Exercise 11. Botanical descriptions

Name of exercise: Writing a complete botanical description

Tools: Herbarium specimens, reference books, CD-ROMs, access to Internet, live materials of the species described.

Time needed: 2 hours, if compiling information from various sources; longer if the botanical description is based on personal measurements, observations and interviews.

Description: Writing a complete botanical description is an important step in summarizing information from personal observations, interviews, field experiments and existing literature. The description should begin with the complete scientific name and botanical family of the plant, followed by information about the general habit of the plant, its leaves, flowers and fruits, with an emphasis on any distinguishing morphological or anatomical features. Measurements of the size of the overall plant, and of its individual parts, allows other researchers to accurately distinguish the species from related ones. Ethnobotanical data, including information on indigenous classification, management and use, should follow the morphological description. Supplementary information on the nutritional components (for edible plants), phytochemical components (for medicinal plants) and other analytical data is valuable. The geographical distribution of the species should be discussed and, if it is a domesticated plant, any insights on its origin, ancestors and wild relative should be added.

How to do it: Select a number of economic plants that are known to the participants; it is particularly appropriate to choose plants that have been used in other exercises. Divide the class into subgroups, and assign one botanical species to each. Explain the objective of the exercise, and discuss the various reference materials that are available. Allow sufficient time for participants to gather, discuss, synthesize and write the information. Once the botanical descriptions are complete, have a representative of each subgroup present the results to the whole group.

References:

For general information on writing a botanical description, consult Forman, L. and D. Bridson, eds. 1991. The Herbarium Handbook. Kew, Royal Botanic Gardens.

Specific guidelines for collecting ethnobotanical information are available in Chapter 3 "Collecting ethnobotanical data: an introduction to basic concepts and techniques" of Alexiades, M.N., editor, Selected Guidelines for Ethnobotanical Research: A Field Manual. New York, The New York Botanical Garden.

For some ideas on collecting original ethnographic information on plant classification use and mangament, consult Chapter 2 "In the field: participating, observing and jotting notes" of Emerson, R.M., R.I. Fritz and L.L. Shaw. 1995. Writing Ethnobographic Fieldnotes. Chicago, University of Chicago.

Example:

Students used various references available at Khon Kaen University to compose botanical descriptions of the fruit trees popular in Thailand, especially those used in previous sorting, ranking and other exercises. Given the limited amount of time available for the exercise, these descriptions were not expected to be original texts, but rather compilations of information found in books, CD-ROMs and on the Internet. The students relied heavily on the ICRAF Agroforestree CD-ROM, further described in Exercise 10.

The various groups chose Cocos nucifera (Arecaceae), Dimocarpus longan (Sapindaceae), Lansium domesticum (Meliaceae), Nephelium lappaceum (Sapindaceae), Psidium guajava (Myrtaceae), and Salacca zalacca (Arecaceae). The following description of papaya provides an example of a botanical description.

Carica papaya L. (Caricaceae)

An evergreen, tree-like herb with an extensive rooting system, 2-10 m tall, usually unbranched, although sometimes branched due to injury, containing white latex in all parts. Stem cylindrical, 10-30 cm in diameter, hollow with prominent leaf scars and spongy-fibrous tissue. Leaves spirally arranged, clustered near apex of trunk; petiole up to 1 m long, hollow, greenish or purplish-green; lamina orbicular, 25-75 cm in diameter, palmate, deeply 7-lobed, glabrous, prominently veined; lobes deeply and broadly toothed. Flowers tiny, yellow, funnel-shaped, solitary or clustered in the leaf axils, of 3 types; female flowers 3-5 cm long, large functional pistil, no stamens, ovoid-shaped ovary; male flowers on long hanging panicles, with 10 stamens in 2 rows, gynoecium absent except for a pistillode; hermaphrodite flowers larger than males, 5-carpellate ovary; occurrence depends on the season or age of the tree. Fruits large, cylindrical, with fleshy orange pulp, hollow berry, thin yellowish skin when ripe, varied. Fruits formed from female flowers are oblong, spherical, pear-shaped; from hermaphrodite flowers, long, obovoid or pyriform. Seeds numerous, small, black, round, covered with gelatinous aril. Small latex vessels extend throughout the tree and are particularly abundant in fruit that has reached full size but has not yet begun to ripen.

The generic name is from the Latin ‘carica’, meaning ‘edible fig’, on account of the similarity of papaya leaves to those of figs. The genus Carica is indigenous to tropical America, and the papaya must have originated from natural hybridization involving C. peltata. From tropical America, it was brought to the Caribbean and Southeast Asia during the Spanish exploration in the 16th century. It then spread rapidly to India, Oceania and Africa, and today it is widely distributed throughout the tropical and warmer subtropical areas of the world. Carica papaya grows satisfactorily in a wide range of areas from the equatorial tropics to temperate latitudes. However, it must be grown in warm, sunny sites sheltered from wind; preferably below 1500 m. Strong winds are detrimental, particularly on soils that cannot make up for large transpiration loss. Carica papaya is not frost hardy; exposure to frost or cold wind usually results in leaf damage and subsequent death of the tree. Roots are very sensitive to waterlogging, and even short periods of flooding can kill the plant. The ideal range of altitude is 0-1600 m, and the preferred climatic conditions include a mean annual temperature of (minimum 15) 21-33 degrees C, and a mean annual rainfall of 1000-2000 mm. Papayas grow well in well-drained, permeable, well aerated, root-knot nematode free, fertile loamy soil, preferably rich in organic matter with neutral reaction (pH 6-7).

Usually male and female flowers are on different trees, but some flowers are bisexual. Pollinating agents include various insects such as larger bees (Xylocarpa, Trigona), honeybees, long-tongued sphinx moths (Sphingidae), humming-bird moths (Macroglossa) and wind. With open (uncontrolled) pollination, a cultivar may loose its identity in a few generations.

Ripe papaya is a favorite breakfast and dessert fruit that is available year-round. It can be used to make fruits salads, refreshing drinks, jam, jelly, marmalade, candies and crystallized fruit. Green fruit is pickled or cooked as vegetable or as a substitute for applesauce. About 60% of the ripe fruit is edible. The approximate content per 100 g edible portion is water 86.6 g, protein 0.5 g, fat 0.3 g, carbohydrates 12.1 g, fibre 0.7 g, ash 0.5 g, potassium 204 mg, calcium 34 mg, phosphorus 11 mg, iron 1 mg, sodium 3 mg, vitamin A 450 mg, vitamin C 74 mg, thiamine 0.03 mg, niacin 0.5 mg, and riboflavin 0.04 mg. The energy value is 200 kJ/100 g. Major sugars are sucrose (48.3%), glucose (29.8%) and fructose (21.9%). In Java, a sweetmeat is made from the flowers. Young leaves are sometimes eaten.

In some countries, Carica papaya is grown in sizeable plantations for the extraction of papain, a proteolytic enzyme present in the latex, collected mainly from green fruit. Papain has varied uses in beverage, food and pharmaceutical industries: in chill-proofing beer, tenderizing meat, drug preparations for digestive ailments and treatment of gangrenous wounds. It is also used in bathing hides, degumming silk and softening wool. The latex yield can be about 70-130 kg of papain/ha per year.

Carapine, an alkaloid present in papaya, can be used as a heart depressant, amoebicide and diuretic. The fruit and juice are eaten for gastrointestinal ailments; a fresh leaf poultice is used to treat sores. The fresh root with sugarcane alcohol can be taken orally or as a massage to soothe rheumatism. A flower decoction is taken orally for coughs, bronchitis, asthma and chest colds. In some countries, the seeds are used as an abortifacient and vermifuge.

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