Chapter 38 ~Plant Reproduction and Development

I. Sexual Reproduction

A. Alternation of generations: haploid (n) and diploid A. Alternation of generations: haploid (n) and diploid (2n) generations take turns producing each other(2n) generations take turns producing each other 1. Sporophyte (2n): 1. Sporophyte (2n):

a. produces haploid spores by meiosis; these a. produces haploid spores by meiosis; these spores divide by mitosis giving rise to male and spores divide by mitosis giving rise to male and female haploid plants called….female haploid plants called….

b. Gametophytes (n): develop and produce b. Gametophytes (n): develop and produce gametesgametes

Have you labeled a flower lately?

B. Floral variations

1. Floral organs: sepals, 1. Floral organs: sepals, petals, stamens (male ), petals, stamens (male ), carpels (female)carpels (female) a. complete: all 4 floral a. complete: all 4 floral

organsorgans b. incomplete: lacking 1 or b. incomplete: lacking 1 or

more floral organsmore floral organs c. perfect: both stamens c. perfect: both stamens

and carpels on 1 flowerand carpels on 1 flower

d.imperfect: lacking either a d.imperfect: lacking either a stamen or carpelstamen or carpel

e. monoecious: staminate and e. monoecious: staminate and carpellate flowers on 1 plant) carpellate flowers on 1 plant)

f. dioecious: staminate and f. dioecious: staminate and carpellate flowers on separate carpellate flowers on separate plantsplants

C. Gametophyte development

1. Male gametophyte: 1. Male gametophyte: microsporocytemicrosporocyte (in pollen (in pollen sacs of anther) divides by meiosis into 4 haploid sacs of anther) divides by meiosis into 4 haploid microspores; microspores; a. mitosis produces a generative cell (sperm) and a a. mitosis produces a generative cell (sperm) and a

tube cell (pollen tube)= a pollen graintube cell (pollen tube)= a pollen grain 2. Female gametophyte2. Female gametophyte: : megasporocytemegasporocyte (in ovule) (in ovule)

divides by meiosis to 4 cells, only 1 survives to a haploid divides by meiosis to 4 cells, only 1 survives to a haploid megaspore; megaspore; a. 3 mitotic divisions forms the embryo sac; a. 3 mitotic divisions forms the embryo sac; b. includes: 1 egg cell (female gamete) and 2 polar b. includes: 1 egg cell (female gamete) and 2 polar

nuclei (synergids)nuclei (synergids)

D. Pollination – pollen grain lands on stigma

1. pollen lands on stigma – pollen has 2 1. pollen lands on stigma – pollen has 2 sperm cells & a vegetative nucleussperm cells & a vegetative nucleus

2. veg. nucleus grows a tube down the 2. veg. nucleus grows a tube down the style to the ovarystyle to the ovary

3. ovule contains 1 egg & 7 accessory 3. ovule contains 1 egg & 7 accessory cells inside the embryo saccells inside the embryo sac

4. pollen tube enters embryo sac via 4. pollen tube enters embryo sac via micropyle (small opening) micropyle (small opening)

Pollen tube with haploid male gametophyte nuclei.

Allergenic Pollen (poplar, alder, timothy grass, ragweed, sagebrush, scotchbroom)

E. Plant fertilization - sperm combo’s with egg 1. one sperm fertilizes the egg1. one sperm fertilizes the egg 2. nucleus of 2nd sperm fuses w/2 of the 2. nucleus of 2nd sperm fuses w/2 of the

accessory cell nuclei forming a triploid nucleus – accessory cell nuclei forming a triploid nucleus – this grows to form into the endosperm which is the this grows to form into the endosperm which is the food for the embryofood for the embryo

3. using 2 sperm for fert. = Double Fertilization 3. using 2 sperm for fert. = Double Fertilization 4. The seed grows from the fertilized ovule…..4. The seed grows from the fertilized ovule…..

a. mature seed:a. mature seed: 1) seed coat (protection) 1) seed coat (protection) 2) cotyledons (seed leaves)2) cotyledons (seed leaves) 3) hypocotyl (lower embryonic axis)3) hypocotyl (lower embryonic axis) 4) radicle (embryonic root)4) radicle (embryonic root) 5) epicotyl (upper embryonic axis)5) epicotyl (upper embryonic axis) 6) plummule (shoot tip)6) plummule (shoot tip) 7) coleoptile (sheath for embryonic shoot)7) coleoptile (sheath for embryonic shoot)

The seed

Seeds in a Pod

F. The fruit 1. Fruit protects seeds and aids in their dispersal1. Fruit protects seeds and aids in their dispersal 2. Pericarp (thickened wall of fruit forms from the 2. Pericarp (thickened wall of fruit forms from the

ovary wall)ovary wall) 3. Fruit types:3. Fruit types:

a. simple (1 ovary/1 flower)~ cherry, soybean a. simple (1 ovary/1 flower)~ cherry, soybean

b. aggregate (1 flower with many ovaries) b. aggregate (1 flower with many ovaries) blackberry blackberry

c. •multiple (inflorescence; groups of flowers w/ c. •multiple (inflorescence; groups of flowers w/ gps of ovary) ~ pineapplegps of ovary) ~ pineapple

G. Seed germination – breaking out of seed dormancy – triggers vary in dif

species 1. Seed dormancy (low metabolic rate and 1. Seed dormancy (low metabolic rate and

growth suspension) – some can growth suspension) – some can stay stay dormant for thousands of years!dormant for thousands of years!

2. Imbibition (uptake of water) – water 2. Imbibition (uptake of water) – water instigates the growth processinstigates the growth process

3. Radicle grows 1st, then shoot tip 3. Radicle grows 1st, then shoot tip (hypocotyl); stimulated by light(hypocotyl); stimulated by light