Organs and Tissues
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What does a plants structure reflect?
Its interactions with the environment of two time scales (over the long term and short term).
How do plant structures reflect interactions with the environment over long term?
Natural selection causes species to accumulate morphological adaptations that enhance survival and reproductive success.
How do plant structures reflect interactions with the environment over short term?
Over short term, plants exhibit structural responses to their specific environments. (eg. feathery leaves to enhance uptake of CO2)
What type of response is even faster than the short term response?
A physiological (functional) response/adjustment. - eg. releasing a hormone which causes the stomata to close
What are the three basic organs of plants?
1) roots 2) stems 3) leaves
What is an angiosperm?
a flowering plant
What are the principal division of angiosperms?
1) monocots 2) dicots
What is special to monocots?
EMBRYOS: one cotyledon LEAF VENATION: parallel venation STEMS: vascular bundles randomly allocated ROOTS: fibrous root system FLOWERS: multiples of 3
What is special to dicots?
EMBRYOS: two cotyledons LEAF VENATION: netlike venation STEMS: vascular bundles arranged in a ring ROOTS: taproot is present FLOWERS: multiples of 4 and 5
What are the two places where plants inhabit their resources? What comes from each specific resource?
1) SOIL: water and minerals 2) AIR: CO2 and light
What two systems have plants evolved?
1) a subterranean (underground) root system 2) aerial shoot system
Are the two systems (root and shoot) independent of each other? Why?
No, both systems depend on each other. - roots (lacking chloroplasts, living in the dark, not obtaining sugars from photosynthesis) would starve, - shoot systems (reproductive tissue, flowers, etc.) depend on water and minerals absorbed from the soil.
What are the primary roles of the root system?
• anchor the plant in the soil • absorb minerals and water • store food
What does a fibrous root system allow monocots to do?
extend its (the plants) exposure to soil water and minerals, as well as anchor it to the ground.
What does a taproot root system allow dicots to do?
• anchor the plant • store food • support flowering • support fruit production
Where does most water and mineral absorption take place?
in the root tips
What increases the roots surface area?
root hairs
What are root hairs?
Root hairs are extensions of individual epidermal cells on the root surface.
What are “adventitious” roots?
roots which arise above ground from stems or leaves.
What are roots called which arise above ground from stems or leaves?
adventitious roots
What is the purpose of an adventitious root?
props which help support tall stems.
What does a shoot consist of?
stems and leaves
What are the two types of stems?
1) vegetative (leaf bearing) 2) reproductive (flower-bearing)
What is a stem?
• a system of nodes (the points at which leaves are attached), • a system of internodes (stem segments between nodes)