Bio lab 4
Evolution of heavy metal tolerance
The differentiation of populations is considered the first step towards geographic speciation in plants
3 articles: populations of Agrostis tenuis resistant to lea and zinc posioning
1st, Bradshaw grew plants in soil,
Terms:heavy metal t any element that has a atomic number bigger than 20
Tillers t a shoot at the base of a grass plant from which leaves and toor afrom to yield another plant
Results t a few plants from the unpolluted site did show tolerance to polluted soil, suggested that even
in a normal population, there are potential adaptive variants. but genrally, the unpolluted cannot
survive in polluted soil, and the plants from polluted soil cannot grow very well in the local soil neither.
Why are metal-tolerance individuals rare in the pasture population?
1st, could due to the strong natural selection agaist the metal-tolerance
2nd, there is a growth or competitive cost to having the physiological mechanisms to tolerate haevy
differs in their tolerance. Additional, whethewr plants tolerant to one metal are also tolerant to havey
metals in general.
This time use solution hydroponic solutions!
Why? Because the solutions contains calcium nitrate, a substance which promotes roots growth and
reduces the toxicty of the metals in test solutions.
Jowett calculate the tolerance index (T.I)
T.I = root growth in metal solution/root growth in non-mental solutionh100%
Control solution: non-metal solution t in order to avoid compounding the treatment
In addition to having high levels of some metals, the mine soild are acidic.
Null hypothesis: there is no difference in heavy metal tolerance between population
When T.I is larger than 60%, we consider this population to be tolerant
No co-tolerance (the tolerance to one metal confer tolerance to other heavy metals.
Basal meristem t from where new roots will grow
Apical meristem t tip of each root