Chapter 124
Gra.s.s blades grow at the base of the blade and not from elongated stem tips. This low growth point evolved in response to grazing animals and allows gra.s.ses to be grazed or mown regularly without severe damage to the plant.
The success of the gra.s.ses lies in part in their morphology and growth processes and in part in their physiological diversity. Most of the gra.s.ses divide into two physiological groups, using the C3 and C4 photosynthetic pathways for carbon fixation.
The C4 gra.s.ses are "warm season" gra.s.ses. These have a photosynthetic pathway, linked to specialized Kranz leaf anatomy, which allows for increased water use efficiency, rendering them better adapted to hot, arid environments and those lacking in carbon dioxide.
The C3 gra.s.ses are referred to as "cool-season" gra.s.ses.
Annual cool-season – wheat, rye, annual bluegra.s.s (annual meadowgra.s.s, Poa annua), and oat.
Perennial cool-season – orchardgra.s.s (c.o.c.ksfoot, Dactylis glomerata), fescue (Festuca spp.), Kentucky bluegra.s.s and perennial ryegra.s.s (Lolium perenne).
Annual warm-season – maize, sudangra.s.s, and pearl millet
Perennial warm-season – big bluestem, Indiangra.s.s, Bermudagra.s.s and switchgra.s.s.
Shena was fascinated with the information being provided and said that she never knew that the cereals we ate were also from the gra.s.ses.
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To a question from Chris about further information, the
The gra.s.s also added that there was more information and it had just given us an overview. It had not been programmed to go into full details.
It requested us to be patient and that it would answer any questions as long as they were included in its program. It then started to give some more information.
Gra.s.ses are unusual in that the meristem is located near the bottom of the plant; hence, they can quickly recover from cropping at the top. The evolution of large grazing animals in the Cenozoic Era contributed to the spread of gra.s.ses. Without large grazers, fire-cleared areas are quickly colonized by gra.s.ses, and with enough rain, tree seedlings. Trees eventually outcompeted most gra.s.ses. Trampling grazers kill seedling trees but not gra.s.ses.
There are about 12,000 gra.s.s species in about 771 genera that are cla.s.sified into 12 subfamilies.
Gra.s.ses are, in human terms, perhaps the most economically important plant family. Their economic importance stems from several areas, including food production, industry, and lawns. They have been grown as food for domesticated animals for up to 6,000 years and the grains of gra.s.ses such as wheat, rice, maize (corn) and barley have been the most important human food crops. Gra.s.ses are also used in the manufacture of thatch, paper, fuel, clothing, insulation, timber for fencing, furniture, scaffolding and construction materials, floor matting, sports turf, and baskets.
Agricultural gra.s.ses grown for their edible seeds are called cereals or grains (although the latter term, agriculturally, refers to both cereals and legumes). Of all crops grown, 70% are gra.s.ses. Three kinds of cereal—rice, wheat, and maize (corn)—provide more than half of all calories consumed by humans. Cereals const.i.tute the major source of carbohydrates for humans and perhaps the major source of protein, including rice (in southern and eastern Asia), maize (in Central and South America), and wheat and barley (in Europe, northern Asia, and the Americas).
Sugarcane is the major source of sugar production. Additional food uses of sugarcane include sprouted grain, shoots, and rhizomes, and in drink, they include sugarcane juice and plant milk, as well as rum, beer, whiskey, and vodka.
Lemongra.s.s is a gra.s.s used as a culinary herb for its citrus-like flavor and scent.
Many species of gra.s.s are grown as pasture for foraging or as fodder for prescribed livestock feeds, particularly in the case of cattle, horses, and sheep. Such gra.s.ses may be cut and stored for later feeding, especially for the winter, in the form of bales of hay or straw, or in silos as silage. Straw (and sometimes hay) may also be used as bedding for animals.
In the industry, gra.s.ses are used as raw material for a mult.i.tude of purposes, including construction and in the composition of building materials such as cob, for insulation, in the manufacture of paper and board such as Oriented structural straw board. Gra.s.s fiber can be used for making paper, and for biofuel production. Bamboo scaffolding is able to withstand typhoon-force winds that would break steel scaffolding. Larger bamboos and Arundo donax have stout culms that can be used in a manner similar to timber, Arundo is used to make reeds for woodwind instruments, and bamboo is used for innumerable implements.
Common reed is important for thatching. Reeds are used in water treatment systems, in wetland conservation and land reclamation in Afro-Eurasia.
The front of a building normally comprises gra.s.ses as the primary plant, used in lawns, which themselves derive from grazed gra.s.slands. They also provide an important means of erosion control (e.g., along roadsides), especially on sloping land. Gra.s.s lawns are an important covering of playing surfaces in many sports, including football (soccer), American football, tennis, golf, cricket, softball, and baseball. In some sports facilities, including indoor domes and other places where maintenance of a gra.s.s field would be difficult, gra.s.s may be replaced with artificial turf, a synthetic gra.s.s-like subst.i.tute.
In cricket, the pitch is the strip of carefully mowed and rolled gra.s.s where the bowler bowls. In the days leading up to the match, it is repeatedly mowed and rolled to produce a very hard, flat surface for the ball to bounce off.