The life of a floweing plant

Question 1

Monocots

Answer 1

-A monocot embryo has one seed leaf.

• Leaves with pararell veins.
• Vascular tissues (internal tissues that transport water and nutrients) in a scattered pattern.
• Pollen grain with one opening.
• Floral parts usually in multiples of threes.
• Fibrous root system.

Question 2

Eudicots

Answer 2

-A eudicot embryo has two seed leaves.

• Leaves with branched veins.
• Vascular tissues (internal tissues that transport water and nutrients) arranged in a ring.
• Pollen grain with three openings.
• Floral parts usually in multiples of four or five.
• Taproot.

Question 3

Roots

Answer 3

Organ that anchors a plant in the soil, absorbs and transports minerals and water, and stores food.
Root hairs are tiny projections that greatly increase the surface are and provide an extensive outer layer for absorbtion.
Large taproots store food as starch or sucrose.

Question 4

Stems

Answer 4

The main support structure of a plant that transports water, nutrients, and food.

Functions:
Support: Holds leaves and flowers.
Transport: Moves water (xylem) and food (phloem).
Storage: Stores nutrients in some plants.
Growth: Enables plant growth and branching.

Parts:
Node: Where leaves attach.
Internode: Space between nodes.
Buds:
Apical Bud: Tip of the stem, promotes vertical growth (apical dominance).
Axillary Bud: Located at leaf axils, can grow into branches.
Types:
Herbaceous: Soft, green stems (e.g., grasses).
Woody: Hard, rigid stems (e.g., trees).

Special Forms:
Rhizomes: Underground stems that spread and create new plants (e.g., ginger).
Tubers: Swollen, storage stems (e.g., potatoes).
Stolons: Above-ground, spreading stems that create new plants (e.g., strawberries).
Bulbs: Short stems with fleshy leaves for storage (e.g., onions).

Question 5

Leaf

Answer 5

The primary photosynthetic organ of a plant, consisting of a blade and a petiole.

Functions:
Photosynthesis: Converts sunlight into energy.
Gas Exchange: Takes in CO2 and releases O2.
Transpiration: Regulates water loss.

Parts:
Blade: The flat, broad part of the leaf that captures sunlight.
Petiole: The stalk that attaches the blade to the stem.

Types:
Simple Leaf: A single, undivided blade.
Compound Leaf: A blade divided into leaflets.
Other Features:

Veins: Transport water, nutrients, and food; support the leaf.
Stomata: Openings on the leaf surface for gas exchange.
Leaves are vital for plant energy production and gas exchange, with structures optimized for these functions.

Question 6

Plant tissues and tissue systems

Answer 6

The organized groups of cells that perform specific functions in plants.

Tissue Systems:
Dermal Tissue System: Outer protective covering.
Cuticle: Waxy layer that prevents water loss.
Stomata: Pores on leaf surfaces for gas exchange, regulated by guard cells.

Vascular Tissue System: Conducts water, nutrients, and food.
Xylem: Transports water and minerals from roots to leaves.
Phloem: Transports sugars and nutrients from leaves to the rest of the plant.

Ground Tissue System: Functions in photosynthesis, storage, and support.
Pith: Central part of the stem, stores nutrients.
Cortex: Outer layer of the stem and root, involved in transport and storage.
Mesophyll: Photosynthetic tissue of the leaf, containing chloroplasts.

Specialized Tissues:
Endodermis: Inner layer of cells in the root cortex, regulates water and nutrient uptake.
Plant tissues and tissue systems are essential for protection, transport, and storage, each specialized to support plant growth and survival.

Question 7

Plant cells

Answer 7

The basic structural and functional units of plants, possessing unique organelles and structures adapted for photosynthesis, support, and storage.

Chloroplasts:
Function: Site of photosynthesis, converting light energy into chemical energy (glucose).
Structure: Double membrane-bound organelles containing chlorophyll, the green pigment responsible for capturing light energy.
Location: Abundant in cells of mesophyll tissue in leaves.

Central Vacuole:
Function: Stores water, ions, pigments, and waste products; provides structural support to the plant cell.
Structure: Large membrane-bound organelle occupying much of the cell volume.
Role: Maintains turgor pressure, which helps support the plant and maintain cell shape.

Cell Wall:
Function: Provides structural support and protection to the cell; determines cell shape and rigidity.

Composition: Made primarily of cellulose, a complex polysaccharide.
Permeability: Porous structure allows for the passage of water, nutrients, and signaling molecules between adjacent
cells.

Location: Surrounds the cell membrane, providing an additional layer of protection.
Plant cells are characterized by these unique features, which contribute to their specialized functions in photosynthesis, support, and storage within the plant organism.

Question 8

Secondary growth

Answer 8

Process in plants that leads to an increase in the girth or thickness of stems and roots. This type of growth is most commonly found in woody plants, such as trees and shrubs, and is essential for supporting the plant as it grows taller and for conducting water and nutrients between the roots and leaves. Secondary growth occurs due to the activity of two lateral meristems: the vascular cambium and the cork cambium.

Question 9

Vascular cambodium

Answer 9

The vascular cambium is a cylinder of meristematic tissue that forms between the primary xylem (toward the inside) and primary phloem (toward the outside) in stems and roots. It produces secondary xylem (wood) on the inside and secondary phloem on the outside. The secondary xylem contributes to the thickness and strength of the stem or root, while the secondary phloem is involved in the transport of nutrients.

Question 10

Cork cambodium

Answer 10

The cork cambium forms a layer of cells just beneath the epidermis. It produces cork cells (phellem) on the outside and phelloderm on the inside. The cork cells eventually become the outer protective layer, known as the periderm, replacing the epidermis in mature plants. The periderm serves as a protective barrier against physical damage and pathogens and helps reduce water loss.

Question 11

Importance of secondary growth

Answer 11

Structural Support: Secondary growth provides structural support, allowing plants to grow taller and withstand various environmental stresses.

Transport: Increased girth enhances the plant’s ability to transport water, minerals, and nutrients between roots and leaves.

Protection: The formation of the periderm protects the plant from physical damage, pathogens, and water loss.

Question 12

Process of secondary growth

Answer 12

Initiation: Secondary growth begins with the formation of the vascular cambium from the procambium (in stems) and pericycle (in roots).

Activity of Vascular Cambium: The vascular cambium continuously produces secondary xylem and secondary phloem. Over time, the accumulation of secondary xylem leads to an increase in the diameter of the stem or root.

Formation of Annual Rings: In temperate regions, the vascular cambium activity varies with the seasons, creating distinct annual rings in the wood. These rings can be used to determine the age of a tree.

Cork Cambium Activity: The cork cambium produces cork cells, which replace the epidermis as the protective outer layer. As secondary growth progresses, the outer layers of the stem or root are periodically shed and replaced by new periderm formed by the cork cambium.

Question 13

Flower

Answer 13

Stigma
|
Petal Style Petal
_____ | _____
/ \ | / \
| Sepal |——-|——| Sepal |
\____/ Ovary \____/
/ \
/ \
Ovule Ovule

Flowers are the reproductive structures of angiosperms (flowering plants) and are key to their reproductive cycle. They come in a wide variety of shapes, sizes, and colors, but they generally have the same basic parts, each playing a role in the plant’s reproduction.

Question 14

Sepals

Answer 14

Description: Usually green and leaf-like structures.

Function: Protect the developing flower bud before it opens.

Question 15

Petals

Answer 15

Description: Often colorful and sometimes fragrant.

Function: Attract pollinators such as insects, birds, and bats.

Question 16

Stamen (male reproductive part)

Answer 16

Components:
Anther: Produces pollen grains, which contain the male gametes (sperm cells).
Filament: A stalk that supports the anther.
Function: Produce and release pollen.

Question 17

Carpel/pistill (female reproductive system)

Answer 17

Components:
Stigma: The sticky top part that captures pollen.
Style: The stalk that connects the stigma to the ovary.
Ovary: Contains ovules; develops into fruit after fertilization.
Ovules: Structures within the ovary that develop into seeds upon fertilization.
Function: Receive pollen, house the ovules, and support the development of seeds and fruit.

Question 18

Overview: The life cycle of a flowering plant (angiosperm)

Answer 18

Involves alternating generations of a diploid sporophyte and a haploid gametophyte. This cycle includes several key stages: pollination, fertilization, seed development, germination, and plant growth.

Mature Sporophyte –> Flower –> Pollination –> Fertilization –> Seed and Fruit Development –> Seed Dispersal –> Germination –> Seedling Growth

Question 19

Sporophyte

Answer 19

Definition: The sporophyte is the diploid (2n) generation in the plant life cycle.
Role: Produces spores through meiosis.
Characteristics:
Diploid: Contains two sets of chromosomes.
Dominant in Vascular Plants: In ferns, gymnosperms, and angiosperms, the sporophyte is the dominant and most visible stage.
Structure: Includes the entire plant body (roots, stems, leaves) in vascular plants, and the stalk and capsule in bryophytes (like mosses).
Process: Spores produced by the sporophyte develop into gametophytes.

Question 20

Gametophyte

Answer 20

Definition: The gametophyte is the haploid (n) generation in the plant life cycle.
Role: Produces gametes (sperm and eggs) through mitosis.
Characteristics:
Haploid: Contains one set of chromosomes.
Dominant in Non-Vascular Plants: In bryophytes, the gametophyte is the dominant and most visible stage.
Structure: Includes the leafy structure in mosses and the small, reduced structures in vascular plants (such as pollen grains in angiosperms).
Process: Gametes produced by the gametophyte fuse during fertilization to form a diploid zygote, which develops into the sporophyte.

Question 21

Development of male gametophyte (in pollen grain)

Answer 21

1) Cells within anthers undergo meiosis to form four haploid spores.
2) Each spore then divides by mitosis into two haploid cells.

3) A thick wall forms around these cells, and the resulting pollen grain is ready to be released from the anther.

Question 22

Development of female gametophyte (embryonic sac)

Answer 22

1) Within an ovule, a central cell enlarges.

2) And then undergoes meiosis, thereby producing four haploid spores. Three of the cells usually die but the surviving one enlarges.

3) Divides by mitosis, producing the embryo sac. The sac contains a large central cell with two haploid nuclei. One of its other cells is the haploid egg, ready to be fertilized.

Question 23

Fertilization

Answer 23

1) Pollination: transfer of pollen from the anther (male part) to the stigma (female part) of a flower.
Mechanisms: Can occur via wind, insects, birds, water, or other animals.

2) The pollen grain germinates on the stigma. One of the cells of the male gametophyte divides by mitosis.

3) Forming two haploid sperm that travel to the ovule through a pollen tube that grows out from the pollen grain.

4) One sperm fertilizes the egg, forming the diploid zygote. The other sperm gives its haploid nucleus to the large diploid central cell of the embryo sac.

This cell with a triploid (3n) will give rise to a food storing tissue called the endosperm. Formation of both a zygote and a triploid is called double fertilization.

Question 24

Seed formation

Answer 24

The ovule containing the zygote and the triploid cell, begins developing into a seed.
The zygote divides by mitosis into a ball of cells that becomes the embryo. The triploid cell divides and develops into the endosperm.
The endosperm nourishes the developing embryo.
A seed is a plant embryo and endosperm packaged within a protective coverage called seed coat.
Embryo stops developing until the seed germitates.

Question 25

Seed germination

Answer 25

Seed germination is the process by which a dormant seed begins to sprout and grow into a new plant. It typically involves the following stages:

1) Imbibition: The seed absorbs water, causing it to swell and activate metabolic processes.

2) Activation of Enzymes: Enzymes within the seed are activated, which trigger biochemical reactions necessary for germination.

3) Respiration: The seed begins to respire, breaking down stored nutrients (such as starches and proteins) into energy for growth.

4) Radicle Emergence: The radicle (embryonic root) emerges from the seed first, anchoring the seedling in the soil and absorbing water and nutrients.

5) Shoot Emergence: The shoot (embryonic stem) emerges from the seed, developing into the stem and leaves of the seedling.

6) Photosynthesis: Once the seedling has emerged from the soil and developed leaves, it can perform photosynthesis to produce its own food.

Question 26

Annuals

Answer 26

Annuals are plants that complete their life cycle in one growing season, from germination to seed production. Examples include marigolds and petunias.

Question 27

Biennials

Answer 27

Biennials are plants that take two years to complete their life cycle. They grow leaves and roots in the first year, then flower, produce seeds, and die in the second year. Examples include carrots and foxgloves.

Question 28

Perennials

Answer 28

Perennials are plants that live for more than two years, often flowering annually. Unlike annuals and biennials, they don’t die after flowering but instead continue to grow and reproduce for multiple years. Examples of perennials include roses, hostas, and daylilies.

Question 29

Primary growth

Answer 29

Primary growth refers to the vertical growth of a plant that occurs primarily at the apical meristems, which are regions of actively dividing cells located at the tips of roots and shoots. It is responsible for the increase in length or height of the plant and is mainly associated with the elongation of roots and stems.

In primary growth, cells produced by the apical meristems undergo elongation and differentiation, leading to the extension of the root and shoot systems. This process allows the plant to explore new soil for water and nutrients (roots) and to reach sunlight for photosynthesis (shoots). Primary growth also involves the development of primary tissues, such as the primary xylem and phloem, which function in water and nutrient transport.

Overall, primary growth is essential for the initial establishment and growth of plants, contributing to their structural integrity and overall development.