions 1 Cloning is the production of new offspring with identical genetics as the parents. 2 Benefits include offspring having the same desirable genetic information as the parent; only one parent is required for reproduction; offspring can be cloned from the meristematic cells of a parent plant. Disadvantages include a limited gene pool: large numbers of identical offspring cause a small gene pool and a reduction in genetic information. If the environment changes, the species may not be able to adapt and may die out hence causing a decrease in biodiversity. Cloning can be labour intensive and time costly. 3 Tissue culture produces new individuals by means of a labour-intensive, human process. Runners can produce new individuals naturally without human intervention. 4 Native plant Lignotuber Epicormic bud Eucalyptus yes yes Grevillea no yes Hakea yes yes Banksia yes yes Copyright © Pearson Australia (a division of Pearson Australia Group Pty Ltd) 5 Heinemann Senior Science 1 Further questions 1 2 Continuous lighting also provides heat. Plants are not naturally accustomed to receiving continuous light, the increase in heat can therefore cause overheating of plants. 3 An example would be to set up different trays with varying amounts of light exposure, e.g. 12, 15, 20 and 24 hours. Use a datalogger to monitor light in lux, and temperature of the plants and surroundings. 4 Plants grown by seed establish the fastest, then runners, then tissue culture. Copyright © Pearson Australia (a division of Pearson Australia Group Pty Ltd) 6 Heinemann Senior Science 1 2.6 Biodiversity Questions 1 Biodiversity refers to the number of different species living in a particular environment. 2 Medicinal purposes; they are suited to our conditions; aesthetic value; for food for native animal species. 3 A gamete is a sex cell; it has genetic information from one parent. A zygote is formed from the union of two gametes; it contains genetic information from both parents. 4 For continuation of endangered species, to increase numbers. 5 It has competed with native species for area and resources; it has crowded out native species and is reducing native species numbers. Further questions 1 Answer depends on organisation student chooses. 2 a When a particular species is threatened or endangered, large numbers of offspring can be produced quickly from small numbers of parent plants. This can aid biodiversity by maintaining species variation. b When organisms are cloned, the genetic information passed on is identical to that of the parents. This results in a reduced gene pool. In an environment where conditions may change (perhaps due to human interference) the organisms may not be adapted to the changed conditions and thus die out, reducing biodiversity. 3 Fencing, planting of native plant species, removal of introduced species, working with Landcare to manage land, removal of grazing animals. 4 To maintain the health of our planet. 5 Introduced species compete with or prey on native species. Land management has destroyed the environment that native plants grow in. People’s ignorance of the importance of native species. 6 The Australian attitude is much more positive now, readily adopting conservation principles. Governments are providing funding and support for conservation projects through environmental policies, Landcare, CSIRO and grants, as often seen advertised on television. Copyright © Pearson Australia (a division of Pearson Australia Group Pty Ltd) 7 Heinemann Senior Science 1 Exam-style questions 1 B 2 C 3 D 4 C 5 A 6 C 7 Growth will be very stunted, yellowing of leaves. 8 In general, attach temperature probe, enter the frequency of recordings required, enter number of recordings required, place probe in appropriate position, start recordings. Note, procedure will vary for each brand of datalogger. 9 Cactus Fern Low or irregular rainfall High rainfall Low to high temperatures Moderate temperatures Low humidity High humidity 10 Stilt roots lift the mangrove out of the water to prevent waterlogging and collect oxygen. Salt glands release excess salt from plant to maintain osmotic balance. Pneumatophores collect oxygen from the air during periods of high tide when generally the roots would be submersed by water. 11 Little publicity and/or not notifying the public of the location so that they cannot interfere. Tissue culture of plant and cuttings and seed collection of plant. 12 Eucalypts possess lignotubers and epicormic buds which provide new growth after fire. Hakeas demonstrate epicormic growth after fires. Banksia seeds are protected in a hard nut which bursts open after fire and releases the seeds ready for germination. 13 Behavioural—how an organism responds to the environment, e.g. resting in the heat of the day. Structural—characteristics of an organism’s body that suit it to the environment, e.g. sunken stomates. Physiological—the way an organism’s body functions, e.g. dropping branches to conserve water loss. Copyright © Pearson Australia (a division of Pearson Australia Group Pty Ltd) 8 Heinemann Senior Science 1 14 Obtain four xerophytic plants, e.g. cacti, and four non-xerophytic plants, e.g. ferns. Pot each plant in a pot containing the same soil or potting mix. Place each pot under the same environmental conditions, e.g. in a greenhouse. Only water with a predetermined amount (depending on plant size and pot size) once a week. Record observations of each plant at the start and once a week before watering. Cacti should continue growing and show no detrimental effects. The ferns should wilt, leaves should go pale in colour and, if left long enough, die. This would show that xerophytic plants are adapted to low water availability. 15 The plant utilised the water from the soil and carbon dioxide from the air to photosynthesise and produce food for the plant to grow. 16 a To determine the ideal temperature for acacia seeds to germinate. b 100C provided the best germination percentage for acacia seeds. c temperature d Yes; 100C gave the best germination. e Copyright © Pearson Australia (a division of Pearson Australia Group Pty Ltd) 9 Heinemann Senior Science 1 17 Species Smoke Abrasion Scarification Leaching √ Acacia Dianella √ Xanthorrhoea √ √ √ Banksia Grevillea √ Clianthus √ Deep yellow wood 18 Heat √ Vacuum packaging removes all air and prevents entry of moisture to the seeds which prevents the seeds from germinating or spoiling from fungal growth. 19 In the technique of tissue culture a small piece of meristematic tissue is taken and grown in a nutrient solution to produce clones of an adult plant. 20 Having an understanding of how plants function allows us to manipulate plant growth to meet our needs, to improve the quality of plants and to increase plant numbers. 21 Increasing the light and temperature will increase plant growth until the temperature reaches too high a level. Copyright © Pearson Australia (a division of Pearson Australia Group Pty Ltd) 10 Heinemann Senior Science 1 22 Plants have different water requirements depending on their means of reproduction, e.g. ferns need moisture to reproduce, and if they require water for support, e.g. herbaceous plants such as geraniums use water for turgidity. Plants such as xerophytes are adapted to low water availability. Copyright © Pearson Australia (a division of Pearson Australia Group Pty Ltd) 11