LAB 3: Plants on Land
Types of Species:
Alien or exotic species: introduced to a region beyond their native range (originated
from a different country/region)
Considered to be a problem because their proliferation is occurring at an
alarming rate and because they can have serious effect on native taxa
Invasive species: colonize and disperse rapidly
Native or endemic species: originally present in a region
Anthriscus sylvestric came from Eurasia and is found in moderately disturbed
habitats (require moist or wet sites)
How can the negatively affect ecosystems?
Release chemicals that may affect other plants ability to colonize
Fed upon cattle = low nutrition = reduce milk production
Quantify the abundance of Plants:
Transects: straight line marked along the ground to define where sampling will be
Quadrats: circular/square areas that are delineated and used to define the area in
which the plant community will be quantified
Plant Hormones and Growth Regulation:
A terrestrial existence requires a plant to respond to the environment
Plants respond by modifying how they grow (growth regulation)
Hormones regulate many responses
Indolacetic acid (IAA) found in a group of hormones called auxins: increase the
size of cells formed from the apical meristem
Plant growth is controlled by variation of IAA levels
Apical Dominance and Growth Hormones:
Apical dominance: the suppression of lateral branches that normally appear from
lateral buds located in leaf axils. This suppression results from a high level of IAA in the
growing tip of the stem
Effect of Gibberellin:
Gibberellin: effects on seed germination and stem growth, promote cell elongation and
Do gibberellin and IAA have the same effects?
No. The application of Gibberellins on dwarf plants promotes stem elongation so
that the dwarf plants are close in size to normal plants. (Normal plants are LAB 3: Plants on Land
unaffected by gibberellins.) IAA does not affect dwarf plants. Dwarf plants
sprayed with IAA will be the same size as the control dwarf plants.
If any of the growth regulators make the dwarf plants into tall plants, can you see
differences between these and the true tall variety? Can you explain the results?
There are no differences. The dwarf plants are small because they lack giberellins.
If they are supplies, then they are normally tall.
Change in the direction of growth of a plant
Auxins produce the changes in growth while gravity, unilateral light/touch
cause them to occur
Positive Gravitropism: the response of roots to gravity; grow downwards in response
to gravity (the root tip responds)
Negative Gravitropism: the response of shoots to gravity; grow upwards against
Phototropism: the response of plants to lights
Thigmotropism: growth response of plants to touch
How do these plants respond to the stimulus of contact?
As they grow taller, they will bend in the