ch.12 grasses Flashcards
grass family: Poaceae
- corn, wheat, rice formed the basis of civilization. allowed easy storage, were able to keep dry, and did not rot. mass production allowed other people to lay off on agriculture and work on other things
- sugar cane: largest production of grain
what are the three main structures that make up grass
- culm: vertical stem
- rhizome: below ground, horizontal stems that form the basis of new growth. dont grow deep into the ground
stolon: above ground; horizontal stem - floret: flower, made of lemma, palea, 3 stamen, and one carpel
why do grasses have a feather like stigma?
grass is wind pollinated, having a feather like stigma traps pollen better
describe the fruit that is formed once the carpel is fertilized
- the fruit wall and seed coat (bran) fuse together
- contains the endosperm and embryo
- aleurone layer: high protein layer between the seed coat and endosperm
what does the germ of grass contain
- protein containing
- high protein, B and E complex
what structures are removed to make refined grains
the bran and germ (embryo) are removed
- allows the production of delicate pastries, rises better, and stores better
wheat characteristics
- wild form: diploid, 14 chromosomes
- tetraploid natural formed when diploid combine, has 28 chromosomes
- bread wheat is hexaploid with high protein content, has 42 chromosomes
bread vs gluten free bread
- leavened bread requires flour with gluten
- gluten free adds xanthomonas bacterial polysaccharide xantham gum (provides elesticity and rises with yeast)
refined flour has:
- mostly starchy endosperm, long shelf life, lower nutritional value
corn characteristics
- monoecious
- tassel: panicle of staminate flowers
- ear: spike of carpellate flowers
- silk: stigma and style (of each individual carpel)
- a human creation
what forms the differences between the corn varieties?
- depends on starch:
- unbranched amylose (more in ‘hard’ starch): packs tightly
- highly branched amylopectin: packs less tightly
corn varieties
- popcorn: hard kernel with water and soft starch in the center, expands with heat
- dent: hard starch on sides, soft starch at top and center; dominant for animal foods, corn starch and meal
- sweet: more sugar than starch in endosperm; forms a softer kernel
what makes the mixed colors in corn
- each kernel is individually fertilized
what is the significant of hybrid corn
- male sterile lines developed to eliminate detasseling
- first commercial hybrid was developed by Henry Wallace
what are two theories of the origination of corn?
- george beadle: crossed modern corn with teosinte and got fertile offspring. developed the one gene, one enzyme hypothesis. *teosinte was the origin of corn. molecular studies have supported his discovery
- paul mangelsdorf: corn and teosinte derive from extinct popcorn
what is the value of knowing the ancestor of corn or other domesticated crops?
- provides insight to impve water use, pest resistance, protection from pathogens
- use genetic information to incorporate into others and grow different kinds of corn
- helped get out of the corn famine
- important in case genes of corn start to go away and other genes from different varieties can be used to save the corn
what did Barbara McClinktock support?
- in 1950, she reported on reportable transposable elements (transposons)
- use corn in the study, genes that caused pigments had different patterns than expected.
- now expected to occur in all organisms
rice (Oryza sativa)
- grown in southern US and 11% of farmland worldwide
- can be used as grain for beer
- lowland rice grown in 5-10 cm standing water
what are other grains?
rye, triticale, oats, barley, millet, sorghum
how are grasses used to make bioethanol
- corn kernel: to ethanol yields 10% more energy than used to produce. The yield of ethanol from corn is energy consuming and is not as efficient. It is used in gas, farmers and political reasons support its production
- sugarcane: it is more efficient to covert to ethanol. takes less energy to convert sugar into ethanol
- cellulosic ethanol: requires enzymes to break down cellulose into glucose. As of now it is energy demanding, but it could be useful because cellulose is found in all plants.
North American Prairie
- dominated by grass, sunflower, and bean family
- there are roughly 200 plant species in native prairie
- tallgrass: big bluestem, indian grass, switchgrass; historically grow into today tall grass corn
- mixed grass: little bluestem; have cultivated to wheat
- shortgrass: blue gramma, buffalo grass; have stayed intact
