Biology Chapter 25 (Plant Responses and Adaptions)

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Meristems

Regions of tissue which can produce cells that later develop into specialized tissues.

Hormone

A substance that is produced in one part of an organism and affects another part of the same individual. They are chemical substances that control a plant's patterns of growth and development, and its responses to environmental conditions.

Target cell or target tissue

Two types of areas which are a portion of an organism which is affected by and contains hormone receptors for a particular hormone.

Phototropism

The tendency of a plant to grow toward a source of light.

Auxins

Substances which are produced in the apical meristem and are transported down to the rest of the plant. They regulate cell growth. In stems, they stimulate cell elongation. In roots, they inhibit cell growth and elongation, causing them to grow downward.

Gravitropism

The response of a plant to the force of gravity.

Lateral bud

A meristematic area on the side of a stem that gives rise to side branches. Their growth can be inhibited by auxins.

Apical dominance

The phenomenon in which because auxins move out from the apical meristem, the closer a lateral bud is to the meristem, the more its growth is inhibited.

Herbicides

Compounds which are toxic to plants and mimic the effects of auxins.

Cytokinins

Plant hormones that stimulate cell division and the growth of lateral buds or cause dormant seeds to sprout. They often produce opposite effects to those of auxins, by inhibiting cell elongation and causing cells to grow thicker. They are produced in growing roots and in developing roots and seeds.

Gibberellins

Compounds which produce dramatic increases in size, particularly in stems and fruit.

Ethylene

A plant hormone which causes fruit to ripen. It is also a minor component of natural gas.In response to auxins, fruit tissues release small amounts of it.

Tropisms

The responses of plants to external stimuli.

Thigmotropism

The response of plants to touch. One effect is that plants curl and twist around objects.

Short-day plants

Plants that flower when days are short.

Long-day plants

Plants that flower when days are long.

Photoperiodism

When plants respond to periods of light and darkness. It is responsible for for the timing of seasonal activities such as flowering and growth.

Phytochrome

The plant pigment which is responsible for Photoperiodism. It absorbs red light and activates a number of signaling pathways within plant cells.

Dormancy

The period during which an organism's growth and activity decrease or stop. When it starts getting cold, deciduous plants turn off photosynthetic pathways, transport materials from leaves to roots, and seal leaves off from the rest of the plant.

Leaf Abscission

What it's called when flowering plants lose their leaves for the colder months

Abscission Layer

A layer of cells at the petiole which seals the leaf off from the plant's vascular system.

Aquatic Plant

This type of plant has adapted to its environment by having large air-filled spaces through which oxygen can diffuse in order to take in sufficient oxygen.

Salt-tolerant plants

The leaves of these plants have specialized cells that pump salt out of the plant tissues and onto the leaf surfaces, where it is washed off by rain.

Xerophytes

Plants that live in the desert biome. Plant adaptions to this climate include extensive roots, reduced leaves, and thick stems that can store water.

Carnivorous Plants and Parasites

2 types if plants that have specialized features for obtaining nutrients.

Epiphytes

Plants that are not rooted in the soil but grow directly on the bodies of other plants but are not parasites. They gather their own moisture and produce their own food. (Ex: Moss or Orchids)

Insects

Many plants defend themselves against ______ by manufacturing compounds that have powerful effects on animals.

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