Lecture 10- Plant Physiology Flashcards
What makes up the root system?
Roots
What makes up the shoot system?
Above ground- stems, leaves, flowers, fruit
What are the functions of plant roots?
Anchor to ground, absorb minerals and water, store carbohydrates (and other reserves)
What are the functions of root hairs?
Root hairs are designed to increase the surface area of the plant roots (the more surface area-> the more the root can absorb)
What are stems/ what are the functions of stems?
Stems are plant organs bearing leaves and buds. They elongate and orient the shoot to maximize photosynthesis, and elevate reproductive structures to promote pollen and seed dispersal. Sometimes do photosynthesis.
What are leaves/ what are the functions of leaves?
Leaves are the main photosynthetic organ in vascular plants. They capture light and facilitate gas exchange.
Define the following:
- Reproductive shoot
- Apical bud
- Node
- Internode
- Vegetative shoot
Reproductive shoot: Flower
Apical bud: Buds at the tip of the stem or branch, responsible for growth in length
Node: The origin of leaves, buds, or branches on a plant stem
Internode: Between nodes
Vegetative shoot: Responsible for development of plant leaves, stems, etc
What are the three main tissue systems in plants?
Dermal tissue, Vascular tissue, Ground tissue
What are the two distinct organ systems of vascular plants?
Root system and Shoot system
During the growing season, the mature leaves and stems produce excess sugars which are transported to storage locations via a process known as ___________
Translocation (source -> sink)
What are the main functions of the dermal tissue system?
Absorption of water, minerals at root hairs
Reduce water loss, reflect sunlight, protect
Guard cells- specialized cells in shoots that surround stomata and regulate gas exchange
Dermal tissue system differences in nonwoody and wood plants
Nonwoody plants-
Have epidermis: Single layer of tightly packed cells
Cuticle: Waxy coating- prevent water loss
Wood plants-
Periderm (bark) replaces epidermis
What are guard cells and where are they found?
Specialized cells in shoots of dermal tissue. They surround the stomata and regulate gas exchange.
What is the Ground tissue system?
Makes up majority of plant
Includes cells specialized for:
- Storage
- Photosynthesis
- Support
- Short distance transport
Functions of Vascular tissue system
Transport materials throughout plant body, mechanical support
What are the two types of vascular tissue?
Xylem and Phloem
Xylem
Found in vascular tissue. Conducts H2O, dissolved minerals upward from roots.
Phloem
Found in vascular tissue. Transport sugars from where made (mostly leaves) to where needed (usually roots and sites of growth)
H2O Movement through Xylem
- Soil
- Root tissue
- Root xylem
- Stem xylem
- Leaf xylem
- Leaf mesophyll
- Stomata
- Atmosphere
Cohesion-Tension Hypothesis
During photosynthesis, stomata open, H2O exits leaves through transpiration. This creates tension like a soda straw, because H2O is attracted through cohesive forces (sticks to itself). This tension causes H2O in stem xylem to be pulled into leaves, and H2O in root xylem is pulled into stem. Defies gravity as a result of cohesion-tension forces.
How does the phloem conduct dissolved sugar?
Bidirectional movement- Translocation. The phloem can conduct dissolved sugars in any direction, from source to sink.
Source: Area with excess sugar (e.g. leaf)
Sink: Area of storage or metabolism (e.g. roots)
Pressure-Flow Hypothesis
Explanation for movements of sugars in phloem. Suggests translocation occurs via pressure gradient.
At source- high pressure- sugar loaded into phloem
At sink- low pressure- sugar removed from phloem
Plasmodesmata
Cytoplasmic connections
Allows molecules, ions to pass between cells
Important for plant transport
Pathways through the cytoplasm
Do plants have determinate or indeterminate growth?
Indeterminate. They are able to continuously grow throughout their lifespan as long as they have favorable conditions.
Where does plant growth take place?
Meristems. At the tips of roots and shoots.
Explain meristems and plant growth
Indeterminate growth, occurs throughout life of plant.
Due to perpetually dividing, unspecialized tissue
Occurs at meristems.
Primary growth
Increases length of plant by adding more cells. All plants have primary growth.
Secondary growth
Increases girth (circumference) of plant. Only woody plants have secondary growth.
What kinds of plants have primary growth? What kinds of plants have secondary growth?
All plants have primary growth. Only woody plants have secondary growth.
Plant Hormones
- Organic compounds- chemical messengers
- Control specific physiological responses in plants
- Also known as plant growth regulators
- Active at very low concentrations
- Can have multiple effects
- Interact- hard to tell the cause of a specific effect
- Natural or synthetic
What is phototropism?
Light exposure -> auxins produced
-> moves laterally to shaded side, down stem
Triggers cell elongation
The growth of a plant in response to a light stimulus. Auxin distribution plays a key role in this process. When a plant is exposed to light from one direction, auxin gets redistributed within the shoot tip. Auxin tends to accumulate on the shaded side (away from the light) of the shoot tip. This uneven distribution of auxin triggers a cellular response. Auxin stimulates cell elongation on the shaded side, causing that side to grow faster than the side exposed to light. As a result, the plant bends towards the light source because the shaded side elongates more rapidly.
Auxins
1st plant hormone discovered- affects phototropism (causes plant to bend towards light source because shaded side elongates more rapidly).
Plant hormone that causes cell elongation in shoots and is involved in regulating plant growth.
Tropisms
Directional growth response to environmental stimulus- often due to hormones
Directional
Positive tropism- grows towards stimulus
Negative tropism- grows away from stimulus
Explain Darwin’s Experiments
Study on growth of plants in response to light.
Shielded or removed tip -> no bending
Shield with transparent cap -> bending
Shield below tip -> bending
Conclusion: Seedling tip responsible for light sensing
Postulated: Signal transmitted from tip to elongating region
Explain Boysen-Jensen Experiment
Followed up on Darwin’s experiment
Separated tip with gelatin (permeable)-> bending
Separated with mica (impermeable)-> no bending
Conclusion: there must be a hormone involved.
Cytokinins
Affect cell division and differentiation
Produced in actively growing tissue (roots, embryos, fruit)
Stimulate cytokinesis (where they got their name)
Cytokinins act with _______
Auxin.
What is unique about Ethylene?
It is the only gaseous plant hormone.
Ethylene
Fruit ripening
Triple response to mechanical stress- Produced when growing shoot encounters obstacle
3 components:
- Slow elongation
- Thicken stem
- Curve, grow horizontally
__________ is characterized by an increase in thickness or girth of a plant.
Secondary growth
What does the pressure-flow hypothesis state?
A high concentration of sugar in the phloem creates an osmotic gradient that draws water into the adjacent xylem, which creates hydrostatic (turgor) pressure in the phloem. As a result, the sucrose is drawn down into the sink from the source.
What are the main functions of the vascular tissue system?
Support/Transport of water/sugars/minerals
The increase in length of the shoot and the root is referred to as _____________
Primary growth (vertical)
________ is the action or property of like molecules sticking together.
Cohesion
During the growing season, the mature leaves and stems produce excess sugars which are transported to storage locations via a process known as ________.
Translocation
What is transpiration?
Evaporation of water at the surface of leaves (through stomata)
Primary growth is a result of rapidly dividing cells in the ________ at the shoot tip and root tip.
Apical meristems
