Download Plant propagation I

Plant propagation
Objective
continuation
Seeds and sexual reproduction
Vegetative reproduction
Rationale
Plants reproduce themselves by different
methods to ensure continuation of a species.
Easiest way to reproduce, yet not all plants
produce viable seeds.
Maturation is reached sooner so that fruit
production is earlier.
Compare sexual and vegetative reproduction in plants.
Plants may use two methods to achieve continuation:
1. Produce seeds or
2. Parts of the parent plant may be used; stem, leaves, canes, buds. Vegetative
propagation occurs without sexual means from the root, stem or shoot but not a seed.
Seed production
This is achieved with the fusion of special cells called gametes; one male and the other
female.
Sexual reproduction
Plants have female and male organs also. The male organ is the stamen, while the female part
is the pistil. The pistil consist of the stigma, style and ovary (know what these look
like). In some plants the stamens and a single pistil are contained in the same flower, seen in
avocado and citrus. These flowers are said to be bisexual or hermaphrodite. Some plants may
have stamens and no pistil such as the tassel in corn and are described as staminate. Flowers
may have pistils only, axils in corn leaves, and are pistillate.
A bisexual flower consists of four parts;

The outermost part of leaf live protective sepals,

Within the sepals are the petals brightly coloured to attract insects to pollinate,

Male part of the flower has a number of stamens and

The innermost part of the flower consists of the pistil or pistils.
The stamens filament and the anther consist of two lobes each with two pollen sacs where
pollen grains are produced. The pistil consists of three parts; stigma, style and ovary. The
stigma may be sticky as seen in the pear, mango, citrus or feathery as in the grasses. The
ovary contains little roundish bodies called ovules, that when fertilised by the male gametes
produce seeds. Ovules are attached to the ovary wall in a number of ways. The ovule is
attached to a fleshy tissue called the placenta; at the bottom is called basal, along the margin
is called marginal. There are three other ways: parietal, axile and free central Google!
Pollination and Fertilisation
Once pollen grains are deposited on the stigma the flower is pollinated. Each grain produces a
tube which grows down through the style to the ovary where the male gametes are released to
unite with the egg in the ovule to produce a zygote. Union of the gametes is called
fertilisation. The zygote develops into a seed. Insects transfer pollen from flower to flower. If
pollen comes from another flower; cross pollination. If pollen comes from the same flower or
from the flower of another plant; self pollination. Cross pollination is more desirable since it
produces a hybrid which is improved hardiness of the new plant.
Fertilisation initiates both seed and fruit production. Most fruits will not develop without
fertilisation such as plantain.
Fruit Structure
When the ovary of a flower develops into fruit its walls may divide into two or three distinct
regions;
 Outer- epicarp or exocarp
 Middle- mesocarp
 Innermost- endocarp.
 All three regions are seen in the mango.
Types of Fruit
This is based on the number of pistils and flowers involved.
1. Simple formed from a single flower with on pistil, example tomato.
2. Aggregate formed from a single flower with many pistils, examples soursop and
strawberry.
3. Compound or multiple formed from several small flowers, examples pineapple and
jackfruit.
Fruits are either fleshy or dry- whether fruit wall is succulent or dry.
Fleshy fruits


Berry – whole ovary wall, pericarp, becomes fleshy except for this membranous
epicarp; tomato and guava.
Drupe- mesocarp is fleshy, endocarp either stony, coconut, or leathery, avocado.

Hesperidium- epicarp and mesocarp fuse forming a leathery rind; citrus.
Dry Fruits
Dehiscent
Indehiscent.
Dehiscent
Capsule- pericarp splits longitudinally in 3 or more sections- Jamaican ackee.
Schizocarp- fruit breaks up into a number of one seeded parts- castor oil.
Legume or pod- fruit splits longitudinally along its two sutures. Only produced by plants of
the legume family.
Follicle- similar to the pos in shape, but it splits on only on side in one suture; frangipani.
Indehiscent Fruit
Nut- the whole pericarp becomes hard. The receptacle ballons into a succulent edible; aril.
Caryopsis- one seeded fruit the pericarp of the fruit and testa of the seed are fused. What
looks like a seed is really a fruit. Fruits of all grasses. A grain of corn is a fruit.
Achene- a one seeded fruit but the pericarp and testa are not fused; carrot.
Cypsela- like and achene, pericarp bears hairs to aid in the dispersal of the seed; sunflower
and marigold.