PhD

Black pepper (Piper nigrum L.) is an important cash crop of Kerala and
contributes significantly to the agrarian economy of the State. In spite of
achievements in crop improvement and technological advances In crop
management, the productivity of black pepper is consistently low. Hence an
experiment entitled 'Physiological and biochemical aspects of flowering, berry set
and development in black pepper (Piper nigrum L.)' was conducted at Pepper
Research Station, Panniyur and College of Horticulture, Vellanikkara during 1997
to 1998 to analyse the physiological basis of productivity in this crop. The
objectives of the experiment were to trace the chronological events in the growth
and development of laterals and to analyse the influence of morphological,
physiological, biochemical and photosynthetic parameters on productivity and to
elucidate the seasonal pattern in the accumulation of photosynthates in component
organs of the laterals. The cultivar Karimunda and a hybrid, Panniyur 1, were
selected for the study.
Flushing of the vines commenced within a week after continuous rains
during the monsoon in June and the variety Panniyur 1 was earlier to flush. The
leaf area development completed in about 35 days in both the varieties. Fresh and
dry weights of leaf increased till 50 days after flushing and thereafter these
parameters registered wide fluctuation up to berry maturity. Leaf production was
more in Karimunda and upper canopy levels produced more leaves. The
plastochron index was 23 days on an average in both the varieties.
There was synchronous flushing and flowering and the emergence of spike
was delayed up to 6-9 days after flushing among the varieties. Spike growth was
completed within 35-42 days after emergence. The fresh weight of spikes
increased up to 150 days after berry set. The number of spikes produced per
lateral and per vine was significantly higher in Karimunda and spike production
was more in the upper canopy levels.

The fresh weight and volume of berries increased up to 165 to 180 days
after berry set and increase in dry weight continued for another fortnight. The
extension growth of laterals ceased after a period of 13 to 14 weeks.
The leaf and spike productions in the laterals were more in Karimunda and
the leaf area was more in Panniyur 1. The leaf production, leaf area and spike
production increased towards upper canopy levels.
The total fresh weight and dry weight of the lateral during a season was
more in Panniyur 1 and was higher in the upper canopy levels. Biomass
partitioning to the spikes at berry maturity period also showed superiority of
Panniyur 1. Partitioning of fresh weight and dry weight was in the decreasing
order of spike, leaf and stem in Panniyur 1, while this was in the order of leaf,
spike and stem in Karimunda. The partitioning of fresh weight and dry weight to
spikes were also more in the upper canopy levels.
Spike length, berry size, number of developed berries and total number of
berries per spike, average spike weight and green and dry pepper yield was more
in Panniyur 1. However, more number of spikes per lateral and per vine were
observed in Karimunda.
Specific leaf weight and spike to leaf ratio were higher in Karimunda and
leaf area duration was more in Panniyur 1. The variety Panniyur 1 recorded a
higher average leaf photosynthetic rate compared to Karimunda. Maximum
photosynthetic rate coincided with flushing and flowering, and the spike bearing
laterals recorded higher photosynthetic rate.
Stomatal conductance, leaf surface temperature, transpiration, vapour
pressure deficit and PAR at leaf surface recorded by the leaves are more in
Panniyur 1. The sub-stomatal C02 level and stomatal resistance of leaves were
higher in Karimunda. The leaves of the upper canopy recorded higher stomatal
conductance, sub stomatal CO2 level, transpiration rate, leaf surface temperature,
PAR and VPD. The stomatal conductance, sub stomatal CO2 and stomatal
resistance declined gradually towards berry maturity. Transpiration rate, leaf
surface temperature and VPD increased towards berry maturity.

Chlorophyll development was completed in 35 days after flushing and
chlorophyll 'a' and total chlorophyll content of leaves were higher in Karimunda.
Middle canopy recorded more chlorophyll content and spike bearing laterals had
higher chlorophyll content of leaves.
Carbohydrate content was more in the leaves of Panniyur 1 while the
phenolic content was higher in Karimunda. There was no significant difference in
the amino acid content between varieties. Carbohydrate accumulation was more in
the lower canopy while the upper canopy levels recorded higher phenolic and
amino acid contents. The carbohydrate and amino acid contents of leaves
fluctuated with the season while the phenolic content of leaves was almost stable
except at berry maturity. The spike bearing laterals recorded more foliar
carbohydrates, phenols and amino acids.
The electrpophoretic pattern of proteins in the berries showed variation
between varieties. The number of bands seen was six and eight respectively for
Karimunda and Panniyur 1.
The pattern of partitioning of labelled photosynthates among component
organs showed that in Karimunda, maximum amount of photosynthates were
fixed by the fed leaf itself during flushing, flowering and berry set. In Panniyur 1,
except at flushing stage, the berries partitioned the maximum labelled
photosynthates. During all the stages, the percentage of labelled photosynthates
partitioned by the spikes was higher in Panniyur 1 compared to Karimunda.
Fresh weight and dry weight of the lateral, fresh weight and dry weight of
spikes, number of developed berries in a spike, spike length and number of spikes
showed significant correlation with dry pepper yield. Leaf photosynthetic rate,
chlorophyll and carbohydrate content of leaves also were significantly associated
with economic yield in black pepper.