Indian 1. Plant Physiol., Vol. 6. No.1. (N.S.) pp. 38-40 (Jan.-March.
200
n
DIURNAL CHANGES IN PHOTOSYNTHESIS
RATE AT DIFFERENT LEVELS OF
CANOPY IN MUSA PARADASIACA (LINN.) CV. NENDRAN
KP. GENESHAN
Biomass Research Centre, Department of Botany, University of Calicut. Calicut-673635.
Kerala.
Received on 17 Jan .. 2000. Revised on 9 Feb., 200 I
SUMMARY
An experiment was conducted on Mwm parallasillCll cv. Nedran to investigate the photosynthesis rate
during different times of the day at different stages (30 days before anthesis, during anthesis, 30 days after
anthesis and 60 days after anthesis). The leafnumber 1,2,3,4 and 5 from top showed maximum photosynthesis
rate in all the reproductive stages. The maximum photosynthesis rate at 30 days before anthesis, during
anthesis and 30 days after anthesis was above 25 ~lmol CO2 m-2 sec'·; while 60 days after anthesis the maximum
photosynthesis rate was below 18 ~mol CO2 m·2 sec". At all reproductive stages the photosynthesis rate was high
during the forenoon. The decrease in photosynthesis towards afternoon in photosynthetically active leaf may
be due to accumulation of photosynthates causing a feedback inhibition. In Nendran, the presence of green
foliage which looks productive is always having a positive carbon gain.
Key words: Anthesis, diurnal changes, Musa parlulasiaca, photosynthesis
INTRODUCTION
Nendran banana is a much favoured, large fruited,
fast growing type, widely cultivated throughout Kerala
state of South India. Under optimum conditions Nendran
banana produces about 27 leaves after transplanting the
suckers. The sizeofthe leaves produced after transplanting
(i .e.,from the time, plant gets establ ished as an independent
entity) progressively increases from the initial leaf and
the twenty second leaf registers the rniaximumsize. The
last five leaves (23rdto 27th) characterised by the reduced
lamina area, initiate the flowering stage.
knowledge about leaf photosynthetic behaviour under
different environment. The productivity of plant depends
on net photosynthesis rate (Pn), total leaf area, and the
duration of leaf retention on the plant (Samsuddin and
Impens 1979). Therefore, the duration of active
photosynthesis rather than the presence of green foliage
must be determined to study the productivity of plants.
Present study attempted to examine photosynthesis rate
ofNendran banana during different reproductive stages at
different canopy levels.
MATERIALS AND METHODS
The leaf photosynthesis characteristics change with
leafage and growing seasons, following some genetically
determined patterns (Sestak 1985). The total number of
functional leaves retained by Nendran banana is 10 to 12.
The leaf photosynthetic characteristics also varied with
environment and age (Salasimha 1991) and with nitrogen
content (Field and Moorey 1986). However, these aspects
have often been neglected in crop modelling. Ecophysiological studies of plants require a quantitative
A plantation of Mus a paradasiaca(Linn.)cv. Nendran
near the Calicut University campus was selected for the
study. Three plants were tagged with date after emergence
of 23rd, 24th and 25th leaves. The photosynthesis was
recorded by CO2 infra red gas analyser (Cop, 201, CID,
Inc, U.S.A.) from 8.30 AM to 4.30 PM in the above three
plants atone hour intervals. The leafnumber(LI, L2, LJ,
etc ...) was considered from top to base. After a period of
one month, a plant tagged on 24th leahvas flowered and
38
Indiol/./. Plant Physiol.. Vol. 6. No. I, (N.S.) pp. 38-40 (Jan.-March:2001)
'PHOTOSYNTHESIS
IN BANANA
the photosynthesis taken from different leaves. This was
repeated in the same plant after 30 days and 60 days of
anthesis. The mean of five replications was taken.
--Li"--l
30
f-+-L2
I
!"*-L(4+5Y2
i
I-.-L3
RESULTS AND DISCUSSION
--L(6+7+8Y3
During the course ofleaf ontogeny the maximum rate
of photosynthesis mostly differ in the leaves developed
from different primordia at different phase of plant
developmental conditions (Ticha et al. 1984). At 30 days
beforeanthesis, LJ leafshowed maximum photosynthesis
rate followed by L2, L4 and Ls (Fig. I). The lowest
photosynthesis rate was noticed in basal leaves (L9, LJO
and L,). Flag leaf showed maximum photosynthesis rate
followed by L4 and Ls leaves during anthesis (Fig. 2). At
both the stages the maximum photosynthesis rate was
above 25 Ilmol C02m·2sec·l. The rate of photosynthesis
was high during forenoon and declined in the afternoon.
-+-L1
30
---L2
---L3
25,
--L(4+5)/2
Ii
"
!!! 20
_.~- L(6+ 7+8)/,;
~
---.- L(9+1O.11 );3
8' 15 J
'0
I
E
.
.=,
101
z
Q.
o .•--~~_._
..__
.
_
-
... .. --,.-- ... -.----,--.
----
-.,-..-
~
I!.:"!:"_ ~;.!Q~~!)!~.J
'0
E
..:,
Z
Q.
5 ..
oJ
.---,--
..-.------------.- .....--... - "''---'-'M--l
8:30
9:30
10:30
11:30
12:30
1:30
2:30
3:30
4:30
AM
AM
AM
AM
PM
PM
PM
PM
PM
Time in hours
Fig. 2, Net photosynthesis rate of different leaves (L I . L2 ..... ) at
ditrerent times of the day in Musa paradaslGca (Linn.)
cv. Nendran. at anthesis
Nendran banana has retained ] 1 functional leaves
upto 30 days after anthesis. Afterwards it was reduced to
9 only. That means the reduction in photosynthesis. as
well as reduction in number of functional leaves occurs
after 30 days of anthesis. The rate of photosyntheis
declined in the afternoon in all the reproductive stages.
This may be due to accu111ulation of photosynthates
causing a feeback inhibition (Setter and 8run 1980,
Sharma-Natu and Ghildiyal 1992).
.---
8:30
9:30
10:30
11:30
12:30
1:30
2:30
3:30
4:30
AM
AM
AM
AM
PM
PM
PM
PM
PM
i1
--L1
___ L2
I
Time in hours
;=:~~4+5Y2
!----
Fig. I. Net photosynthesis rate of different leaves (L I . L2 .. ,..) at
different times of the day in Musa paradasiaca (Linn.)
cv. Nendran. 30 days before anthesis
The assimilatory capacity of the plants depends on
the size, age of the leaves and efficiency of photosynthetic
system (Evans ]972). Here also older leaves showed
lower photosynthesis rate than newly formed leaves.
After 30 days of anthesis, maximum photosyntheis rate
was shown by L3 leaffollowed by the flag leaf (Fig. 3).
The maximum photosynthesis ,rate was more than 25
Ilmol CO2 m·2sec'l• After 60 days of anthes is the maximum
rate declined to below] 8 1111101
C02m·2sec·1 (Fig. 4).
Indian J Plant Physiol .• Vol. 6. No. I, (N.S.) pp. 38-40 (Jan.-March. 2001)
i
L(S+ 7+8)/3
1--.!:(9:!~11)'.~
.~---.-----, -...•.... --~---.
8:30
9:30
10:30
11:30
12:30
1:30
2:30
3:30'
4:30
AM
AM
AM
AM
PM
PM
PM
PM
PM
Time in hours
Fig. 3. Net photo::ynthesis rate of different leaves (1.1 . L2 •.... ) at
dilTerent times oflhe day in Musa paradasiaca (Linn.)
CV. Nendran. 30 days aller anthesis
39
K.P. GENESHAN
U
.•..1Il••
~
0
()
'0
E
..;
18
r.:;:. L1---1
16
l--11-L2
I
!...••. L3
14
Ii
:--L(4+5V2!
:--L(6+7v21
12
10
L:!:.L(8+~
8
6. I
Z
Q.
'~---I----'-r~
9:30
AM
10:30 11:30 12:30
AM
AM
PM
1:30
2:30
3:30
4:30
PM
PM
PM
PM
Time In hour.
Fig. 4. Net photosynthesis rate of different leaves (L 1 , L2, .... ) at
different times of the day in Musa paradasiaca (Linn.)
cv. Nendran, 60 days after anthesis
It has been reported that the duration of active
_photosynthesis rather than the presence ofgreeen foliage
must be determined to study the productivity of plants
(Nelson 1995). In Nendran, however, the presence of
green foliage which looks productive is always having a
positive carbon gain.
ACKNOWLEDGEMENTS
Author is grateful to Dr. K. Unnikrishnan, Investigator,
Biomass Research Project for providing necessary
facilities during the investigation.
40
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Indian J. Plant Physiol., Vol. 6, No. I, (N.S.) pp. 38-40 (Jan.-March, 2001)