Reproductive Biology Cell Division –Somatic cell division (Mitosis) –Reproductive cell division (Meiosis) Flowering and Anthesis –Megagametogenesis (EMC to Egg Cells) –Microgametogenesis (PMC to Pollen Grains) Pollination and Fertilization –Pollen germination on stigma –Pollen tube growth through style tissue –Double fertilization

Mitosis - Somatic Cell Division - Ends up with same number of chromosomes in divided cells - Divided cells are genetically identical to maternal cells 2N ► 2N + 2N

Meiosis Reproductive cell division Undergoes 2 separate divisions Forms gametes Divided cells have a half of the chromosome numbers Ends up with genetic re- assortment by chromosomal translocation (cross-over) 2N --- ► --- ► N + N + N + N

An Example of Meiosis

Chromosome Numbers Terminology x = Number of chromosomes in a genome Genomic chromosome number A set of different chromosomes “Oneness” n = Number of chromosomes in gametes Gametic chromosome number “Halfness” 2n = Number of chromosomes in somatic cells Somatic chromosome number “Wholeness”

Fertility in Polyploid (Euploidy) Plants PloidySomaticGameticFertility Monoploid2n=1xn = ?Very low Diploid2n=2xn = xHigh Triploid2n=3xn = ?Very low Tetraploid2n=4xn = 2xVariable Pentaploid2n=5xn = ?Variable Hexaploid2n=6xn = 3xVariable Heptaploid2n=7xn = ?Variable Octoploid2n=8xn = 4xVariable Nonaploid2n=9xn = ?Variable Decaploid2n=10xn = 5xVariable

Polyploidization Use of Cholchicine to induce polyploids Colchicine interferes with spindle fiber function during metaphase of meiosis

Production of Seedless Watermelon

Example of Ploidy Variation Chromosome Number SpeciesPloidy Somatic (2n) Gametic (n) Genomic (x) Spinach2x1266 Corn2x2010 Potato4x Strawberry8x56287

Polyploidy Terminology (continued) Euploidy Variation between chromosome sets Aneuploidy Variation within a chromosome set Autoploidy Multiplication of the complete set of genomes of a species Alloploidy Polyploid containing genetically different sets of chromosomes derived from 2 or more species

Aneuploidy Variation within a chromosome set Aneuploidy Somatic chromosome number Examples Trisomic 2n + 1 (extra) Monosomic 2n - 1 (deficient) _ Double-trisomic 2n (2 extra) of one chromosome 2n + 2 (2 extra) A diploid plant (2n=2x=14) would contain the following chromosome numbers depending on aneuploidy conditions:

Life Cycle Alternation of gametophytic (n) and sporophytic (2n) stages in a cycle Sporophytic (2n) stage is long and gametophytic (n) stage is brief

Pollen Tetrad and Microgametophyte - One tube nucleus - Two sperm nuclei

Megagametophyte 1 egg nucleus 2 polar nuclei 3 antipodal nuclei 2 synergids

Pollination and Fertilization, Angiosperms

Double Fertilization A process of fertilization in which one male gamete (sperm nucleus, n) unites the egg nucleus (n) to form embryo (zygote, 2n) and the other sperm nucleus (n) unites polar nuclei (2n) to form endosperm (3n)

Female (left) and Male (right) Flowers of Pumpkin

Confectionery Seed Pumpkin Production Near Hatton, ND Honeybees

A Hermaphroditic Flower of Peony

Lady Slipper Orchid

Chasmogamous Flowers of Salpiglossis

Red, Delute Flower (RRdd)

Floral Parts

Influence of Pollination on Seed Set Salpiglossis sinuata No. tetrads placed Capsules setting seed (%) Avg. no. of seeds per capsule Avg. no. of seeds per tetrad

2. Hybridization

Inheritance of Flower Color in Velvet Flower ( Salpiglossis sinuata) RR or R-= Red flower color rr= Yellow flower color DD or D-= Solid color pattern dd= Dilute color pattern

P1P1 P2P2 x Dilute Red (RRdd) Solid yellow (rrDD) Solid Red (RrDd) F1F1 Solid red (R-D-) 9 Dilute red (R-dd) 3 Solid yellow (rrD-) 3 Dilute yellow (rrdd) 1 F2F2

RRDD or R-D- (red, solid) RRdd or R-dd (red, dilute) rrDD or rrD- (yellow, solid) rrdd (yellow, dilute)