Plant Life Cycles CHAPTER 30

Animals vs. Plants Plant Reproduction Animal Reproduction Life cycle Alternation of generations No alternation of generations Gametes Haploid gametes Spores Haploid spores No spores Gametes made by Haploid gametophyte, by mitosis Diploid organism, by meiosis Spores made by Diploid sporophyte, by meiosis

Alternation of Generations Plants have a double life cycle with two distinct forms: Sporophyte: diploid, produce haploid spores by meiosis. Gametophyte: haploid, produce gametes by mitosis.

Non-flowering plants Mosses, ferns, and related plants have motile, swimming sperm. What kind of environmental conditions would be required for reproduction in these plants? What kinds of limits does external reproduction impose on these plants? Reproduction in these plants requires wet conditions, and requires having male and female parts close together. Living conditions, plant size, and genetic mixing is limited.

Life cycle of mosses Follow the link and write down in your notes 1 page on the life cycle of mosses http://www.microview.org.uk/millennium/pages/moss_lifecycle.htm http://www.sumanasinc.com/webcontent/animations/content/moss.html

Moss Life Cycle

Life cycle of ferns Ferns, unlike some other plants, do not flower in order to propagate. Instead, they reproduce sexually from spores. The life cycle of a fern is very different from the life cycle of many other plants. While many plants grow a mature adult form straight out of the seed, ferns have an intermediate stage, called a gametophyte, which then grows into a mature fern. There are two distinct stages in the life cycle of ferns. The first stage is that of the gametophyte. Spores are produced on the underside of mature plants. These will germinate and grow into small, heart-shaped plants called gametophytes. The gametophytes produce both sperm and egg cells, and will fertilize itself, or others. Once the fertilization occurs, the adult fern will begin growing. The second stage in the life cycle of a fern is the adult stage. The fertilized gametophytes begin to look like a mossy growth.

Conifers Conifers (also non-flowering plants) have reduced gametophytes. Male gametophyte is contained in a dry pollen grain. Female gametophyte is a few cells inside of the structures that become the seed.

Conifer life cycle

Conifer pollination Conifers are wind-pollinated plants. Chance allows some pollen to land on the scales of female cones. Pollen germinates, grows a pollen tube into the egg to allow sperm to fertilize the egg. What are some advantages and disadvantages to wind pollination?

Flowering Plant Reproduction

Angiosperms (flowering plants) Plants that protect their seeds within the body of a fruit. Make up ¾’s of all plants, including: Trees, shrubs, herbs, grasses, water plants…

Structure of a Flower 1. Pistil 2. Stigma 3. Style 4. Ovary 5. Stamen 6. Filament 7. Anther 8. Petal 9. Sepal 10. Receptacle 11. Stem

Male Reproductive Structure The stamen consists of two parts: Anther and Filament The anther is where meiosis occurs to produce haploid pollen The filament is a stalk that supports the anther

Female Reproductive Structure The pistil consists of the stigma, style and ovary The sticky stigma receives the pollen from the anther The pollen grows a tube down through the style Meiosis occurs in the ovary to produce haploid ovules

Reproductive Structures Petals: colourful structures that attract pollinators. Sepals: surround and protect the flower bud.

Pollination Wind, insects or other animals transfer pollen from the anther of one flower to the stigma of another Flowers vary depending on pollination mechanism

Pollination Animation

Pollination Vectors Wind Pollination: Dull, scentless flowers with reduced petals Bees/Butterfly Pollination: Bright color, nectaries, scent. They sip nectar, get pollen on coats, transfer pollen from flower to flower Bird Pollination: Nectaries, bright colors, tube-like flowers Moth Pollination: White petals, open at night Fly Pollination:Rank odor, flesh colored petals

Pollen Grain Anther Sac Pollen grains contain two haploid cells produced through meiosis. 1- The Tube cell – will grow the pollen tube. 2- The Generative cell – will go through mitosis to create two sperm cells.

Ovary Each ovule within an ovary has a micropyle (an opening for the pollen tube). The ovules’ megasporangium undergo meiosis to produce four haploid cells (3 die leaving 1 megaspore) The megaspore undergoes mitosis 3 times to produce 8 haploid cells within the embryo sac.

Fertilization After pollen lands on the stigma, a pollen tube grows down through the style to ovary Generative cell creates the two sperm nuclei Double fertilization occurs: one sperm fertilizes the egg one sperm the two polar nuclei together

Result of Double Fertilization The sperm nucleus and egg nucleus join to form a 2n (diploid) embryo The other sperm nucleus and the two polar nuclei join to form a 3n (triploid) endosperm. The endosperm is the food supply for the embryo. First link

Seed and Fruit Development After fertilization, the petals and sepals fall off flower Ovary “ripens” into a fruit The ovule develops into a seed

Seed Dispersal Mechanisms- Allow plants to colonize new areas and avoid shade of parent plant Wind Dispersal - Flight mechanisms, like parachutes, wings, etc. Ex. Dandelion, maples, birch Animal Dispersal - Fleshy fruits which animals eat, drop undigested seeds in feces or burrs which stick to animals’ coats

Gravity Dispersal - Heavy nuts fall to ground and roll ex. acorns Water Dispersal - Plants near water create floating fruits ex. coconuts

Plant Responses CHAPTER 31 How plants move and communicate

Plant Hormones

Plant Hormones Plant hormones can be divided into two classes: Growth promoters: Auxins, Gibberellins, Cytokinins Growth inhibitors: Ethylene gas, Abscisic acid

Growth promoters Hormones can promote plant growth in two ways: Stimulating cell division in meristems to produce new cells. Stimulating elongation in cells.

Auxins

Auxin activity Auxins stimulate genes in cells associated with plant growth.

Auxin roles Auxins carry out multiple roles having to do with plant growth including: Tropisms Apical dominance Growth of adventitious roots Fruit growth

Tropisms Tropisms are the growth of a plant toward or away from a stimulus, including: Phototropism: in response to light Gravitropism: in response to gravity Thigmotropism: in response to touch

Nastic Movements

Nastic movement in the sensitive plant (Mimosa pudica)

Hinge control in Venus Fly Trap - Nastic movement

How it works Nastic movements are rapid, reversible movements in a plant. Electrical potentials across cell membranes, similar to those in our nerve cells, signal plant cells at the base of the Mimosa leaf to rapidly lose water. This causes the leaf to droop.

Movies Sensitive Plant: http://www.youtube.com/watch?v=BVU1YuDjwd8 Venus Fly Trap: http://www.youtube.com/watch?v=ktIGVtKdgwo&feature=related

Other examples Sunflowers follow the sun during the day. Leaves of many plants turn to follow the sun.

Day/Night length Some plants flower in response to the length of periods of darkness. Spring-blooming flowers are long night (short day) plants, while summer-blooming flowers are short night (long day) plants. Some plants are day-neutral.

Plant Communication Plants communicate chemically. Injured plants send out chemical signals that may signal other plants to prepare for an attack. attract other insects that eat the insects that are attacking the plant.