Week 12 powerpoint 2013

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propagation, seeds and vegetative

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Week 12 powerpoint 2013

  1. 1. RHS Level 2 Certificate Week 12 – Plant Propagation introduction
  2. 2. Learning outcomes        Plant propagation – introduction Define the terms: ‘seed propagation’ and ‘vegetative propagation’. Describe the characteristics of plants that can be propagated (a) from seed (b) vegetatively. State 5 benefits and 5 limitations of propagating plants (a) from seed (b) vegetatively Describe the preparation of fleshy berries for seed storage, under the following headings: harvesting; maceration; separation; cleaning and drying. State Five NAMED examples of seeds requiring cool dry storage State Two NAMED examples of seeds requiring cool moist storage
  3. 3. Plant propagation - definitions  Meaning of ‘propagation’ – human-mediated production of plants; as opposed to ‘reproduction’ which is the plant’s natural processes without human intervention.  Seed propagation – producing plants in a human controlled manner from seeds  Vegetative propagation - producing plants in a human controlled manner from parts of a plant.
  4. 4. Seed propagation – advantages/disadvantages Advantage Disadvantage The ability to breed new varieties Open pollinated plants may not come true from seed Large volumes of seed – cheap way to produce new plants Takes time and space to grow from seed to plants ready to plant out. Choice – a huge range of seed available Seeds for single colour of some flower varieties may not be available. Storage – most seed can easily be stored for some time Slower to maturity than vegetatively propagated plants. Guaranteed germination rates and certified disease free Guarantee and certification only applies to vegetable seeds.
  5. 5. Varieties normally propagated by seed  Hardy Annual – Centaurea cyanus (Cornflower)  Half Hardy Annual – Impatiens walleriana (Busy Lizzie)  Tender perennial – Heliotropium aborescens (Cherry Pie plant) usually grown as an annual  Hardy perennial – Liatris spicata (Gay Feather)
  6. 6. Vegetative propagation – advantages/disadvantages Advantages Disadvantages True to type – each is a clone of the Little chance of a new variety parent. Only way for some varieties arising. Monocultures are e.g. variegation. susceptible to disease. Uniformity – each will be exactly the same. Cost – requires skilled labour and aftercare. The only way to reproduce sterile varieties such as Vitis vinifera ‘Thompson’s Seedless’ Time – each plant has to be individually propagated. Speed to maturity is much quicker. Gradual loss of juvenility unless care of parent plants is very skilled. Ability to adapt plant to environment Smaller volumes in general – but using rootstock choice e.g. Malus NB - tissue culture.
  7. 7. Varieties normally propagated vegetatively Wisteria sinensis – perennial climber; desirable flower form and colour not reliable from seed. Long juvenility.  Petunia ‘Surfina’ (P. hybrida x P. pendula) – will not reproduce from seed; PBR applies.  Mallus domestica ‘Bramley’s Seedling’ – all apple varieties are produced vegetatively by grafting. This enables reproduction of the variety characteristics and also the control of the size of the eventual tree by choice of rootstock. 
  8. 8. Conditions for germination        The limiting factors for respiration Water – required for imbibition. Seeds that dry out after imbibition may die, or enter a deep dormancy (double dormancy). Temperature – the ideal varies between species. Oxygen – required for respiration Food – provided by the endosperm or cotyledons. If seeds are planted too deep or are only marginally viable they may use up their food supply before the shoot breaks the surface. Light – may trigger or prevent germination dependent on species. Not all species are light sensitive. Time – required for imbibition, breaking of dormancy etc.
  9. 9. Seed harvesting and storage  Why? Free seed; keep your favourites even if they fall out of fashion; share seed with friends or neighbours; grow plants that are not generally available commercially.  Harvesting – mature seed, dry (not after rain), clean to avoid rotting in storage or after sowing.  Storage – controlling respiration. Two main types of seed – orthodox and recalcitrant.
  10. 10. Seed Harvesting and storage  Plant must be healthy, vigorous and true to type. Must produce fertile, viable seed.  Aim is to collect ripe seed, clean it and store it in the correct conditions.  Orthodox seeds need cool, dry conditions. How cold depends on the species. Viable storage time depends on the species.  Recalcitrant seeds need cool (not cold), moist conditions – and do not retain viability for long.
  11. 11. Effects of storage on seed  Viability – if respiration is not controlled then the percentage of seeds that will germinate is reduced.  Vitality – if respiration is not controlled then seeds may use up food required for strong germination.  Dormancy – some seeds may become dormant if stored. The seeds of Baptisia australis (Wild Indigo) develop seed coat dormancy when the seed coat dries.
  12. 12. Learning outcomes        Plant propagation – introduction 1.1 Define the terms: ‘seed propagation’ and ‘vegetative propagation’. 1.2 Describe the characteristics of plants that can be propagated (a) from seed (b) vegetatively. 1.3 State 5 benefits and 5 limitations of propagating plants (a) from seed (b) vegetatively 1.4 Describe the preparation of fleshy berries for seed storage, under the following headings: harvesting; maceration; separation; cleaning and drying. 1.5 State Five NAMED examples of seeds requiring cool dry storage 1.6 State Two NAMED examples of seeds requiring cool moist storage

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