PhD

The present investigations on "Physiomorphological and biochemical
responses of black pepper (Piper nigrum L.) to irrigation, pruning and hormone
application for flushing, flowering and berry set" were conducted under three
experiments at pepper garden, Department of Plantation Crops and Spices, College of
Horticulture, Vellanikkara during 2000-2003.
The first experiment was conducted with an objective to elucidate the effect
of dry spell on yield of black pepper by substituting irrigation at periodic intervals from
December to April for two consecutive years starting from 2000. The summer irrigation
was found to improve the production of spike bearing laterals and well developed
berries, spike compactness, weight and volume of green berries, green yield and dry
yield per vine. The plants irrigated @ 10 litres per vine per week by basin method up to
March showed 48 per cent enhancement in dry yield per vine compared to unirrigated
plants.
Significant effect of irrigation treatments was also observed on biochemical
parameters like chlorophyll 'a', total chlorophyll, polyphenol oxidase activity (PPO),
nitrate reductase activity (NRA), total C, and total N. Among quality parameters, only
oleoresin content was influenced by the application of irrigation treatments with
maximum content in plants treated with fogger irrigation up to February. With respect
to physiological parameters, the plants treated with basin irrigation up to March
registered highest photosynthetic rate. The irrigation during summer period did not
record a significant effect on the leaf water potential of the treatment plants measured
before and after the application of irrigation.
The maximum BCR was recorded with the treatment basin irrigation up to
March. Basin irrigation @10 litres week" vine-I up to March was co~cluded as the best
among the treatments given. Since continuous irrigation did not have much pronounced
effect on yield compared to basin irrigation up to March, it was understood that a short
span of dry period just before flushing and flowering is needed for better yield in black
pepper.

The second experiment aimed at improving the yield and quality of black
pepper with the application of different growth regulators at spike initiation period.
Growth regulators were found to enhance most of the morphological parameters like
leaf area per lateral, lateral length, number of spike bearing lateral per 0.25 m2, spike
production per lateral, spike length, 1000 green berry weight, green and dry yield per
vine. All growth regulator treatments resulted in lower recovery percentage of berries
compared to untreated plants. The highest yield was noticed with the application of 100
ppm GA3 that enhanced the dry yield 50 per cent over absolute control.
The growth regulators enhanced biochemical characters like, chlorophyll
content, NRA, total e, total Nand CtN ratio. All growth regulator treatments except 200
ppm kinetin and 300 ppm BAP reduced the total phenol content. In general, reduced
ctivity of PPO and peroxidase were noticed with most of the growth regulator
treatments. Essential oil content of berries was improved with the application of 150
ppm kinetin. The physiological parameters like photosynthetic rate, stomatal
conductance and transpiration rate also increased with the application of growth
regulators.
Among the growth regulator treatments, only GA3 treatments showed a BeR
higher than one. Based on relative efficiency and improvement in growth and yield
characters, 50 ppm GA3, 150 ppm kinetin, and 250 ppm BAP were selected as efficient
growth regulators. However, considering the BeR, among the growth regulators tried,
50 ppm GA3 was concluded as the economically feasible growth regulator for
improving growth and yield characters of black pepper.
The third experiment was conducted to study the influence of pruning on
growth and yield of black pepper. The study revealed that pruning failed to enhance
almost all morphological characters observed. However, one node pruning significantly
enhanced the number of leaves per lateral, leaf area per lateral and lateral length during
. 200 I but failed to maintain the statistical significance in the subsequent year. One node
pruning also expressed higher values with regard to the production of spike bearing
laterals, green yield and dry yield per vine. Significant increase in spike length was

observed in two node pruned plants in the first year of pruning while in the second year,
control plants produced longer spikes. Similar trend was observed in number of berries
per spike and spike compactness also. Results indicated that two node pruning
negatively affects yield characters in pepper. Though pruning failed to have a significant
effect, on~ node pruned treatment expressed higher values in most of the growth and
yield characters during both years of study.
Pruning could not influence leaf chlorophyll, NRA, C:N ratio, and quality
parameters in black pepper whereas, total phenol content, PPO activity and foliar N
registered higher values in pruned plants. Two node pruned plants showed highest
phenol content and polyphenol oxidase activity while one node pruned plants exhibited
maximum peroxidase activity. Among physiological parameters, only photosynthetic
rate was significantly influenced by pruning and one node pruned plants recorded
maximum photosynthetic rate. The BCR was higher in one node pruning treatment
compared to two node pruning but the highest BCR was recorded in control treatment.
Correlation analysis of morphological, biochemical and physiological
characters with dry yield revealed that the characters like angle of insertion of lateral to
the main stem, number of berries per spike, spike length, berry weight, berry volume,
green yield per vine, chlorophyll 'a', photosynthetic rate and transpiration rate had
significant positive correlation with dry yield per vine. Path coefficient analysis of
morphological characters revealed that only green yield per vine registered high positive
direct effect on dry yield. All other characters influenced the dry yield indirectly
through green yield per vine.