Bio 102 Lecture 10 Plant resource acquisition and transport

Gasses, Water, Light, Minerals (acquired) and Sugars, Signaling molecules, and other metabolites (usually made)

Plant resources refer to:

phototropism

Plants also have mechanisms to aim their photosynthetic tissue towards the light

Mycorrhizae

Plants significantly increase the available surface area for absorption (~300X) through a mutualistic association with fungi

Transmembrane route

out of one cell, across a cell wall, and into another cell

-by active transport, diffusion, or aquaporins

Symplastic route

via the continuum of cytosol through the plasmodesmata

Apoplastic route

via the cell walls and extracellular spaces

Diffusion

Active transport

Osmosis

Local transport: If the water or solutes are only going a short distance (in and out of cells or through tissues):

Diffusion

The tendency of solutes to spread down a concentration gradient until there is a uniform distribution

Active Transport

-Plants use Proton Pumps (which require ATP) to move free H+ out of the cytoplasm.

-Most often the potential is used to take up solutes into the cell

—Direct cation uptake

—Co-transport

——Anions and Neutral molecules

Osmosis

_____ is still just the diffusion of water (based on solute concentrations)

Water Potential

affects uptake and loss of water by plant cells

plasmolysis

If a flaccid cell is placed in an environment with a higher solute concentration, the cell will lose water and undergo _____

turgid

If the same flaccid cell is placed in a solution with a lower solute concentration, the cell will gain water and become ____

Turgor pressure

___ is the pressure exerted by the cell wall against the protoplast

-Turgor loss in plants causes wilting, which can be reversed when the plant is watered

-Also used to swell guard cells to open and close stomata

Bulk Flow

___ is the movement of a fluid driven by pressure

Xylem Sap

Bulk Flow of water and minerals ___ is conducted through the tracheids and vessel elements from the roots to the leaves largely by negative pressure

Phloem Sap

Bulk Flow of sugars and some other solutes ___ is conducted through the sieve-tube elements from the sugar sources to sugar sinks by positive pressure

Transpirational Pull

Xylem sap is transported mostly by negative pressure due to __ __

Transpiration

___ is the evaporative water loss from leaves

-It occurs via open stomata because the air outside the plant is often much drier

-The negative pressure generated in the leaves by transpiration pulls the sap from the xylem

sugar source

A ___ ___ is where sugar is generated (by photosynthesis or the breakdown of starch)

sugar sink

A __ __ is a net consumer or depository of sugar (fruits, roots, growing parts, etc.)

-Phloem sap flows through sieve tube elements

9 Macronutrients, needed in relatively large amounts

8 Micronutrients, needed in smaller quantities

The 17 elements essential for plant survival are:

Nitrogen

___may be the most “important” of the macronutrients for several reasons

Biological activity: Nitrogen availability contributes more than any other element to plant growth and crop yield

Biological availability: Nitrogen must be in a biologically usable form. This must happen through the activity of prokaryotes or fertilizer companies

Ecological activity: Nitrogen is the most abundant non-point source pollutant, contributing to algal blooms, loss of fisheries, etc. Fertilizer manufacture is a fossil fuel intensive procedure

Economic impact: Incalculable

mobile nutrients

Deficiency of ___ ___ usually preferentially affect older organs

-Magnesium deficiency causes chlorosis in older leaves

less mobile nutrients

Deficiency of ___ __ ___ often affects the younger organs

-Iron deficiency causes a yellowing in younger leaves

nitrogen, potassium, and phosphorus

The most common deficiencies are those of:

Cations

___(for example K+, Ca2+, Mg2+) adhere to negatively charged soil particles

-this prevents them from leaching out through percolating groundwater

anions

Negatively charged ions ___ do not bind with soil particles and can be lost from the soil by leaching

cation exchange

During ___ ___, cations are displaced from soil particles by other cations

-Displaced cations enter the soil solution and can be taken up by plant roots

Nitrogen Fixation

Bacteria break down organic compounds or use N2 to produce NH3 (called ___ ___), which is converted to NH4+

Nitrification

___is carried out by bacteria that convert NH3 into NO3–

mutualism

The utilization of nitrogen fixing bacteria by plants is an example of:

rhizobacteria

Inoculation of seeds with ___ can increase crop yields

nodules

Along a legume’s roots are swellings called ____, composed of plant cells “infected” by nitrogen-fixing Rhizobium bacteria (Not to be confused with Nodes)

bacteroids

Inside the root nodule, Rhizobium bacteria (A specific rhizobacteria) assume a form called ____, which are contained within vesicles formed by the root cell

rhizosphere

The layer of soil bound to the plant’s roots is the ___

-has high microbial activity because of sugars, amino acids, and organic acids secreted by roots

epiphyte

An ____ grows on another plant and obtains water and minerals from rain – technically it only uses the other organism for support and sometimes protection

Parasitic plants

absorb sugars and minerals from their living host plant

Carnivorous plants

are photosynthetic but obtain nitrogen by killing and digesting mostly insects