Plants responding to their environment
Plants responding to the need for water
- with a cuticle
- with root hairs:
- with guard cells
- Guard cells cause stomata to open and close based on
- light triggers
- CO2 triggers
- Circadian rhythms
- hormones
- Adaptations
- Stomata crypts
- Modified leaves
- More modified leaves:
Plants responding to the need for sunlight
By gaining height quickly using a plant hormone gibberellin. Causes an increase in internode length
Phototrophism – plants growing toward the sunlight. Caused by the action of another plant hormone: Auxin
Plants responding to the need for sunlight and water
oriented correctly with roots going down and shoot going up : Geotrophism. Also caused by auxin
One more plant hormone
Ethylene Gas. - released by ripening fruit. Causes fruit to ripen. Which causes the fruit to ripen. Which causes more ethylene gas to be released.
Great example of POSITIVE FEEDBACK!!
“One bad apple spoils the bunch” is accurate due to ethylene gas
Symbiosis in Plants
Symbiosis is a close long term relationship between/among 2 or more species.
Three kinds of symbiosis:
Mutualism: (+,+)
Parasitism: (+,-)
Commensalism: (+,0
Mutualism
Mycorrhizae
Fungus – associates with plant roots and helps increase surface area of roots…greatly increases amount of water available to plant
Plant – photosynthesizes – sends sugar down to roots to feed the fungus
Rhizobia
Bacteria – invades the roots of plants making nodules. They convert N3 (can’t be used by the plant) to NO3 (nitrate) which is usable by the plant. Plant must have this usable form to build amino acids
Plant – photosynthesizes to produce sugar that feeds the bacteria in the roots
Parasitism
Mistletoe, Indian Paintbrush and Indian Pipe
Commensalism
Spanish Moss
(not really a moss) grows on branches to access sunlight
Doesn’t hurt or help the tree
Other bromeliads
Not a plant but in keeping with the symbiosis theme
Lichen
Algae – photosynthesizes to provide food for a fungus
Fungus – photosynthesizes to provide water for the algae
Homework
Again, A good idea for the quiz that we might have…
1. Name 3 ways plants respond to their need for water
2. Name 3 ways plants respond to their need for sunlight
3. What does Auxin do?
4. What does Ethylene gas do? How is that positive feedback
5. What is symbiosis
6. Explain what kind of symbiosis illustrated the following relationships. In addition, who are the participants and what do each get out of the relationship:
MycorrhizaeRhizobiaMistletoeIndian pipeSpanish MossLichen