Angiosperm reproduction and biotechnology

1. Angiosperm reproduction and biotechnology By: Josh Proal, Ben Shapero, and Zach Evans Ch. 38

2. Life Cycle Life cycle alternates between haploid and diploid Sporophyte – diploid, makes haploid gametes called gametophytes Gametophyte – haploid, makes diploid gametes called sporophytes Sporophyte is the dominant generation due to its size and lifespan

3. Flower Structure • Stamen – male parts: anther and filament • Anther – terminal spot where pollen grains with male gametes form • Filament – stalk of a stamen • Carpel – female parts: stigma, style, and ovary • Stigma – sticky part of a flower’s carpel which traps pollen grains • Style – stalk of a flower’s carpel • Ovary – where the egg-containing ovules develop • Pistil – one or many fused carpels • Petal – modified leaf of a flower designed for attracting insects and other pollinators • Sepal – modified leaf that helps enclose and protect the flower bud before it opens

4. Characteristics of flowers Complete Flowers – possess all four floral organs Incomplete Flowers – lacks on or more of the four floral organs Symmetry – radial (roses) or bilateral (tulips) in flowers Ovary Location – superior, semi-inferior, and inferior In superior, stigma is above stamen (III) In semi-inferior, stigma is planar with stamen (II) In inferior, stigma is below stamen (I) Inflorescence – cluster of incomplete flowers (sunflowers) Monoecious – stamen and carpels are on the same plant (maize) Dioecious – stamate flower and carpellate flowers are on different plants (willows)

5. Development of gametophytes

6. Spores Microspore - a spore from a heterosporous plant species that develops into a male gametophyte Megaspore – a spore from a heterosporous plant species that develops into a female gametophyte Self-incompatibility – the ability of a plant to reject its own pollen and sometimes pollen of closely related individuals • RNA hydrolyzing enzymes kill pollen with recognizable self-alleles within the style Examples: Dioecious plants can’t self-pollinate Different flowers mature at different times

7. Double Fertilization • Plants have twice as much fun: two sperm per pollen grain. One fertilizes the egg, the other fertilizes the polar nuclei • Zygote = egg + sperm • Endosperm nucleus = 2 polar bodies + sperm Holds the nutrition for the new plant

8. Endosperm / Embryo development Endosperm development precedes embryonic development: • Triploidy nucleus divides, forms a multinucleate “supercell” with a milky consistency (coconut milk) • Eventually, the naked cells form cell walls and become solid endosperm (coconut “meat”) Embryonic development • Egg splits into terminal and basal cells: terminal cell forms proembryo and cotyledon, basal cell forms suspensor – anchors the embryo to the parent

9. Fruit Simple fruit Aggregate fruit Multiple fruit Cotyledon – a seed leaf of an angiosperm embryo Monocot– has only cotyledon (maize and other grasses) Eudicot– has more than one cotyledon (castor bean)

10. Seed germination • Dormancy – condition of low metabolic rate and suspension of growth • Germination of seeds depends on imbibition – process of water using the low water potential of the dry seed, causes the coat to rupture and the seed to leave dormancy

11. Reproduction • Asexual Reproduction – offspring derived from a single parent without genetic recombination • Vegetative Reproduction – type of asexual reproduction in plants, offspring are usually mature fragments from the parent plant. Good if the organism is well-adapted, bad if the environment changes • Fragmentation – when a parent plant separates into parts, creating new plants • Apomixis – Seeds have diploid cells like an embryo, so seeds are clones of the original plant without recombination (ex dandelions)

12. Biotechnology • Cutting – growing a plant from a section of another plant • Grafting – attaching a scion (branch) to a root system (stock) to create a chimera plant with characteristics of both (ex: growing potatoes and tomatoes on the same plant) • Protoplast Fusion – enzymatically removing the cell walls of two plants cells, then fusing those cells to create a new polyploidy species • Artificial Selection – breeding for certain traits

13. Issues with Biotechnology • Ethics – can we make new species? • Health – what if they’re bad for us? What if their genes have harmful consequences? • Transgene Escape – weeds hybridize with chimera crop or transgenic seeds escape • Modified plants are designed with defunct chloroplast DNA that only works in F1 generation • Terminator genes are inserted to kill the plant when exposed to certain factors