Crops and life Test 1

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What is a CROP?

Crops are plants grown for a specific intended use by humans. Crops can be used for:

Food and cooking (grain, vegetables, fruit, cooking oil, spices)

Drugs (medicinal and recreational)

Fibers (textiles, rope, nets, etc.)

Materials (industrial oils, rubber, construction)

Energy (biofuels, charcoal)

Erosion Control (cover crops, roadsides, building sites)

Recreation (sod for lawns, parks, sports fields etc., cut flowers)

How Long Have We Had Crops?

Research suggests humans began altering the evolution of plants at least 30,000 years ago. Most wild plants spread seeds: pods break, shatter, rot, etc. - allows the seeds to scatter. Certain plants selected to retain their seeds by began the transition to being crops. Evidence of "non-shattering" genes among an archaeological site in northern Syria.

Basic Life Cycles of Plants

1. Annual

2. Perennial

3. Biennial

Annuals

Complete their entire life cycle in growing season.

Must plant new seed for every crop

The vast majority of plants used as crops are annuals OR managed as annuals.

We do have some additional specialization of these annuals

Summer Annuals

Germinate in spring /summer.

Flower and produce seeds in late summer or early fall.

Die in late fall or early winter

Winter Annuals

Germinate fall / winter.

Flower and produce seed in late winter or early spring.

Die in late spring or early summer.

Sometimes annual crops can be

grown out of season in controlled environments

Perennials

Live more than 2 years

Forage, fruit, turfgrass, and tree crops are managed as perennials

We have lots of crops that were originally perennials but we grow them as annuals

Examples: cotton, strawberry, potato

Biennials

Germinate

Grow vegetatively for ONE YEAR.

Then, in the second year they go into the reproductive phase.

The flower is typically large and showy. This is Year 2.

Die in Year 2.

I cannot think of any crop plants that are purposely grown as biennials.

Carrots are biennial – but we manage as an annual.

Another way we group plants is

by the daylength they need to flower

Photoperiodism

The physiological reaction of organisms to the length of night or a dark period.

Photoperiodism can also be defined as the developmental responses of plants to the relative lengths of light and dark periods

Short-day plants

flower when day length is about 12 hours or less

*Cotton (There are some day-neutral cotton varieties.) Rice, Soybeans, Poinsettias

Long-day plants flower when

day length is about 12 hours or longer.

Barley, Lettuce, Wheat, Spinach, Sugar beets

Day Neutral Plants

Plants that flower regardless of day length are "day neutral" plants.

Tomatoes, Cucumbers, Roses

Most crop plants are

flowering plants (angiosperms)

A few gymnosperms are cultivated

Some ferns are edible, but not usually farmed