Biology213-BotQ2

plant root evolution

plants evolved from algae

as plants evolved and grew in number, competition became more intense

mutations to adaptations that resulted in organs like roots, leaves, bark, etc. allowed plants to proliferate.

stem/trunk arms race

plants are autotrophs (need sunlight)

sunlight is limited

one method of guarenteeing sunlight is to be the tallest plant

leaf diversity

when a plant can’t be the tallest, they need to work with what is around the,

this has led to diversity in both structure, arrangement, and function

ex: leaf shape

leaf area index

LAI=total leaf area/ground area

gives a measure of the available light

can be measured with a fisheye camera (hemispherical photos)

Sun leaves

able to photosynthesize much more than shade leaves

shade leaf

more efficient with sun light at low levels

self-pruning

when branches do not have leaves that photosynthesize enough the tree might initiate programmed cell death

this process happens for leaves or branches

leaf angle

determines how much sunlight a leaf is receiving

leaves can alter this to receive more or less sunlight—often through changes in water pressure potential

angle of the sun

sun’s energy can be assumed constant

sun’s energy is spread out over a larger area as the sun gets lower in the sky

angle of the sun (aspect)

aspect can increase or decrease energy the earth’s surface receives based on angle

aspect

the direction that a hill slope or mountain is facing

soil properties (affecting nutrient acquisition)

what nutrients are there

nutrient concentration

nutrient availability

rate of nutrient movement

changes in plant properties

may increase mychorrhizal colonization

may increase root hair length and density

may increase root biomass

may increase root architecture

may increase root absorption capacity

dichotomous branching

these systems are better at acquiring immobile nutrients

this is accomplished through fine-scaling forgaging for intensive soil exploration

less soil is explored, but the soil is explored more thouroughly

heavy branching

herringbone branching

these systems are thought to be more efficient at intercepting mobile nutrients

mobile nutrients move with soul water, so more soil needs to be covered

more soil explored less thoroughly