R3101 PLANT TAXONOMY, STRUCTURE & FUNCTION

Transcription

1 INCLUDING EXAMINERS COMMENTS R3101 PLANT TAXONOMY, STRUCTURE & FUNCTION Level 3 Wednesday 8 February :30 11:10 Written Examination Candidate Number:. Candidate Name:. Centre Number/Name: IMPORTANT Please read carefully before commencing: i) The duration of this paper is 100 minutes; ii) iii) iv) ALL questions should be attempted; EACH question carries 10 marks; Write your answers legibly in the spaces provided. It is NOT necessary that all lined space is used in answering the questions; v) Use METRIC measurements only; vi) vii) viii) Use black or blue ink only. Pencil may be used for drawing purposes only; Where plant names are required, they should include genus, species and where appropriate, cultivar; Where a question requires a specific number of answers; only the first answers given that meet the question requirement will be accepted, regardless of the number of answers offered; ix) Please note, when the word distinct is used within a question, it means that the items have different characteristics or features.. Ofqual Unit Code H/505/966 Please turn over/..

2 ANSWER ALL QUESTIONS MARKS Q1 a) Describe the structural characteristics of conifers. 6 Please see over/..

3 b) State FOUR ways by which the reproduction in conifers differs from that of ferns by completing the table below. 4 Conifers Ferns Total Mark Please turn over/.. 3

4 Q a) b) State what is meant by the term tissue. Explain how the structure of epidermal tissue enables it to fulfil THREE distinct functions. MARKS 1 9 Please see over/.. 4

5 Total Mark 5 Please turn over/..

6 Q3 a) State the optimum conditions for prolonging the storage life of fruit. 4 b) State the difference between modified and controlled atmospheres used in fruit storage. 6 Please see over/..

7 c) Explain how control of the gaseous atmosphere affects fruit storage life. 4 Total Mark 7 Please turn over/..

8 Q4 a) b) State the difference between endogenous and synthetic plant growth regulators (PGRs). State what is meant by the term apical dominance. MARKS Please see over/.. 8

9 c) Describe how endogenous PGRs control apical dominance. 6 Total Mark Please turn over/.. 9

10 Q5 a) Name the type of fruit shown below, giving ONE NAMED plant example. MARKS Type of fruit: Plant example: 10 Please see over/..

11 b) Name and describe the characteristics of EACH of the structures labelled A - D on the diagram in part a), by completing the table below. A Name Characteristic B C D 8 Total Mark Please turn over/.. 11

12 Q6 a) List FOUR environmental conditions that can affect water loss from plants. MARKS 4 b) Describe TWO ways by which bog plants are adapted to their environment giving a NAMED plant example for EACH.. 6 Please see over/.. 1

13 ... Total Mark Please turn over/.. 13

14 Q7 Describe the use of supplementary and replacement lighting, by completing the table below. Supplementary lighting Replacement lighting Meaning of term Horticultural situation where used Choice of lamp Two distinct reasons for choice of lamp Total Mark 14 Please see over/..

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16 Q8 a) Differentiate between the terms genus and species. 4 Please see over/.. 16

17 b) State what is meant by the following types of plant hybrid giving a NAMED plant example for EACH: i) intergeneric; ii) interspecific; iii) graft. Total Mark Please turn over/.. 17

18 Q9 a) In a plant, sucrose is transported from source to sink. Give an example of: i) a source; ii) a sink. 1 1 b) Explain how the following processes enable sucrose to be transported: i) phloem loading and unloading; ii) mass flow Please see over/..

19 .. Total Mark Please turn over/.. 19

20 Q10 Compare how flowers are adapted for pollination by moths and butterflies, by completing the table below: Moths Butterflies Plant example Flowering time Inflorescence/ flower structure Scent Flower colour Total Mark ******* Please turn over/.. 0

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24 These questions are the property of the Royal Horticultural Society. They must not be reproduced or sold. The Royal Horticultural Society, Wisley, Woking, Surrey GU3 6QB. Charity Registration Number: 879/SC0386 4

25 R3101 PLANT TAXONOMY, STRUCTURE & FUNCTION Level 3 Wednesday 8 February 017 Candidates Registered 136 Total Candidates Passed 85% Candidates Entered 118 Passed with Commendation 48% Candidates Absent/Withdrawn 17 Passed 37% Candidates Deferred 1 Failed 15% Senior Examiner s Comments On the whole this paper was well answered with the majority of candidates attempting and completing all the questions. The following guidelines should be of help to future candidates. 1. Where named plant examples are asked for, full botanical names (genus and species) are required to achieve full marks. Common names will not be given a mark.. Use the command statements e.g. list or name (single words only), state (a few sentences), describe or explain (a fuller answer) together with the mark allocation, to judge the depth of the answer. Half marks are often allocated where the basic information given is correct but needs further qualification to gain the full mark. 3. Where a number of answers are specified in the question, the examiner will not select correct answers from a list e.g. if the question states State TWO plant names, only the first two names given will be marked. 4. Labels on diagrams should be correctly positioned to avoid ambiguity and diagrams should be clearly drawn and annotated. No marks will be awarded for artistic merit. 5. Candidates should use unambiguous plant examples as reference sources from, for example, the RHS Find a Plant Service available on the RHS Website. 5

26 Q1 a) Describe the structural characteristics of conifers. 6 MARKS Q1 b) State FOUR ways by which the reproduction in conifers differs from that of ferns by 4 completing the table below. Conifers Ferns Q1 a) Marks were awarded for naming structural characteristics and for describing them, including xerophytic adaptations. For example, needle-shaped leaves, sunken stomata, xylem tissue made up of tracheids, resin ducts. Many candidates gave reproductive characteristics rather than structural ones. Q1 b) Some candidates found it difficult to give paired statements comparing conifer and fern reproduction e.g. Conifers disperse by means of seeds whereas ferns disperse by means of spores, The conifer male gamete is transferred by wind in pollen whereas the fern male gamete is transferred in sperm which swim in water. Most candidates recognised that ferns require water for reproduction whereas conifers do not. Many confused the role of spores in ferns and pollen in conifers. Fern spores give rise to a prothallus which produces the male and female gamete. They are not the gamete itself. A number of candidates wrongly stated that ferns produce pollen or undergo pollination. All plants undergo alternation of generations in their life cycle but the gametophyte phase is much reduced in conifers compared to ferns. Negative statements e.g. conifers produce seeds whereas ferns do not were not fully credited. 6

27 Q a) State what is meant by the term tissue. 1 Q b) Explain how the structure of epidermal tissue enables it to fulfil THREE distinct functions. 9 a) Almost all candidates were able to state that a tissue is a group of cells performing a specific function. Information beyond this was not required. b) Candidates who scored well approached this part of the question by identifying three distinct functions then went on to describe the related epidermal structure e.g. Reducing water loss from transpiration by having tightly packed epidermal cells with no air spaces between them, a waterproof cuticle, leaf hairs which increase humidity close to the leaf or the ability to close stomata. Enabling light penetration for photosynthesis in underlying cells due to epidermis being one cell thick and not containing chloroplasts. The question asked about the structure and function of epidermis not the periderm. Epidermis does not contain sclerenchyma, collenchyma or chloroplasts and stomata do not take water into the leaf for photosynthesis. Several candidates conflated protection and control of water loss which are different functions. MARKS Q3 a) State the optimum conditions for prolonging the storage life of fruit. 4 Q3 b) State the difference between modified and controlled atmospheres used in fruit storage. Q3 c) Explain how control of the gaseous atmosphere affects fruit storage life. 4 a) It was generally known that low temperatures and oxygen levels and high carbon dioxide levels prolong the storage life of fruit. Most candidates were able to state four conditions for optimising storage life such as increasing CO, decreasing O, cool temperature, suitable humidity (neither dry nor high) and good fruit quality. Storage in the dark is not necessary. Many candidates gave information about storage conditions in this section which was more appropriate to part c). b) Very few candidates knew the difference between modified and controlled atmosphere storage which relates to the gaseous atmosphere surrounding produce. In modified atmosphere storage produce is sealed e.g. in a package with no further manipulation. In controlled atmosphere storage, generally large scale stores, the atmosphere changes and is continuously monitored and modified during the storage period. 7

28 c) Where candidates noticed that this question was about the gaseous atmosphere i.e. oxygen, carbon dioxide, ethylene, nitrogen levels and relative humidity, rather than other storage conditions, they scored highly. Marks were awarded for stating how the levels of these gases affect storage and the methods used to control them. Marks were also awarded for demonstrating an understanding of the effects of the gaseous atmosphere on the progression through ripening and senescence and how this is linked to respiration and ethylene production. The relationship between humidity, water loss and development of rots was also relevant. MARKS Q4 a) State the difference between endogenous and synthetic plant growth regulators (PGRs). Q4 b) State what is meant by the term apical dominance. Q4 c) Describe how endogenous PGRs control apical dominance. 6 a) Almost all candidates were able to state that endogenous PGRs are produced within the plant whereas synthetic PGRs are manufactured and applied externally. b) Better candidates provided a succinct definition of apical dominance i.e. the suppression of later growth by the apical but, rather than describing the effects of apical dominance e.g. the type of branching in trees. Many candidates described the mechanism of apical dominance here rather than in part c). c) Most candidates were able to state that auxin promotes apical dominance and that cytokinin acts antagonistically to it. More than one PGR needed to be mentioned for full marks. Gibberellin is not involved in apical dominance since it only acts to stimulate lateral growth once the apical but is removed but does not overcome apical dominance itself. Ethylene is probably involved in inhibiting auxin transport. Any suitable theory was accepted the most popular being the attraction of sugars and cytokinin, produced in the leaves, to the apical bud which prevents the axillary bud from breaking. Auxin is produced in the apical bud/meristem and translocated to the region behind it. Auxin movement is polar, with the result that the apical dominance effect weakens down the stem. Several candidates described tropisms rather than apical dominance. 8

29 Q5 a) i) Name the type of fruit shown below, giving a NAMED plant example: MARKS Type of fruit: Plant example: b) Name and describe the characteristics of EACH of the structures labelled A - D 8 on the diagram in part a), by completing the table below. A B C D Name Characteristic a) The majority of candidates correctly identified the fruit as a drupe and were able to give a suitable example, the most popular being any Prunus spp. b) Most candidates correctly identified the labelled parts specifically as epicarp (not the epidermis or pericarp), mesocarp, endocarp and seed and were able to describe a characteristic of each. The seed contains the embryo (it is not the embryo itself). Drupes are endospermic seeds. 9

30 Q6 a) List FOUR environmental conditions that can affect water loss from plants. 4 b) Describe TWO ways by which bog plants are adapted to their environment giving a NAMED plant example for EACH. 6 a) Many candidates described environmental conditions rather than just listing them so used up valuable time. Full marks were awarded for relative humidity (not just humidity), temperature, light and windspeed (not just wind). b) Marks were awarded for suitable named bog plants such as Taxodium distichum or Gunnera manicata rather than aquatic plants such as Nymphaea spp. Insectivorous plants such as Drosera spp. were also appropriate examples. Most candidates mentioned adaptations such as pnematophores and aerenchyma and were able to describe these and their function of channeling oxygen down to the submerged roots from the aerial parts of the plants. Other mechanisms included physiological adaptations such as conversion of ethanol to non-toxic malic acid, digestion of insects to supply nitrogen and other nutrients which are unavailable in waterlogged soils and prop roots to improve stability. Some candidates described large leaves as in Gunnera being a mechanism to remove excess water through increased transpiration but large leaves exist simply because there is plenty of water so plants can optimise their leaf area for photosynthesis rather than this being an adaptation enabling them to live in waterlogged soils. 30

31 Q7 Describe the use of supplementary and replacement lighting, by completing the table below. Meaning of term Horticultural situation where used Choice of lamp Supplementary lighting Replacement lighting MARKS Two distinct reasons for choice of lamp 4 Describing a horticultural situation, supplementary lighting is used for example in glasshouses to boost light levels or extend the daylight hours whereas replacement lighting is used in growth rooms or cabinets. Marks were also awarded for mentioning suitable crops for each situation e.g. bedding plants vs. micropropagation. Replacement lighting is not used for AYR Chrysanthemums. Better candidates were able to give two distinct and suitable lamps and justify their choice. For example, High Pressure Sodium lamps are widely used in glasshouses for supplementary lighting because they can have a suitable spectral quality, they generate heat so can be used for heating, and are economical. LEDs can be used for replacement lighting as they generate little heat and can be used near the crop, their spectral quality can be manipulated easily, the rig is small so there is less shading and they are economical and long lasting. High Pressure Mercury and LEDs were also accepted for supplementary lighting and fluorescent lamps and Low Pressure Mercury for replacement lighting. Q8 a) Differentiate between the terms genus and species. 4 b) State what is meant by the following types of plant hybrid giving a NAMED plant example for EACH: i) intergeneric; ii) interspecific; iii) graft. a) Candidates needed to state that a genus is a group of species (not just plants) for full marks. Marks were awarded for stating the position of genus and species in the taxonomic hierarchy and that plants within a species can interbreed. Many stated that subsequent offspring are true to type but this is not always the case. 31 MARKS b) Most candidates were able to define intergeneric and interspecific hybrids and give a correct example for each. Very few understood that a graft hybrid is new tissue which arises out of the grafting together of two plants and contains genetic material from both. Many candidates incorrectly described grafting e.g. in apples.

32 Q9 a) In a plant, sucrose is transported from source to sink. Give an example of: i) a source; ii) a sink. b) Explain how the following processes enable sucrose to be transported: i) phloem loading and unloading; 4 ii) mass flow. 4 a) Most candidates understood that a source is where carbohydrates are made e.g. mature leaves and a sink is where they are used e.g. apical buds. Perennating organs such as tubers and bulbs act as sinks and sources at different times of year so candidates who used these examples only obtained full marks if this was stated correctly. b) The answers to parts i) and ii) were often mixed up in this part of the question. Better candidates described phloem loading and unloading in terms of the movement of sugars into and out of the phloem sieve tubes via transfer cells. This involves active transport, across the cell membrane on protein carries at the source (loading) and removal (unloading ) at the sink which can be active or passive. Mass flow is the movement of sugars through the phloem from source to sink under a pressure gradient. Many accurately described how sugars loaded into the phloem increase the sugar concentration and cause water to move into the sieve tubes by osmosis setting up a positive hydrostatic pressure. Water then carries the sugar dissolved in it along the phloem under this pressure to where it is unloaded. This continues as long as sugars are loaded and unloaded at each end of the phloem tissue. Some candidates described transpiration pull in the xylem and focussed on water circulation rather than sugar transport. Munch s mass flow hypothesis was sometime described with a diagram and marks were awarded as long as this was related to what was happening in the plant. 3

33 Q10 Compare how flowers are adapted for pollination by moths and butterflies, by completing the table below: 10 Plant Example Moths Butterflies Flowering Time Inflorescence / Flower Structure Scent Flower Colour This question was generally well answered and better candidates made paired comparisons under each heading. Some plant examples were rather obscure and could not be verified. Flowering time could relate to time of opening during the day with moth pollinated flowers or the time of year for the chosen plant example. Details of flower structure and/or inflorescence structure (rather than type) together with a description explaining how this was an advantage to a moth or butterfly gained full marks. Presence and absence of scent together with scent strength and character were awarded marks, as were specific flower colours. 33