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PART 4: REPRODUCTION OF FLOWERING PLANTS Flowers are reproductive organs that are composed of four kinds of specialized leaves: 1. petals 2. Sepals 3. stamens 4. Carpels (also called Pistils) Petals – Brightly colored structure just inside the sepals; attracts insects and other pollinators to a flower. Sepals – Outermost circle of flower parts that encloses a bud before it opens and protects the flower while it is developing. Male Part of Flowers Stamen – Male part of the flower; Made up of an anther and a filament. •
Anther produces pollen containing sperm. •
Filament supports the anther Female Part of Flowers Pistil (or Carpel) – female part of a plant; Innermost part of a flower that produces the female gametophyte. •
Stigma-­‐ Sticky portion located at the top of the style where pollen frequently lands •
Broad base forms an ovary which contains one or more ovules (contains eggs inside). •
The diameter of the carpel narrows into a stalk called a style. A complete flower has all four organs, and an incomplete flower lacks one or more organs. Pollination Pollination – Transfer of pollen from the stamen to the pistil. Methods of Pollination: 1. wind 2. animals (most are pollinated by animals) Pollination Adaptations That Attract Animals: 1. Nectar 2. Petal Color 3. Scent
4. Types of Pollination Self-­‐Pollination – stigma receives pollen from the same plant Cross-­‐Pollination – Pollen from one plant is carried to the stigma of another plant -
Must be the same type of plant -
Allows for exchange of genetic material
Reproduction of Flowers Reproduction in flowers is similar to gymnosperms in that both produce seeds and gametophytes are within the body of the sporophyte. Fertilization in Flowers 1. Pollen grain lands on the stigma 2. The pollen tube cell grows a tube to the ovule 3. The two sperm cells move through the tube into the ovule •
One sperm joins with the egg in the ovule. •
The other joins with the central cell (2N) to form the endosperm (3N) •
The process is called double fertilization •
Double Fertilization -­‐ Fertilization in angiosperms, in which two distinct fertilization events take place between the male and female gametophyte. Seed Formation 1. After fertilization occurs, the flower dies and the seed develops 2. Ovule becomes the seed coat which protects the embryo 3. The zygote divides becoming the embryo. 4. The 3N central cell develops into the endosperm which is food-­‐storage tissue. Fruits ● The ovary develops into a fruit, which can be dry (nuts and grains) or fleshy (oranges, peaches, squash, or tomatoes). ● Fruits have two main jobs: To protect the seed and to aide in dispersal Seeds ● Seeds can remain dormant until conditions are right for development and growth. o -­‐Water, oxygen, and favorable temperatures are usually needed. ● Germination – Early plant stage of a plant embryo o Germination is the development of the seed into a new plant ● During growth, the roots appears first, and then the stem and finally the leaves Plant Growth and Development Plants respond to stimuli from the environment. This process is called tropism -­‐Positive Tropism -­‐ Growth towards the stimulus. -­‐Negative Tropism – Growth away from the stimulus -­‐Phototropism – Growth towards light -­‐Gravitropism – Response to gravity -­‐Thigmotropism-­‐ Response to response to touch