Plant Reproduction Biotechnology II

Essential Questions How do angiosperms reproduce? What defines a model organism?

Angiosperms Plants that produce flowers Angiosperms – most diverse group in plant kingdom. Why? Evolved flowers and fruits. This allowed Increased successful mating of stationary organisms Flowers protect the egg and improved odds of fertilization Allowed plants that were considerable distance to mate through pollinators Fruit that surrounds the seeds –aided in dispersal with the help of animals

Development of flower-Why? Being terrestrial and lack locomotion –poses several problems: Gametes delicate cells. To achieve cross-fertilization, two gametes must reach each other safely. Must have a mechanism for dispersal Must be far enough away from parent so not to compete for light, water, and soil minerals.

Types of flowers Perfect flower – have both microsporangia (male) and megasporangia (female) Imperfect flower – have either microsporangia (male) or megasporangia (female)

Development of the flower Develop from flower buds- each bud has 4 concentric whorl of tissues Whorl of sepals – calyx Whorl of petals - corolla Stamens – where microsporangia(sperm) form Carpels – where megasporangia (egg) form

Anatomy of the Flower

Sexual Reproduction Pollen (contains sperm)is released from the anther Carried to the carpel, female reproductive organ Attaches to stigma Pollen germinates – forms pollen tube Pollen tube carries sperm to the egg in the ovule

Sexual Reproduction Animation of pollen germination and pollen tube growth

Pollination Pollen tube when it reaches ovule –releases the sperm Sperm nucleus and Egg nucleus combine to become the zygote Zygote divides and forms the embryo

Self-incompatibility Many angiosperms have mechanisms that prevent self-fertilization by rejecting its own pollen Prevent the pollen from germinating Promote genetic variation

Seed Once fertilized, each ovule develops into the seed A plumule – made up of two embryonic leaves, which become the first true leaves of the seedlings. Cotyledons Dicot – two cotyledons – ex. bean seed Monocot-one cotyledon- ex. corn seed

Seed Radicle – primary root Hypocotyl- part of the stem below the first node where the plumule is attached

Fruits Develop from the ovary wall Seeds mature release hormone auxin –stimulates the ovary wall to develop into fruit

Plant Breeding Also known as artificial selection Takes advantage of sexual reproduction in plants Collect pollen with desired phenotypic traits Pollinate flowers on neighboring plants Majority of Agriculture crops grown today were developed using artificial selection

Brassica rapa Belong to the mustard family Same family as cabbage, cauliflower, broccoli, and arabidopsis

Economic Importance Important economically as oilseed crop and animal fodder Crucifer oil, known as rapeseed oil, is the third most commonly traded vegetable oil in the world Rapeseed contains 40% oil-released when the seed is pressed Remaining seed meal is high in protein and used in animal feed and nitrogen fertilizer

Development of Rapid Cycling Brassica Wanted to incorporate efficiently traits of economic important, such as disease and pest resistance Needed an ideal plant type to speed research in genetics and plant breeding Began to breed Brassica rapa

Breed plants for Selective Traits Traits included Minimum time from planting to flowering Rapid seed germination Absence of seed dormancy Small plant size High female fertility – ovules once fertilized would develop into seeds rather than abort

Final Product Through this plant breeding created a plant with a rapid life cycle Plant has an average life cycle of 35 days compared to a normal 6 to 12 month life cycle

Life Cycle of Brassica

Other traits that make it ideal as a model organism Small in size; grow many in a small space Developed mutants for studying the growth and development of the plant

Lab Activity Use the model plant, Brassica Rapa, to monitor seed germination

Answer the following questions What was the evolutionary significance of flowers? What organs in the flower are the male (sperm) gamete and female (egg) gamete found, respectively Explain the process by which the pollen fertilizes the egg. What does it mean to be self-incompatible? What is the economic importance of Brassica rapa? What is Brassica rapa considered a model organism for studying plants? Read pp. 286-292; answer questions on p. 289 and 292.