American Journal of Plant Sciences, 2013, 4, 1960-1967
http://dx.doi.org/10.4236/ajps.2013.410243 Published Online October 2013 (http://www.scirp.org/journal/ajps)
Influence of Carbohydrates, Mineral Nutrients and Plant
Hormones in Alternate Bearing of Black Pepper (Piper
nigrum L.)
K. S. Krishnamurthy*, S. J. Ankegowda, V. Srinivasan, S. Hamza
Indian Institute of Spices Research, Kozhikode, India.
Received July 30th, 2013; revised August 29th, 2013; accepted September 19th, 2013
Copyright © 2013 K. S. Krishnamurthy et al. This is an open access article distributed under the Creative Commons Attribution Li-
cense, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
ABSTRACT
Alternate bearing habit, a common phenomenon prevalent in some of the fruit trees is observed in black pepper variety
Panniyur-1 also. In this study, an attempt was made to investigate the role of carbohydrates, mineral nutrients and plant
hormones (IAA and zeatin riboside) in alternate bearing in Panniyur-1 variety. The experiment was conducted for three
consecutive years at Murugarajendra estate, Madikeri, Karnataka, India (12.42˚ N, 75.73˚ E). Carbohydrate, mineral
nutrient and plant hormone (IAA and zeatin riboside) statuses of the leaves as well as fruiting branches (stem) were
compared between good fruiting year (on year) and low fruiting year (off year). Results revealed that concentration of
mineral nutrients in leaves was more during on year compared to off year while the reverse was true on the stem. Both
stem and leaf metabolite levels at harvest were higher in off year compared to on year suggesting that remobilization of
nutrients to the developing berries must have been affected during off year, thus leading to accumulation of more nutri-
ents at harvest in off year compared to on year. Leaf had higher concentration of most of mineral nutrients compared to
stem. Spraying of 1% solution of complex fertilizer 19:19:19 (percent N:P:K) three times at an interval of 3 weeks from
flower primordial initiation to flowering period enhanced the yield to the extent of around 30% during off year. Auxin
to cytokinin ratio was 6.6 and 6.1 in on year and 6.3 and 5.7 in off year at flowering and 3 months after flowering re-
spectively, suggesting that this ratio itself may not play a major role in flowering during on and off years, though the
ratio was slightly more during on year. Results of the study indicate that efficient utilization of metabolites and nutrients
in on year may render vine weak in the subsequent year coupled with poor remobilization into developing berries,
which could make it an off year.
Keywords: Remobilization; Starch; IAA; Zeatin Riboside; Reducing Sugars; Essential Oil; Oleoresin
1. Introduction
The term alternate bearing refers to fruit bearing habit of
some of the fruit trees such as mango, citrus, olives, pis-
tachio, dates etc. and the same has been extended to
black pepper also in this study. It is hypothesized that in
alternate bearing behavior, yield in one year affects yield
in the subsequent year. This bearing habit is also observ-
ed in predominantly cultivated black pepper hybrid Pan-
niyur-1. In Panniyur-1, following a good crop, in the en-
suing year very limited new vegetative growth takes place
which generally bears inflorescence, thus limiting flower
production. It is suggested that three mechanisms are ap-
parently involved in the maintenance of the alternate
bearing condition in fruits: 1) flowering site limitations;
2) hormonal control; and 3) nutritional control [1]. Alter-
nate bearing theory in pecan is that the flowering is first
controlled by growth regulators produced by fruit and
leaves, and then by the size of the carbohydrate pool near
budbreak. Nitrogen reserves have also been proposed to
be limiting after large crops, thus reducing return bloom
[2]. In date palm, an off tree could be possibly identified
by lower levels of leaf boron [3], thus highlighting the
role of mineral elements controlling flowering. Evidence
indicates that in some species, the young fruit somehow
interferes with flower bud differentiation, imposing a flo-
wering site limitation. As seedless fruits have little effect
on next year’s flowering, whereas seeded fruits are in-
hibitory, a role for seeds in alternate bearing was hypo-
*Corresponding author.

Influence of Carbohydrates, Mineral Nutrients and Plant Hormones in
Alternate Bearing of Black Pepper (Piper nigrum L.)
1961
thesized in several tree crops [1]. The alternate bearing
pattern associated with inflorescence bud abscission in
“Kerman” pistachio may be a function of mid-season
mobilization of stored carbohydrates in current-season
stems resulting in stimulation of inflorescence bud ab-
scission [4]. It has been frequently reported that the re-
productive effort during the “on” year leads to a serious
depletion of carbohydrate reserves and mineral nutrients.
Carbohydrate starvation involves dramatic changes in
gene expression. Alternate bearing could have an evolu-
tionary significance also. Domestication of fruit trees
would have eliminated natural stresses which would have
resulted in irregular bearing. So, the alternate bearing
may help in maintaining homeostasis [1]. Domestication
theory could be applicable to black pepper also, as black
pepper basically is a forest crop which was domesticated.
In black pepper though alternate bearing is not a com-
mon phenomenon, it is observed frequently in Panniyur-
1 hybrid. As this variety is highly yielding and very re-
sponsive to fertilizers and irrigation under optimum light
conditions, nutrient exhaustion could be one of the rea-
sons for such a behavior. So, nutrition is another aspect
which may control flowering and fruit set. It has also
been reported that auxins may have been involved in the
fruit induced inhibition of flowering. A depletion of car-
bohydrates in flower buds in “on” year trees was found
by some researchers during seed development [5]. It has
been suggested that threshold levels of carbohydrates
might be required for flower bud differentiation. Fruit set
and abscission are closely dependent upon carbohydrate
levels in some crops. But no reports are available on fac-
tors influencing alternate bearing in black pepper. Hence,
the present investigation was undertaken with the objec-
tive of understanding the role of carbohydrate reserves as
well as nutritional and hormonal influence on alternate
bearing in black pepper variety Panniyur-1.
2. Materials and Methods
2.1. Experimental Material and Experimental
Site
Black pepper variety Panniyur-1 was selected for the stu-
dy as this variety shows alternate bearing behaviour. Ex-
perimental site was Murugarajendra estate, Madapur, Ma-
dikeri, Karnataka, India (12.42˚ N, 75.73˚ E).
2.2. Metabolites, Nutrients and Plant Hormones
All recommended package of practices for cultivation of
the crop were followed. In the absence of monsoon rains,
the vines were irrigated at the basin during March to May
at fortnightly intervals @ 50 litres per vine to maintain
soil moisture at around 16% - 17%. Twenty vines which
were about 15 years old were tagged for carbohydrate
and hormone study. For carbohydrate and hormone esti-
mations, leaves and stem from the fruiting branches of
these tagged vines were collected just before flower ini-
tiation and also after the harvest of the crop. Youngest
fully mature leaf samples were used for all the analyses.
2.3. Quantification of Metabolites and Mineral
Nutrients
Leaf and stem samples were washed thoroughly in dou-
ble distilled water, blotted and dried in oven at 55˚C to a
constant weight. The samples were then powdered using
a powdering mill and were used for the analysis of car-
bohydrates, reducing sugars, starch and minerals by adop-
ting standard procedures. Nitrogen was analysed through
Kjeldal’s method, phosphorus through vanado molybdate
method and all the other elements through atomic absorp-
tion spectrophotometer (model 240FS) after wet oxidation
of the tissue samples. Total carbohydrates, starch and re-
ducing sugars were extracted and estimated by adopting
the standard procedures as described by Sadasivam and
Manickam [6].
2.4. Extraction and Quantification of Plant
Hormones
Fresh samplesafter thorough washing in double distilled
water were blotted, weighed (250 mg) and extracted in
80% cold methanol (10 ml), centrifuged at 10,000 rpm
for 20 minutes at 4˚C and the supernatant was used for
the assay of plant hormones. For IAA estimation, the me-
thanol in the supernatant was removed by rotary flash
evaporation system at 35˚C and further extraction was
done as per Aniket et al. [7] with minor modifications
and estimated as per Glickmann and Dessaux [8] using
Salkowski’s reagent. For Quantification of zeatin ribo-
side, the methanol in the supernatant was removed by ro-
tary flash evaporation system at 35˚C, the residue was re-
dissolved in 2 ml methanol and 50 - 100 µl of aliquot
was used for estimation through indirect ELISA utilizing
the antibody kit supplied by M/s Sigma Chemicals Ltd.
2.5. Nutrient Solution Sprays
For nutrient spray studies, 20 vines per treatment were
given either water or 0.5%, 1.0%, 1.5% and 2% sprays of
commercially available complex fertilizer mixture
19:19:19 (%N:P:K) during flower primordialinitiation to
flowering stage. The spray was given 3 times at an inter-
val of 3 weeks and the spray was taken up after the har-
vest of a good crop, as the good crop is followed by a lean
crop. Observation on yield and quality parameters was
recorded after harvest of the crop.

Influence of Carbohydrates, Mineral Nutrients and Plant Hormones in
Alternate Bearing of Black Pepper (Piper nigrum L.)
1962
2.6. Yield Parameters
Spike length: Spike length was measured in at least 10
spikes from 10 vines in each treatment and expressed in
cm.
Number of spikes m−2: Number of spikes present in
0.5 m2 area of the canopy was counted by holding a
frame of 0.5 m2 area against the canopy and counting the
number of spikes present inside the frame from 10 vines
in each treatment and expressed as spikes m−2.
Berry yield: Fresh berries from 10 vines in each treat-
ment (after harvest) were dried separately in oven at
60˚C till it attained constant weight and expressed as
kg·vine−1.
2.7. Quality Parameters
Essential oil and oleoresin from sundried berry samples
were estimated by the ASTA method [9]. Essential oil
was extracted by hydro distillation (using Clevenger trap
for lighter than water type) of powdered berry sample
and the oil collected was measured and expressed as per-
centage (volume/weight). Oleoresin was extracted from
the powdered sample by cold percolation technique and
the viscous mass obtained was regarded as oleoresin and
expressed as percentage (weight/dry weight).
3. Statistical Analysis
Statistical analysis (ANOVA as well as t-test) was con-
ducted using MSTATC package.
4. Results and Discussion
4.1. Metabolite Levels
Total carbohydrates, reducing sugars and starch were es-
timated in black pepper variety Panniyur-1 before flow-
ering and immediately after harvest in on year as well as
off year. In general, stem showed higher metabolite con-
tent compared to leaves. Both stem and leaf metabolite
levels before flowering were higher in on year compared
to that in off year (Figure 1) except for reducing sugars
at flowering which was more in off year compared to on
year. But the trend was reverse at harvest. Both stem and
leaf metabolite levels at harvest were higher in off year
compared to that in on year (Figure 2). Total stem car-
bohydrate content at flowering was 16.6% and 14.1%
(a) (b) (c)
Figure 1. Metabolite levels before flowering.
(a) (b) (c)
Figure 2. Metabolite levels after harvest.

Influence of Carbohydrates, Mineral Nutrients and Plant Hormones in
Alternate Bearing of Black Pepper (Piper nigrum L.)
1963
respectively during on and off years while it was 14.7%
and 15.9% respectively during on and off years at harvest.
Similarly, stem starch content at flowering was 5% and
4.5% respectively during on and off years while it was
3.8% and 5.2% respectively at harvest.
In mango, changes in reducing, non-reducing and total
sugars, as well as starch, were lower in regular-bearing
than alternate-bearing cultivars. In regular-bearing trees,
reducing sugars were highest at fruit bud differentiation
(FBD), declined during fruit development and increased
at maturity. Non-reducing and total sugars followed a
rise-and-fall pattern from FBD to maturity. In alternate
bearing trees, reducing, non-reducing and total sugars
increased during FBD to flowering, then decreased from
fruit development to maturity. The starch content de-
clined from FBD to maturity [10]. In the present study,
metabolite status of the vines was high at flowering in on
year compared to off year while at harvest, it was reverse.
But reducing sugars content at flowering was less in on
year as compared to off year. This indicates that carbo-
hydrate status of the plant may have some influence on
flowering in black pepper. This may be due to the fact
that the stem may try to accumulate metabolites which
were exhausted in on year. Later, once the threshold level
is reached, it may be mobilized for growth. Hence, we
may witness higher carbohydrate and starch levels at har-
vest during off year which can be utilized for flower and
fruit production in the ensuing year, thus making it an on
year.
It has been reported that stem carbohydrate content
along with nitrate reductase activity and photosynthetic
rate of juvenile black pepper plants can be considered as
determinators of yield to identify high yielding black
pepper vines in the juvenile stage itself which suggests a
role for carbohydrates in flowering and productivity [11].
In olive, mannitol was higher than the other sugars and
the content of mannitol in off-year was lower than that in
on-year [12]. Spann et al. [4] reported that the alternate
bearing pattern associated with inflorescence bud abscis-
sion in “Kerman” pistachio may be a function of mid-
season mobilization of stored carbohydrates in current-
season stems resulting in stimulation of inflorescence bud
abscission. In black pepper also, mobilization of stem
reserves to the developing fruits seems to be affected du-
ring off year.
But there are some reports which suggest no role for
carbohydrates in flowering. Monerri et al. [13] reported
that in sweet orange, carbohydrate reserves played little
or no role over fruit set, which actually relied on current
photosynthesis. Smith et al. [2] reported that crop load in
pecan was not related to nonstructural carbohydrates, N,
or K in the roots and shoots in the well-managed trees.
Stored nonstructural carbohydrates, N, and K were not
related to return bloom also. There are some instances
where the developing fruits suppress flower production
in the next season. For example in citrus, fruit growth
suppresses CiFT (a flowering-related gene, citrus flow-
ering locus T) expression and decreases the flower num-
ber the next spring. Also, a long fruit-bearing period sup-
presses CiFT expression in vegetative shoots, thus limit-
ing flower production [14]. But such a phenomenon was
not observed in black pepper.
4.2. Carbohydrates and Hormones
Equal quantity of both stem and leaf samples was ground
together for estimation of zeatin riboside (cytokinin), in-
dole acetic acid (IAA) and total carbohydrates. Results
revealed that the contents of all of them reduced 3 months
after flowering compared to the contents at flowering
both in on and off years but the reduction was very less
in the off year compared to on year except for cytokinin
in the off year which showed a small increase (Tabl e 1).
Total carbohydrates content reduced from 8.1% to 7.2%
in on year (from flower initiation to 3 months after flow-
ering) while the reduction was from 6.5% to 6.3% only
in off year. Similarly, IAA content reduced from 732 to
570 ngg−1 in on year and from 538 to 518 ngg−1 FW in
off year.
Total carbohydrates decreased from 8.1% to 7.2%, ze-
atin riboside from 111 to 93 ng and IAA from 732 to 570
ng from flowering to three months after flowering in on
year. But such a decrease was not evident in the off
Table 1. Total carbohydrates, indole acetic acid and zeatin
riboside as influenced by bear ing habit.
Sl. NoTreatment
Total
carbohydrates
(%)
IAA
(ng/g FW)
Zeatin
riboside
(ng/g FW)
Off year
1 During flower
initiation 6.5 538 85
2 3 months after
flowering 6.3 518 91
3 Mean 6.4 528 88
On year
4 During flower
initiation 8.1 732 111
5 3 months after
flowering 7.2 570 93
6 Mean 7.7 651 102
CD (0.05)
between 1 &2NS NS NS
CD (0.05)
between 4 & 50.3 39.3 18.5
CD (0.05)
between 3 & 60.42 31.1 NS

Influence of Carbohydrates, Mineral Nutrients and Plant Hormones in
Alternate Bearing of Black Pepper (Piper nigrum L.)
1964
year although both carbohydrates and IAA showed a
slight decreasing trend while zeatin riboside showed a
small increase (Table 1). This could be due to rapid uti-
lization by the developing fruits (sinks) in the on year
compared to off year. Plant hormones do play a role in
alternate bearing in some fruit crops. There were signifi-
cant differences in IAA, abscisic acid, GA3-like, and ki-
netin-like cytokinins between “on” and “off” cropping
years in various tissues of olive trees. In Pistacia vera,
IAA, zeatin and ABAlevels in the leaf were high in the
first year (on year), and was low in the second year (off
year) [15]. Baktir et al. [16] opined that the relative bal-
ances between GA3-like compound and abscisic acid
concentrations of tissues may act as a key regulator of
floral development and alternate bearing. Hegele et al.
[17] reported hormonal regulation of flowering through
maintenance of auxin cytokinin ratio. In the present study
auxin to cytokinin ratio was 6.6 and 6.1 in on year and
6.3 and 5.7 in off year at flowering and 3 months after
flowering respectively suggesting that this ratio may not
play a major role in flowering during on and off years.
Though the ratio was slightly high in on year the differ-
ences were not significant. Also, exogenous application
of plant hormones (combination of auxin, gibberellin and
cytokinin) during post flowering to early berry develop-
ment stage did not improve per vine yield in black pep-
per (data not presented). It remains to be investigated if
the yield per vine could be improved in off year through
growth regulator sprays during flower primordial initia-
tion stage as was done for nutrient spray in the present
study.
4.3. Leaf and Stem (Lateral Branch) Nutrient
Levels in Relation to Alternate Bearing
Major (N, P, K), secondary (Ca, Mg) and micro (Mg, Fe,
Mn, Zn and Cu) nutrients were quantified in leaves and
stemsthree months after flowering during both on and off
years. It was observed that N, K, Fe, Mn and Cu were
more in leaves in on year compared to off year while P,
Ca, Mg and Zn were on Par. But the stem from off year
had higher quantity of most of the nutrients compared to
that from on year. It had higher N, P, K, Ca, Mg, Fe, Mn,
and Zn while only Cu was on par. In general, leaf had hi-
gher nutrient content compared to stem (Table 2).
When total carbohydrates, starch and reducing sugars
were quantified in stem and leaves during on and off years
three months after flowering, it was found that leaves had
higher total carbohydrates in on year compared to off
year while stem had higher content in off year compared
to on year. Total carbohydrates in the stem ranged from
13.6% (on year) to 15.7% (off year) while in the leaves,
it ranged from 6.5% (off year) to 7.9% (on year). Starch
and reducing sugars in both leaves and stem were higher
in off year compared to on year (Table 3). Berry yield
(dry) was 6.1 kg·vine−1 during on year and 3.8 kg·vine−1
during off year.
4.4. Leaf Nutrient Spray to Regulate Alternate
Bearing
Nutrient supplementation during pre-flowering stage
(flower primordial initiation stage) is not a recommended
practice in black pepper. Nutrients are provided at flow-
ering initiation stage with the onset of monsoon during
June I week. To investigate if spiking (flowering) can be
improved in off year by providing nutrients during pre-
flowering stage (flower primordial initiation to flowering
period), three rounds (April II week, May I week and
May IV week) of sprays of 19:19:19 complex fertilizer
(% N:P:K) were given. Four nutrient spray treatments
(0.5%, 1.0%, 1.5% and 2.0% nutrient solution of
Table 2. Nutrient element levels during on and off years.
Treatment N (%) P (%) K (%) Ca (%) Mg (%)Fe (ppm)Mn (ppm) Zn (ppm) Cu (ppm)
Leaf—On year 2.36 0.09 1.47 2.44 0.42 288.24 660.92 23.11 552.09
Leaf—Off year 2.05 0.09 1.03 2.55 0.39 181.42 549.67 22.92 488.54
Stem—On year 1.64 0.09 1.27 1.58 0.20 112.67 67.59 32.07 317.59
Stem—Off year 1.87 0.12 2.05 2.20 0.35 201.42 132.67 40.99 313.00
CD (0.05) 0.21 0.02 0.40 0.33 0.06 66.2 57.6 3.8 49.3
Table 3. Metabolite levels in on and off years during berry de velopment period.
Treatment Total carbohydrates (%) Starch (%) Reducing sugars (%) Berry yield (kg·vine−1)
Leaf—On year 7.9 5.3 2.2
Stem—On year 13.6 5.1 5.5 6.1
Leaf—Off year 6.5 5.8 2.6
Stem—Off year 15.7 5.8 8.3 3.8
CD (0.05) 0.62 0.45 0.51

Influence of Carbohydrates, Mineral Nutrients and Plant Hormones in
Alternate Bearing of Black Pepper (Piper nigrum L.)
1965
19:19:19NPK complex fertilizer) were included with wa-
ter spray as control. Among the nutrient sprays, 1.0%
spray recorded the maximum berry yield (5.4 kg dry
yield vine−1) followed by 1.5% spray (4.9 kg·vine−1).
Control recorded the least (3.8 kg·vine−1) which was on
par with 2% spray (3.9 kg·vine−1). Spike length and num-
ber of spikes per 0.5 m2 were lowest in control followed
by 2% nutrient spray while essential oil content was on
par among the treatments. Oleoresin was highest in 0.5%
spray (Table 4). Results indicate that yield levels can be
enhanced in off year (by about 30%) through nutrient
sprays during pre-flowering period, thus reducing the ef-
fect of alternate bearing.
In avocado, P, Ca, and S were higher, and Fe was lo-
wer in high-yielding years in all rootstocks studied [18].
N, P, K and Mg contents were affected by crop load,
showing lower values following the “on” year in olive
[19]. No effect of crop load was observed on micronu-
trient accumulation in leaves. But in pistachio, minerals
and protein concentrations in leaves from fruiting bran-
ches were in most cases lower than that of non-fruiting
ones [20]. In date palm “on” trees produced boron levels
above about 3.5 mg·kg−1, and the “off” trees could be
characterized by boron levels below this value [3]. In the
present study, most of the nutrient elements were more in
leaves in on year compared to that in off year when
quantified three months after flowering. This shows that
good nutrient build up in leaves at the time of flower
initiation may help in good bearing. But the stem (fruit-
ing branch) showed a reverse trend. In stem, all the nu-
trient levels were high in off year compared to on year.
Stem carbohydrate level was also high during off year
compared to on year (Table 3 ). This indicates that nutri-
ent remobilization from stem to the developing fruits
must have been affected in off year. It is unclear why this
nutrient remobilization is affected. It may be possible
that stem may receive some kind of cue as to not to tran-
sport nutrients to the developing fruit till a threshold le-
vel is reached. But when stem and leaves samples were
pooled for carbohydrate estimation, the carbohydrate con-
centration was more in on year compared to off year (Ta-
ble 2) implicating that total carbohydrate status of the
vine is high during on year compared to off year. Nutri-
ent mobilization problem in alternate bearing trees has
been reported in pistachio also. In pistachio, stored car-
bohydrates increased and remained high after the initial
growth flush in off trees. In on trees, stem carbohydrates
increased temporarily in early summer, but were mobi-
lized in mid-season during kernel fill, and then increased
again after nut harvest [4]. But in pecan, neither root nor
shoot N, K, or nonstructural carbohydrate concentrations
appeared to be closely related to the alternate-bearing
characteristics.
Table 4. Yield and quality as affected by nutrient spr ay du-
ring spike initiation period.
Nutrient
solution
(%)
No. of
spikes m−2
Dry yield
(kg·vine−1)
Spike
length
(cm)
Essential
oil (%)
Oleoresin
(%)
0.5 68 4.3 12.4 2.02 9.10
1.0 66 5.4 12.2 2.05 8.41
1.5 70 4.9 12.1 1.89 8.62
2.0 60 3.9 11.5 1.82 8.75
Control54 3.8 10.3 2.05 8.72
CD (0.05)2.22 0.53 0.71 NS 0.62
Results of the present study indicated that most of the
metabolites and nutrient elements were more in leaves at
the time of flowering in on year. This lead us to think
that we may be able to reduce the alternate bearing effect
if metabolic status of the plant is improved before flow-
ering in the ensuing year (which is supposed to be off
year) through nutrient supplements. So, we took up spray
of complex fertilizer 19:19:19 (per cent N:P:K) @ 0.5%
to 2% three times at 3 weeks interval from flower pri-
mordial initiation to flowering period. Flowering started
8 - 10 days after the last spray. We found that, as expect-
ed, spraying of complex fertilizer reduced the alternate
bearing effect. All the concentrations except 2% spray
significantly increased dry berry yield per vine compared
to water spray. The increase in yield was maximum (29%)
in 1% spray over water spray. Use of nutrient spray to
reduce the impact of alternate bearing has been reported
in a few other crops also. Urea spraying along with au-
tumn nitrogen application, as well as spring pruning re-
duced the alternate bearing cycle in Satsuma mandarin in
Iran [21]. But in pecan, low alternate bearing habit of the
cultivars was associated with their ability to produce as
many or more flowers and flowering shoots the next year
on previously bearing terminal shoots compared with pre-
viously vegetative shoots. In high alternate-bearing cul-
tivars, return bloom of bearing terminal shoots was sup-
pressed relative to their vegetative shoots [22].
There are many studies reporting increased yields due
to foliar application of fertilizers just prior to flowering,
flowering and early seed filling stages. For instance, in
rice, plant height, dry matter production, number of till-
ers, yield attributes and yield of grain and straw were
highest with recommended integrated nutrient manage-
ment (INM) practice + 2% urea phosphate spray at pani-
cle initiation and 10 days later [23]. Combined applica-
tion of 2% DAP + 100 ppm salicylic acid + 0.05% so-
dium molybdate sprayed during vegetative as well as flo-
wering stages increased the yield attributes in green gram

Influence of Carbohydrates, Mineral Nutrients and Plant Hormones in
Alternate Bearing of Black Pepper (Piper nigrum L.)
1966
[24]. Application of thiourea (1000 ppm) at vegetative
and flowering stages in coriander significantly increased
the seed (24.6%) and straw yields and total uptake of N,
P and K as compared to control [25]. In Valencia orange,
foliar spray of 0.5% and 1% urea just 9 weeks before full
bloom promoted flower formation, while 6 weeks before
full bloom resulted in thicker ovary with higher percent-
age of fruit set compared to control. Urea spray @ 1%
had more impact than 0.5% spray [26]. Foliar application
of 2% potassium nitrate, 2% urea and 2% muriate of po-
tash at weekly intervals starting from flowering, recorded
increased seed yields of cotton to the extent of 36.3%,
27.2% and 22.4% respectively over control [27]. But in
Jonsok strawberry plants, foliar fertilization during flow-
ering and rapid growth in spring was effective when there
was stress caused by unfavourable conditions in spring
[28]. These studies indicate the possibility that yields
could be increased in on year also by adopting nutrient
sprays during these stages.
5. Conclusion
To conclude, alternate bearing habit observed in Panni-
yur-1 variety of black pepper seems to be controlled by
carbohydrate pool and nutrients availability at the time of
floral primordial initiation. This carbohydrate pool in
combination with plant hormones, auxin and cytokinin to
some extent may play a role in flowering and fruit set in
black pepper, though it is not very obvious from the
study. Remobilization of stem reserves seems to be af-
fected in off year. Leaf had higher concentration of most
of mineral nutrients compared to stem. Nutrient element
content was also more in the stem during off year com-
pared to on year while in leaves it was more during on
year compared to off year. Spraying of 1% solution of
complex fertilizer 19:19:19 (%N:P:K) three times at an
interval of 3 weeks (from flower primordial to flower
initiation period) doubled the yield in off year. So future
studies may be directed more towards nutrient manage-
ment during off year to obtain higher yields and meas-
ures to achieve higher remobilization into developing
berries and enhancement of hormone levels through ex-
ogenous supplement during flower primordial initiation
and early flowering stages during off year to counter the
alternate bearing effect.
6. Acknowledgements
Authors sincerely acknowledge the Director, Indian In-
stitute of Spices Research, Calicut, Kerala for providing
the facilities to conduct the study. Authors also thank Mr
Jayaraj, owner of the plantation for all the support to con-
duct the study at Murugarajendra Estate.
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