Biol.105

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Questions and Answers

What is the primary means by which water enters plant cells?

Osmosis through cell walls and root hairs (correct)

Active transport through cell membranes

Capillary action in root systems

Diffusion through the xylem

What occurs during plasmolysis in plant cells?

Uptake of nutrients and water

Formation of new xylem vessels

Water loss leading to cell shrinkage (correct)

Increase in turgor pressure

What is imbibition primarily responsible for in the germination process?

Attraction of water molecules to large molecules (correct)

Transportation of nutrients throughout the plant

Absorption of sunlight for photosynthesis

Breakdown of starch into sugars

In plant cells, what is water potential a combination of?

Osmotic pressure and pressure potential Signup and view all the answers

What happens to the protoplasm in a cell undergoing plasmolysis?

It shrinks away from the cell wall Signup and view all the answers

What is the primary purpose of active transport in plants?

To absorb and retain solutes against a gradient Signup and view all the answers

How do guard cells function when stomata open?

Water enters the guard cells via osmosis Signup and view all the answers

Which process is responsible for the movement of water columns through plants?

Cohesion-Tension Theory Signup and view all the answers

What occurs to stomata when photosynthesis does not take place?

Water exits guard cells, leading to closure Signup and view all the answers

What enables some plants to survive in salty environments?

Accumulation of organic solutes Signup and view all the answers

What is guttation?

The loss of liquid water through hydathodes Signup and view all the answers

How does the proton pump function in active transport?

It expends energy to move protons out of the cell Signup and view all the answers

What causes guard cells to become turgid?

Inflow of water due to osmosis Signup and view all the answers

What is an inflorescence?

A group of flowers Signup and view all the answers

What is the exocarp of a fruit?

The skin of the fruit Signup and view all the answers

Which fruit type is defined as having a fleshy pericarp and derived from a compound ovary?

Berry Signup and view all the answers

Which of the following fruits is classified as a 'true berry'?

Blueberry Signup and view all the answers

What defines a pome fruit?

Flesh from the enlarged floral tube Signup and view all the answers

What distinguishes a hesperidium from other types of berries?

Thick rind and leathery skin Signup and view all the answers

What is an aggregate fruit?

Fruit derived from a single flower with multiple pistils Signup and view all the answers

What characteristic does a pepo have?

Relatively thick rind Signup and view all the answers

Which type of plant completes its cycle in a single growing season?

Annual plants Signup and view all the answers

Which of the following characteristics differentiates monocots from dicots in leaf structure?

Monocots have parallel primary veins. Signup and view all the answers

What term describes the collective structure of sepals in a flower?

Calyx Signup and view all the answers

Which statement about the vascular cambium is true?

It is absent in monocots. Signup and view all the answers

What is a superior ovary?

An ovary positioned above the calyx and corolla attachment. Signup and view all the answers

Which of the following statements is true regarding the structure of dicots?

Dicots exhibit a network of veins in leaves. Signup and view all the answers

What is the function of petals in flowering plants?

To attract pollinators. Signup and view all the answers

What distinguishes biennial plants from annual and perennial plants?

They complete their life cycle in two growing seasons. Signup and view all the answers

What is the primary characteristic of hypogeous germination?

Hypocotyl remains short Signup and view all the answers

Which condition is NOT known to extend seed viability?

High temperatures Signup and view all the answers

Which structure in a seed develops into the root?

Radicle Signup and view all the answers

What is the role of cotyledons in seeds?

Function as food storage organs Signup and view all the answers

What is vivipary in plants?

Embryo growing while still attached to the parent plant Signup and view all the answers

What initiates the process of germination?

The seed coat breaking down Signup and view all the answers

How does diffusion occur?

From a region of higher concentration to a region of lower concentration Signup and view all the answers

What does osmosis specifically refer to?

Diffusion of a solvent through a semipermeable membrane Signup and view all the answers

Which method can break seed dormancy artificially?

Soaking in water Signup and view all the answers

In epigeous germination, what happens to the hypocotyl?

It lengthens and bends into a hook Signup and view all the answers

What is osmotic pressure?

Pressure required to prevent osmosis Signup and view all the answers

What type of fruits are primarily dispersed by wind?

Lightweight fruits with samaras or plumes Signup and view all the answers

What role do semipermeable membranes play in osmosis?

They permit different substances to diffuse at varying rates Signup and view all the answers

Which factor does NOT affect the rate of diffusion?

Color of the medium Signup and view all the answers

What does scarification refer to in seed germination?

Scoring the seed coat to aid embryo growth Signup and view all the answers

What is the relationship between the embryo and cotyledons after fruit ripening?

The embryo has only a few cells at ripening Signup and view all the answers

Study Notes

Plant Categories

Annual plants complete their life cycle in a single growing season.
Biennial plants complete their life cycle in two growing seasons.
Perennial plants live for several or many growing seasons.

Flowering Plant Classes

Magnoliopsida (dicots)
Liliopsida (monocots)

Monocots and Dicots - Leaf Venation, Vascular Cambium/Cork Cambium, Vascular Bundles, and Pollen Grains

Leaf venation:
- Dicots: Network of veins
- Monocots: Parallel primary veins
Vascular Cambium and Cork Cambium:
- Dicots: Present
- Monocots: Absent
Vascular bundles of stem:
- Dicots: Bundles arranged in a ring
- Monocots: Bundles scattered
Pollen grains:
- Dicots: Grains have three apertures
- Monocots: Grains have one aperture

Sepals and Petals

Sepals are the outermost whorl, collectively known as the calyx.
Sepals protect the flower while it's in bud form.
Petals are the next whorl inside the sepals, collectively known as the corolla.
Showy corollas attract pollinators.
Inconspicuous or missing corollas are found in trees, weeds, grasses, and wind-pollinated plants.
Sepals and petals together form the perianth..

Ovaries

Ovaries are derived from carpels with inward-rolled margins.
Carpels are leaf-like structures containing ovules along their margins.
Carpels can fuse into compound ovaries.
Pistils can consist of one or more carpels..
Superior Ovary: Calyx and corolla attached to receptacle at the base of the ovary.
Inferior Ovary: Receptacle grows up and around the ovary; calyx and corolla appear attached at the top of the ovary.
Ovules develop into seeds after fertilization.

Inflorescences

Flowers are either produced singly or in groups called inflorescences.
Inflorescence is a group of flowers.
Examples of inflorescence types include panicle, spike, raceme, catkin, simple umbel, corymb, dichasium, head, composite umbel.

Exocarp, Endocarp, and Mesocarp

Exocarp: The skin of the fruit.
Endocarp: The inner boundary around the seed(s).
Mesocarp: The tissue between the exocarp and endocarp.
Pericarp: The collective name for exocarp, endocarp, and mesocarp

Berries

Berries develop from compound ovaries, have more than one seed, and have fleshy pericarp.
True berries have thin skin and relatively soft pericarp (e.g., tomatoes, grapes, peppers, blueberries, bananas)
Pepo berries have a relatively thick rind (e.g., pumpkins, cucumbers), while Hesperidium berries have a leathery skin containing oils (e.g., citrus fruits).

Pomes

Pomes have flesh derived from enlarged floral tubes or receptacles that grow around the ovary.
The core and a little adjacent tissue come from the ovary, while the remainder is from the floral tube and receptacle.
Apples and pears have a papery or leathery endocarp.

Aggregate Fruits

Aggregate fruits develop from a single flower with several to many pistils.
Individual pistils mature as a clustered unit on a single receptacle.
Examples include raspberries, blackberries, and strawberries.

Fruit and Seed Dispersal (Wind)

Fruits can be dispersed by wind, often through samaras (winged fruits), plumes, or hairs.
Seeds can also be dispersed by wind, often being small and lightweight or bearing wings.

Seeds - Structure

Ovules develop into seeds.
Cotyledons store food and function like seed leaves.
Embryo is the cotyledons and plantlet.
Plumule is the embryo shoot.
Epicotyl is stems above the cotyledon.
Hypocotyl is stems below the cotyledon.
Radicle develops into the root.

Germination

Germination is the beginning or resumption of seed growth.
Some seeds require a period of dormancy, which can be broken by mechanical abrasion, thawing, freezing, bacterial action, or soaking in rain.
Scarification artificially breaks dormancy.
After ripening, the embryo is composed of only a few cells, and seeds won't germinate until the embryo develops fully.

Epigeous and Hypogeous Germination

Epigeous germination: The hypocotyl lengthens, bends, and becomes hook-shaped. Top of the hook emerges from the ground and pulls the cotyledons above the soil.
Hypogeous germination: The hypocotyl remains short and the cotyledons do not emerge above the soil surface.

Seed Longevity

Seed viability varies depending on species and storage conditions.
Viability can be extended by low temperatures and dryness.
Vivipary is when the embryo continues to grow while the fruit is still attached to the parent plant, and there is no period of dormancy.

Diffusion

Diffusion is the movement of molecules from a region of higher concentration to a region of lower concentration.
Diffusion leads to a state of equilibrium where molecules are distributed throughout the available space.
The rate of diffusion depends on pressure, temperature, and the density of the medium.

Osmosis

Osmosis is the diffusion of a solvent (typically water) through a semipermeable membrane from a region of higher water concentration to a region of lower water concentration.
It can be measured using an osmometer..

Osmotic Pressure and Osmotic Potential

Osmotic pressure is the pressure required to prevent osmosis.
Osmotic potential is balanced by the resistance of the cell wall.
Pressure potential (turgor pressure) develops against the cell wall from water entering the cell.
A turgid cell is firm due to water gained through osmosis.
Water potential = osmotic pressure + pressure potential.

Pathway of Water Through a Plant

Osmosis is the primary method of water entry into plant cells.
Water moves through cell walls and intercellular spaces of the epidermis and root hairs to reach the endodermis.
Water then crosses the endodermal cells to reach the xylem, travelling throughout the plant.
It diffuses out through stomata.

Plasmolysis

Plasmolysis is the loss of water through osmosis in plant cells, accompanied by shrinkage of the cytoplasm away from the cell wall.

Imbibition

Imbibition is the initial step in seed germination. Large molecules like cellulose and starch develop electrical charges when wet, attracting water molecules.
Water molecules adhering to large molecules causes tissue swelling.

Active Transport

Active transport absorbs or retains solutes against a diffusion or electrical gradient, using energy.
Proton pumps in the plasma membrane (energized by ATP) are involved.
Transport proteins facilitate solute movement into or out of cells.

The Cohesion-Tension Theory

The cohesion-tension theory explains water transport in plants.
Transpiration generates tension that pulls water columns through the plant from roots to leaves.
Water molecules adhere to and cohere with each other within tracheids and vessels of the xylem.

When Stomata Open

Stomata open during photosynthesis.
Guard cells expend energy to take up potassium ions from adjacent epidermal cells, leading to a lower water potential in guard cells.
Water moves into guard cells via osmosis, causing them to become turgid and the stomata to open.

When Stomata Close

Stomata close during periods when photosynthesis does not occur.
Potassium ions leave guard cells.
Water leaves guard cells via osmosis, causing them to become less turgid and the stomata to close.

Guttation

Guttation is the loss of liquid water.
It occurs if a cool night follows a warm, humid day, with water droplets forming on the tips of veins.
In the absence of transpiration, pressure in xylem elements forces water out.

Transport of Food (Organic Solutes)

Water plays a vital role in transporting food (organic solutes) through the phloem.
The pressure-flow hypothesis describes the movement of organic solutes from sources (where they are made) to sinks (where they are used).
Organic solutes move along concentration gradients between sources and sinks.

Macronutrients and Micronutrients

Macronutrients are needed in larger amounts by plants (e.g., nitrogen, potassium, calcium, phosphorus, magnesium, and sulfur).
Micronutrients are needed in smaller amounts (e.g., iron, sodium, chlorine, copper, manganese, cobalt, zinc, molybdenum, and boron).
Deficiencies in any required element can cause characteristic symptoms in plants..

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