Guide to Texas Grasses

1. Why Grasses Are Important

The Poaceae (Gramineae) consists of approximately 785 genera and 11,000 species (Watson and Dallwitz 1992; Chen et al. 2006). Based on genera, the grasses are the third-largest family of flowering plants after the Asteraceae (sunflowers) and Orchidaceae (orchids). Grasses are fifth in the number of species behind the Asteraceae, Fabaceae (legumes), Orchidaceae, and Rubiaceae (madders) (Good 1953). Two-thirds of the earth’s land surface is used for grazing, and one-third is composed of grasslands (Schantz 1954). Grasses occur on every continent and within nearly every terrestrial ecosystem. Hartley (1954) estimates that there are more individual grass plants than all other vascular plants combined. Based on completeness of representation in all regions of the world and percentage of the world’s vegetation , grasses far surpass all other plant families (Gould and Shaw 1983). The economic, ecological , and geographic importance of grasses cannot be overestimated or overemphasized (Clark and Kellogg 2007). Food for Human Consumption The cereal grains (barley, corn, millet, oat, rice, rye, sorghum, wheat) supply the bulk of food that humans consume (fig. 1.1a). Rice feeds more people than any other food product . Wheat cultivation covers more area than any other crop. No crop covers a wider geographic range than corn. A major portion of the world’s sugar comes from sugarcane (Saccharum officinarum). Even the “woody” grasses are a source of nutrition (bamboo shoots and caryopses during mass flowering). The major dietary substance found in grass caryopses is carbohydrates. These carbohydrates are stored in the endosperm, nutritive tissue used during seed germination and seedling establishment, which along with the embryo forms the major part of the grass caryopsis . The seed containing the endosperm is of most value to humans. From the seed comes flour, corn meal, rice, oats, and intoxicants (beer, rice and barley wine, corn and rye liquor, etc.). For this reason all cereal species are almost exclusively annual plants. Annuals put most of their energy into reproduction (more seeds) rather than roots and/or vegetative structures, which die at the end of the growing season. Humans harvest and put to multiple uses the seeds that ensure propagation of the annual species. Carbohydrates in the endosperm are the substance upon which most civilizations have developed and been maintained. The ability of farmers to feed many individuals, not just themselves and their families, allows others to pursue such activities as the arts, manufacturing, trade, education, bureaucracies, and, alas, war—all the fabric of human civilizations. The classic example of endosperm is the large, white, “exploded” portion of a piece of popcorn. The soft, sweet portion of a partially popped kernel , sometimes referred to as “old maids” or “duds,” is the embryo. The golden covering of the endosperm and embryo, which more often than not gets stuck between one’s teeth, is the seed coat. Chapter 1 : WHY GRASSES ARE IMPORTANT Figure 1.1a. Grasses are the major source of grain, including corn, used for human consumption. b. Texas produces more hay than any other state. c. Texas produces more cattle and livestock products than any other state. d. Turfgrasses for lawns, athletic fields, and so on, as well as goods and services to maintain them are a major industry. e. Bamboo (Phyllostachys aurea) culm showing diverse branching pattern. Bamboo has long been grown as an ornamental. f. Pampasgrass (Cortaderia selloana) is one of the most common and easily recognized ornamental grasses. (Photographs by Robert B. Shaw) 1.1a 1.1d 1.1c 1.1b Why Grasses Are Important 3 Grasses and grass by-products dominate the Texas agricultural economy. Over $4.5 billion in grass crops (hay [dry and silage], grain [corn, rice wheat, sorghum], sugar) is produced annually (fig. 1.1b). More land is used for hay, grass silage, and greenchop in Texas than in any other state (5 million acres). Texas ranks second in sorghum for grain and total value of agricultural products sold (USDANASS 2007). Forage for Wild and Domestic Animals The majority of large herbivores characteristic of the expansive grasslands of the world are dependent upon grasses as a major portion of their diet. Humans, in turn, depend upon wild and domestic herbivores as a major source of protein and nutrients in the form of meat, blood, and milk (fig. 1.1c). These animals are also significant as the source of leather (hides) and animal fiber (wool, mohair, etc.). In Western societies large infrastructures have been developed to...