Leaves and stems are not easily distinguished anatomically, i.e., stems are collections of leaf bases, especially in monocots - vascular strands are scattered. In dicots, it is a little more complicated as the vascular strands are in a ring.

Functionally, leaf is site of photosynthesis, stem is the supporting structure.

Roots are not always underground and not all underground structures are roots. Roots do not have leaf scars and axillary buds. Roots are also different in that they:
1. Lack stomata
2. Do not phytosynthesize
3. Have root hairs
4. Organization of vascular tissues (xylem and phloem) is different. Primary xylem forms radial strands.

Meristems - regions of cell division
terminal meristems- ends of stems, branches and roots
Lateral meristems are parallel to sides of plant parts and increase girth.

Annual - completes life cycle in one year

Biennial - completes life cycle in 2 years, stores food, often in tap root, during 1st year, flowers and fruits 2nd year, then dies; are used for both leaves and root products; cultivars are selected for maximization of one or the other; example is turnip greens and turnips; leafy cultivars do not make very good turnips and root cultivars do not produce as much leafy mass

Perennial - long-lived, rarely used for food crop and when used, grown as annuals.

Brassica oleracea

Kale - leafy, ancestor to all B. oleracea

Collards - grown for greens, very popular in Southeastern U.S.

Cabbage - suppression of terminal bud; lateral buds are undeveloped; long storage; sauerkraut was developed to allow long-term storage of cabbage.

Brussel Sprouts - cabbage mutant, terminal bud is not suppressed, axillary buds form heads.

Kohlrabi - unusual "baseball" with enlarged stem

Broccoli - derived from inflorescence, fertile flowers

Cauliflower - derived from inflorescence, sterile flowers, leaves tied around it to blanch.

Lactuca sativa - lettuce - Asteraceae or sunflower family, heads are formed by suppression of terminal bud

Heading - iceberg is most common in U.S.

Loose - leaf

Cos- stiff, long leaves - romaine

Endives and chicory - Cichorium intybus- closely related to Lactuca, escaped wild plant in U.S. with small heads, roots are roasted, ground and used as a coffee substitute

Spinach - Spinacia oleracea, substitute for lettuce. Thought to be good source of iron but compounds in leaves form a complex with iron, preventing its absorption.

Celery -Apium graveolens, umbel family, cultivated by Greeks and Romans, seeds are used as herbs but mostly grown for swollen petioles.

Swiss chard - Beta vulgaris - also sugar beets and beets

Turnips - Brassica campestris, often held in low esteem, people in NE U.S. eat turnips, in SE eat turnip greens; Europeans eat great amounts of turnips, which store well over the winter.

Rutabagas - Brassica napus - strong flavored, possible source is hybridization between cabbages and turnip, food for livestock in Europe, marketed in grocery stores in US.

Radishes - Raphanus sativus - should probably be a Brassica, mostly used as a garnish in US but widely consumed in other cultures. Larger forms are grown in the orient. Bright red color is a fairly recent mutation.

Carrots - Daucus carota (Queen Anne's Lace) biennial that stores reserves in taproot, important source of vitamin A (from carotene) native to eastern Mediterranean

Parsnips - Pastinaca sativa, also an umbel, pale yellow, sweeter than carrots

Beets - Beta vulgaris, one of most important crops in world due to sugar beets
STARCHY AND TUBEROUS ROOTS

Manioc or cassava - Manihot esculenta, Euphorbiaceae, very important in tropical regions, hundreds of local varieties (land races), is variable and has been cultivated by many different groups for a very long period of time in tropical areas. Plants grow easily in a variety of soils and produce high yields of starch but very little protein, no vitamins and poisonous compounds (cyanogenic), bitter forms have lots of cyanogens, sweet small amounts; also characterized as smooth and rough-skinned (no correlation with cyanogens). Sweet varieties are most common in Africa and roots are boiled, peeled or dried. Both varieties are present in South America so more processing is required which results in the production of flat, hard breads which store well.

Sweet Potatoes - Ipomoea batatas, Convolvulaceae, native to South America 10,000 year old fossils found from Andes, unclear how sweet potato reached Old World, grown throughout world as an annual but persists as a perennial in the tropics, cannot divide as you can a tuber, must have whole plant to propagate - use pieces of aerial stems (slips). Not related to yams. China is world's leading producer.

Celeriac is the swollen basal stem from Apium graveolens, more popular in Europe than in US

Asparagus - Asparagus officinalis, Liliaceae, dioecious perennial - flowers are unisexual, male and female plants, native to areas subject to burning, S. Europe, W. Asia and N. Africa. Plants in fire habitats have ability to sprout back from a system of rhizomes. Asparagus is young unexpanded shoots, some must be allowed to mature so plant can continue to grow
BULBS

Onions - Allium cepa, Liliaceae, from central Asia, produces single bulb

Garlic - A. sativum, central Asia, bulbs are called cloves, produces a cluster, usually three.

Leek - A. ampeloprasum, near East

Chive - A. schoenoprasum, leaves only are used

Crying is caused by sulfur compounds which combine with film over eyes to produce sulfuric acid.

TUBERS

Potatoes - Solanum tuberosum, Solanaceae, very important nongrain food, from Andes in S. America. Introduced into Europe by Spaniards. Grew very well in Europe and became staple of diet. Potato cultivation allowed a family to grow enough food to survive on a relatively small plot of land; this resulted in a large increase in population. When potato blight hit in 1840's, all potato crops in Ireland and England were destroyed. >1 million died and about 1 million immigrated to U.S. Grown throughout temperate areas and tropical uplands. Seed potatoes are still just tubers but varieties that can be grown from real seed are being developed. Disease is less of a problem when potatoes are grown from seed.

Yams - Dioscorea, Dioscoreaceae, different species from Africa, Asia and New World have been developed separately. D. rotundata is most commonly grown worldwide, propagated asexually, contain varying amounts of oxalic acid

Other tubers

Taro - Colocasia esculenta (Araceae) - is processed to produce poi
SWEETS

Sugar we use for sweetening is sucrose which is a dissacharide composed of glucose and fructose

Sugarcane - Saccharum officinarum, Poaceae, from Far East, processing of sugar from sugarcane is about 5000 years old (India). Europeans could not grow sugar until they established plantations in New World. Cane was produced in W. Indies, made into rum in Conneticut, rum was used to buy slaves in Africa and slaves were used to provide labor to grow sugar cane. Cane is propagated vegetatively by setts, which are stems which includes lateral buds and a circle of cells which produce adventitious roots. Can harvest multiple crops/year then must establish new fields. One of few examples of perennial cropping.
Harvesting - fields are often burned
Refining - raw sugar is produced by crystallization, brown liquid left over is molasses, raw cane sugar is still brown (brown sugar), white sugar is produced by further refining, powdered sugar by fine grinding of crystals.

Sugar beets - Beta vulgaris, Germans in 18th century discovered beet roots contained large amounts of sugar. Selection of higher sugar content began and has resulted in increase from 2% to 20%. Lots produced in Europe but not in US because we get most of ours from sugarcane in Hawaii, P.R. and Gulf Coast states.

Sorghum bicolor - sorghum molasses

Zea mays - corn syrup

Maple syrup - Acer saccharum, very low yield and expensive, tap sap which is boiled down to yield marketable syrup.

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