Jebunnesa Chowdhury

The Grasses The grass family is of greater importance to humanity than any other family of flowering plants. Cereals are the basic foods of civilization with wheat, rice and corn the most extensively grown of all food crops. Other important cereals are barley, sorghum, oats and rye.

Characteristics of the grass family: Vegetative characteristics  The Poaceae are usally herbaceous.  Linear leaves with parallel venation typical of monocot.  Have an alternate arrangement and sheath.  Stems are unbranched.  Many species have horizontal stems.  Cereal: Annual, Pasture and lawn grasses: Perennials  The primary root system is fibrous. From erect stem adventitious roots may form as prop roots, or from rhizomes or stolons.

Picture of vegetative parts and floral parts

The flower  Born in inflorescence, individual flowers are small, inconspicuous and incomplete.  Sepal and petal lacking completely or replaced by small structure called lodicules.  Three stamens and single ovule in the gynoecium bur two styles and stigmas( enlarged and feathery).  Two bracts: outer lemma, inner palea  Floret: Flower and two bracts  One to 12 floret arrenged on a spikelet, may be subtended by 2 bracts called glume.  Awn: A slender bristle can be seen extending from either a glume or lemma,this structure is called awn.

The grain  Grain: Dry indehiscent single –seeded fruits.  Chaff: Bract that surround the grain.  Bran: Outer wall of the grain( fruit wall fused to the seed coat).  Aleuron layer: Interior to the bran is a layer of enlarged cell which is high in protein.  Germ: The embryo with its sheath.

Picture of grain

Economic Importance  The large amount of stored food in the grain makes this family valuable as a food crop.  The endosperm is mostly starch and in the refining process, the chaff, germ and bran are removed.  This refined product is available as white flour, corn stach and white rice.  The bran provide fibers as well as some protein from the aleurone layer.  The germ is a good source of vitamins, proteins and some oils.  Brown rice, whole –wheat flour and popcorn are more nutritious than refined grains.  Three grains are the dietary staples for the world population and the chief source of carbohydrate and proteins.

Wheat: The Staff of Life  One of the widely cultivated cereals. Appearance:  Grass but the spikes are tightly packed with grains.  Long awns, giving the fruit in head a bearded appearance.  Best in temperate grassland biomass ( cm rain per year) and have cool temperature.

Origin and evolution of wheat Polyploidy involving several species of wheat. 3 groups can be identified on the basis of chromosome number: o One group has 14 chromosome ( Diploid species) o The second group has 28 ( Tetraploid species) o The remaining group has 42 chromosome ( Hexaploid species)

Evolution of domesticated wheat

The evolution of bread wheat: Triticum aestivum Bread wheat was the result of hybridization between Triticum turgidum and Triticum tauschii. The genetic contribution of t. tauschii were a higher protien content in the endosperm and greater tolerance to environmental condition. Gluten, an important component of flour for the elasticity it provide.

Modern Cultivers 2 types of wheat are widely cultivated:  Durum wheat ( T. durum): Has high glutent content and yield semolina flour. Used to make spaghetti,macaroni and noodles  Bread wheat ( T. aestivum): Used for bread, pasta and breakfast cereals.

Nutrition Nutrient rich cereals. Wheat is missing only four of the known essentials nutrients-Vitamin A, B₁₂,C and iodine. The protein content is good ( 12.9%). The whole grain provides the greatest nutritional benefits.

Corn: An Unusual Cereal Much larger than other cereals. Have separate staminate and carpellate inflorescence. The tassel arranged in a panicle with each floret consisting of three stamens surrounded by bracts. The carpellate inflorescence gives rise to the familiar ear of corn. The grains ( kernels) are naked ( lack bracts around each grain)but the entire ear is tightly covered husks. The silk can be seen beneath the husk. Poorly adapted for survival under natural conditions.

Types of corn: Characterized by the nature of the starch present in the endosperm. Starch has two component:  Amylose : An unbranched chain of glucose molecules.  Amylopectin: A highly branched chain of glucose molecules. Types of corn:  Popcorn  Flint corn  Flour corn  Dent corn  Sweet corn  Waxy corn  Pod corn

Different varieties of corns

Description of different types of corn: Popcorn: Kernels with hard starch swell and burst when heated. Flint corn: Hard starch near the outer part of the kernel. Flour corn: Softer endosperm makes it easier to grind and prepare a dough by mixing with water. Dent corn: Both hard and soft starch.Upon drying,the kernel shows a characteristics dent as the soft stach dent. Sweet corn: High concentration of sugars instead of starch in the cells of endosperm. Waxy corn: Glossy, wax- like appearance of the cut kernels that is due to the presence of only amypectin in the endosperm. Pod corn: Each kernel in pod corn is covered with glumes.

Culture conditions of corn growth. Summer annual that grows best under moderate conditions of temperature and moisture. Temperature: Avg, temp. 23⁰c or above with lots of sunshine. Rainfall: cm rain spread over a 3-5 month growing season are ideal. Soil: Nutrient rich soil.

Hybrid corn Results from crossing inbred lines. Hardier because of hybrid vigor or heterosis. Have desirable traits of both parents. Improved seed production with desirable traits and large number of kernels. Method:  A row of female parent is planted next to a male parent line.  Then detasseled to prevent self- pollination. Disadvantage: Need to purchase new hybrid seed each year. Advantage: A new enterprise has created in planting inbred lines to produce the hybrid seeds.

Value of corn Used as animal feed. Small part is eaten directly as a vegetables, most processed for food production or industrial application. Good nutrient source of carbohydrates, fats and protiens. Corn oil from corn kernel used as salad oils, cooking oils, salad dressing and margarine. Industrial uses:  Pharmaceutical fillers, glues,lubricants,ethanol for use in gasohol and biodegradable plastics and packing materials from corn starch among many products.

Rice: Food for billions Oryza sativa and Oryza glaberrima are the cultivated species. Oryza sativa is the main cultivated rice with 20 species Able to grow under many different environmental conditions.

A plant for flooded fields Large, multistalked annual growing to an average 1 meter height with the typical vegetative apperarence. Each stalk is terminated by panicle bearinggrains surrounded by bracts. Air chambers in the stem that permit the diffusion of air from stomata in the leaves through the stem and eventually down to the roots( permits rice to adapt in flooded soils). Cultivated in flooded fields or paddies with 5-10 cm of standing water. The paddies are diked with earthen dams and filled by rain or irrigation. Young seedlings started in seedbeds are transplanted by hand into the paddies.

Harvesting When the grain are mature the fields are drained to prepare for harvesting. Done by hand using sickles. Threshing follows to free the grain from the outer bracts or chaff. Winnowing then separates the grain from the fragments of chaff. Brown rice is dehulled whole grain and is nutritionally superior to white rice ( milled and polished). Brown rice contains more protein( 8.5% to 9.5%) than white rice ( 5.2%-7.6%) and more vitamins especially thiamine and vitamin B1.

Varieties Varieties can be grouped into 3 subspecies:  Indica: Tropical, long grains, do no stick togather when cooked.  Japonica: Subtropical to temperate,short grains, sticky when cooked.  Javanica: Indonesian, tall, thick stem and large grains. Golden rice: Able to synthesize beta carotene in the endoperm.

Flood –Tolerant Rice Most varieties cannot tolerate complete submerge for more than 3 days. Flood resistant variety( can tolerate complete submerge upto 17 days) has been identified from India by IRRI researchers. Their ability to tolerate submergence is due to the presence of gene –Sub l. Sub l has transferred to high yielding local varieties and showed good performance and taste the same as traditional types.

Forage grasses Any vegetation consumed by domestic herbivorous animals includes grasses and legumes Grasses also provide nourishment for livestock in the form of forage. Herbaceous perennials are grown for their vegetative structures ( leaves and stems), not for their grains or seeds. The nutritive value is in the form of cellulose and hemicellulose.

Forage grasses Herbivores are able to digest these compounds through the action of symbiotic microorganisms within their digestive tract. Forage can be consumed directly during grazing, the crop can also be cut, dried and baled as hay. It can be harvested and fermented by bacteria to produce silage. Hay and silage have value as stored food reserves when climatic conditions prevent grazing. Example : Kentucky blue grass (Poa pratensis), Alfalfa( Madicago sativa).

Legumes Members of the bean family, Fabaceae, which includes all types of beans and peas as well as soybeans, peanut and clover. Also includes various trees and ornamentals such as black locust, wisteria and lupine.

Characteristics of the legume family Dicot, similar flower and fruit structure. Five petaled flower is irregular with bilateral symmetry and described as either butterfly-shaped or boat- shaped. The fruit is a pod or legume with one row of seeds which contain two food storing cotyledons. The seeds are rich in oil and protein, often called ‘poor man’s protein’. Legume is correlated with the presence of root nodules which contain nitrogen fixing bacteria that enrich soil.

Important legume food crops:Beans Oldest and common food crops. Come in all shapes, sizes and colors: kidney beans, lima beans, pinto beans, navy beans, green beans, wax beans and butter beans. Good source of protein with values ranging from 17%-31% and the average about 25%. Warm season annual, require moderate amount rainfal. Tolerate most types of soil. Vicia faba- old world species.cultivated and eaten in Meditteranean region. Favism – a disease associated with its consumption.