Grasses

Grasses are Plants which are generally characterised by having specialized reduced flower parts. They belong to the family of Plants known as the Graminae or Graminoids. The Graminae family consists of over 6,000 Species which is one of the largest Plant Families. The Total number of Grass Species worldwide is about 10,000. Habitats or Biomes dominated by Grasses are called Grasslands. The major Grasslands of the World cover about  31% of the Earth's land. Grasses have been used by humans since ancient times. They have been cultivated as a food source for domesticated animals for up to 10,000 years, and have been used to make paper since at least as early as 2400 B.C. Agricultural Grasses grown for their edible seeds are called Cereals. Of all Crops, 70% are Grasses. Grasses are also used for ornamental purposes in garden and parks. The primary ingredient of Beer is usually Barley or Wheat, both of which are Grasses. Animals which feed primarily on Grass are known as Graminivores. Hippopotamuses, Grasshoppers, Geese are some of the Graminivores.

Classification of Grasses

Division - Magnoliophyta.
Class - Liliopsida.
Order - Cyperales.
Family - Gramineae.

Subfamilies of Grass

Anomochlooideae - It is a small lineage of Broad-Leaved Grasses that includes 2 Genera (Anomochloa, Streptochaeta).

Pharoideae - It is a small lineage of Grasses that includes 3 Genera, including Pharus and Leptaspis.

Puelioideae - It is a small lineage that includes the African genus Puelia.

Pooideae - It includes Wheat, Barley, Oats, Brome-Grass (bromus), Reed-Grasses (Calamagrostis).

Bambusoideae - It  includes Bamboo.

Ehrhartoideae - It includes Rice, Wild Rice etc.

Arundinoideae - It Include Giant Reed, Common Reed etc.

Centothecoideae - It is a small subfamily of 11 Genera that is sometimes included in Panicoideae.

Chloridoideae - It including the Lovegrasses (Eragrostis, ca. 350 Species, including teff), Dropseeds (Sporobolus, some 160 species), Finger Millet (Eleusine coracana (L.) Gaertn.), and the muhly Grasses (Muhlenbergia, ca. 175 species).

Panicoideae - It includes Panic Grass, Maize, Sorghum, Sugar Cane, Most Millets, Fonio, and Bluestem Grasses.

Micrairoideae.

Danthonioideae - It includes Pampas Grass

Poa - It is a genus of about 500 Species of Grasses, native to the temperate regions of both hemispheres.

Types of Grasses

Cool Season Grasses - Cool Season Grasses are those Grasses which grow well in areas where sunlight intensity is moderate, temperatures are moderate, carbon dioxide concentrations are around 200 ppm or higher, and ground water is plentiful. They can can go dormant i.e. turn brown, during extended hot, dry conditions. They are also known as C3 Plants because their carbon- fixation products have three carbon atoms per molecule. Examples Cool Season Grasses are Rice, Barley, Kentucky Bluegrass, Fine Fescue, Perennial Ryegrass, Tall Fescue, Red Fescue etc.

Warm-Season Grasses - Warm-Season Grasses are those Grasses which grow well in areas where climate is warmer. They also require less watering than Cool Season Grasses and as such are tough and durable Grasses. Warm Season Grass types will turn brown i.e. become dormant when cooler temperatures arrive. They are also known as C4 Plants because of the 4-carbon atoms present in the first product of carbon fixation in these Plants, in contrast to the 3 carbon atom products in C3 Plants. Examples of Warm-Season Grasses are Bermuda Grass, Corn, Sudan Grass, Pearl Millet etc.

Characteristics \ Features of Grasses

• Monocotyledonous - Grasses are typically Monocotyledonous, which means that they have one cotyledon, or embryonic leaf, in their seeds. They are also known as Monocots which itself stands for 'Single Cotyledon'.

• Narrow Leaves - Grasses have narrow leaves which grow from the base. The leaves have two parts: a sheath surrounding the stem called the Culm and a Blade, usually flat and linear. The lower part of the leaf is called the Sheath, and the upper part is called the Blade. The leaves alternate in direction. That is, if the first leaf on a Culm grows to the right, the second leaf will grow to left and the third leaf will grow to the right and so on.

• Vascular Plants - Grasses possess specialized supporting and water-conducting tissue, called Xylem, and food-conducting tissue, called Phloem. The Xylem is composed of non-living cells (tracheids and vessel elements) that are stiffened by the presence of Lignin, a hardening substance that reinforces the cellulose cell wall. The living sieve elements that comprise the Phloem are not lignified. Xylem and Phloem are collectively called Vascular Tissue and form a central column (stele) through the Plant axis.

• Specialized Reduced Flower Parts - The Flowers of Grasses are of a unique form, the inflorescence being subdivided into Spikelets each containing one or more tiny Florets. (In other flowering plants the inflorescences are clusters of separate flowers, never spikelets.) The dry seed-like fruit is called a Caryopsis, or Grain.

• Large Underground Root System - Grasses have a Fibrous Root System. A Fibrous Root System consists of one or several primary roots stemming directly from the seed (seminal roots), as well as roots developed adventitiously from the lower stem nodes (adventitious roots, or crown roots). Both seminal and adventitious roots then produce lateral roots. Subsequently, any of these initial laterals may produce further laterals, and so on. These roots remain active for long periods, and some of them support the Plant during the entire course of its life.

• Lack of Woody Stem - Grass Stems generally don't have Woody Stems. Grass Stems are flexible and strength to withstand the elements.

• Mostly Herbaceous - Grasses have leaves and stems that die down at the end of the growing season to the soil level. Grasses may be either annual or perennial.

• Extraordinary Range of Adaptation - Grasses have adapted to conditions in lush Rain Forests, Dry Deserts, Cold Mountains and even Inter-tidal Habitats. Graminoids are the dominant vegetation in many habitats, including Grassland, Salt-Marsh, Reed Swamp and Steppes.

• Grass Reproduction - Grass reproduce not only by the seeding process, but also by stems that emanate from the crown. Stems that grow above the surface are called Stolons. Stems below the surface are called Rhizomes.

Evolution of Grasses

Until recently Grasses were thought to have evolved around 55 million years ago, based on fossil records. However, recent findings of 65-million-year-old Phytoliths (microscopic body) resembling Grass Phytoliths (including ancestors of rice and bamboo) in Cretaceous Dinosaur Coprolites (fossilised dung), may place the diversification of Grasses to an earlier date. They became widespread toward the end of the Cretaceous period, and fossilized Dinosaur Dung (coprolites) have been found containing Phytoliths of a variety of Grasses that include Grasses that are related to modern rice and bamboo. The evolution of large grazing animals in the Cenozoic Period has contributed to the spread of Grasses. Without large grazers, a clear cut of fire-destroyed area would soon be colonized by Grasses and, if there is enough rain, Tree seedlings. The Tree seedlings would eventually produce shade, which kills most Grasses. Large Animals, however, trample the seedlings, killing the Trees. Grasses persist because their lack of woody stems helps them to resist the damage of trampling.

Importance and uses of Grasses

• Grass is a major food source all over the world.  Three Cereals - Rice, Wheat, And Maize (corn)  provide more than half of all calories eaten by humans. Others like oats, barley, and rye, are also the staple food of World's population.

• Grasses are also used worldwide as Forage by many grazing Mammals such as cattle and other Animals like deer, elephants, moths, butterflies etc.Some of the Grasses used as Hay and Pasture Plants are Sorghum, Timothy, Bent Grass, Bluegrass, Orchard Grass, and Fescue.

• Grass is important in many sports as they provide a cushion for players in Sports. Sports like American football, Association football, baseball, cricket, and rugby require large fields covered with Grass. Other Sports like Golf, Tennis etc. require Grass Courses and Grass Courts.

• Grasses are also a source of industrial ethyl alcohol, corn starch and by-products, various types of paper, and numerous other products which can be used biofuel production.

• Sugarcane is the major source of sugar production. Molasses and Sugar are products of Sugarcane and Sorghum.

• Many liquors are made from Grains and Molasses.

• Lawns are a common feature of private gardens and public landscapes and parks in many parts of the world now. Lawns increase the aesthetic appeal of any landscape and their colour soothes the eyes. Ornamental Grasses, such as perennial Bunch Grasses, are used in many styles of garden design for their foliage, inflorescences, seed heads, and slope stabilization. They are often used in Natural landscaping, Xeriscaping, Contemporary or Modern landscaping, Wildlife gardening and Native Plant gardening.

• Grasses are used for construction. Scaffolding made from bamboo 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, and Grass roots stabilize the sod of sod houses.

• Arundo is also used to make woodwind instruments.

• Phragmites australis (common reed) is important in water treatment, Wetland Habitat preservation and land reclamation in the Old World.

• Because of the their large underground root system, Grasses like Beach Grass are often introduced to prevent erosion.

Some Important Grasses of the World

Grain Crops - Barley, Maize (Corn), Oats, Rice, Rye, Sorghum,Wheat, Millet.

Leaf and Stem Crops - Bamboo, Marram Grass, Meadow-Grass, Reed, Ryegrass, Sugarcane.

Lawn Grasses - Bahia Grass, Bent Grass, Bermuda Grass, Centipede Grass, Fescue, Meadow-Grass, Ryegrass, St. Augustine Grass, Zoysia.

Ornamental Grasses - Calamagrostis, Cortaderia, Deschampsia, Festuca, Melica, Muhlenbergia, Stipa.