I"dian J. Plant Physlol•• Vol. XXXlll. No. I, pp. 16-20 (Match. 1990)
EFFECT OF BENZYL-AMINO PURINE AND GIRDLING SITE ON PHOTOSYNTHESIS, TRANSLOCATlON AND NITROGEN FIXATION IN Y-SHAPED MUNGBEAN J.D.S. PANWAR, S. ABBAS AND SITA RAM
Division of Plant Physiology. Indian Agricultural Research Institute, New Delhi-110 012 Received on 17 Aug. 1989 SUMMARY Effect of girdling site and BAP (6-benzyl amino purine) application on photo­
synthesis, translocation and nitrogen fixation was studied in Y-shaped mungbean plants.
BAP application delayed lcaf senescence and enhanced photosynthetic rate in both treated
and untreated branch. Girdling reduced photosynthetic rate, translocation and nitrogen
fixation drastically. When phloem was removed from the main stem and BAP applied
branch, 9S% of He was found in the applied branch only but when opposite branch was
girdled, the translocation of photosynthates was diverted to main stem and roots (S.l
and 6.4 % respectively). Roots and main stem act as alternate sink and in the intact
plant, the remote effect of BAP was noticed in the opposite branch through roots
only.
INTRODUCTION
Senescence in plants is a complex phenomenon which is influenced by environ­
mental conditions and endogenous plant hormones. Senescence can a1so be regulated
by exogenous hormone application (Osborne et 01., 1982). Cytokinins like BAP
delayed senescence, enhanced photosynthetic rate in the intact Y-shaped mungbean
plants but removal of phloem from main stem altered the remote effect of BAP appli­
cation (Panwar et al., 1988). Accordingly an attempt was made to understand the
effect of girdling site and BAP appJication on photosynthesis, translocation and
nitrogen fixation in mungbean.
MATERlALS AND METHODS
Studies were carried out on V-shaped mungbean plants (cv, Pusa 105) grown,
11
in pots. Aqueous solution of BAP at 20 ppm was sprayed on the 4th leaf of sym­
metrical branches separately (Panwar et aI, 1988) The same concentration ofBAP
was also applied on the leaf after removing the phloem tissue at different sites such
as (a) girdling just below the applied leaf on the sprayed branch (b) girdle on the
opposite unsprayed branch and (c) girdle on the main stem just below the junction
of the two symmetrical branches.
Photosynthetic rate (Pn) was measured by Infra Red Gas Analyser (ADC, Eng­
land) and leaf area by leaf area meter (Licor, USA). For translocation studies,14C
feeding (20 !Lci) was done by smearing technique on the leaf followed by hormonal
application. Sampling was done afTer 24 hours of feeding (Sairam, 1916) and radio­
activity was measured in a Packard Liquid Scintillation Counter. The incorporation
of 14C and its translocation was expressed as per cent J4C translocated in different
plant parts.
Nitrogenase activity was measured by acetylene reduction assay (Schweitzer
and Harper. 1980) at 24 and 48 hrs after girdling at different sites.
RESULTS AND DISCUSSION
Application of BAP on one branch of V-shaped plant altered the growth be­
haviour of the other branch connected through a single node main stem. The photo­
synthetic rate (Pn) was higher in the treated as well as untreated leaf at 60 days than
at 50 days after sowing. Girdling of the main stem as well as the treated branch
drastically reduced Pn. Girdling at the opposite branch did not alter Pn of the
treated leaf. However, the rate was reduced in the leaf situated on the girdled
branch. The leaf area was drastically reduced when phloem was removed from the
.
main stem (Table 1).
Nitrogenase activity was considerably reduced in the girdled plants as com­
pared to control, particularly 48 hours after treatment. The significant differences
were, however, observed when the main shoot was girdled. By girdling of either
branch, decreased the nitrogenase activity although at a slower rate (Table I).
The dry matter of stem and leaf was significantly higher when the girdle was
made on the sprayed branch and most of the photosynthates accumulated in the stem
and leaf. When the girdling was done on the opposite branch, most of the photo­
synthates were diverted to main stem and root (Table II).
Variation in both HC incorporation and its translocation from one branch to
the other parts was observed in the same plant. In the control, 84% of 14C was
translocated to the opposite branch and the main shoot, whereas 98 % was retained in
the treated leaf, in case the phloem tissues were removed either from main stem ro
3.3
3.4
1.2
5.3'"
4.7
4.9
1.9
59.7
55.8
57.0
46.4
66.9
68.9
68.5
40.9
IIj.9·
9.9
10.0'"
4.6
13.9'"
9.6
15.7'"
4.0
21.1'"
18.1
15.0
7.2
20.9·
18.2
20.2'"
5.3
0.613
0.472
0.288
0.265
"'Significant at 5% P.
1.063'"
0.709
0.354
0.737
0.901'"
0.763
0.546
1).217
Control (Y-shaped+BAP)
BAP+ girdle on
sprayed branch
BAP+girdle on
unsprayed branch
:SAP +girdle on
main stem­
Total
Leaf
Stem
Treatment
Sprayed Br anch
0.297
0.172
0.224
0.237
Stem
0.455
0.544
0.491
0.498
Leaf
0.752
0.716
0.715
0.735
Total
Unsprayed Branch
0.112
0.271
0.257
0.214
Main
stem
0.173
0.296
0.316
0.231
Root
weight
Table II. Dry matter production of stem and leaf of two symmetrical branches in Y-shaped mungbean
plants (g/plant).
"'Significant at 5% P.
Control (Y-shaped+BAP)
BAP+girdling on
sprayed branch
BAPt girdling on
llDsprayed branch
BAPtgirdling on
main stem
Treatment
Nitrogenase activity
Leaf area
Photosynthetic rate (mg C02dm2h- 1
It moles C2H./Plant h·1
50 DAS
Cm'
60 DAS
Unsprayed Sprayed Unsprayed 24 hrs. 48 hrs
Sprayed
Sprayed
Unsprayed
after
after
Branch Branch
Branch
Branch
Branch
Branch
Table I. Effect of girdling on the photosynthetic rate, leaf area and nitrogenase activity in Y-shaped
mungbean.
......"..~--.
('\I
-.
a..
~.
i
i'>
.....
t:t
00
-
" ,.....
19
treated branch and very negligible amount was translocated to other plant parts.
When the girdle was made on the opposite branch, most of the photosynthates were
diverted towards main stem and root (8.1 and 6.4 % respectively) and 80% were
retained by the treated leaf (Fig. 1).
Sprayed broneh um
Unoprayed branch fl3
'Maln.1IooI
Rool
~
8aa7
5,43
-
641
.
•
•
SI>~taY::JJl
UDl~r~f-cl
-Glrdle­
8,08
8J
'
a,31
lIbtn .hool
-
Rool -
.
a,43
Fig. 1. Effect of girdling site on He translocation (%) in Y-shaped mungbean.
It has been shown earlier that cytokinins like BAP delayed senescence in leaves
and its application had remote effect ou the other branch (Sirohi et al. 1988 and
Panwar et al. 1988). BAP enhanced effect on rate and duration of photosynthesis
was nOticed through the active coordination of root. Its effect was nuHified when
the phloem was removed (girdling) from the main stem below the junction of the
two symmetrical branches in Y-shaped plant (Panwar et al. 1988).
The data revealed that girdling site plays a very important role, the photosyn­
thetic area, photosynthetic rate and its duration and growth pattern was affected by
girdling site. When girdling was done on the sprayed branch, the photosynthates
were not diverted to other plant parts and the same branch accumulated more photo­
synthates causing more dry matter production. But when girdling was done at the
main shoot, the plant roots were depriVed of the current photosynthates and there
was a severe reduction in all plant processes like photosynthesis, nitrogen fixa­
tion etc.
The girdling site has influenced the nitrogen fixation of the plant. Removal of
phloem from the stem caused the reduction of nitrogenase a<.tivity at 24 and 48 hrs
after treatment. The severe reduction was noticed in case the phloem tissues were
removed from main shoot by keeping the plants deprived of the current photosyn­
thates. Since the nitrogenase activity was related with the availability of current
photosynthates (Panwar et a/., 1988), the severe reduction was noted when phloem
.t.D.S. PANWAR et al
was removed from main stem. When the availability of current pbotosynthate was
restricted through making girdle on either of the branches, the nitrogenase activity
declined at slower rate.
BAP application has shown its remote effect on the opposite branch through
enhanced photosynthesis and translocation but when the pbloem was removed from
the main shoot or sprayed bra~ch, the effect was nullified. In the intact plant the
data indicated that BAP acts through roots only.
REFERENCES
Osborne, D.J. and Kathryn, S.E. Cheah (1982). In: Growth Regulators in Plant Senescence.
British Plant Growth Regulators Group, Monograph, pp. 57-77.
Panwar, J.D.S., Abbas, S., Sita Ram and Sirohi, G.8. (1988). Effect of BAP, ethrel and stem
girdling on growth and partitioning of photosynthates in V-shaped mungbean. lnd. J.
Plant Physiol., 31 : 418-422.
Panwar, J.D.S., Chandra R. and Sirohi, G.S. (1988). Effect of temperature on growth, nodula­
tion and nitrogen fixation in summer mung (Jligna radillta (L.) Wilczek). Ann. Plant
Physiol., 2: 121-129.
Sairam, R.K. (1976). Studies on photosynthesis and nitrate assimilation in sunflower: Ph. D.
Thesis, P.G. School, IARI, New Delhi.
Schweitzer, L.E. and Harper, J.E. (1980). Effect of light, cark and temperature on root nodule
activity (acetylene reduction) on soybean. Plant Physiol., 65 : 51-56.
Sirohi, G.S., Panwar, J.D.S. and S. Abbas (1988), Remote effects of BAP and Ethrel on growth
and senescence in V-branched mungbean (Jljgna radiata (L.) Wilczek) plant. Ind. J.
Plant Physiol., 31 : 45-49.