01 Crop Plant Reproduction


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01 Crop Plant Reproduction

  1. 1. Crop plant reproduction ALBIO9700/2006JK
  2. 2. The structural features of a wind pollinated plantCharacteristic Meadow fescue (wind pollinated)Petals no petals (small, inconspicuous, often green) no nectaries no scent no landing platformFlowers borne at the end of long stalks, held well above the foliage flowers can appear before the leavesStamens hang outside flower to catch winds stamens and anthers swing freely in air currentsPollen light, small, smooth surfaced relatively large amount producedStigma large, feathery and hangs outside, therefore traps pollen more easily ALBIO9700/2006JK
  3. 3. Wind pollinationMeadow fescue (Festuca pratensis) ALBIO9700/2006JK
  4. 4. The genetic outcomes of self and cross pollination Self pollination Cross pollinationDecreased genetic variation/increased Increased genetic variation/decreasedgenetic uniformity genetic uniformityIncreased homozygosity/decreased Increased heterozygosity/decreasedheterozygosity homozygosityHarmful recessive characteristics more Harmful recessive characteristics lesslikely to be expressed likely to be expressedReduction in gene pool Maintenance of gene poolInbreeding depression reduces fitness Gives hybrid vigour (= heterosis = outbreeding enhancement), so fitness maintained ALBIO9700/2006JK
  5. 5. Self- vs cross-pollination• Self-pollination more reliable• Self-pollination advantageous in harsh environments• Self-pollination results in self-fertilisation (inbreeding/genetic disadvantage)• Cross-pollination is less reliable, more wasteful of pollen• Cross-pollination has genetic advantages (producing variation/outbreeding) ALBIO9700/2006JK
  6. 6. The structure of the fruit in maizeand the function of the endosperm• The individual fruit of maize is a dry fruit (caryopsis) and contains a single seed• Seed contains 2 structures: – Germ: from which new plant will develop • Consists of a miniature plant axis to which is attached ~5 embryonic leaves and a radicle • Source of maize ‘vegetable oil’ – Endosperm: a store of nutrients which will be made available to the germinating seedling until it has established sufficient leaf area to photosynthesise • Takes up about 2/3 of the volume of the seed and accounts for around 86% of its dry weight • Principle component – starch and 10% protein (gluten) • To provide the nutrition required by the germinating seedling • Whole, ground maize meal has 1500 kJ per 100g ALBIO9700/2006JK
  7. 7. Corn grain• Pericarp (fruit wall protecting corn kernel)• Aleurone layer (produces a-amylase, an enzyme that breaks down starch and thus mobilizes energy for germination)• Endosperm (rich in starch which serves as the energy source for the germinating seed and seedling)• Cotyledon (does not serve as the storage tissue of the seed )• Coleoptile (acts as a protective sheath surrounding young leaves and apical meristem of a plumule)• Plumule (embryonic plant)• Apical meristem• Radical (embryonic root)• Coleorhiza (seals and prevents pathogens from entering the kernel through the rupture made by the elongating radicle during germination)• Black layer (once formed, it indicates physiological maturity) ALBIO9700/2006JK
  8. 8. The significance of the inclusion of cereal grains in the human diet• Nutritional value of cereal grains: – 70-80% carbohydrates (starch) – important source of energy – Source of protein (6-14%) – millets, rice, maize; rye, barley; wheat, oats – low in lysine – Low in fat (2-4%; oats 7.5%) – high in essential fatty acids (linoleic acid) – fat found in germ of grain – Vitamins – B groups vitamins (thiamin, riboflavin, niacin, B6, folic acid, biotin and pantothenic acid) and fat soluble vitamin E – deficient in vitamins A, D and C – Minerals – potassium, calcium, magnesium, phosphorus, iron and zinc – Fibre – wholegrain meal or flour contain much more fibre than grains which have been processed and refined ALBIO9700/2006JK
  9. 9. ALBIO9700/2006JK