* 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. 30.13a
*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. *
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*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 *
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*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 *