Presentation on theme: "Grasses The most important group of plants to humankind."— Presentation transcript:
Grasses The most important group of plants to humankind.
The grass family (Poaceae) Genera : 600 - 650 Species: 7500 - 10,000 cereal crops (food & sugar) grazing/pasture/forage crops ornamentals building materials source for matting
What is a grass? Grasses are monocots, and thus have parallel-veined leaves and flower parts which occur in multiples of three Perennial or annual herbs (mostly), stems erect, ascending, prostrate or creeping, round, hollow or solid at internodes, solid at nodes Leaves - alternate, composed of an open sheath, ligule, and blade, sheath encloses the stem Flowers: spikelets contain 1 or more florets; usually subtended by glumes
Taxonomic classification CategoryNameCharacteristics KingdomPlantaeOrganisms with rigid cellulose cell walls, chlorophyll a & b, … DivisionAnthophytaFlowering seed plants ClassMonocotyledonesEmbryo with one seed leaf OrderCommelinales FamilyPoaceaeGrass family Genus
The planting of cereal grains may have been the most important event in the beginning of civilization. Ca. 10,000 years ago, someone had the idea of planting seeds, caring for the plants, and harvesting them months later. Thus, hunting and gathering societies became agrarian.
wheat -Most widely-clutivated cereal. -Does best in temperate grassland biomes. (i.e., on the cool & dry side). -Origin is Near-East ca. 10,000 years ago. -Top producers: U.S., Canada, Ukraine, China, India, Argentina, France. -Relatively better nutritionally than corn & rice (more protein & other nutrients). -Susceptible to many diseases. -13% protein, with low tryptophan & lysine -missing Vit A, B12, C, iodine -leavened (wheat) bread discovered by Egyptians ca. 4000 years ago
Types of wheat Bread wheat (T. aestivum) : –This has a high gluten content and hard grain. It is used to make flour from which bread is made. Gluten (type of wheat proteins) good for baking qualities (elasticity). –90% of world production. Durum wheat (T. durum): –Unsuitable for bread making, but is used to make pasta. –Yields semolina flour.
Types of wheat (cont.) Spring wheat: Northern U.S. & Canada; planted in spring, harvested in fall. Winter wheat: rest of U.S.; planted in fall, harvested in early summer. Hard wheat: higher protein content, used for bread. Soft wheat: better for pastries.
Making flour Whole-grain (has germ & bran) White flour (only endosperm) –83 percent of the nutrients are removed –Stores longer, cause little oil –See overheads Milling –Stone milling more nutritious, but shorter shelf-life compared to steel-roller milling
Maize: Gift from America's First Peoples Columbus did not realize that the gift of maize was far more valuable than the spices or gold he hoped to find. He had no way of knowing that the history of maize traced back some 8,000 years or that it represented the most remarkable plant breeding accomplishment of all time. He might have been embarrassed if he had understood that then, as now, this plant developed by peoples he judged poor and uncivilized far outstripped in productivity any of the cereals bred by Old World farmers --wheat, rice, sorghum, barley, and rye. Were he alive today, he would certainly be astonished to see the extent to which the advent of maize has affected land use, food production, cuisine, and population growth around the world. Walton Galinat, 1992, "Chillies to Chocolate"
Corn facts Originated from Southern Mexico (sub- tropics), so from a warm climate. Plus, corn is a C4 species. Thus, corn likes it warm, and needs lots of sunshine. And requires lots of water, for a grass. Domesticated ca. 10,000 years ago. Modern corn has naked seeds, but can’t disperse them due to husk covering.
Corn facts (cont.) United States is the largest producer of corn in the world. In 1997, U.S. planted 80,227,000 acres. Ca. 65% of the maize produced in the world is used as animal feed. 5 major categories, mainly the dents (most of the modern corns; for feed, starch, meal), flints (“Indian” corn), flour (also “Indian” corn), pop, and sweet corn (higher sugar content). Almost all is hybrid corn. All of maize production is based on 5% of corn varieties available in the world. High in fiber, 7-10% protein, low in trp & lys and niacin.
Rice - Feeds more people than any other crop. -Origins in Far East (China & India). -Domesticated ca. 11,500 years ago. -U.S. produces only 2% of world rice, but is a big exporter.
Rice -Most modern rice is Oryza sativa –Japonica and indica sub-types –African rice is another species -Both lowland & upland varieties. -Wild rice is another genus (Zizania). -Origins from tropical periodically-flooded lowlands, so needs lots of water (during seedling establishment). -So, very flood & heat tolerant.
Rice (cont.) White rice: husk, bran, and germ removed. –Long-grain rice is four to five times longer than it is wide aromatic rices, i.e., basmati and jasmine varieties –Medium-grain rice has shorter, fatter grains and a medium starch content –Short-grain rice is plump, almost round, with high starch easy to handle with chopsticks Brown rice –Only the inedible outer husk has been removed –More protein (e.g., 9 vs. 6%)
Some other major cereals Rye –Cold & drought tolerant –Makes leavened bread –Lower protein content than wheat, but w/ lys Tricale –Cross between wheat & rye –Not a good bread cereal Oats –High protein (15%), good overall nutrition –Best in moist cool climates Barley –One of oldest grains, from Near East –Cold and salt tolerant Sorghum & Millets –Sorghum used for food or feed, or for molasses –Millet used as food or birdseed
Short, Mixed and Tall grass prairie Over 90% of the tall grass prairie has been converted to crop land Mixed grass prairie- mixture of crop and range land Short grass prairie- limited amount of crop land, majority is still considered range land
Remnant patch of tall-grass prairie Dominated by: big bluestem, indian-grass, switch-grass, little bluestem. The kind of prairie that was found in Ohio.
Short grass prairie Over 90% is still considered range land Produces most of the beef in the United States Grasses are adapted for heavy grazing 1) hidden meristems 2) evolved with large grazing ungulates 3) 75% of biomass is located belowground
Mixed-grass prairie Mixed grassland has both tall- grass and short-grass species The ratio between short grass and tall is dependent on moisture Typically more growing-season moisture produces a greater amount of tall-grass species The boundary between short- mixed-tall grass prairie is constantly moving Farming is either boom or bust (typically too dry for crop land)
Pacific Northwest (PNW) grassland Unique grassland comprised of bunch forming grasses Majority of the PNW bunchgrass has been converted to cropland PNW is not adapted for heavy livestock grazing **Meristems are easily removed by grazing**
California Annual grassland California grassland historically resembled the PNW bunch grass region. Early settlers transported non- native grass species from there home-land. California grassland region was undergoing changes before settlers due to the rise of the costal range and the Sierra Nevada. Today, no bunch-grass plants remain.
Salt desert shrub Unique range land characterized by high soil salt levels, caused by poor water drainage. Only a few species are able to tolerate the growing conditions. Adaptations Some plants are able to secrete salt through special glands on their leaves.
crested wheat grass Story of crested wheat grass in 1950s: planted to increase range production. What they didn’t know is that there were 3 sub-varieties: one which is unpalatable, one intermediately palatable, and other palatable. Their seed blend was mostly unpalatable, so that cattle preferentially ate up the native crops and left the wheat grass, which eventually took over.
. Crested Wheat Grass Non-native grass widely planted in the 1940-1950 to promote livestock production and soil stabilization Two varieties: Agropyron cristatum cristatum Agropyron cristatum desertorum cristatum is highly palatable desertorm is moderately palatable
Cheat grass Bromus tectorum (cheat grass) was introduced as a second season crop for grazing, alternating with native bunch grasses. Cheat grass was adapted to more frequent fire than bunch grasses, and when it dried out, fire favored cheat grass re-establishment over the native grasses.
Historical movement of cheat grass How does cheat grass spread? 1)Cheat grass is a winter annual (jump start on growth) 2)Dies early in the year 3)Wildlife and livestock only graze it during the early season 4)Some ranchers planted it thinking they could get an early season of grass production 5)Thrives in disturbed sites
Cheat grass facilitates fire Why is it a problem? 1)Cheat grass can out compete higher-quality native grasses. 2) Cheat grass fills in the interspaces between native vegetation creating a continuous fine fuel load. 3) Cheat grass promotes fire and allows fires to start earlier in the season. The increase in fire frequency and the increased fire season creates a condition that stresses the native vegetation.
Kentucky bluegrass Kentucky bluegrass is a non-native species. Sod grass- can create a monoculture. **out competes native grasses** Location of meristems allow the grass to be grazed to less than an inch. Why is this a problem? 1)Low rooting depth causes problems with soil stability. 2)Has the ability to out-compete native grasses. 3)Very attractive to cattle and elk during from spring to fall.
Vegetation shift Cattle grazing creates disturbed areas where Kentucky bluegrass can out-compete native riparian vegetation. Low rooting structure of Kentucky Blue grass facilitates bank sloughing. Bank sloughing increases the disturbed area that in turn increases area infected with Kentucky bluegrass. ** Positive feedback loop** Bank sloughing causes: Increased water temperature Increased sedimentation Reduction in water depth All of which have an effect on fisheries and micro invertebrates.
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