This document summarizes key concepts about the absorption spectrum, action spectrum, and two photosystems in plant photosynthesis. It explains that chlorophyll a absorbs mainly in the blue and red regions of the light spectrum. The effectiveness of different light wavelengths in photosynthetic processes like CO2 fixation is known as the action spectrum. The rate of photosynthesis declines sharply after 680nm, known as the red drop phenomenon, but combining 680nm and 700nm light results in higher photosynthesis than individually. This led to the conclusion that there are two photosystems - PSI which uses 700nm light and PSII which uses 680nm light, and they work cooperatively during photosynthesis.

1. BACHELORS OF SCIENCE 3RD YEAR
SUBJECT: BOTANY
TOPIC : RED DROP & EMERSON’S EFFECT,CONCEPTS
OF TWO PHOTOSYSTEMS
CREATED AND PRESENTED BY : ATIF ALI ZAKIR

2. ABSORPTION SPECTRUM & ACTION SPECTRUM
 ONLY VISIBLE LIGHTS TAKE PART IN THE PHOTOSYNTHESIS
 CHLOROPLAST PIGMENTS ABSORBS LIGHT OF CERTAIN SPECIFIC
WAVELENGTH
 THE AMOUNT OF ABSORPTION OF DIFFERENT WAVELENGTH
OF LIGHT BY A PARTICULAR PIGMENT IS CALLED AS
ABSORPTION SPECTRUM OF THAT PIGMENT
 CHLOROPHYLL-A ABSORBS MAXIMUM IN THE BLUE AND RED
REGIONS OF THE LIGHT SPECTRUM
 THE EEFECTIVENESS OF DIFFERENT WAVELENGTHS OF LIIGHT
UTILIZED IN THE ACTION OF A PROCESS IS CALLED AS ACTION
SPECTRUM,IN CASE OF PHOTOSYNTHESIS ,IT IS UTILIZED IN
CO2 FIXATION O2 PRODUCTION & NADP REDUCTION
THEREFORE IT IS CALLED AS THE ACTION SPECTRUM OF
PHOTOSYNTHESIS

3. ACTION SPECTRUM & ABSORPTION SPECTRUM

4. RED DROP AND EMERSON’S EFFECT
 IT GIVES AN IDEA ABOUT THE RATE OF PHOTOSYNTHESIS
AT DIFFERENT WAVELENGTHS
 QUANTUM YEILD: AMOUNT OF OXYGEN RELEASED PER
QUANTUM OF LIGHT ABSORBED
 RED DROP: A SUDDEN DECLINE IN THE RAT OF
PHOTOSYNTHESIS AFTER 68Onm
 P.S. at 700nm= 10 Q.Y (indivivually)
 P.S at 653nm= 52-53 Q.Y (indivivually)
 P.S at 700 & 653nm= 72 Q.Y (Together)
EMERSON’S ENHANCEMENT EFFECT
 HERE THEY CONCLUDED THAT IT IS BECAUSE THAT THERE
ARE TWO PHOTOSYSTEMS WHICH ARE WORKING DURING
PHOTOSYNTHESIS
A.PSI-700
B.PSII-680

5. RED DROP AND EMERSON’S EFFECT

6. CONCEPT OF PHOTOSYSTEMS
CHLOROPLAST
HAVE PIGMENTS
P.S. ARE
CLUSTER OF
LIGHT
ABSORBING
PIGMENTS
P.S. CONTAIN 200
MOL OF CHL &
50 MOL.OF
CAROTENOIDS
ENERGY
TRAPPED BY CHL
& OTHERS
PIGMENT
CONVERGE INTO
TRAP CENTRE
i.e., PSI & PSII
PSI & PSII
COOPERATE
EACH OTHER
RESULT IN
FUCTIONING
PHOTOSYNTHES
IS
PRESENT IN
THYLAKOID
MEMBRANE OF
CHLOROPLAST

7. PHOTOSYNTHETIC PIGMENTS
PIGMENT SYSTEM I (PSI) PIGMENT SYSTEM II (PSII)
 IT IS MADE UP OF 200 -400
CHOLOROPHYLL –A
MOLECULES & 50 CAROTENOIDS
MOLECULES
 CHLOROPHYLL-B MOLECULES
IS LESS
 ITS REACTION CENTRE IS P700
 IT IS LOCATED ON THE OUTER
SURFACE OF THYLAKOID
 IN THIS SYSTEM ,MOLECULAR
O2 IS NOT EVOLVED
 IT PARTICIPATE IN BOTH
CYCLIC AND NON CYCLIC
PHOTOPHOSPHORYLATION
 IT IS MADE UP OF 200
CHOLOROPHYLL MOLECULES ,50
CAROTENOIDS MOLECULES
 CHLOROPHYLL-B MOLECULES IS
MORE
 ITS REACTION CENTER IS P680
 IT IS LOCATED ON THE INNER
SURFACE OF THYLAKOID
 IN THIS SYSTEM , MOLECULAR O2 IS
EVOLVED DUE TO THE
BREAKDOWN OF WATER
 IT PARTICIPATES ONLY IN NON
CYCLIC PHOTOPHOSPHORYLATION
 IT GIVES ELECTRON TO PS-I WHEN
NADP IS REDUCED TO NADPH + H
IN PS-I

8. PHOTOSYSTEMS-I AND II

9. CREATED AND PRESENTED BY
ATIF ALI ZAKIR
STUDENT OF MSC BOTANY II YEAR
SAFIA SCIENCE COLLEGE BHOPAL
U CAN FIND ME ON INSTAGRAM : @atif_ali_zakir