ORIGINAL PAPER

Genotypic variation in partitioning of dry matter and manganesebetween source and sink organs of rice under manganese stress

Shalini Jhanji • Upkar Singh Sadana

Received: 10 February 2014 / Revised: 19 March 2014 / Accepted: 27 March 2014

� Springer-Verlag Berlin Heidelberg 2014

Abstract

Key message Genetic variability in dry matter and

manganese partitioning between source and sink organs

was the key mechanism for Mn efficient rice genotypes

to cope with Mn stress.

Abstract Considerable differences exist among cereal

genotypes to cope manganese (Mn) deficiency, but the

underlying mechanisms are poorly understood. Minimal

information regarding partitioning and/or remobilization of

dry matter and Mn between source and sink organs exists

in rice genotypes differing in Mn efficiency. The present

study was aimed to assess the growth dynamics in terms of

dry matter and Mn remobilization in the whole plant

(leaves and tillers as source and panicles and grains as sink)

during the grain development in diverse rice genotypes.

The efficient genotypes accumulated higher dry matter than

inefficient genotypes under low Mn level. The transloca-

tion index i.e., uptake in grain/total uptake was 0.11 in

efficient genotype (PR 116) and 0.04 in inefficient geno-

types (PR 111). The efficient genotype had higher grain Mn

utilization efficiency of 0.71 in comparison to 0.48 of

inefficient genotype indicating that in efficient genotype,

Mn in grain produces more dry matter than inefficient

genotypes. The efficient genotypes also had higher flag leaf

area and nitrate reductase activity. The source of efficient

genotypes contributed to a greater extent to developing

sink but further mobilization to grain was hindered by

panicle. The panicle of inefficient genotypes had higher per

cent of Mn uptake than efficient genotypes indicating that

Mn was least mobilized from panicle to grain in inefficient

genotypes. The lower per cent uptake of Mn in efficient

genotypes indicated that Mn was mobilized from panicle to

developing grain and this led to higher Mn translocation

index in grain of efficient genotypes. The uptake parti-

tioning revealed that source of all genotypes mobilized the

Mn towards the sink to almost same extent but it was the

panicle where highest per cent uptake per plant was in

inefficient genotypes and lowest in efficient genotypes. The

lowest per cent uptake in panicle of efficient genotypes

revealed that it supported developing grain to have highest

translocation index.

Keywords Manganese � Dry matter partitioning � Grain

filling period � Remobilization � Source–sink relationship

Abbreviations

ANOVA Analysis of variance

C Carbon

CaCO3 Calcium carbonate

DAA Days after anthesis

DTPA Diethylenetriaminepentaacetic acid

HClO4 Per chloric acid

HNO3 Nitric acid

K Potassium

KCl Potassium chloride

KH2PO4 Potassium dihydrogen phosphate

KNO3 Potassium nitrate

L Leaves

LSD Least significant difference

Mn Manganese

Communicated by A. Dhingra.

Electronic supplementary material The online version of thisarticle (doi:10.1007/s00299-014-1611-x) contains supplementarymaterial, which is available to authorized users.

S. Jhanji (&) � U. S. Sadana

Department of Soil Science, Punjab Agricultural University,

Ludhiana 141004, India

e-mail: shalini_jhanji@yahoo.com

123

Plant Cell Rep

DOI 10.1007/s00299-014-1611-x

MnSO4�H2O Manganese sulphate

NRA Nitrate reductase activity

P Phosphorus

ppm Parts per million

PQ Partitioning quotient

r Correlation coefficient

SPAD Soil plant analysis development

T Tiller

Introduction

Since the ‘‘Green Revolution’’, intensive cropping, culti-

vation of high-yield genotypes, improved agricultural

mechanization, production of macronutrient fertilizers with

low impurities of trace elements, and using modern irri-

gation system have resulted in higher crop production per

unit area and greater depletion of soil phytoavailable

micronutrients (Khoshgoftarmanesh et al. 2010). Devel-

oping micronutrient-efficient genotypes would be sustain-

able and cost-effective method for alleviating food-chain

micronutrient deficiency, malnutrition in humans.

In last few decades, manganese deficiency has emerged

as an important nutritional problem worldwide affecting

the crop growth and yield in calcareous soils with high pH

(Yang et al. 2007). In Punjab, where rice wheat cropping

system is predominant, several studies have been done to

screen diverse wheat genotypes for high Mn efficiency and

understand the mechanism for their differential efficiency

(Sadana et al. 2002, 2005; Jhanji et al. 2013a, b) but such

studies with rice are scanty. Visual symptoms of Mn

deficiency are not observed in flooded rice, as reducing

conditions on soil submergence increase Mn solubility, but

Mn deficiency imposes threat on growth, yield, and grain

nutritional status in rice. Till date, few reports are available

revealing Mn efficiency in diverse rice genotypes (Fageria

et al. 2008; Jhanji et al. 2012).

Rice is one of the world’s most important staple food

crops, and second most cultivated cereal after wheat (Fa-

geria 2007). Breeding for Mn dense cultivars of rice is a

powerful tool to combat Mn malnutrition worldwide.

Keeping in view the increasing scenario of Mn deficiency

in soils, importance of rice as a staple food crop and lack of

reports pertaining to Mn efficiency in rice, field experi-

ments were conducted with diverse genotypes to screen Mn

efficient genotypes. The genotypes with high relative yield

i.e., yield at low Mn/yield at high Mn and high relative Mn

uptake were considered to be efficient genotypes (Jhanji

et al. 2012). Jhanji et al. (2011) reported that morpho-

physiological characteristics such as longer roots, more leaf

area, higher nitrate reductase activity and soil plant

analysis development (SPAD) index were also associated

with efficient genotypes of rice.

Plants that grow in Mn deficiency during grain filling

stage will depend on the amount of Mn taken up by the

roots during grain development and the amount redistrib-

uted to the grain from vegetative tissue via phloem i.e.,

remobilization (Waters and Grusak 2008). Fang et al.

(2008) reported that Fe concentration in rice grains could

be increased by enhanced root uptake combined with stem/

leaf efflux transport activity. Remobilization of reserves to

supply rice grains has been also emphasized in the earlier

studies (Wu et al. 2010; Yoneyama et al. 2010). The Mn

uptake and/or mobility within shoot and to the grain (i.e.,

mobilization) is mainly affected by Mn application and

growth stages (Pearson and Rengel 1994); sucrose status

and humidity (Pearson et al. 1996); heat stress which

generally increases Mn uptake (Dias et al. 2009) and plant

genotypes (Hocking et al. 1977). So, we need to focus on

the behavior of Mn in terms of its mobility within different

organs leading to its better distribution and partitioning in

plant. Phloem mobility of Mn is very low and it can reach

glumes directly via xylem in mature wheat plants or can be

first transferred from xylem to phloem and then reach the

glumes via phloem in young plants (Riesen and Feller

2005) though the extent of Mn mobility in phloem varies

with plant species (Epstein 1971). Pearson and Rengel

(1994) reported poor remobilization of Mn in wheat grains

due to poor phloem mobility where as Sperotto et al.

(2012) reported remobilization of Mn from stem/sheath in

rice. On the contrary, good reproductive phase mobiliza-

tion of Mn to grains at harvest stage with an increased

spike Mn concentration (along with flag leaf) accompanied

by decreased Mn concentration in the other plant parts

including older leaves has been reported recently in barley

by Birsin et al. (2010). Mn moves readily from roots, stems

and petioles to developing sinks, including seeds in lupin

(Hannam et al. 1985). Under Mn deficiency, Mn content of

stem, peduncle and flag leaf decreases and that of glumes

increases towards maturity (Pearson and Rengel 1994).

Sharp decline of mineral nutrient content from vegetative

organs during reproductive growth stage occurs because

nutrient uptake generally decreases, mainly as a result of

decreasing carbohydrate supply to the roots (Marschner

1995). So, the citied literature suggests that the higher

yield of efficient cultivars under Mn deficiency may be

related to superior Mn partitioning to grain and lesser

retention of Mn in the vegetative parts. On this hypothesis,

we assessed the organ-specific changes in dry matter and

Mn uptake to monitor the Mn dynamics between source

(leaves, L and tiller, T) and sink (panicle, P and grain, G)

during reproductive development i.e., from anthesis to

maturity.

Plant Cell Rep

123

Materials and methods

Experimental design and plant sampling

A greenhouse experiment was conducted at the Punjab

Agricultural University, Ludhiana, India (30�560N, 75�320Eand 247 m above MSL) to understand the influence of

source sink relationship on differential Mn efficiency of

four diverse rice genotypes. These genotypes were cate-

gorized into Mn efficient (PR 116, PR113) and Mn inef-

ficient (PR 111, PR115) on the basis of relative grain yield

and Mn uptake determined by Jhanji et al. (2012).

Manganese deficient soil samples were collected from

Mn deficient field (0–15 cm) in Bhatha Dhua, Ludhiana.

The soil was loamy sand (85 % sand, 6 % silt and 9 %

clay) of great group Ustochrepts with bulk density

1.53 g cm-3, pH 8.3, 6 % CaCO3, 0.6 g kg-1 soil organic

C and 1.54 mg kg-1 soil DTPA-extractable Mn. A basal

dose of 120 mg N through urea, 13 mg P through KH2PO4

and 25 mg K through KCl kg-1 soil was applied to all the

pots. Five healthy 30-day old seedlings of 4 rice genotypes

were transplanted in plastic pots filled with 9 kg of Mn

deficient soil.

The treatments consisted of two Mn levels viz. low Mn

(no Mn fertilizer, 0 ppm) and high Mn (50 mg Mn kg-1

soil applied as MnSO4�H20) and five stages of grain

development (from 7DAA to 35 DAA/maturity). A com-

pletely randomized design was used in a factorial

arrangement of the eighty pots, where each treatment was

replicated ten times. Ten plants were collected at a weekly

interval from 7 days after anthesis (DAA) to maturity.

Sample analyses for different parameters

Following morphophysiological parameters were recorded

at 7 DAA and 21 DAA:

SPAD index of 10 leaf samples was recorded using

SPAD 502. Maximum length and width of the subsidiary

leaves and the flag leaf were recorded and leaf area was

calculated by multiplying leaf length and width with a

constant (0.83) for rice leaf. Nitrate reductase activity

(NRA, l moles KNO3 reduced g-1 fresh weight h-1) of

fresh leaf segments was estimated by in vivo method of

Jaworski (1971).

At each stage of grain development, the plants were

separated into leaves, tillers, panicles and grains. The leaf

and tiller together constituted the source and the panicle

and grain, sink. Different plant parts were dried in an oven

at 60 �C up to a constant dry weight and then their weights

were recorded.

The dried plant parts were then milled. Ground material

was digested with 2:1 mixture of nitric (HNO3) and per-

chloric acid (HClO4) and analyzed for manganese

concentration (ppm) by atomic absorption spectroscopy

(Isaac and Kerber 1971) using atomic absorption spectro-

photometer Model A A 240 F S, Company 96 Varian,

Germany.

Calculations

The following parameters were then calculated:

1. Manganese uptake in grain (lg/plant) = grain yield

(g/plant) 9 grain Mn content (lg/g) (Graham 1984).

2. Manganese efficiency index = grain yield at low Mn/

grain yield at high Mn 9 100 (relative yield).

3. Manganese efficiency = grain Mn uptake at low Mn/

grain Mn uptake at high Mn 9 100 (relative Mn

uptake).

4. Dry matter partitioning of individual organ = dry

weight of the organ/total shoot dry weight 9 100.

5. Manganese uptake partitioning of individual

organ = Mn uptake in the organ/total Mn uptake.

6. Partitioning Quotient (PQ) = Per cent Mn uptake in

an organ/per cent dry weight of organ 9 100 (Waters

and Grusak 2008).

7. Dry matter translocation = Dry matter at anthesis -

dry matter at maturity.

8. Dry matter translocation efficiency = Dry matter

translocation/dry matter at anthesis x 100.

9. Dry matter accumulation = Dry matter at maturity -

dry matter at anthesis.

10. Dry matter accumulation efficiency = Dry matter

accumulation/dry matter at maturity x 100.

11. Contribution of pre-anthesis assimilates to the grain

weight = Dry matter translocation/grain weight at

maturity.

Statistical analyses

The data were subjected to analysis of variance (ANOVA)

appropriate for completely randomized design to evaluate

difference between the treatment means. Least significant

difference (LSD) was used for all comparisons where

significant F-probabilities (P B 0.05) were found. Standard

error of mean for each treatment was calculated. Correla-

tion coefficient between yield and morphophysiological

parameters was worked out (Singh et al. 2001).

Results

The results indicated that Mn deficiency decreased the

grain yield in all genotypes but the efficient genotypes were

affected to a lesser extent than inefficient genotypes. The

differential Mn efficiency of genotypes was due to

Plant Cell Rep

123

difference in dry matter and Mn uptake partitioning

between source and sink.

Analysis of variance

The data pertaining to dry matter accumulation at different

stages of grain development in four rice genotypes at two

Mn levels were subjected to analysis of variance (Table 1).

The total dry matter, dry matter accumulation in leaf, tiller,

panicle and grain varied significantly with stage of devel-

opment, genotype and Mn level except panicle in which no

significant variation between genotypes for dry matter

accumulation was observed and leaf where dry matter

accumulation was independent of Mn level.

Grain yield

The grain yield increased significantly in all genotypes

with Mn application. Under low Mn, the efficient

genotypes, PR 116 and PR 113 retained 87 and 81 %,

respectively, of the grain yield at adequate Mn, whereas the

corresponding values for inefficient genotypes, PR 115 and

PR 111 were 65 and 75 %, respectively (Fig. 1).

To unravel the mechanism of differential Mn efficiency in

these genotypes source sink relationship in terms of dry matter

accumulation and Mn uptake during grain filling period was

studied. A genotype showed similar accumulation pattern at

low and high Mn with only difference in absolute values

(Table 2). Thus, for better understanding of the mechanism,

the data from the low Mn treatment are explained.

Dry matter accumulation

The dry matter accumulation in different plant parts (leaf,

tiller, panicle and grain) was recorded at weekly interval

during grain filling period. Dry matter accumulation sig-

nificantly decreased in leaf and tiller (source) throughout

grain filling period in all genotypes (Fig. 2). The highest

decline in leaf dry weight was 28 % for PR 116 during

grain filling period, whereas least for PR 113 (7 %,

Table 2). The tiller dry weight declined by 32 % in PR

113, whereas by 13 % in PR 116. The inefficient geno-

types showed reduction in leaf dry weight by 23 % (PR

115) and 25 % (PR 111), whereas no changes were

observed for their tiller dry weight during grain filling

period (Table 1).

The dry matter accumulation in panicle and grain (sink)

increased during grain filling period in all genotypes

(Fig. 2). An increase of about two folds in panicle dry

weight was observed for PR 115 and PR 111(inefficient),

whereas increase was 17 and 68 %, respectively, for PR

116 and PR 113 during grain filling period. The accumu-

lation of dry weight in grain was higher for efficient

genotypes (PR 116 and PR 113) than inefficient genotypes

(PR 115 and PR 111). The dry matter mobilized from

source to developing sink up to 21 DAA in efficient

genotypes, whereas up to 14 DAA in inefficient genotypes.

The source (L & T) in PR 116 and PR 113, respectively,

contributed about 20 and 23 % dry weight to grain

throughout grain development in comparison to 11 and

Table 1 Analysis of variance

for total dry matter (g/plant),

dry matter in leaf, tiller, panicle

and grain (g) at different stages

of grain development growing

at two Mn levels

No. of replications = 3

Parameter Factor Total dry matter Leaf Tiller Panicle Grain

LSD (5 %) Stage of development (S) 0.54 0.24 0.26 0.59 0.42

Genotype (G) 0.48 0.22 0.24 NS 0.37

S 9 G NS 0.49 0.53 NS 0.83

Mn level (M) 0.34 NS 0.17 0.38 0.26

S 9 M NS 0.34 0.37 0.84 0.59

G 9 M 0.68 0.31 0.33 0.75 NS

S 9 G 9 M NS 0.69 NS NS NS

CV (%) 5.09 11.23 8.94 10.16 10.66

Bc

Bb Bb

Ba

Ac

Ab

Aa

Aa

0.0

2.0

4.0

6.0

8.0

10.0

12.0

14.0

16.0

PR 116 (87) PR 113(81) PR 115(65) PR 111(75)

Gra

in y

ield

(g

/pla

nt)

Genotypes

High Mn Low Mn

Fig. 1 Grain yield (g/plant) of four diverse rice genotypes under

different Mn levels. Values in the parentheses on X-axis represent Mn

efficiency index. Different upper case letters indicate statistically

significant differences between mean of the grain yield at low and

high Mn supply in a genotype and different lower case letters indicate

significant differences between mean of the grain yield of different

genotypes at high or low Mn level (P \ 0.05)

Plant Cell Rep

123

7 % by PR 115 and PR 111, respectively (Fig. 3). The

contribution of preanthesis assimimilates from source to

sink was least for PR 115 (33 %) and PR 111 (34 %) and

highest for PR 113 (44 %, Table 3). The contribution of

dry weight from source and panicle together to grain

decreased to 15 and 6 % in PR 116 and PR 113, respec-

tively, indicating that panicle hinders the mobilization to

grain. The dry weight of source and panicle in PR115 and

PR 111 increased during grain development by 15 and

12 %, respectively, indicating that the source was mobi-

lizing dry weight to developing sink but panicle was

accumulating dry weight instead of mobilizing it to grain.

The results pertaining to differential source–sink parti-

tioning of dry weight at maturity in efficient and inefficient

genotypes are presented in Fig. 4. The grain in efficient

genotypes accumulated 49 % (PR 116) and 46 % (PR 113)

of total dry weight per plant at maturity, whereas the

inefficient genotypes accumulated 35 % (PR 115) and

33 % (PR 111) of total dry weight in grain. The panicle of

PR 116, PR 113, PR 115 and PR 111, respectively, accu-

mulated 10, 18, 21 and 19 % of total dry matter and the

corresponding values for tiller were 23, 17, 26, and 29 %.

The leaf in all genotypes accumulated about 16–17 % of

total dry matter. Thus, among the vegetative parts, PR 116

accumulated highest dry matter in tiller, PR 113 almost

same in the leaf, tiller and panicle, whereas PR 115 and PR

111 in tiller.

Mn uptake

The Mn uptake was recorded at weekly interval during

grain filling period. The uptake of Mn decreased in source

during grain filling period to support developing sink

(Table 4; Fig. 5). The Mn uptake in leaf of PR 116 and

PR 113, respectively, decreased by 24 and 14 % from

anthesis to maturity i.e., during grain development,

whereas the corresponding values were 2 and 8 %,

respectively, for PR115 and PR 111. The highest decrease

in tiller dry weight during grain development was

observed in PR 113 (54 %) followed by PR 116 (31 %),

PR 115 (34 %), and PR 111 (8 %). During grain devel-

opment, Mn uptake increased in both panicle and grain.

The Mn uptake in panicle increased by 64 % in both

efficient genotypes, whereas 78 % in PR 115 and 75 % in

PR 111. The Mn uptake increased by 85 and 83 %,

respectively, in grain of PR116 and PR 113 during grain

filling period, whereas in inefficient genotypes, PR 115

and PR 111, the corresponding values were 73 and 67 %,

respectively (Table 4).

The contribution of source to Mn uptake in grain was

32 % in PR 113, 27 % in PR 116, 19 % in PR 115, and

12 % in PR 111 during grain development (Fig. 6). The

contribution of source and panicle to Mn uptake in devel-

oping grain decreased to 15 and 13 %, respectively, in PR

116 and PR 113, whereas the total uptake in source and

Table 2 Dry matter (g/plant)

partitioning in different plant

parts of four rice genotypes

during grain filling period under

different Mn supply

Stage of

development

Cultivar Low Mn High Mn

Leaf Tiller Panicle Grain Total Leaf Tiller Panicle Grain Total

7 DAA PR116 4.98 5.91 1.91 1.36 14.15 6.42 6.73 3.25 1.78 18.18

PR113 3.72 4.94 2.07 0.92 11.65 5.52 6.92 2.76 1.01 16.21

PR115 4.21 5.19 1.28 0.85 11.53 3.74 5.51 2.26 0.93 12.45

PR111 4.44 5.00 1.40 0.93 11.76 3.76 5.34 1.87 0.93 11.90

14 DAA PR116 4.19 5.98 1.81 7.29 19.27 5.15 6.32 2.632 7.51 21.61

PR113 3.88 4.40 2.83 5.93 17.04 4.40 4.59 1.803 8.18 18.98

PR115 4.05 5.29 2.48 5.80 17.62 3.66 5.52 1.903 6.94 18.03

PR111 3.77 5.69 2.34 4.34 16.14 3.71 5.55 2.545 5.82 17.62

21 DAA PR116 3.83 5.57 1.79 9.41 20.60 3.42 5.68 2.405 11.30 22.81

PR113 3.31 3.50 3.83 7.03 17.68 3.51 3.81 3.444 9.30 20.06

PR115 3.90 5.36 4.26 5.31 18.83 3.52 5.44 2.274 8.14 19.37

PR111 3.59 5.56 3.04 4.72 16.91 3.64 5.28 1.729 7.16 19.14

28 DAA PR116 3.63 5.32 2.28 10.60 21.83 3.27 5.27 3.029 12.56 24.13

PR113 3.50 3.35 3.45 8.53 18.83 3.00 3.53 2.470 10.81 19.82

PR115 3.38 5.13 4.00 6.80 19.31 2.73 5.21 1.433 10.40 19.78

PR111 3.44 5.39 3.68 5.81 18.32 3.53 5.19 1.840 8.29 20.18

Maturity PR116 3.56 5.14 2.24 10.88 21.82 3.24 5.29 3.419 12.50 24.45

PR113 3.43 3.34 3.47 8.91 19.16 3.02 3.39 2.470 11.01 20.89

PR115 3.25 5.14 4.16 6.84 19.39 2.63 5.15 1.590 10.48 19.85

PR111 3.32 5.42 3.60 6.25 18.59 3.51 5.10 2.102 8.36 19.41

Plant Cell Rep

123

*

*

*

2.5

3

3.5

4

4.5

5

5.5

5.5

Lea

f D

ry W

eig

ht(

g/p

lan

t)

APR116 PR113

PR115 PR111

*

*

*

2.5

3

3.5

4

4.5

5

5.5

6

6.5

7

7.5

Till

er D

ry W

eig

ht(

g/p

lan

t) B

**

*

*

*

*

*

*

1

1.5

2

2.5

3

3.5

4

4.5

5

7 14 21 28 Maturity

Pan

icle

Dry

Wei

gh

t(g

/pla

nt)

Days after anthesis

C

*

*

*

**

*

* *

*

* *

0

1

2

3

4

5

6

7

8

9

10

11

7 14 21 28 Maturity

Gra

in D

ry W

eig

ht(

g/p

lan

t)

Days after anthesis

D

Fig. 2 The dry weight of the (a) leaf, (b) tiller, (c) panicle and

(d) grain of four diverse rice genotypes at different stages of grain

development. The bars indicate the LSD (P B 0.05) between the

genotypes at each stage of development/harvest, otherwise not

significantly different. Asterisks indicate differences (P B 0.05) from

previous stage of development in a genotype, otherwise not signif-

icantly different

-20

-25

-11

-7

-15

-6

1512

-30

-25

-20

-15

-10

-5

0

5

10

15

20

PR116 PR113 PR115 PR111

Per

cen

t d

ry w

eig

ht

source

source+panicle

Fig. 3 Differential contribution of dry weight from source and

panicle to grain at maturity by four diverse rice genotypes under low

Mn

0%

10%

20%

30%

40%

50%

60%

70%

80%

90%

100%

PR116 PR113 PR115 PR111Per

cen

t p

arti

tio

nin

g o

f d

ry w

eig

ht

at m

atu

rity

leaf tiller panicle grain

Fig. 4 Partitioning of dry weight in various plant parts of four

diverse rice genotypes at maturity under low Mn

Plant Cell Rep

123

panicle increased by 3 and 6 %, respectively, for PR 115

and PR 111 indicating that towards maturity the panicle

might be accumulating Mn in itself instead of mobilizing it

to grain.

The results pertaining to differential source–sink parti-

tioning of Mn uptake at maturity in efficient and inefficient

genotypes are presented in Fig. 7. At maturity, the source

in PR 113 had 64 % of total Mn uptake and sink had 36 %,

whereas corresponding values for Mn uptake were 72 and

28 %, respectively, in PR 116; 71 and 29 % in PR115 and

74 and 26 % in PR 111. Out of 36 % of total Mn uptake in

sink of PR 113, 27 % was in panicle and only 9 % in grain.

In PR 116, out of 28 % of total Mn uptake in sink, 16 %

was in panicle and 12 % in grain. The corresponding val-

ues for PR 115 and PR 111 were, respectively, 29 and

26 % in sink, 23 and 21 % in panicle and 6 and 5 % in

grain (Fig. 7). The translocation index i.e., uptake in grain/

total uptake in shoot was 0.12 in PR 116 and 0.05 in PR

111. The uptake partitioning revealed that source of all

genotypes mobilized the Mn towards the sink to almost

same extent but it was the panicle that immobilised Mn.

The highest per cent Mn uptake in panicle was in PR113

and lowest in PR 116. The lowest percent uptake in panicle

of PR 116 revealed that it supported developing grain to

have highest translocation index.

Partition quotient (PQ)

Partition quotient values were calculated to check the

concentration of Mn in an organ irrespective of the dry

matter or size of that organ. The leaf, tiller, panicle, and

grain of efficient genotype, PR 116, respectively, had

highest PQ values of 262, 123, 163, and 23 than inefficient

genotype, PR111 where corresponding values were 230,

114, 107, and 14 (Fig. 8). A significant and positive cor-

relation was found between Mn concentration in a part and

its dry matter (r = 0.87**).

Nitrate reductase activity

The highest NR activity of 0.15 and 0.18 was recorded in

leaf and panicle of PR 116, whereas least in PR111 (0.03 in

leaf and 0.05 in panicle) at 7 DAA (Fig. 9). The corre-

sponding values at 21 DAA were 0.07 in both leaf and

panicle of PR 116, and 0.01 and 0.05, respectively, in leaf

and panicle of PR 111.

*

*

*

**

*

*

*

*

**

*

603

633

663

693

723

753

783

813

843

873

903

933

Lea

f u

pta

ke(µ

g/p

lan

t)

A PR116 PR113

PR115 PR111

**

**

*

* *

*

*

203

253

303

353

403

453

503

553

603

653

703

753

803

Till

er u

pta

ke(µ

g/p

lan

t)

B

**

**

*

**

*

*

*

*

*

*

*

**

1

51

101

151

201

251

301

351

401

451

7 14 21 28 Maturity

Pan

icle

up

take

(µg

/pla

nt)

Days after anthesis

C

*

**

*

**

** *

**

**

0

20

40

60

80

100

120

140

160

180

200

7 14 21 28 Maturity

Gra

in u

pta

ke(µ

g/p

lan

t)

Days after anthesis

D

Fig. 5 The Mn uptake in the a leaf, b tiller, c panicle and d grain of

four diverse rice genotypes at different stages of grain development.

The bars indicate the LSD (P B 0.05) between the genotypes at each

stage of development/harvest, otherwise not significantly different.

Asterisks indicate differences (P B 0.05) from previous stage of

development in a genotype, otherwise not significantly different

Plant Cell Rep

123

Leaf area and flag leaf area

The total leaf area of inefficient genotypes, PR 115

(177 dm2) and PR 111 (217 dm2), was higher than efficient

genotypes, PR116 (129 dm2) and PR 113 (143 dm2) but

flag leaf area was highest for PR 116 (1,712 dm2) at 7

DAA (Fig. 10). At 21 DAA, the total leaf area declined in

all genotypes but flag leaf area which is the photosyn-

thetically active source increased in all genotypes. The flag

leaf area of PR 116, PR113, PR 115, and PR 111 con-

tributed to about 15, 5, 4, and 4 % of the total leaf area at

21 DAA. Thus, the photosynthetically active source was

more active in efficient genotypes than inefficient

genotypes.

SPAD index

SPAD index measures the relative chlorophyll content.

There was no significant difference in the value of SPAD

index among different cultivars at 7 DAA and 21 DAA, but

PR 116 at 21 DAA retained 78 % of the SPAD value at 7

DAA, whereas the corresponding value was 60 % for PR

115 and PR 111 (Fig. 11).

The grain yield was significantly and positively corre-

lated to flag leaf area (r = 0.74**) and nitrate reductase

activity (NRA) in panicle (r = 0.76**) and NRA in flag

leaf (r = 0.79**). The leaf area (r = -0.75**) was sig-

nificantly but negatively correlated to grain yield. Thus,

efficient genotypes with higher flag leaf area as well as

NRA activity and lower total leaf area had higher yield in

comparison to inefficient genotypes.

Discussion

Manganese deficiency suppressed the grain yield in several

crop species (Abbas et al. 2011; Bansal and Nayyar 1998;

Jhanji et al. 2011). The reduced grain yield under Mn

deficiency could be explained by the role of Mn in cascades

of metabolic and physiological processes of growth and

development (Millaleo et al. 2010). The application of Mn

significantly increased the yield of all genotypes (Table 1),

suggesting the role of Mn in appropriate partitioning of

nutrients and assimilates between vegetative and repro-

ductive parts (Soylu et al. 2005). The efficient genotypes

PR116 (87 %) and PR113 (81 %) had higher Mn efficiency

index than inefficient genotypes, PR 115 (65 %) and

PR111 (75 %). A significant and positive correlation

between grain yield and Mn efficiency index (r = 0.91**)

supports our finding that genotype with high yield at low

Mn had high efficiency index. The results that efficient

genotypes had high Mn efficiency index i.e., retain high

grain yield under low Mn supply than inefficient genotypes

were in accordance to our previous studies related to field

screening of diverse rice (Jhanji et al. 2012) and wheat

(Jhanji et al. 2013a) genotypes.

Dry matter production of efficient genotypes was more

than inefficient genotypes at all stages during grain

development (Table 1). Higher dry matter production of

efficient genotypes than inefficient genotypes had been

reported earlier in rice (Jhanji et al. 2011) and wheat

(Jhanji et al. 2013b). Dry matter accumulation in a plant is

the product of cascades of metabolic processes, such as

photosynthesis, respiration, partitioning of assimilates;

internal factors, such as chlorophyll, carotene and other

pigment contents, capacity to store food reserves; genetic

factors providing resistance to climatic, edaphic and bio-

logical stresses, and environmental factors. The photosyn-

thetic efficiency of a plant determines the dry matter

production (Singal et al. 1992). Thus, higher dry matter

production in efficient genotypes might be due to higher

photochemical efficiency or lower Mn requirement. The

measures of photosynthetic efficiency viz. SPAD index and

NRA were higher in efficient genotypes. Higher NRA in

efficient genotypes indicates higher photochemical effi-

ciency because reduction of nitrate requires reducing

power i.e., NADPH generated by the photochemical reac-

tions as well as the activity of nitrate reductase enzyme.

Table 3 Dry matter related parameters of four rice genotypes under low Mn supply

Cultivar Dry matter

translocation

from source (g/

plant)

Dry matter

translocation

efficiency of

source (%)

Contribution of

pre-anthesis

assimilates to

sink (%)

Dry matter translocation

(?)/accumulation (-) in

source and panicle (g/

plant)

Dry matter translocation

(?)/accumulation (-)

efficiency of source and

panicle (%)

Contribution of

pre-anthesis

assimilates to

grain (%)

PR 116 4.1b 32b 38b ?1.86b ?14b ?17b

PR 113 4.0b 37c 44c ?0.49a ?4a ?5a

PR 115 2.3a 21a 33a -1.87B -17B -27B

PR 111 2.1a 19a 34a -1.5A -13A -24A

Different lower case letters indicate statistically significant differences between the genotypes for the mean of values in a column (P \ 0.05)

Different upper case letters indicate significant differences between the genotypes for the mean of values in a column (P \ 0.05). (Comparison of

treatment means with LSD; No. of replications = 3)

Plant Cell Rep

123

The NR activity was highest in leaf and panicle of efficient

genotype (PR 116) at both stages indicating high photo-

synthetic activity of source and developing sink supporting

high dry matter accumulation and grain yield. Low NR

activity of leaf of inefficient genotypes revealed that during

grain development, source becomes photosynthetically less

active and thus, contribution to developing grains reduces.

High NR activity of panicle than leaf indicates that panicle

itself remains photosynthetically active during grain

development for a longer time to support developing grain

in all genotypes but panicle of efficient genotypes showed

higher activity than inefficient genotype.

Flag leaves are the main photosynthetic tissues and the

photochemical efficiency also depends upon the area of

Table 4 Partitioning of Mn uptake (lg/plant) in different plant parts

of four rice genotypes during grain filling period under low Mn supply

Stage of

development

Cultivar Low Mn

Leaf Tiller Panicle Grain Total

7 DAA PR116 910 680 98 28 1,716

PR113 751 667 149 23 1,590

PR115 642 734 83 25 1,484

PR111 708 625 83 25 1,441

Mean 753 677 104 25 1,558

14 DAA PR116 774 632 112 132 1,650

PR113 871 538 191 98 1,698

PR115 695 666 203 132 1,696

PR111 676 588 148 92 1,504

Mean 754 606 164 114 1,638

21 DAA PR116 733 650 137 161 1,681

PR113 741 439 333 123 1,636

PR115 784 481 375 104 1,744

PR111 747 559 231 88 1,625

Mean 744 532 269 119 1,664

28 DAA PR116 715 598 244 175 1,732

PR113 724 328 361 120 1,533

PR115 679 432 343 118 1,572

PR111 714 539 304 104 1,661

Mean 708 474 313 129 1,625

Maturity PR116 693 472 271 188 1,624

PR113 647 306 409 135 1,497

PR115 631 486 372 91 1,580

PR111 651 527 329 75 1,582

Mean 656 448 345 122 1,572

LSD (0.05) S 18.8 9.9 7.4 5.6 28.1

G 16.9 8.9 6.6 5.0 25.1

S 9 G 37.7 19.8 14.8 11.3 56.2

CV (5 %) 3.16 2.19 3.75 6.70 2.11

Statistical analysis: two way ANOVA and comparison of treatment

means with LSD; No. of replications = 3

S stage of development, G genotype

-27

-32

-19

-12

-15-13

3

6

-35

-30

-25

-20

-15

-10

-5

0

5

10

PR116 PR113 PR115 PR111

Per

cen

t M

n u

pta

ke

source

source+panicle

Fig. 6 Differential contribution of Mn uptake from source and

panicle to grain at maturity by four diverse rice genotypes at low Mn

0%

10%

20%

30%

40%

50%

60%

70%

80%

90%

100%

PR116 PR113 PR115 PR111Per

cen

t p

arti

tio

nin

g o

f M

n u

pta

ke a

t m

atu

rity leaf tiller panicle grain

Fig. 7 Partitioning of Mn uptake in various plant parts of four

diverse rice genotypes at maturity at low Mn

c

a

c

c

b

a

c

b

b

a b

ba

a

a a

a0

50

100

150

200

250

300

leaft tiller panicle grain

Par

titi

on

qu

oti

ent

(PQ

)

PR116 PR113 PR115 PR111

Fig. 8 Partition quotient of Mn in different plant parts of four diverse

rice genotypes at maturity. Different lower case letters indicate

significant differences between mean of PQ of a plant part of different

genotypes at maturity (P \ 0.05)

Plant Cell Rep

123

the photosynthetic tissue. The efficient genotypes had

higher flag leaf area than inefficient genotypes to support

the assimilate production. This supports our findings that

efficient genotypes contributed more to developing sink,

as the photosynthetically active source itself remains

active up to 21 DAA to a greater extent than in inefficient

genotypes.

The Mn uptake in a plant part is the product of dry

matter accumulation and concentration of Mn in that

part. Mn distribution from sources to sinks takes place

via phloem (Marschner 1995). and its redistribution

depends on the plant species and stages of development

(Herren and Feller 1994). Several transporter gene

families have been implicated in Mn2? transport,

including cation/H? antiporters, natural resistance-asso-

ciated macrophage protein (Nramp) transporters, zinc-

regulated transporter/iron-regulated transporter (ZRT/

IRT1)-related protein (ZIP) transporters, the cation dif-

fusion facilitator (CDF) transporter family, and P-type

ATPases (Ducic and Polle 2005; Pittman 2005). So, the

differential transport of Mn might be due to difference in

genetic inheritance of these transporters in efficient and

inefficient genotypes.

The results revealed similar trend in Mn uptake in

source and sink of efficient and inefficient genotypes as of

dry matter accumulation and translocation. Fageria et al.

(2008) reported that there are certain genotypes that can

Bb

Aa Ba Ba

Bc

BbBb

Aa

Ac

Bb

Aa Aa

Ac

AaAa Ab

0.00

0.02

0.04

0.06

0.08

0.10

0.12

0.14

0.16

0.18

0.20

PR116 PR113 PR115 PR111 PR116 PR113 PR115 PR111

PanicleLeaf

(µ m

ole

s o

f K

NO

3re

du

ced

/g f

resh

wt/

hr)

7 DAA 21 DAA

Fig. 9 The nitrate reductase

activity in leaf and panicle of

four diverse rice genotypes at 7

and 21 days after anthesis

(DAA). Different upper case

letters indicate statistically

significant differences between

mean of NRA at 7 and 21 DAA

in a genotype and different

lower case letters indicate

significant differences between

mean of NRA of different

genotypes at 7 or 21 DAA

(P \ 0.05)

75%

80%

85%

90%

95%

100%

7

DAA

21

DAA

7

DAA

21

DAA

7

DAA

21

DAA

7

DAA

21

DAA

PR116 PR113 PR115 PR111

Per

cen

t d

ry w

eig

ht

of

leaf

an

d

fla

g le

af p

er p

lan

t

Leaf Flag leaf

Fig. 10 The per cent of dry weight of flag leaf and other leaves out of

total leaf in a plant of four diverse rice genotypes at 7 and 21 DAA

A A A A0.0

5.0

10.0

15.0

20.0

25.0

30.0

35.0

40.0

45.0

c b a a

PR116 PR113 PR115 PR111

SP

AD

ind

ex7 DAA 21DAA

Fig. 11 The SPAD index in leaves of four diverse rice genotypes at 7

and 21 days after anthesis (DAA). Different upper case letters

indicate statistically significant differences between mean of SPAD

index of different genotypes at 7 DAA and different lower case letters

indicate significant differences between mean of SPAD index of

different genotypes at 21 DAA (P \ 0.05)

Plant Cell Rep

123

adapt to variable amounts of Mn and can be induced to

higher uptake of Mn under limiting conditions.

From anthesis to maturity, the dry matter production

decreased in the source of all genotypes (Fig. 2). The

loss of dry matter from source to sink during the grain

filling period was higher from efficient genotypes, sug-

gesting active transport of assimilates to the panicles

(Guindo et al. 1994). The dry matter production espe-

cially from 21 DAA to maturity in all genotypes showed

non-significant changes which could be explained par-

tially by the senescence of the lower leaves (Norman

et al. 1992). Fageria (2007) also reported reduction in

dry matter of upland rice from flowering to physiological

maturity.

The different response of efficient and inefficient

genotypes could be explained due to their differential

partitioning of dry matter between different plant parts.

The dry matter partitioning is the end result of a coor-

dinated set of transport and metabolic processes govern-

ing the flow of assimilates from source organs to the sink

organs (Marcelis 1996). The grain harvest index was 0.49

for PR 116 and 0.34 for PR111, explaining the higher

yield of PR 116 due to better partitioning of dry matter

towards grain. Dry matter translocation from source to

sink of PR116, PR 113, PR115, and PR111 was 4.1, 4.0,

2.3, and 2.1 g/plant. The dry matter translocation from

source and panicle’s vegetative parts to grain decreased to

1.86 and 0.49 g/plant, respectively, for PR 116 and PR

113, but for PR115 and PR 111 instead of translocation,

dry matter accumulated in source and panicle’s vegetative

parts by 1.87 and 1.5 g/plant, respectively. This clearly

revealed that in both efficient and inefficient genotypes,

the source (leaf and tiller) translocated dry matter to grain

although with different translocation efficiency (PR116,

PR 113, PR115, and PR111, respectively, had 32, 37, 21,

and 19 %) but it was the panicle in inefficient genotypes

that accumulated dry matter instead of translocating to

grain. Jiang and Ireland (2005) and Sperotto et al. (2012),

respectively, reported Zn and Fe translocation from veg-

etative parts to grain during reproductive development in

rice.

PQ values allow the comparison of partitioning of

mineral in different parts regardless of differences in dry

matter accumulation in the part. The high PQ values in

efficient genotypes than inefficient genotypes revealed

higher accumulation or uptake of Mn in different parts of

efficient genotypes even under low Mn supply. The higher

accumulation or uptake of Mn might be due to better root

growth of efficient genotypes (Shankar et al. 2013). The

efficient genotypes of rice (PR 116 and PR113) had longer

roots than inefficient genotypes (PR115 and PR 111; Jhanji

et al. 2011).

Conclusions

Mn efficiency of a genotype could be explained on the

basis of different uptake rates, root morphology, and dif-

ferential physiology or storage and translocation of the

nutrient (Marschner 1995). Thus, the results revealed that

the translocation of dry matter and Mn from source to sink

or vegetative parts to grain was higher in efficient geno-

types under low Mn than inefficient genotypes which

accounted for their higher efficiency.

Future research should target on the root uptake,

mechanism controlling distribution of Mn during vegeta-

tive growth and grain development, source efflux trans-

porters to increase Mn accumulation in sink and pathways

through which Mn enters the developing grain.

Contribution of Authors The planning and execution of

the experiment was done together. The co-author was

involved in compiling and analysis of data. Both the

authors contributed towards the writing of the manuscript.

Conflict of interest The authors declare that they have no conflict

of interest.

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