Flowers Seeds Pollination Germination

* In order for plants to be successful in many different environments they must be able to reproduce themselves. * The reproductive patterns of plants reflect the reproductive patterns of any other organism.

* Male must meet female in some way. * Male reproductive cells are smaller, numerous and motile (able to move). * Female reproductive cells are large, single and sessile (not able to move)

* A plant will spend most of it’s time and energy on making sure that the ovuole is taken care of as there is only one per flower. * Some flowers are only female, some flowers are only male and some flowers have both male and female gametes (pollen and ovuole). * These flowers are considered hermaphroditic (can fertilize themselves).

* A flower is a specialized shoot with four circles of modified leaves: sepals, petals, stamens, and carpals. Fig a

* The sepals at the base of the flower are modified leaves that enclose the flower before it opens. * The petals lie inside the ring of sepals. * These are often brightly colored in plant species that are pollinated by animals. * They typically lack bright coloration in wind-pollinated plant species. * Neither the sepals nor petals are directly involved in reproduction.

* Stamens, the male reproductive organs, produce microspores (pollen) that will give rise to gametophytes (new plants). * A stamen consists of a stalk (the filament) and a terminal sac (the anther) where pollen is produced. * Carpals are female reproductive organs that produce megaspores (ovuole) and their products, female gametophytes. * At the tip of the carpal is a sticky stigma that receives pollen. * A style leads to the ovary at the base of the carpal. * Ovules and, later, seeds are protected within the ovary.

* Fruits are produced by the ovary developing. The fruit will protect the seeds and aid in dispersal. Fruits in angiosperms include vegetables and fruits.

* Plants use pollination as a way to reproduce. * As the pollen matures, the anther bursts open releasing all the pollen. * This is carried to the stigma of the same or other flowers. * Process is called pollination * Definition: transfer of pollen from anther to stigma

* There are 2 types of pollination: * 1) Self Pollination – is when the pollen of one flower falls on the stigma of the same flower or another flower of the same plant. * 2) Cross Pollination – is the transfer of pollen from the stigma or one flower to the anther of a flower of another plant of the same species. * Cross Pollination can be by wind or animals but mostly insects.

* During fertilization, the pollen nucleus fuses with the female nucleus to produce the zygote. * The zygote grows into the seed. * The ovary grows into the fruit – different adaptations for seed dispersal. * Fruit forms from concentration of nutrients

* Fruits can be dry – roses, dandelions or peas. * Fruits can be juicy – apples, cherries or plums.

* Seed and Fruit Dispersal results in the spreading of fruits and seeds to other environments and ecosystems. * Important because: * 1) The seeds will not overcrowd in an area and this minimizes competition for resources. * 2) It spreads the seeds to other environments which might offer better chances of survival for these plants.

Fruits – Seed dispersal - Wind

Fruits – Seed dispersal - Water

Fruits – Seed dispersal - Animals

Internal/External Structure, Metabolic events and Needs for Germination – Why do we have seeds?

* Plumule: develops into the stem. * Cotelydon: stores or absorbs food for the developing embryo. * Radicle: first part of a seedling (a growing plant embryo) to emerge from the seed during the process of germination – primitive root * Micropyle: small pore on the seed coat for absorption of water. * Testa: outer seed coat, protective layer

* 1) Water is needed to: * Activate hormones and enzymes * Swelling of the seeds = bursting of seed coat. * Transport of simple materials to the embryo – to be used for respiration and growth. * Metabolic and enzyme actions – occur in solution, therefore need water. * Conversion of storage compounds into simple components (i.e. starch to glucose)

* 2) Oxygen is needed for aerobic respiration. * Without a supply of oxygen, seeds fail to germinate because of the lack of energy – in the form of ATP.

* 3) Suitable temperature * All reactions (in germination) are controlled by enzymes. * Optimal temperature for enzyme activity leads to faster rate of germination. * Freezing = inactivates enzymes * Very high temperatures = denatures enzymes

* 1) Water enters the seed through a hole in the seed coat – microplye. * 2) Water moves into the tissues and cells by osmosis. * 3) The seed swells and the seed coat bursts. * 4) Water activates gibberelline, the hormone needed for breaking the dormancy of the seed.

* 5) Gibberelline activates amylase which catalyzes the break down of starch to maltose to glucose. * 6) Glucose is mobilized (transported) to the embryo. * 7) Embryo absorbs glucose and uses it for respiration (oxygen needed). * 8) Cell division, growth and elongation occurs in the embryo = radicle to root, plumule to stem.

* 9) Nutrients needed for growth all supplied by food stored in cotelydons. * 10) As nutrients are consumed, first leaves start to appear = photosynthesis. * 11) When photosynthesis starts, seedling absorbs water and minerals from the soil, Co2 from the atmosphere and sunlight.

Starch, Proteins and Lipids

* Plants make glucose in the process of photosynthesis. * Glucose is used for respiration to produce energy which powers different processes in the plant such as active transport. * Excess glucose can be converted to storage materials.

* There are 3 main types of storage materials: * 1) Starch * 2) Proteins * 3) Lipids

* Examples include: * Corn seeds * Potato tubers * Rice and wheat grains

* Examples include: * Seeds of leguminous plants: * Peas * Beans * Lentils

* Examples include: * Olive fruits and seeds * Sunflower seeds