Chapter 9: Plant Growth and Development

Question 1

more cells=become bigger

Answer 1

growth

Question 2

changes that occur in an
organism starting from its beginning till its death may collectively be termed as .

Answer 2

development

Question 3

, the complex process that unfolds from the beginning to the end of an
organism’s life

Answer 3

Development

Question 4

two primary mechanisms of development:

Answer 4

morphogenesis and differentiation

Question 5

is the shaping and structuring of an organism. This process involves the
organization of cells into tissues and organs, ultimately giving the organism its unique form.

Answer 5

Morphogenesis

Question 6

, on the other hand, is the specialization of cells to perform
specific functions.

Answer 6

differentiation

Question 7

Three Stages of Growth

Answer 7

Cell Division
Cell Enlargement
Cell Differentiation

Question 8

During
____, a single cell divides into two identical daughter cells. This division results in an increase
in the total number of cells within the organism.

Answer 8

mitosis

Question 9

increase in size as their cytoplasm, the jelly-like substance within the cell, expands.

Answer 9

Cell Enlargement

Question 10

cells begin to specialize and take on specific functions.
This process, known as , __transforms generic cells into cells with unique structures
and roles.

Answer 10

cell differentiation

Question 11

three distinct phases of s-shapes growth curve

Answer 11

Lag Phase
Log Phase
Stationary Phase

Question 12

This is the initial stage of growth, characterized by a very slow rate of growth.
During this phase, the organism is adjusting to its new environment and preparing for rapid
growth.

Answer 12

Lag Phase

Question 13

This phase is marked by rapid and exponential growth. The organism is
actively dividing and increasing in size at its maximum rate. This period of rapid growth
is essential for the organism to reach its full potential.

Answer 13

Log Phase

Question 14

rate of growth begins to decline.
Eventually, the growth rate slows down and eventually stops altogether

Answer 14

Stationary Phase

Question 15

Organic compounds produced in small amounts, influencing plant growth and
development.

Answer 15

Phytohormones

Question 16

chemical substances act as essential signaling molecules, coordinating and
regulating a vast array of physiological processes that govern plant growth, development, and
response to environmental stimuli.

Answer 16

Phytohormones

Question 17

five major classes of phytohormones

Answer 17

auxin
Gibberellins
Cytokinins
Ethylene
Abscissic acid

Question 18

synthetic chemicals that can influence plant
growth; mimic the structure and function of natural
plant hormones

Answer 18

, growth regulators,

Question 19

auxin= greek word ___ means ___

Answer 19

auxein; to grow

Question 20

hormone that promotes growth and is generally produced by the growing apical part of the stem
and root

Answer 20

Auxins

Question 21

naturally produced auxin=
synthetic auxins (3)

Answer 21

natural= Indole-3-Acetic Acid (IAA)
syhthetic-= Indole-3-butyric acid (IBA), 2,4- Dichlorophenoxy Acetic Acid (2,4-D), and Naphthalene acetic
acid (NAA).

Question 22

Physiological Effects of Auxin (6)

Answer 22

Root-shoot differentiation ;
cell elongation ;
Apical dominance;
Phototropism and Gravitropism;
Fruit development ;
Leaf abscission

Question 23

Auxin in root elongation:

high levels=
low levels=

Answer 23

high levels= inhibits root elongation
low levels= promotes root initiation

Question 24

Auxin (what physiologic effect):

at low concentrations, auxin promotes root initiation and development by
stimulating cell division in the ___, a layer of cells surrounding the vascular tissue. This leads
to the formation of ___, which increase the root system’s surface area for nutrient and
water uptake.

Answer 24

(Root-shoot differentiation)
pericycle;
lateral roots

Question 25

Auxin promotes cell elongation through the ____mechanism.

Answer 25

acid growth

Question 26

auxin: (what physiologic effect?) It induces the acidification of cell walls by stimulating ___, which lower the pH of the cell wall. This acidic environment activates ___, enzymes that loosen the cellulose fibers and other components of the cell wall, making it more flexible

Answer 26

(Cell elongation) proton pumps; expansins

Question 27

is a phenomenon where the apical meristem, located at the tip of a plant shoot, inhibits the growth of lateral buds.

Answer 27

Apical dominance

Question 27

Auxin (what physiological effect): Auxin is transported basipetally (toward the base of the plant) and accumulates in lateral buds, where it inhibits cell division and elongation. This inhibition prevents the lateral buds from growing and competing with the main shoot for resources

Answer 27

(Apical dominance)

Question 28

auxin (what physiological effect): auxin can promote the degradation of ___, a hormone that promotes cell division and lateral bud growth.

Answer 28

(Apical dominance) cytokinin;

Question 29

auxin (what physiological effect): Auxin accumulates on the ___side of a plant stem in response to light or gravity. This differential distribution of auxin stimulates cell elongation on the shaded side, causing the stem to bend towards the light or upward against gravity.

Answer 29

(Phototropism and Gravitropism ) shaded

Question 30

Auxin (what physiological effect): Auxin stimulate cell division and enlargement in the ovary, leading to fruit set and growth. Additionally, auxin can delay fruit ripening by inhibiting the production of ____, a hormone that promotes ripening.

Answer 30

(Fruit development ); ethylene

Question 31

Auxin (what physiological effect): By inhibiting the production of ___, a hormone that promotes leaf aging and shedding, auxin can delay these processes

Answer 31

(Leaf abscission); ethylene

Question 32

Gibberellin originates from ____, a hormone-producing fungus in the Ascomycota phylum known for causing excessive growth and reduced yields in rice plants

Answer 32

Gibberella fujikuroi

Question 33

are key regulators in the formation and maturation of reproductive organs and are essential for fruit ripening and the production of viable seeds; promote seed germination

Answer 33

Gibberellin

Question 34

These hormones also drive cell division and elongation, contributing to hypocotyl and stem growth, and have a positive impact on leaf size and the expansion of the root meristem

Answer 34

Gibberellin

Question 35

Physiological Effects of Gibberellin (4)

Answer 35

Elongation of the internodes; breaks dormancy of seeds and buds; induces parthenocarpy; Sex expression

Question 36

Gibberellin (what physiological effect): Gibberellins significantly influence stem elongation by stimulating cell division and cell elongation; The mechanism involves the activation of specific genes, which in turn regulate the production of proteins that loosen cell walls and promote cell expansion.

Answer 36

Elongation of the internodes

Question 37

Gibberellin (what physiological effect): Gibberellin mobilize stored food reserves and overcoming dormancy mechanisms. By stimulating the synthesis of hydrolytic enzymes like ___, gibberellins break down starch into sugars, providing energy for the developing embryo or bud.

Answer 37

(breaks dormancy of seeds and buds); α-amylase

Question 38

Gibberellin (what physiological effect): embryo to release gibberellin (GA) to the ___ layer, the outer layer of the seed coat. In response, the aleurone secretes the enzyme α-amylase, which breaks down stored starch in the ___into simple sugars. These sugars are then absorbed by the ___, a specialized cotyledon, and utilized as an energy source to support the growth and development of the embryo.

Answer 38

(breaks dormancy of seeds and buds); aleurone; endosperm ; scutellum

Question 38

formation of seedless fruits without fertilization

Answer 38

parthenocarpy

Question 38

Gibberellin (what physiological effect): This process involves stimulating ovule development, even without fertilization, and promoting fruit growth. By inducing cell division and enlargement in the ovary, gibberellins can lead to the development of fruits without the need for seed formation.

Answer 38

induces parthenocarpy

Question 38

Gibberellins can influence (physiological effect) in plants by promoting or inhibiting the development of specific floral organs.

Answer 38

sex expression

Question 39

phytohormones that function as growth factors necessary for cell division and cell differentiation; cause inhibition of senescence by inhibiting the breakdown of proteins and nucleic acids in plants.

Answer 39

Cytokinins

Question 40

was the first artificial cytokinin to be discovered.

Answer 40

Kinetin

Question 41

Physiological Effects of Cytokinins (6)

Answer 41

Cell division; Cambial activity; Lateral growth; Flowering induction and inhibition; Regulates photosynthesis via stomatal regulation; Translocation of Solutes

Question 42

Cytokinins play a crucial role in plant growth and development by stimulating (physiologic process/effect). They activate specific genes that encode proteins involved in the cell cycle, resulting in the formation of new cells,

Answer 42

cell division

Question 43

Cytokinins play a crucial role in regulating (Physiological process/effect), the process of cell division in the cambium, a layer of meristematic tissue responsible for secondary growth. By stimulating cell division in the cambium, cytokinins promote the formation of new ___ cells, leading to an increase in stem and root diameter.

Answer 43

cambial activity; xylem and phloem

Question 44

Cytokinins play a crucial role in promoting (physiological process or effect) by counteracting the inhibitory effects of auxin,

Answer 44

lateral bud growth

Question 45

cytokinin (what physiological effect): When the ___ is removed or its ___production is reduced, cytokinin levels in lateral buds increase. This increase in cytokinin stimulates cell division and elongation in the lateral buds

Answer 45

lateral growth apical meristem; auxin

Question 46

cytokinin (what physiological effect): By promoting stomatal opening, cytokinins facilitate the uptake of ___), a key substrate for photosynthesis. When stomata are open, CO2 can diffuse into the leaf mesophyll cells, where it is used to synthesize sugars through the Calvin cycle.

Answer 46

(Regulates photosynthesis via stomatal regulation) carbon dioxide (CO2

Question 47

cytokinin influence the movement of nutrients, such as sugars and amino acids, from source tissues, like mature leaves, to sink tissues, such as developing fruits, roots, and young leaves.

Answer 47

Translocation of Solutes

Question 47

is a highly volatile, making it a gaseous plant hormone; best known for its role in fruit ripening

Answer 47

Ethylene

Question 47

ethylene physiological effects/process (5)

Answer 47

Fruit Ripening; Leaf Abscission; Senescence; Stress Responses and Adaptation; Growth Modulation

Question 47

Ethylene promotes ___, which is the process by which plants shed leaves, in turn helps reduce water loss during the dry season and conserve energy during winter seasons;specialized cells at the “abscission layer” will eventually weaken the ___, forcing the leaf to detach to its stem

Answer 47

leaf abscission; petiole

Question 47

Ethylene is known to increase the production of enzymes that are involved in the ___ process. Enzymes like ___and ___break down the cellulose and pectin contents of the cell wall, leading to its softening. Another enzyme called ___helps convert starches to sugars.

Answer 47

fruit ripening; polygalacturonase; cellulase; amylase

Question 48

Ethylene induces a response called ____”, where it inhibits the elongation of the seedling’s tissues, and promotes thickening and horizontal growth.

Answer 48

“triple response

Question 48

Ethylene is also known to be involved with ___, also known as the “aging” process of plant tissues, where they exhibit signs of degradation like wilting and fading in color; heightened level of ethylene promotes the breakdown of ___, causing it to change its color and eventually die

Answer 48

senescence; chlorophyll

Question 49

famously known as the stress hormone; only synthesized if a plant experiences environmental stresses such as flooding, droughts, and other unfavorable conditions.

Answer 49

Abscisic Acid (ABA)

Question 50

Abscisic Acid (ABA) physiological effect/process (4)

Answer 50

Stomatal Closure; Seed Dormancy and Germination; Growth Inhibition; Cold and Salinity Stress

Question 51

During water deficiency, the plant responds to the high transpiration rate and synthesizes ABA. The transport and accumulation of ABA to the leaves will signal the ____, reducing water loss.

Answer 51

closure of stomata;

Question 52

, abscisic acid encourages ions such as ___to flow outside from ____cells, making them lose their ___thus forcing it to close the stomata.

Answer 52

potassium; guard; turgor pressure

Question 53

The presence of abscisic acid on seeds ensures the inhibition of ___, helping seeds remain dormant until conditions are ideal for growth.

Answer 53

premature seed germination

Question 54

Abscisic acid primarily acts as a ____, in which if ABA is present, it will signal the plant to conserve energy; ABA can slow down plant cell division and elongation

Answer 54

growth inhibitor

Question 55

In plant growth, ___are important chemical messengers that facilitate the regulation of the various physiological processes of a plant

Answer 55

phytohormones

Question 56

are the primary growth hormone of a plant; in which they promote cell elongation in the apical regions of the plant. They are also involved with gravitropism and phototropism.

Answer 56

Auxins

Question 57

promote the elongation of the stem, is the major phytohormone for seed germination, and also aids in flowering.

Answer 57

Gibberellins

Question 58

are the phytohormones that primarily stimulate cell division in plants. Counteracted by auxins, are responsible for the lateral branching of the plant, and is also connected to senescence of the leaves

Answer 58

Cytokinins

Question 59

is the primary phytohormone for fruit ripening, leaf abscission, and also plays a role in the plant’s stress responses.

Answer 59

Ethylene

Question 60

, is the known stress hormone in the plant. It is synthesized only during unfavorable conditions in order to modulate the normal physiological and molecular responses of a plant, prioritizing survival and adaptation.

Answer 60

Abscisic acid or simply ABA