Reproduction in plants
● Reproduction is the process of making more of the same kind of organism
● There are 2 types of reproduction
○ Asexual reproduction
○ Sexual reproduction
● Asexual reproduction
○ Asexual reproduction is the process resulting in the production of genetically identical offspring
from a single parent
● Advantages of asexual reproduction
○ Quick
○ Only single parent required
○ Good genetic characteristics always passed on
○ No dispersal so offspring will grow in the same favorable environment
● Disadvantages of asexual reproduction
○ Little variation, less adaptability to changing environment
○ Unlikely to withstand disease if parent not resistant
○ Lack of dispersal lead to increased competition for nutrients
● Sexual reproduction
○ Sexual reproduction is the process involving the fusion of 2 gametes to form a zygote. This
results in the production of offspring that is genetically different from the parents
○ Gametes are sex cells that have half of the normal chromosome number (haploid)
○ Therefore when male and female gamete fuse together, they form a new cell with normal
chromosome number (diploid)
● Advantages of sexual reproduction
○ Variation among offspring and therefore more adaptability to a changing environment
○ More likely to withstand disease
○ In plants, seed dispersal reduces competition for nutrients as offspring will grow in a different
environment
● Disadvantages of sexual reproduction are
○ Requires the fusion of 2 gametes
○ Slower process
● Plant reproduction
○ The sexual reproduction in plants involves the fusion of the male gamete (pollen) and the
female gamete (ovule)
○ A plant has both a male part containing the pollen and the female part containing the ovule
○ Male part - stamen
○ Female part - pistil/carpel
● Sexual reproduction occurs when the pollen from
the stamen of one flower successfully reaches the
ovule of either the same flower or a different flower
● The transfer of pollen is called pollination
● The carpel is the female reproductive part of the plant. It is made of 3 important structures
○ Stigma - the sticky surface that catches pollen
○ Style - links stigma to ovary
○ Ovary - contains ovules which develop into seeds after fertilization
● The stamen is the male reproductive part of the plant. It is made of two important structures
○ Anther - contains pollen
○ Filament - supports the anther
● Pollination
○ Pollination is the transfer of the pollen (male sex cells) from the anther to the stigma
○ Once the pollen lands on the stigma, it is transferred to the ovule (female sex cell)
○ The fusion of the pollen and ovule leads to what we call fertilization
● There are 2 methods by which plants facilitate pollination
○ Insect pollination
○ Wind pollination
● Insect pollination
○ Insect pollination uses insects that land on the flower to carry pollen
○ As insects move around within the flower, some pollen gets caught onto the insect's body. The
insect therefore physically carries pollen and successful pollination occurs when it rubs its body
against a stigma of the same flower or a different flower
● Wind pollination
○ Wind pollination uses the wind to carry pollen
○ Pollen that gets carried by the wind may end up on the stigma of the same flower or a different
flower
● Self pollination
○ It is the transfer of pollen from the anther of one flower to the stigma of the same flower, or a
different flower of the same plant
● Advantages
○ Only one parent required so less reliance on pollinators
○ Less competition among offspring
● Disadvantages
○ Less variation (since genes are all from the same plant)
○ Less adaptable to changing environment and resistance to disease
● Cross pollination
○ It is the transfer of pollen from the anther of one flower to the stigma of another flower on a
different plant of the same species
● Advantages
○ Increased variation
○ Greater adaptability to changing environment and more resistant to disease
● Disadvantages
○ More reliance on pollinators
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● Fertilization
○ When a pollen grain lands on the stigma of the correct
species, a pollen tube will begin to grow
○ It grows through the style, enters through a small gap in
the ovary called the micropyle and eventually reaches the
ovule
○ The nucleus of the pollen then passes along the pollen
tube and fuses with the nucleus resulting in successful
fertilization
○ The zygote eventually develops into a seed. The seed
remains dormant until the conditions are right and
germination occurs
● Germination
○ Germination is the development of a plant from a seed or spore after a period of dormancy
○ The conditions that must be met for germination
■ Water - for activation of enzymes
■ Oxygen - for respiration for growth
■ Temperature - optimum temperature for enzymes
