Plant Biology: Cell Hierarchy and Organ Systems

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Questions and Answers

Which of the following is NOT a benefit of multicellular organisms?

Enhanced nutrient transport

Dependency on a single cell (correct)

Specialized cell functions

Division of labour

What are the two main organ systems in plants?

Vascular system and dermal system

Leaf system and flower system

Shoot system and root system (correct)

Stem system and seed system

Which type of tissue in plants is responsible for the transport of materials?

Root tissue

Dermal tissue

Vascular tissue (correct)

Ground tissue

What is the role of ground tissue in a plant's root?

Food and water storage Signup and view all the answers

Which part of the shoot system is specialized for food storage?

Tubers Signup and view all the answers

What is the function of the waxy cuticle in the dermal tissue of a plant's shoot?

Moisture retention Signup and view all the answers

What type of cell division occurs in meristem regions of a plant?

Mitosis Signup and view all the answers

Which of the following is a characteristic of unicellular organisms?

They can perform all necessary life functions within a single cell. Signup and view all the answers

Which mechanisms work together to pump water to the leaves of a plant?

Cohesion, adhesion, and tension Signup and view all the answers

What occurs in a plant when it is hot?

Transpiration occurs faster Signup and view all the answers

What is the pressure flow theory primarily concerned with?

Sugar transport through phloem Signup and view all the answers

How do stems exhibit positive phototropism?

By growing toward light Signup and view all the answers

What happens to a cell placed in a hypotonic solution?

The cell swells and may become turgid Signup and view all the answers

What did F.W. Went discover regarding plant growth?

Auxin is a hormone that regulates growth Signup and view all the answers

What is termed as a signal that causes a reaction in a plant?

Stimulus Signup and view all the answers

What is the upward force produced by water entering root hairs called?

Root pressure Signup and view all the answers

What is negative gravitropism?

Stems growing away from the gravitational force Signup and view all the answers

What is the role of auxin in plant growth?

Speeds up the rate of growth of plant cells Signup and view all the answers

What is the primary function of xylem tissue in plants?

Move water and dissolved minerals to leaves Signup and view all the answers

What are sieve tube cells responsible for in phloem tissue?

Transporting sucrose and dissolved sugars Signup and view all the answers

What do guard cells regulate?

Gas exchange through stomata Signup and view all the answers

What is the role of chlorophyll in photosynthesis?

Converts light energy into chemical energy Signup and view all the answers

What is the primary product of photosynthesis?

Glucose Signup and view all the answers

What is the main difference between photosynthesis and cellular respiration?

Photosynthesis occurs only in daylight, while cellular respiration happens continuously. Signup and view all the answers

What happens to guard cells when they absorb potassium ions?

They swell, opening the stomata. Signup and view all the answers

Which type of mesophyll tissue is primarily responsible for most of the photosynthesis in leaves?

Palisade mesophyll Signup and view all the answers

What is the chemical formula for glucose produced in photosynthesis?

C6H12O6 Signup and view all the answers

In plants, what is the name of the energy currency produced through cellular respiration?

ATP Signup and view all the answers

What is turgor pressure in plant cells?

Pressure that water molecules exert against the cell wall Signup and view all the answers

What is the process of transpiration in plants?

Evaporation of water from leaf surfaces Signup and view all the answers

What do lenticels provide for a plant?

Gas exchange pathways Signup and view all the answers

What happens to the rate of cellular respiration in plants during the night compared to daytime?

Decreases due to lack of photosynthesis Signup and view all the answers

Study Notes

Cell Hierarchy

Cells are organized in a hierarchical structure: molecule → organelle → cell → tissue → organ → organ system → organism
Unicellular organisms are composed of a single cell, not necessarily simple.
Multicellular organisms have specialized cells, exhibit division of labor, and are larger, allowing for better nutrient transport. Interdependence exists, but malfunction in one cell can affect others.

Plant Organ Systems

Two main organ systems in plants: shoot system and root system.
Shoot system includes leaves, stems, buds, flowers, fruits, and tubers (modified stems). Specialized for photosynthesis, reproduction, storage, and transport.
Root system includes aerial roots. It specializes in anchorage, water and mineral absorption, and transport.

Meristems

Meristems are regions of active cell division, responsible for plant growth, with distinct shoot and root meristems.

Plant Tissues

Three tissue types make up both shoot and root systems: dermal, ground, and vascular.
Dermal tissue (epidermis) is the outermost layer, acts like skin, typically one cell thick, covers non-woody plants. A waxy cuticle helps retain moisture. Shoot epidermis facilitates gas exchange and protects; root epidermis absorbs water and nutrients.
Ground tissue forms the bulk of the plant, beneath the epidermis; loosely packed for gas diffusion, offers strength and support in shoots and storage in roots. Photosynthesis occurs in leaf ground tissue.
Vascular tissue is a transport system with xylem and phloem.

Xylem

Transports water and dissolved minerals from roots to leaves.
Xylem cells are non-living at maturity.

Phloem

Transports sucrose and other dissolved sugars from leaves to other parts of the plant.
Phloem consists of sieve tube cells, connected by cytoplasm to form continuous ducts, requiring companion cells for their functioning.

Cell Differentiation

Cells become differentiated as they develop, specializing for particular tasks.

Root Hairs and Guard Cells

Root hairs increase surface area for nutrient and water absorption.
Guard cells regulate gas exchange through stomata, pores on the leaf underside.

Photosynthesis

Light energy is captured by chlorophyll in chloroplasts converting it to chemical energy (glucose), where CO2 and water form reactions to produce oxygen plus energy.
Balanced chemical equation: 6CO₂(g)+ 6H₂O(l) +light → C₆H₁₂O₆(s) + 6O₂.(g)
Photosynthesis occurs in plant cells during the day, producing oxygen with reduced carbon dioxide.

Cellular Respiration

Cellular respiration is the reverse of photosynthesis, using glucose and oxygen to produce carbon dioxide, water, and usable energy (ATP) in the mitochondria.
Balanced chemical equation: C6H12O6 + 6O2 −→ 6CO2 + 6H2O
Occurs constantly in plants and animals.
Plant cellular respiration is comparatively less than that of animals.

Stomata and Lenticels

Stomata, tiny pores surrounded by guard cells, regulate gas exchange, prevent water loss, and control gas intake and output from the plant.
Lenticels are pores facilitating gas exchange in woody plants and mature stems and roots.

Guard Cell Function

Guard cells swell/lose water to open/close stomata; opening and closing control gas exchange and prevent water loss.
The process of becoming turgid involves active transport of potassium into the guard cells, increasing water uptake and pressure.
Depletion of light triggers potassium ions to exit, lowering the concentration inside and causing water loss and the guard cells to go limp hence closing the stomatas.

Turgor Pressure

Turgor pressure is the pressure exerted by water against a cell wall.

Mesophyll Tissue

Mesophyll tissue in leaves is specialized for photosynthesis, with two types:
Palisade mesophyll has tightly packed cells, maximizes light absorption.
Spongy mesophyll contains air spaces, facilitating gas diffusion.

Transpiration

Transpiration is the evaporation of water from plant leaves.

Vascular Bundle (Vein)

A vascular bundle contains xylem and phloem, embedded in the mesophyll; xylem moves water; phloem moves glucose.

Mechanisms of Water Transport

Cohesion, adhesion, and transpiration pull work together to move water against gravity in plants. (Cohesion is the attraction between water molecules; Adhesion is an attraction between water and other substances; Transpiration pull is the pull on water molecules in the xylem due to evaporation from stomata or lenticels.)
Transpiration rate is temperature dependent; high temperatures increase transpiration rates.

Root Pressure

Root pressure is the upward force driving water in transport tubes.

Plasmolysis/Hypotonic Solutions

Plasmolysis occurs when a cell is placed in a hypertonic solution, causing water loss and shrinkage.
If a cell is placed in a hypotonic solution, water enters the cell making it swell.

Pressure Flow Theory

Sugars are actively transported into the phloem; build-up creates pressure which forces the water (and sugars) through the phloem to other parts of the plant.

Tonicity

Tonicity is the ability of a surrounding solution to cause a cell to gain or lose water.

Plant Responses to Stimuli

Plants react to stimuli via tropisms (growth responses), either positive (towards) or negative (away).
Two main types of tropisms: phototropism (response to light) and gravitropism (response to gravity).
Stems exhibit positive phototropism (grow towards light) and negative gravitropism (grow away from gravity).
Roots exhibit negative phototropism (grow away from light) and positive gravitropism (grow towards gravity).

Auxin and Plant Growth

Auxin is a plant hormone that influences cell growth rates.
Charles and Francis Darwin and Peter Boysen-Jensen contributed to the idea of chemical communication directing plant growth via auxin.
F.W. Went isolated auxin.

Plant Perception of Gravity

Plants hypothesize that starch grains are used as gravity indicators.

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Description

This quiz explores the hierarchical organization of cells, including the differences between unicellular and multicellular organisms. It also delves into plant organ systems, meristems, and the various plant tissues involved in growth and function. Test your knowledge on the fundamental principles of plant biology!