Plant Structure & Growth - 9.3

Question 1

Define Meristem

Answer 1

Region of plant tissues containing undifferentiated cells capable of indeterminate growth.

Question 2

Define Indeterminate Growth

Answer 2

When cells go through mitosis to grow or add new structures forever, as long as they have the resources to do so.

Question 3

Define Node

Answer 3

An area on a stem where buds are located. Where small buds develop into leaves, stems or flowers.

Question 4

Define Tropism

Answer 4

A directional response in a plant to an external stimulus (light, chemicals, gravity, touch).

Question 5

Define Phototropism

Answer 5

A positive tropism in plant stems (they grow toward the light) and is a negative tropism in plant roots (they grow away from the light - into the ground). Controlled by auxin.

Question 6

Define Shoot

Answer 6

Part of the plant that grows above the ground (including stems, leaves, etc.)

Question 7

Define the top of the plant / shoot.

Answer 7

Shoot Apex

Question 8

Define Pollination

Answer 8

When pollen (from the anther) is transferred to / placed on the stigma of a flower (by means/ vectors of animals, wind, or water).

Question 9

Define fertilization.

Answer 9

The haploid nuclei in male pollen grain fuses with the haploid nuclei in female ovule to produce a diploid zygote.

Question 10

Define seed dispersal.

Answer 10

When seeds are moved away from the parent plant (to reduce competition for resources) in various ways (animals, water, wind, or fruit - fruits provide more protection too).

Question 11

Define germination.

Answer 11

Process where a seed begins to sprout.

Question 12

Define self-pollination.

Answer 12

Pollen from anther of same plant falls on its own stigma – less genetic variation.

Question 13

Define cross pollination.

Answer 13

Pollen from anther of one plant carried to stigma of different plant – increased genetic variation, but longer distance for pollen to travel.

Question 14

Define photoperiodism.

Answer 14

A plant’s response to the lengths of the night (flowering).

Question 15

Vascular plant, produces seeds and flowers, monocot or dicot.

Answer 15

Angiosperms

Question 16

Vascular plant, produces cone-shaped / naked seeds.

Answer 16

Gymnosperms (Conifers)

Question 17

Vascular plants, pinnate leaves (leaflets on stalks); reproduce using spores – ex: ferns

Answer 17

Filicophytes

Question 18

Non-vascular plants, small; lacking leaves/ stems; no xylem/ phloem tissue; reproduce using spores – ex: mosses.

Answer 18

Bryophytes

Question 19

What is a plant that has ONE seed leaf when sprouting?

Answer 19

Monocot

Question 20

What is a plant that has TWO seed leaves when sprouting?

Answer 20

Dicot

Question 21

What are the ONLY type of plants that have both apical and lateral meristems?

Answer 21

Gymnosperms (conifers) and dicots

Question 22

Compare Apical and Lateral Meristems.

Answer 22

Similarity:
BOTH rely on mitosis of undifferentiated cells for growth - develops volume & mass
Differences:
apical - found at the tips(apex) of roots and stems
apical - add vertical growth
apical - primary growth
apical - produce new leaves and flowers/ fruits.
lateral - found on side (cambium)
lateral - add horizontal growth
lateral - secondary growth
lateral - Produces secondary xylem / phloem

Question 23

Explain the role of auxin in apical growth in plant stems and in apical dominance.

Answer 23

Auxin (IAA - Indole-3-acetic acid) promotes growth in the shoot apex by promoting cell division AND cell elongation by changing patterns of gene expression. Auxin also promotes growth in the shoot apex by inhibiting growth in the lateral / axillary buds (apical dominance). This allows the plant to continue to grow upward toward more light/ CO2.

Question 24

Explain the role of auxin in phototropism in plants.

Answer 24

Auxin efflux pumps actively transport auxin out of certain parts of the plant and create a concentration gradient, which means some parts of the plant have higher auxin concentration than others. Efflux pumps causes stems to grow TOWARDS light by pushing auxin into the shaded side of the plant, this lowers the pH and activates enzymes that break down bonds in the cell wall, loosening the bonds allows water to enter the cell and increase turgor pressure. Increasing the growth on the shaded side tilts the other side of the plant closer to the sun.

Question 25

Why does auxin change patterns of gene expression in plants?

Answer 25

In order to promote phototropism and apical growth in plants.

Question 26

Explain the process of micropropagation.

Answer 26

Micropropagation is a technique used to asexually reproduce large numbers of identical plants in vitro.
1- Meristematic plant tissue is removed from shoot tip and sterilized
2- Tissue is paced on sterile nutrient agar gel to grow (high auxin concentration which stimulates cell growth)
3- Roots / shoots grow & create new tissue (a callus), shoots can be divided and separated to form new samples
4- Once roots / shoots are developed, platelets are separated & transferred to soil

Question 27

Explain the applications of micropropagation.

Answer 27

Micropropagation is used for rapid bulking up of new varieties, production of virus-free strains of existing varieties, and propagation of orchids and other rare (or endangered) species.

Question 28

Explain the pros and cons of micropropagation.

Answer 28

Pros -
Highly effective
Quickly creating more healthy plants can help with hunger
More reliable than selective breeding

Cons-
Expensive
Less generic variation (more susceptible to disease)
Not all plants can be successfully tissue cultured

Question 29

Summarize the Darwin’s experiments with the coleoptiles of plants and the conclusions they made from these experiments.

Answer 29

• He removed the tip of the plant, found that there is no bending response (phototropism) to light when the tip of the pant is removed.
• He covered the tip, found that the tip must be stimulated in order to cause a response.
• He covered the bottom part of the plant, but the plant still bent, meaning ONLY the tip needs to be stimulated.
• “Some influence is transmitted from the tip to the more basal regions of the shoot thereby regulating growth and inducing curvature”