Organisms and Their Environment Exam #3

Photosynthesis

the production of energy for autotrophs.

Xylem

Transport water and minerals

Phloem

transport sugars and hormones

Stomata

Openings that take in gases and water evaporates out of.

Roots

take in water and minerals.

Transpiration

The process by which water is pulled up in the plant, from the roots through the xylem and evaporates through the stomata.

Osmosis

the movement of water over semipermeable membranes from higher to lower concentration.

Turgor Pressure

the pressure put on the cell wall caused by water in cells.

Cohesion-tension theory of transpiration

water molecules stick to each other in cohesion due to polarity, and the tiny diameter of the xylem increases cohesion which can pull it up through the plant.

Cavitation

An air bubble can break the tensile strength of a water column and block the xylem.

What controls transpiration rate?

Stomata

Guard Cells

cells surrounding the stomata which control their opening, the more water in the cell the more open and vice versa.

What types of factors can impact transpiration rates?

Temperature, wind, drought, and humidity.

Pressure Flow Theory

Sucrose is transported actively from leaves into sieve-tube cells, allowing for osmosis of water from xylem to phloem, this means the turgor pressure then forces sucrose-water through the phloem, at the sink (root or shoot) the sucrose is actively removed.

Phytochrome (P - P_r —> P_fr)

How the plant sense sunlight and stimulates more growth in sunlight and times flowering to longer days.

Phototropin

Photoreceptor in Guard Cells that is activated by blue light stimulating the opening of ion channels that allow solutes to move into the cells with water following, which opens the stomata.

Phototropism

the growth of plants towards blue light.

Gravitropism

The response of a plant to gravity. Gravity is perceived by the cell, mechanical signal is transmitted into a physiological signal, and differential cell elongation occurs in the up or down directions of the shoot or root.

Amyloplasts

starch granules that sink in gravity sensing cells in the endodermis.

Auxin

Hormone responsible for cell elongation, response to phototropin, produced in the shoot tip

Cytokin

hormone responsible for cell division and growth

Ethylene

Hormone responsible for fruit ripening, flower wilting, and leaf fall

Abscission

leaf dropping resulting from high levels of ethylene

How do plants obtain water and nutrients?

roots and soil

Where are most roots found?

topsoil

How does topsoil loss impact soil?

Soil is less able to hold water, and nutrients are decreased.

CHON

CO₂, O₂, H₂O, and N (C and O from stomata, H from roots, and N from active uptake in roots)

Legume Rhizobium Symbiosis

A nitrogen obtaining strategy of legumes that involves a bacteria (Rhizobium) living in their roots and fixing N₂ so it is usable to the plant.

Carnivory

Some plants have adapted to “eat” animals which provides them nitrogen

Mycorrhizal Fungi

a fungus that most plants have a symbiotic relationship with which can bring them more nutrients from the soil and other plants around them.

Plant response to higher CO₂

Sometimes more growth (but other nutrients like water and N are limiting factors) and they may lower rubisco or decrease stomata.

Threats plants face

weather, frost, fire, viruses and bacteria, fungi, animals, plants, invasive species.

Physical Plant Defense

Dermal tissue, waxy secretions, thick cell walls, thorns and trichomes.

Chemical Plant Defense

Toxins kill or make herbivores ill (Ex. alkaloids [like caffeine, ricin, or nicotine], tannins, and oils) Can also be used to inhibit the growth of other nearby plants to decrease competition.

Tannins

chemicals that bind to plant proteins making them more difficult for herbivores to digest and less nutritious.

Plant Oils

Make plants bitter or disorient herbivores (ex. peppermint)

Plant Defenses Using Animals

Plants like acacia trees use a symbiotic relationship with ants to protect themselves from larger predators.

Crypsis

Camoflauge, a plant can look a certain way to avoid predation (ex. a sensitive plant can look dead or wilted when touched)

What propels nutrients through the hyphal cells of mycorrhizal fungi?

it is driven by the cytoplasmic flow

Mycoheterotophic

the word for the parasitic relationship non-chlorophyll plants have with the mycorrhizae network.

Equation for Photosynthesis

6CO₂ + 6H₂O → C₆H₁₂O₆ + 6O₂

Cavitation

the process whereby a vapor phase is introduced to the xylem water column, creating an embolism

Elodea Leaf Tube

Turned back to pink because the elodea leaf took in the CO₂ that was blown into the tube

Plant Disk Lab

The light and bicarbonate solution allowed the plant disks to undergo photosynthesis, and the O₂ bubble produced resulted in them floating.