15.1 and 15.2

Question 1

Changes in levels of soil water, salt, and temp. → affect

Answer 1

plant’s growth, reproduction + survival

Question 2

Plants are adapted to tolerate temporary stress→by

Answer 2

going dormant

Question 3

Plants react to drought by saving water by

Answer 3

closing their stomata →slows down rate of transpiration

Question 4

adaptations that let plants survive dry climate

Answer 4

-Cacti and succulent plants (Aloe vera) keep water in fleshy stems that help them to thrive in desert

-Succulent plants have thick fleshy leaves
-stems and leaves have a thick cuticle

-Some desert plants have waxy cuticles or an epidermis multiple layers thick

-Stomata of many plants are made inside epidermal pits + protected by epidermal hairs

Question 5

adaptations that let plants survive in cold, dry arctic regions

Answer 5

-small needle-shaped leaves + grow low to ground

-reduces transpiration by reducing exposure to harsh, dry wind

Question 6

adaptations that let plants survive wet habitats

Answer 6

-mangrove trees grow in coastal marshes, but their roots are slightly above ground →provide O2 for underwater roots→negative gravitropism

-plants not able to survive in aquatic habitats have to endure periods of waterlogged soil

Question 7

adaptation for a salty habitat

Answer 7

Halophytes (salt-tolerant plants) have adaptations to remove salt from plant

• some plants have salt glands that remove salt from plant across leaf epidermis + rain washes it away

  - e.g. salt marsh plant called Pickleweed takes extra salt to stems at tips of plant→pickleweed sheds stems→salt removed

Question 8

adaptations that protect plants from infection

Answer 8

When infected→plants use chemicals to defend themselves
- Some chemicals can be used for defence or lignin production (lignin hardens cell walls around infected area + seals off pathogen from taking over

Question 9

adaptations to protect themselves from herbivores

Answer 9

-physical defences (thorns, poisons)

-when in light, potato tubers make a bitter chemical called solanine→fungicide + insecticide
-solanine→natural defence that protects tubers
from being eaten
-chlorophyll can be a clue that tuber has been in
light + contains solanine

Question 10

auxin

Answer 10

chemical messenger produced in shoot tip and is a plant growth hormone

Question 11

plant hormones

Answer 11

Plant hormones: chemical signals made in small amounts in one section of plant that specifically affect another part of the plant

Question 12

5 major plant hormones

Answer 12

Auxins, cytokinins, gibberellins, abscisic acid, and ethene

Question 13

purpose and functions of auxin

Answer 13

Main purpose of auxin is to help plants grow →lengthening stem

Other functions:
-increase secondary growth of plant stem by promoting cell division in vascular cambium
-trigger process of making roots and leaves
-bringing plants to auxin can cause fruit to grow without any pollination or seed development

Question 14

where is auxin made?

Answer 14

Made in apical meristems of plants at tips of shoots

Question 15

process of auxin being used

Answer 15

Seedling gets light from one direction→auxin builds up on shaded side → triggers growth beneath tip→cells on shaded side exposed to more auxin→they lengthen, more than the cells on the lighted side

Uneven growth of cells on the two sides of plant make the shoot bend toward light (smaller on that side)

Question 16

functions of cytokinins

Answer 16

help plants grow by triggering cell division

slows aging of flowers and fruits

encourages branching of plant

can trigger shoot formation

Question 17

where are cytokinins made?

Answer 17

-growing tissues (embryos, roots, seeds, and fruits)

-roots (get to target cells in stems by going up xylem sap)

Question 18

give an example of how effects of cytokinins are affected by concentration of auxins present?

Answer 18

e.g. cytokinins entering shoot system from roots encourage cell division in axillary buds

Question 19

how can cytokinins be used in horticulture

Answer 19

-used in horticulture to make plants and leaves bigger

-e.g. gardeners pinch back terminal buds at growing tips of plant

-lowers auxin levels→plant branches more

-adding cytokinins to leaf, stem, or root cuttings can also trigger shoot formation

Question 20

gibberellins functions

Answer 20

-important in plant growth and development

-increase stem growth by promoting cell division + cell elongation

-crucial to seed germination

Question 21

When combined with auxins, gibberellins can cause

Answer 21

fruits to grow

Question 22

what happens to plants with less gibberellins

Answer 22

Less gibberellin in plants→short, stiff stems + less leaves

Question 23

how are gibberellins crucial to seed germination?

Answer 23

e.g. when in water, embryos in cereal grains (barley) let out gibberellins that trigger breakdown of nutrients held in endosperm

Question 24

where are gibberellins made?

Answer 24

Made at tips of stems and roots

Question 25

during what time is ABA made and taken through
xylem to shoots + leaves?

Answer 25

dormancy

Question 26

Abscisic Acid functions

Answer 26

Stops cell division in buds + vascular cambium → stops primary + secondary growth

Question 27

ABA has opposite effect of ______→causes dormancy in seeds

Answer 27

gibberellins

Question 28

Give an example of how ABA acts like a stress hormone

Answer 28

e.g. plant doesn’t have enough water→ ABA builds up in leaves → stomata closes (reduces transpiration + water loss)

Question 29

Spraying ABA on plants helps them …

Answer 29

survive drought stress in dry seasons

Question 30

ethene

Answer 30

a gas let out when kerosene is burned

Question 31

function of ethene

Answer 31

Natural plant hormone that helps ripen fruits

Question 32

ethene promotes _____

Answer 32

leaf drop

Question 33

describe leafdrop

Answer 33

Promotes leaf drop: leaves falling off deciduous trees every autumn
- Caused by sudden change in amounts of ethene + auxin in leaf petioles