2.4 Hybrids And Fruit Flashcards
Modern hybrid
Production of pollination of a genetically uniform plant with pollen derived from another individual, also being genetically uniform in composition.
Seed companies will select characters specially required by company breeders.
Hybridisation is very controlled; often done manually.
Plants grown from hybrid seed will be the result of desired cross and will be genetically identical.
Seed cannot be self seeded.
Hybrid vigour
Hybrids usually have hybrid vigour.
Yield can be higher than open pollinated crops.
Hybrids don’t breed seed.
Plants will not produce seeds that can germinate to produce progeny that mirrors the parents.
In the new generation the range of genes will tend to segregate into different kinds of modifications this will tend to produce a range of variations in the new generation.
Advantages of hybrids.
Capture and enhance individual, desired qualities of parent plants. Improved vigour (hybrid vigour) eg. Improved seed germination and crops growth. Plants are uniform true to type and high yielding. Early harvest/cropping, resistance to pests and diseases, good holding characteristics in the field, pre harvest - is present in most F. Hybrids. Uniformity of plant habit and maturity, uniformity of shape and size - ideal for mechanical harvesting.
Fruit - definition
Fertilized and ripened ovary that is fouled around seeds.
Word used for all ripe seed vessels.
Ovary wall develops into the fruit wall, technically pericarp.
Types of fruit
Berry - tomato Drupe - plum Legume - pea Capsule - horse chestnut Multiple fruits - fig Achene - sunflower Nut - acorn
Formation of fruit
After fertilisation the ovary wall undergoes changes that lead to the development of the fruit.
Perianth and stamens usually wither and the style dries up unless it acts is dispersal eg. Some Rosaceae
Ovary wall often has distinct layers
1 outer layer - exocarp
2 mesocarp - middle layer
3 endocarp - inner layer
Seed dispersal strategies
Intent - to disperse seed in suitable environment, away from parent plant.
Fleshy covering, eaten by animals - transported to new areas and then deposited.
Development of wing like or parachute like structures>seeds float away from plant.
Some plants can shoot seed some distance from plant.
Dry fruits - indehiscent and dehiscence
Indehiscent - usually only one seed.
Dry fruit which has no seed pod which opens.
Dehiscence - often has several seeds.
Contained in seed pod which opens
Dry indehiscent
Achene and Nut
Achene - small, one seeded, sometimes seed and pericarp and fused. eg. Helianthus annuus
Nut - one seeded, dry, hard or stony pericarp.
Eg. Corylus avellana.
Dry dehiscence fruit.
Follicle & Capsule
Follicle - splits in one side (suture) only. May contain many seeds eg. Aquilegia vulgaris.
Capsule - develops from compound ovaries, each carpel produces several seeds, fruit opens in several ways eg. Longitudinal tears, pores or raising lid.
eg. Papaver somniferum
Dry dehiscence
Legume
Legume - structurally similar time follicle.
Splits along both edges of pod (sutures) eg. pi sum sativum
Fleshy fruits
Fleshy fruits - carpel develops into a thick, fleshy covering.
Fleshy covering encourages consumption by animals - frugivory.
Seed inside fruit must be able to withstand process of digestion.
Fleshy fruits
- drupe
- berry
Drupe - one seed, seed is generally surrounded by a hard endocarp or stone eg. Prunus avium.
Berry - develop from compound ovary. Endocarp and mesocarp become thick and fleshy.
Often there are many seeds embedded in the flesh eg.Lycopersicon esculentum.
False Fruit
Derived from plants where the seed bearing structure is derived from parts of the flower such as the receptacle or pericanth.
Pericanth - calyx, corolla and bracts.
Parts develop into fleshy, coloured structures - pseudo carp
Pseudocarp examples
Strawberries - develops from receptacle seed (archenes) dot surface.
Rosehip - develops from receptacle, small seed (archenes) are contained within.
