Final Exam (concept questions)

Question 1

Describe general characteristics of soil.

Answer 1

Soil solution consists of water and dissolved minerals in the pores between soil particles

Question 2

How does cation exchange help roots absorb dissolved substances in the soil solution?

Answer 2

Cations adhere to negatively charged soil particles; this prevents them from leaching out of the soil through percolating groundwater

Question 3

Why is soil pH important?

Answer 3

Soil pH affects cation exchange and the chemical form of minerals

Question 4

What is the difference between chemical and organic fertilizers?

Answer 4

Organic fertilizers are composed of manure, fishmeal, or compost
Commercial fertilizers are enriched in nitrogen (N), phosphorus (P), and potassium (K)

Question 5

What is an essential element in plant nutrition?

Answer 5

There are 17 essential elements, chemical elements required for a plant to complete its life cycle and reproduce

Question 6

How do plants obtain nitrogen?

Answer 6

Plants can absorb nitrogen as either NO3– (nitrate) or NH4 (ammonium)
Most soil nitrogen comes from actions of soil bacteria

Question 7

Why does crop rotation help with nitrogen availability in soils?

Answer 7

Crop rotation takes advantage of the agricultural benefits of symbiotic nitrogen fixation
A nonlegume, such as corn, is planted one year, and the next year a legume is planted to restore the concentration of fixed nitrogen in the soil

Question 8

What are mycorrhizae and why are they important to plants?

Answer 8

Mycorrhizae are mutualistic associations of fungi and roots
The fungus benefits from a steady supply of sugar from the host plant
The host plant benefits because the fungus increases the surface area for water uptake and mineral absorption
Mycorrhizal fungi also secrete growth factors that stimulate root growth and branching

Question 9

Describe and provide an example of non-mutualistic interactions in plants, such as epiphytes, parasites, and carnivorous plants.

Answer 9

An epiphyte grows on another plant and obtains water and minerals from rain
Parasitic plants absorb sugars and minerals from their living host plant
Carnivorous plants are photosynthetic but obtain nitrogen by killing and digesting mostly insects

Question 10

Describe the parts of a flower.

Answer 10

Flowers consist of four floral organs: carpels, stamens, petals, and sepals
Stamens and carpels are reproductive organs; sepals and petals are sterile

Question 11

Describe the life cycle of a flowering plant….which is more dominant, sporophyte or gametophyte?

Answer 11

Plant life cycles are characterized by the alternation between generations
sporophyte (spore-producing)
gametophyte (gamete-producing)
In angiosperms, the sporophyte is the plant that we see; they are larger, more conspicuous and longer-lived than gametophytes

Question 12

What is the difference between a complete and incomplete flower?

Answer 12

Incomplete flowers lack one or more floral organs, for example stamens or carpels

Question 13

What is seed dormancy? Why is it necessary? What causes a seed to germinate?

Answer 13

Seed dormancy allows seeds to overcome periods that are unfavourable for seedling established and is therefore important for plant ecology and agriculture.

Question 14

What kinds of asexual reproduction occur in flowering plants?

Answer 14

Apomixis is the asexual production of seeds from a diploid cell, Asexual reproduction is also called vegetative reproduction because progeny arise from mature vegetative fragments, Totipotent cells, those that can divide and asexually generate a clone of the original organism, are common in plants

Question 15

How does vegetative propagation work? how does plant tissue culture work?

Answer 15

Asexual reproduction is also called vegetative reproduction because progeny arise from mature vegetative fragments

Question 16

What is a GMO plant? Why were they developed? Give an example of a GMO plant.

Answer 16

Genetically modified plants may increase the quality and quantity of food worldwide
Some transgenic crops have been developed to produce the Bt toxin, which is toxic to insect pests

Question 17

What causes de-etiolation?

Answer 17

It begins when a plant is exposed to sunlight

Question 18

What are the functions of these common plant hormones: auxin, cytokinin, gibberellin, abscisic acid (ABA), and ethylene?

Answer 18

Cytokinins are so named because they stimulate cytokinesis (cell division)
Cytokinins work together with auxin to control cell division and differentiation
Gibberellins have a variety of effects, such as stem elongation, fruit growth, and seed germination
Abscisic acid (ABA) slows growth
The effects of ethylene include response to mechanical stress, senescence, leaf abscission, and fruit ripening

Question 19

How do phytochromes respond to light? How does this affect germination and shade avoidance?

Answer 19

Phytochromes are pigments that regulate many of a plant’s responses to light throughout its life
These responses include seed germination and shade avoidance

Question 20

Compare and contrast photoperiodism in short-day and long-day flowering plants.

Answer 20

.Plants that flower when a light period is shorter than a critical length are called short-day plants
Plants that flower when a light period is longer than a certain number of hours are called long-day plants
Flowering in day-neutral plants is controlled by plant maturity, not photoperiod

Question 21

What are different forms of tropism in plants

Answer 21

Response to gravity is known as gravitropism
Thigmotropism is growth in response to touch
It occurs in vines and other climbing plants

Question 22

How do plants respond to environmental stresses, both abiotic and biotic?.

Answer 22

Abiotic stresses include drought, flooding, salt stress, heat stress, and cold stress
Biotic stresses include herbivores and pathogens