photosynthesis Flashcards
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what is photosynthesis
photo (light reaction) + synthesis (calvin cycle)
complex process by which carbon dioxide, water and certain elts (N,P) are converted into carbohydrates by green plants, algae and certain bacteria using chlorophyll
light energy (hv) converted into chemical energy (C6H12O6) in leaves
types of chlorophyll
Cla wider absorption spectrum (red, blue, purple) and Clb (blue)
PAR
Photosynthetically active radiation : wavelength spectrum where plants absorb sunlight (400-700 nm)
Chlorophyll a
contains Mg, essential nutrient released through weathering
C° of Cla used to estimate algae cC° in water with Org:Cla ratio=50
redfield ratio
C:N:P = 106:16=1
under optimal growth condition, amount removed by phytoplankton from water and gave back when dies, defines stoichiometry of photosynthesis
cyanobacteria and nitrogen
cyanobacteria can use N instead of nitraite for ammonium
while growth of other phytoplankton is limited by nitrate/ammonium C°, N is not the limit nutrient for cyanobacteria
20 essential elements for plants
macronutrients : C,H,O,N,P,K,Ca,Mg,S
micronutrients:Fe,Mn, B,Cl,Cu,Zn,Ni,Co,Na,Si,Mo
extented field ratio
C106 H263 N16 P
(Fe,Mn,Zn)0.01 (Cu,Ni,Cd…)0.001
why is Fe particularly important in the coean as a micronutrient?
idk
what affects PAR
time of the day, amount of clouds, water depth, shading, turbidity, water color, lake ice formation
Iz=I0e(-nz), n light ectinction coeef (m-1)
I = (umol.m-2.s-1
measured with a Secchi disk
euphotic zone
Depth of euphotic zone = 1% of initial sunlight intensity remains
z=(ln(I0)-ln(Iz))/n
I0=1, Iz=0,01=> ln()=4.6