2. The structural features of a wind
pollinated plant
Characteristic Meadow fescue (wind pollinated)
Petals no petals (small, inconspicuous, often green)
no nectaries
no scent
no landing platform
Flowers borne at the end of long stalks, held well above the
foliage
flowers can appear before the leaves
Stamens hang outside flower to catch winds
stamens and anthers swing freely in air currents
Pollen light, small, smooth surfaced
relatively large amount produced
Stigma large, feathery and hangs outside, therefore traps pollen
more easily
ALBIO9700/2006JK
4. The genetic outcomes of self and
cross pollination
Self pollination Cross pollination
Decreased genetic variation/increased Increased genetic variation/decreased
genetic uniformity genetic uniformity
Increased homozygosity/decreased Increased heterozygosity/decreased
heterozygosity homozygosity
Harmful recessive characteristics more Harmful recessive characteristics less
likely to be expressed likely to be expressed
Reduction in gene pool Maintenance of gene pool
Inbreeding depression reduces fitness Gives hybrid vigour (= heterosis =
outbreeding enhancement), so fitness
maintained
ALBIO9700/2006JK
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. The structure of the fruit in maize
and 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. 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. 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
