Section 14.1 cont’d..Plant Reproduction

Section 14.1 cont’d..Plant Reproduction Pages 584-591

Agenda Recap : Asexual & Sexual Reproduction Section 14.1 cont’d : Sexual Reproduction in Angiosperms Reminders: Unit Test on Wednesday Presentations on Thursday & Friday Homework: Page 599, Qn’s: 1-5, 10 & 12

Sexual Reproduction in Angiosperms Female part male part Plants that reproduce through flowers are called angiosperms. Flowers attract insects with their colour, smell, and nectar. This helps in pollination. Many flowers have the stamen (male part) and pistil (female) part in the same flower. The male part produces pollen which houses sperm cells. The female part produces the ovule/egg cells with are housed in the ovary.

Sexual Reproduction in Angiosperms

Flowering plants worksheet! Use your textbook pg 584 to fill in the worksheet

Variations among Flowers Modifications of the four basic components of the flower (sepal, petal, androecium and gynoecium), together with how groups of flowers are arranged in an inflorescence, lead to the world’s overwhelming floral diversity. The details of floral morphology form the basis of flowering plant classification, so accurate descriptions are fundamental to identifying plants. The presence or absence, number, arrangement, form and colour of these structures are all important

Life cycle of Flowering Plant http://www.sumanasinc.com/webcontent/animations/content/angiosperm.html

Section 14.2 Plant Growth & Development Pages 543-597

Plant Hormones: (Pg 593)

How Does Auxin Stimulate Growth? • Causes cell walls to become “looser” and more malleable. Then they can be expanded/elongated

List of Plant Hormones • Auxin – IAA (indoleacetic acid) • Foundin meristems of apical buds; young leaves • Major Functions: • stimulation of stem elongation • Allows for stem cell walls to become pliable so that addition of water will cause elongation • Root growth differentiation, branching • Allows formation of adventitious roots at cut base of stem • Apical dominance • Growth of a stem occurs only at the tip unless the tip is cut off • Absence of auxin from tip will allow lateral buds to emerge • This is why they prune

List of Plant Hormones • Auxin (IAA) cont. • Found • Embryos within seeds • Major Functions • Stimulate growth of fruit from ovary

Cytokinins • Found in actively growing tissues – especially roots. Transported by xylem to other places • Major function: • Role in division and differentiation of plant cells • Work with auxins to control plant growth • Plant tissue treated with auxin w/o cytokiinin – cells will grow but not divide • Control of apical dominance • Cytokinins from roots can counter action of auxin • Anti-aging hormones • May inhibit protein breakdown by stimulating protein synthesis • Slow deterioration of leaves – used by florists

Gibberellins • Found in apical meristems; young leaves/embryos • Major function: • Simulates growth in leaf and stem • Both elongation AND cell division – auxin link • Stem bolting • Rapid elongation of a stem – flower stalk • Fruit growth • Grapes are sprayed with gib to cause them to grow larger and further apart • Germination of seeds • After water is imbibed, gibberellins are released from embryo to signal break from dormancy

Abscisic Acid (ABA) • Found in leaves, stems, roots, seeds, green fruit • Major function: slow down growth • Dormancy for overwintering • Suspends primary and secondary growth • Promotes abscision of leaves (falling off) • In seeds – inhibits growth until ABA can be overcome or diminished by favorable conditions • Heavy rain may wash out ABA • Light may degrade • Increased gib to ABA ratio may determine germination • growth • Stress hormone • When a plant wilts, ABA accumulates causing stomata to close

Ethylene • Found in tissues of ripening fruit, nodes of stems, Ageing leaves and flowers • Major functions • Changes of ovary to become fruit • Degradation of cell walls; softening • Dropping from plant • Leaf abscission • Loss of leaves to prevent water loss • Tissue at base of petiole dies • Senescence (aging) • Autumn leaves; withering flowers

Learning Check!! (pg 595) Qn 18) A group of student plant bean seeds. 1 plant grows rapidly, & within 3 weeks it is twice the height of all the others. The students conclude that this plant has a genetic variation causing excessive auxin production. List 5 questions you would ask about the scientific validity of these results & conclusion

Plants Response to Environmental Stimuli Plants can respond to stimuli in their environment. Tropisms: is a growth in response to a stimulus. It occurs in the direction of the stimulus. The most common tropisms are phototropism (growth in response to light) and hydrotropism (growth in response to water). Nastic Response: Plant’s response to a stimulus may be independent of direction of stimulus

Tropic Responses Phototropism—the way a plant grows or bends in response to light Geotropism—the way a plant grows or bends in response to gravity Hydrotropism—the way a plant grows or bends in response to water Thigmotropism—the way a plant grows or bends in response to touch

Phototropism • Cells elongate on the side of the stem that is in the DARK • This occurs due to an ASSYMETRICAL distribution of auxin from the shoot tip

Gravitropism • Growth in response to gravity • Allows roots to “know” which way is DOWN and to grow in that direction • Allows shoots to “know” which way is UP and to grow in that direction • Hormone is auxin • Mechanism is similar to phototropism, but stimulus is gravity

Thigmotropism • Growth in response to touch • Seen in vines that “know” where a fence post is • Curvature in growth allows them to cling to the post and move up towards light

Other Factors That Affect Plant Growth • Nutrients : • Macronutrients: Nitrogen, Potassium , Calcium, Magnesium, Phosphorous, Sulfur • Micronutrients: chlorine, iron, boron, manganese, zinc, copper & molybdenum • pH: most plants grow within only a very narrow range of pH. • Most plants thrive in slightly acidic soils ranging from pH 6-7. E.g. pines, spruce, dogwood, blueberry • Fewer plants tolerate basic soils pH 7-8, E.g. beans, beets, lettuce, pears and plums

Overview of Plants http://www.learn360.com/ShowVideo.aspx?ID=128194

Homework Page 599, Qn’s: 1-5, 10 & 12

Section 14.1 cont’d..Plant Reproduction