Crop Plant Reproduction (p. 83-94 and chapter 4) Flower Anatomy Components Terminology Legume Grass Types Different management requirements Pollination Fertilization Yield Components Flower growth crucial for maximum yield. Harvest Index

Crop Flower Components Wheat Flowers = inflorescences Components: Sepals: Protect flower bud Petals: Colorful attract insects Stamens (male): Anther: produces pollen Filament: supports anther Carpel (female): Stigma: sticky - collects pollen Style: connects stigma to ovary Ovary: fruit, contains ovules Ovule: seed, contains egg Soybean

Flower Terminology Complete Flower: Incomplete Flower: Perfect Flower: Sepals, petals, stamen, carpel. Incomplete Flower: Missing one of 4 components. Perfect Flower: Stamens and carpel (soybeans). Imperfect Flower: Male or female flower (corn). Monoecious: Male and female on same plant (most crops, corn, cucurbits, oak). Dioecious: Male or female plant (waterhemp, cannabis, ginko, holly). Waterhemp

Flower Type and Farming Flower type affects how a crop is grown and what is harvested. Perfect flowers tend to be self-pollinated. Soybeans, wheat, oats, barley, rye Saving seed can be done according to seed trade laws. Genetics of plant does not change. Imperfect flowers require cross-pollination (wind, bees, etc.) Corn Seed can nor be saved – performance declines each generation. Inbreeding reduces performance.

Legume (Dicot) Flower Complete and Perfect Flower parts in 5’s Sepals (5): Petals: (5) 1 standard 2 wings 2 fused into keel Stamens (10): 1 free 9 fused (most) Carpel/pistil (1): Stigma: Style: Ovary: Ovule:

Grass (Monocot) Flower Anatomy Flower parts in 3’s Incomplete (no sepals, petals) Spikelet: Florets: Rachis: central axis Rachilla: attaches florets to rachis Glumes: protect spikelet Lemma: modified sepals Palea: modified sepals Stamen: Anthers (3): Filaments (3): Carpel/pistil (1): Stigma (2): feathery Style: Ovary: Ovule:

Flower and Inflorescence Types Flower Type: Spike: Spikelet attached to rachis (Wheat) Panicle: Spikelets attached to branches attached to rachis (Oats) Raceme: Flowers attach at leaf axil to stem (Velvetleaf) Head: Flowers attach to receptacle (Sunflower) Umbel: Flowers attach to receptacle(Queen Anne’s Lace). Inflorescence Type: Determinant: meristem terminates inflorescence Indeterminant: new inflorescences continuously develop

Factors Affecting Flowering Plant Nutrition: >N2 > flowering delay Light: Photoperiodism: Short-Day: respond to longer nights Soybeans, corn, warm-season Long-Day: respond to shorter nights Small grains and cool-season Day-Neutral: no response alfalfa, cotton Temperature: Vernalization: cold temps required winter wheat, barley, rye Cool temperature delays flowering

Asexual Reproduction Reproduction and propagation from vegetative parts. Types: Apomixis: seed without fertilization bluegrass, citrus, dandelions Cuttings: sugarcane Layering: develop plant while attached raspberry, blackberry Division: parts divided potato, bermudagrass, pineapple, bluegrass Grafting: joining plant parts fruit trees

Sexual Reproduction Production of Pollen: Production of Embryo Sac: Production of sperm cells. Production of Embryo Sac: Production of egg cell. Pollination: Transfer of pollen from anther to stigma. Double Fertilization: Egg + Sperm = Embryo Sperm + Polar Nuclei = Endosperm

Male: Sperm Cell Development Pollen Sac: In anther Microspores produced by meiosis Pollen grain produced by mitosis Tube cell Generative cell Produce 2 sperm by mitosis Pollen Anther Filament Within the anther, haploid microspores are produced by meiosis. They form pollen grain, which contain sperm. Anther (2n)  pollen sac (2n microsporocyte)  meiosis  microspores (1n)  mitosis  pollen grain (1n male gametophyte) Microspore Mother Cell (2n) 4 Microspores Pollen Grain (Male Gametophyte) 1 Generative Cell 1 Tube Cell 2 Sperm Cells Pollen Tube 1 fertilizes egg 2 Prothallid Cells die

Female: Egg Cell Development Megaspores produced by meiosis. 1 of 4 megaspores lives  2  4  8 nuclei of 7 celled embryo sac (female gametophyte). 3 antipodal cells 1 central cell with 2 polar nuclei 2 synergid cells 1 egg cell Within the ovary, megaspores are produced by meiosis. One develops into embryo sac, which has an egg cell within it and the rest disintegrate. Megaspore Mother Cell (Megasporocyte) 4 Megaspores Embryo Sac (Female Gametophyte) 3 Antipodal Cells 2 Polar Nuclei 2 Synergids 1 Egg Cell

Flower Embryo Sac Double Fertilization Sperm 1 Sperm 2 Pollen Grain: lands on stigma germinates forms pollen tube grows between cells to the ovule. Double Fertilization Sperm 1 1 sperm + 2 polar nuclei = 3N endosperm cell Sperm 2 Sperm enter embryo sac 1 sperm + egg = zygote (2N)

Pollination Transfer pollen from anther to stigma. Artificial: Cross-pollination: Pollen from different plant By insects, wind Corn, alfalfa, clover, sorghum Self-pollination: Pollen from same plant Wheat, oats, soybeans, rice Pollination: transfer of pollen from anther to stigma of pistil by wind or assisted by insects, bats etc. Cross and self pollination.

Terminator Technology Seed is unable to grow. Genetically controlled. Crops: corn Uses: Reduces volunteer the next year. Seed can be stored for longer periods of time. Reduce outcrossing – biotech traits Patent Protection for developer. Opposition

Yield Components Three components determine yield. Plants Per Acre: planting time Seeds Per Plant: floral initiation and pollination Seed Weight: grain filling period Yield = (ppa)(seeds/plant)(seed weight) (28,000ppa)(586k/p)(.314g/k) = 202.6 bu/A Yield Compensation: Components adjust for each other. (33,000ppa)(500k/p)(.312g/k) = 202.4 bu/A

Harvest Index Crops differ in amount of photosynthate and nutrients diverted to yield vs growth. Harvest Index = economic yield / biological yield Corn for grain = .50 Corn for silage = .80