Crop plant reproductionCrop plant reproduction

ALBIO9700/2006JK

ALBIO9700/2006JK

The structural features of a The structural features of a wind pollinated plantwind pollinated plant

CharacteristicCharacteristic Meadow fescue (wind pollinated)Meadow fescue (wind pollinated)

PetalsPetals no petals (small, inconspicuous, often green)no petals (small, inconspicuous, often green)

no nectariesno nectaries

no scentno scent

no landing platformno landing platform

FlowersFlowers borne at the end of long stalks, held well above the borne at the end of long stalks, held well above the foliagefoliage

flowers can appear before the leavesflowers can appear before the leaves

StamensStamens hang outside flower to catch windshang outside flower to catch winds

stamens and anthers swing freely in air currentsstamens and anthers swing freely in air currents

PollenPollen light, small, smooth surfacedlight, small, smooth surfaced

relatively large amount produced relatively large amount produced

StigmaStigma large, feathery and hangs outside, therefore traps large, feathery and hangs outside, therefore traps pollen more easily pollen more easily

Wind pollinationWind pollination

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Meadow fescue (Meadow fescue (Festuca pratensis)Festuca pratensis)

The genetic outcomes of self The genetic outcomes of self and cross pollinationand cross pollination

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Self pollinationSelf pollination Cross pollinationCross pollination

Decreased genetic Decreased genetic variation/increased genetic variation/increased genetic uniformityuniformity

Increased genetic Increased genetic variation/decreased genetic variation/decreased genetic uniformityuniformity

Increased Increased homozygosity/decreased homozygosity/decreased heterozygosityheterozygosity

Increased Increased heterozygosity/decreased heterozygosity/decreased homozygosityhomozygosity

Harmful recessive characteristics Harmful recessive characteristics more likely to be expressedmore likely to be expressed

Harmful recessive characteristics Harmful recessive characteristics less likely to be expressedless likely to be expressed

Reduction in gene poolReduction in gene pool Maintenance of gene poolMaintenance of gene pool

Inbreeding depression reduces Inbreeding depression reduces fitnessfitness

Gives hybrid vigour (= heterosis Gives hybrid vigour (= heterosis = outbreeding enhancement), so = outbreeding enhancement), so fitness maintainedfitness maintained

Self- Self- vsvs cross-pollination cross-pollination

• Self-pollination more reliableSelf-pollination more reliable• Self-pollination advantageous in harsh Self-pollination advantageous in harsh

environmentsenvironments• Self-pollination results in self-fertilisation Self-pollination results in self-fertilisation

(inbreeding/genetic disadvantage)(inbreeding/genetic disadvantage)

• Cross-pollination is less reliable, more Cross-pollination is less reliable, more wasteful of pollenwasteful of pollen

• Cross-pollination has genetic advantages Cross-pollination has genetic advantages (producing variation/outbreeding)(producing variation/outbreeding)

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The structure of the fruit in The structure of the fruit in maize and the function of the maize and the function of the

endospermendosperm• The individual fruit of maize is a dry fruit The individual fruit of maize is a dry fruit

((caryopsiscaryopsis) and contains a single seed) and contains a single seed• Seed contains 2 structures:Seed contains 2 structures:

– Germ: from which new plant will developGerm: from which new plant will develop• Consists of a miniature plant axis to which is attached ~5 Consists of a miniature plant axis to which is attached ~5

embryonic leaves and a radicleembryonic leaves and a radicle• Source of maize ‘vegetable oil’Source of maize ‘vegetable oil’

– Endosperm: a store of nutrients which will be Endosperm: a store of nutrients which will be made available to the germinating seedling until it made available to the germinating seedling until it has established sufficient leaf area to has established sufficient leaf area to photosynthesisephotosynthesise• Takes up about 2/3 of the volume of the seed and Takes up about 2/3 of the volume of the seed and

accounts for around 86% of its dry weightaccounts for around 86% of its dry weight• Principle component – starch and 10% protein (gluten)Principle component – starch and 10% protein (gluten)• To provide the nutrition required by the germinating To provide the nutrition required by the germinating

seedling seedling • Whole, ground maize meal has 1500 kJ per 100gWhole, ground maize meal has 1500 kJ per 100g

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Corn grainCorn grain1.1. PericarpPericarp (fruit wall protecting corn (fruit wall protecting corn

kernel)kernel)2.2. Aleurone layerAleurone layer (produces a-amylase, an (produces a-amylase, an

enzyme that breaks down starch and thus enzyme that breaks down starch and thus mobilizes energy for germination)mobilizes energy for germination)

3.3. EndospermEndosperm (rich in starch which serves (rich in starch which serves as the energy source for the germinating as the energy source for the germinating seed and seedling)seed and seedling)

4.4. CotyledonCotyledon (does not serve as the (does not serve as the storage tissue of the seed )storage tissue of the seed )

5.5. ColeoptileColeoptile (acts as a protective sheath (acts as a protective sheath surrounding young leaves and apical surrounding young leaves and apical meristem of a plumule)meristem of a plumule)

6.6. PlumulePlumule (embryonic plant) (embryonic plant)7.7. Apical meristemApical meristem8.8. RadicalRadical (embryonic root) (embryonic root)9.9. ColeorhizaColeorhiza (seals and prevents (seals and prevents

pathogens from entering the kernel pathogens from entering the kernel through the rupture made by the through the rupture made by the elongating radicle during germination)elongating radicle during germination)

10.10. Black layerBlack layer (once formed, it indicates (once formed, it indicates physiological maturity)physiological maturity)

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The significance of the The significance of the inclusion of cereal grains in the inclusion of cereal grains in the

human diet human diet • Nutritional value of cereal grains:Nutritional value of cereal grains:– 70-80% carbohydrates (starch) – important 70-80% carbohydrates (starch) – important

source of energysource of energy– Source of protein (6-14%) – millets, rice, maize; Source of protein (6-14%) – millets, rice, maize;

rye, barley; wheat, oats – low in lysinerye, barley; wheat, oats – low in lysine– Low in fat (2-4%; oats 7.5%) – high in essential Low in fat (2-4%; oats 7.5%) – high in essential

fatty acids (linoleic acid) – fat found in germ of fatty acids (linoleic acid) – fat found in germ of graingrain

– Vitamins – B groups vitamins (thiamin, riboflavin, Vitamins – B groups vitamins (thiamin, riboflavin, niacin, B6, folic acid, biotin and pantothenic niacin, B6, folic acid, biotin and pantothenic acid) and fat soluble vitamin E – deficient in acid) and fat soluble vitamin E – deficient in vitamins A, D and Cvitamins A, D and C

– Minerals – potassium, calcium, magnesium, Minerals – potassium, calcium, magnesium, phosphorus, iron and zincphosphorus, iron and zinc

– Fibre – wholegrain meal or flour contain much Fibre – wholegrain meal or flour contain much more fibre than grains which have been more fibre than grains which have been processed and refinedprocessed and refined

ALBIO9700/2006JK

ALBIO9700/2006JK