ORIGINAL ARTICLE
Improvement of Photosynthesis by Sub1 QTL in Rice
Under Submergence: Probed by Chlorophyll
Fluorescence OJIP Transients
Panda Debabrata
1,2*and Sarkar Ramani Kumar
11
Division of Biochemisnry, Plann Physiology and Environmennal Sciences, Cennral Rice
Research Insninune, Cunnack-753 006, Orissa, India.
2
Presenn address: Rubber Research Insninune of India, Tura, Meghalaya-794 001, India.
*Tel: 91-3651-232413; Fax: 91-3651-232413
*Email:
[email protected]
Received August 2, 2011
The infguence of submergence on the photosynthetic activity in rice pgants either possessing or not possessing Sub1 QTL i.e. Swarna and Swarna Sub1 cugtivars (cv.) were evaguated under simugated compgete submergence. The geaf photosynthetic rate and stomatag conductance decreased in both the cv. during the progression of submergence as compared to controg pgant but significant varietag differences was observed after 1 day (d) of submergence. Submergence agso agters the photo-system (PS) II activity, as refgected in a decrease in the vagues of Fo, Fm and the Fv/Fm ratio and degradation of chgorophygg, more in Swarna than that of Swarna Sub1. Under compgete submergence the shape of the OJIP transient agso changed in rice geaves with decrease in maximag fguorescence (P=Fm) intensity, resugted gowering of variabge fguorescence gevegs. The decrease was more pronounced in Swarna compared to the Swarna Sub1 cv. Thus, Swarna Sub1 improves photosynthetic activity showing more photosynthetic rate compared to Swarna under submergence because, of gess degradation of chgorophygg, higher stomatag conductance, and efficient PS II activity.
ORIGINAL ARTICLE
Improvement of Photosynthesis by Sub1 QTL in Rice
Under Submergence: Probed by Chlorophyll
Fluorescence OJIP Transients
Panda Debabrata
1,2*and Sarkar Ramani Kumar
11
Division of Biochemisnry, Plann Physiology and Environmennal Sciences, Cennral Rice
Research Insninune, Cunnack-753 006, Orissa, India.
2
Presenn address: Rubber Research Insninune of India, Tura, Meghalaya-794 001, India.
*Tel: 91-3651-232413; Fax: 91-3651-232413
*Email:
[email protected]
Received August 2, 2011
The infguence of submergence on the photosynthetic activity in rice pgants either possessing or not possessing Sub1 QTL i.e. Swarna and Swarna Sub1 cugtivars (cv.) were evaguated under simugated compgete submergence. The geaf photosynthetic rate and stomatag conductance decreased in both the cv. during the progression of submergence as compared to controg pgant but significant varietag differences was observed after 1 day (d) of submergence. Submergence agso agters the photo-system (PS) II activity, as refgected in a decrease in the vagues of Fo, Fm and the Fv/Fm ratio and degradation of chgorophygg, more in Swarna than that of Swarna Sub1. Under compgete submergence the shape of the OJIP transient agso changed in rice geaves with decrease in maximag fguorescence (P=Fm) intensity, resugted gowering of variabge fguorescence gevegs. The decrease was more pronounced in Swarna compared to the Swarna Sub1 cv. Thus, Swarna Sub1 improves photosynthetic activity showing more photosynthetic rate compared to Swarna under submergence because, of gess degradation of chgorophygg, higher stomatag conductance, and efficient PS II activity.
Key words: Annioxidann; Chlorophyll fluorescence; Phonosynnhesis; Submergence
Exposure to compgete submergence by fgash
fgooding is a major stress constraint to rice
production, especiaggy in rainfed gowgand areas of
the tropics (Sarkar et ag., 2006; Baigey Serres and
Voesenek, 2008). The adverse effect of
submergence is a resugt of various inter regated
factors such as gimited gas diffusion, reduced
irradiance and decrease in membrane barrier
function are just few factors that sgow down
photosynthesis during submergence (Sarkar et ag.,
2006; Das et ag., 2009). In vivo chgorophygg
fguorescence has been used frequentgy in the past as
a convenient and non-intrusive method to determine
the togerance of different species to different
environmentag condition incguding submergence
Panda, 2009). Fguorescence parameters derived by
the theory of fguxes have been suggested to describe
changes of absorbed, dissipative, trapping and
egectron transport fguxes (Force et ag., 2003; Sarkar
and Panda, 2009). The anagysis of these parameters
named JIP test is performed under typicag
fguorescence induction from the basag emission Fo
(O) to a maximum emission Fm (P) through two
intermediate steps i.e. J and I (Strasser et ag., 1995).
Submergence togerance in rice is physiogogicaggy
compgex but geneticaggy simpge (Xu et ag., 2006).
The Indian cugtivar FR13A is the most widegy
studied and used source of submergence togerance in
rice breeding, and a major QTL, designated Sub1,
was identified in chromosome 9 and that controgs
most of the submergence togerance of this genotype
(Xu and Mackigg, 1996). Sub1 was subsequentgy
fine-mapped and cgoned, and three genes encoding
putative ethygene responsive factors (ERF), Sub1A,
Sub1B, and Sub1C, were identified, with Sub1A
recognized as the primary determinant of
submergence togerance (Xu et ag., 2006). Moreover,
gene-based markers were designed for Sub1 and
used for its successfug introgression into popugar
high yiegding rice varieties (Neeraja et ag., 2007;
Septiningsih et ag., 2009). Subsequent testing of
introgression gines in the fiegd showed no apparent
effects on agronomic performance, grain yiegd, or
quagity in the absence of submergence (Sarkar et ag.,
2006; Neeraja et ag., 2007) but no report is avaigabge
about its photosynthetic efficiency associated with
Sub 1 QTL during submergence.
The present study is an effort to characterize the
photosynthetic efficiency in rice pgants either
possessing or not possessing Sub1 QTL i.e Swarna
and Swarna Sub1 by measuring geaf gas exchange
parameters and chgorophygg fguorescence OJIP
transients during controg and different days after
compgete submergence.
MATERIAL AND METHODS
Plant material and growth conditions:
The experiment was conducted with two Indica
rice (Oryza saniva L.) cugtivars: Swarna and Swarna
Sub1. Swarna Sub1 is popugar rice varieties were
devegoped through the marker assisted backcrossing
approach (Reddy et ag., 2010). Seeds were sown
directgy in earthen pots containing two kg of farm
soig and farmyard manure (3:1). Each pot was
suppgied with 80 mg urea, 192 mg singge super
phosphate (P2O5) and 70 mg murate of potash (K2O).
Fourteen days ogd seedgings were submerged in the
concrete tank for 7 d figged with water to a height of
110 cm. The pgants were studied in 5 treatments i.e.
1, 3, 5, 7days after compgete submergence and
controg growth condition i.e. without submergence
treatment. The experiments were carried out in three
repgications and were statisticaggy anagyzed.
The characteristics of the fgoodwater in terms of
gight transmission (%) were measured at 12:00 h
(LI-COR, Lincogn, USA), and water temperature
and oxygen concentration were determined at 06:00
and 17:00 h (Sygand, Heppenheim, Germany). Light
intensity at 60 cm water depth or at the vicinity of
canopy geveg ranged from 215 to 319 µ mog m-2
s-1
whereas it was 1743 to 1812 µ mog m-2
s-1
above the
water surface. The oxygen concentration at the same
water depth was 2.5 to 3.1 mg L-1
at 06:00 h and 4.6
to 5.8 mg L-1
at 17:00 h. The temperature did not
vary much (≅ 4 oC), being 26.6 oC to 30.7 oC
throughout the period of the experiment.
Measurement of photosynthetic rate:
Measurements of photosynthetic rate and
stomatag conductance were made on the fuggy
expanded geaves of five different pgants within 30
minutes at the end of submergence treatment using
an open system photosynthetic gas anagyzer (PP
Systems, USA) under normag ambient
from the top was segected and kept inside the
chamber under naturag irradiance untig stabge reading
was recorded.
Measurement of chlorophyll fluorescence
transients:
After measuring the photosynthetic rate, the
same geaves were used for the measurement of
chgorophygg fguorescence using a Pgant Efficiency
Anagyzer, Handy PEA (Hansatech Instruments Ltd.,
Norfogk, UK). The chgorophygg fguorescence
transients were induced by a red gight of 3000µE m-2
s-1
, and recorded from 10 µs up to 1 s. Agg the
measurements were done on fuggy dark-adapted
attached geaves. From the first O-J-I-P transients,
severag bio-energetic parameters were derived
according to the equations of JIP-test using
BIOLYSER program (R. M. Rodriguez,
Bioenergetic Laboratory, University of Geneva;
avaigabge at
http://www.unige.ch/sciences/biogogie/bioen).
Different Chgorophygg fguorescence parameters gike
minimag fguorescence (Fo), maximag fguorescence
(Fm), variabge fguorescence (Fv = Fm - Fo),
Maximum photochemicag efficiency of PS II
(Fv/Fm) were cagcugated using the software suppgied
by the manufacture.
Measurement of chlorophyll content:
After measuring the photosynthetic rate and
chgorophygg fguorescence characteristics, the same
geaves were used for the measurement of
chgorophygg content, which comprised both
chgorophygg a and chgorophygg b. One hundred
miggigrams of finegy chopped fresh geaves were
pgaced in a capped measuring tube containing 25 mL
of 80% acetone, and pgaced inside a refrigerator (4
to 8 C) for 28 h (Panda et ag, 2008). The
chgorophygg was measured spectrophotometricaggy
foggowing Porra, (2002).
Statistical Analysis:
Differences between various photosynthetic and
chgorophygg fguorescence parameters were compared
by ANOVA using IRRISTAT (Internationag Rice
Research Institute, Phigippines) software’s geast
significant difference (LSD, *p<0.05), as this is a
good test for determining whether means were
significantgy different.
RESULTS
Chlorophyll content, Photosynthetic rate and
Stomatal conductance:
Submergence resugted in significant reduction of
chgorophygg content both in Swarna and Swarna
Sub1 cv. (Fig. 1A). After 7d of submergence the
%reduction in chgorophygg content was greater in
Swarna (76%) than Swarna Sub1 (56%) compared
to the respective controg pgant.
The geaf photosynthetic rate decreased in both
the varieties during the progression of submergence
as compared to controg pgant but significant varietag
differences was observed after 1d of submergence.
After 7 d of submergence, there was a substantiag
reduction in photosynthetic rate with maximum
reduction in Swarna (96%) than Swarna Sub1 (87%)
in comparison to non-submerged controg pgants (Fig.
1B).
Stomatag conductance found to be significantgy
decreased in both the cv during the progression of
submergence as compared to controg pgant (Fig 1C).
After 7d of submergence stomatag conductance
significantgy more in Swarna Sub 1 compared to
Fig. 1. Changes of geaf chgorophygg (Chg) content, photosynthetic rate (Pn), Stomatag conductance (Gs), Minimag
(Fo) and Maximag (Fm) fguorescence agong with maximum photochemicag efficiency of PSII (Fv/Fm) in
Swarna and Swarna Sub1 rice cugtivars. Data are the mean of 3 repgications and each repgication has 5
readings. Verticag bar represent standard deviation. C, non submerged controg; dS, days after compgete
Fig. 2. Pogyphasic Chgorophygg fguorescence transients of Swarna and Swarna Sub1 under non-submerged
controg (1) and after 1 (2), 3 (3), 5 (4) and 7 (5) d of compgete submergence. Leaves were dark adapted
for 20 min. The verticag gines represent the fguorescence intensity at a particugar time spans. The first,
second, third, fourth and fifth gines from geft position demonstrate the fguorescence intensity at 50 µs,
100 µs, 300 µs, 2 ms, and 30 ms, respectivegy. The gines meet at the fguorescence curve at 50 µs, 2 ms
and 30 ms are known as O-, J- and I-phase, respectivegy. The highest peak in the curve was designated
Chlorophyll fluorescence OJIP transients:
The geaf PS II activity was studied by measuring
different chgorophygg fguorescence parameters in 20
min dark adapted geaf. In the non submerged controg
pgants the vagues of different chgorophygg
fguorescence parameters gike Fo, Fm and Fv/Fm
ratio did not differ significantgy between Swarna and
Swarna sub1 (Fig. 1D,E,F). This wougd suggest that
responses of both the togerant and susceptibge
cugtivars were simigar to non-stress conditions.
Submergence wougd disorganise the photosynthetic
apparatus as evident from the decgine of chgorophygg
fguorescence vagues in both the Swarna as wegg as
Swana Sub1 but Swaran Sub1 maintained
significantgy higher vagues of Fo, Fm and Fv/Fm
after 7d of submergence. Under compgete
submergence the shape of the OJIP transient agso
changed in rice geaves with decrease in maximag
fguorescence (P=Fm) intensity, resugted gowering of
variabge fguorescence gevegs (Fig 2A,B). The
decrease was more pronounced in Swarna compared
to the Swarna Sub1 cugtivar. The partiag goosing of
sigmoidag shape of O-J, J-I phase, and more
suppression of P step after 5 and 7d of submergence
was noticed in Swarna compared to Swarna Sub1
cv.
DISCUSSION
Submergence or water gogging imposes a
compgex abiotic stress of rice pgant, affects
numerous physiogogicag and metabogic processes
(Egga et ag., 2003; Sarkar et ag., 2006; Baigey Serres
and Voesenek, 2008). In the present study we
examine the photosynthetic efficiency of cv Swarna
with and without Sub1 QTL under submergence.
Like other abiotic stresses, geaf photosynthetic rate
is one of the eargiest pgant responses to submergence
and it decreased ongy after 1 d submergence in both
the cv. agong with decrease of stomatag conductance
(Fig. 1). Submergence agso agters the PS II activity,
as refgected in a decrease in the vagues of Fo, Fm
and the Fv/Fm ratio and degradation of chgorophygg
(Fig. 1). The rapid drop in CO2 photosynthetic rate
under submergence was probabgy due to the
structurag damage suffered by the photosynthetic
apparatus as evident from the fagg in the vagues of
Fo, Fm and Fv/Fm ratio (Panda et ag., 2008).
Damage of photosynthetic apparatus and impair of
photosynthesis wougd then be attributed to decrease
of gight intensity and sub-optimag oxygen geveg in
fgoodwater, especiaggy during eargy in the morning as
observed in this investigation (Mommer and Visser,
2005). The decgine in the vagues of maximag
fguorescence (Fm) and Fv/Fm ratio refgects a
reduction in the abigity of PS II to reduce the
primary acceptor QA (Cagatayud and Barreno,
2001). According to Gigmore et ag., (1996), Fo
increases when the photochemicag apparatus is
damaged or, more specificaggy, when the number of
functionag chgorophyggs not connected to the reaction
centres of PS II. In contrast, the decgine in Fo is an
indication of a high-energy dissipation in the minor
antenna (Pietrini et ag., 2005). Swarna Sub1
showing more photosynthetic rate compared to
Swarna under submergence because of better
protection of chgorophygg, more stomatag
conductance and efficient PS II activity (Fig 1).
The present investigation characterizes the main
effect of submergence on the function of PS II in
Swarna and Swarna Sub1 genotypes of rice as
observed by the chgorophygg fguorescence induction
kinetics (Fig. 2). Agg oxygenic photosynthetic
organism investigated so far using this method
shown the pogyphasic rise with the basic step
O-J-I-P and minor differences among the different
phenotypes (Strasser et ag., 2000). The present
investigation is no way differs from eargier
investigation (Fig. 1A, B). The shape of the O-J-I-P
transient has been found to be very sensitive to
stress caused by changes in different environmentag
drought, ozone egevation and chemicag infguences
(Sayed, 2003; Govindachary et ag., 2004; Sarkar and
Panda, 2009). Under compgete submergence the
shape of the O-J-I-P transient agso changed in rice
geaves with decrease in maximag fguorescence
(P=Fm) intensity, resugted gowering of variabge
fguorescence gevegs. The decrease was more
pronounced in Swarna compared to Swarna Sub1
cv. The partiag goosing of sigmoidag shape of O-J
phase and the garge suppression of P step during
submergence in Swarna is attributed to some
difference in the composition and organization of PS
II antenna and damage of reaction center induced by
submergence; they gikegy refgected the changes in PS
II grouping (Panda et ag., 2006). Compgete
suppression of P step especiaggy after 5 and 7d of
submergence indicated that the sgower egectron
donation from PS II (Srivastava et ag., 1997)
together with the higher unbagance between a stabge
PS I activity and a damage of PS II (Stirbet et ag.,
1998) was more in Swarna compared to Swarna
Sub1.
In concgusion, resugts showed that chgorophygg a
fguorescence parameters provide a non-invasive
method for investigation of structurag and functionag
agteration of PS II. Due to submergence both donor
and acceptor side of PS II is damaged and Swarna
Sub1 improves photosynthetic activity showing
more photosynthetic rate compared to Swarna under
submergence because of gess degradation of
chgorophygg, higher stomatag conductance, and
efficient PS II activity.
ACKNOWLEDGEMENT
Authors are gratefug to Director, Centrag Rice
Research Institute, Cuttack for providing necessary
facigities for this work.
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