MSc

The present study entitled “Pollination biology of black pepper ( Piper nigrum L.) was carried out at College of Agriculture, Vellayani with specific objectives to study the floral morphology, floral phenology, mode of pollination and breeding system in black pepper.
The experiments on floral morphology and floral phenology were carried out in twenty five field grown black pepper plants of variety Panniyur 1. The experiments on the role of wind, insect, rain water and dew on pollination and different types of breeding system were carried out in both field and fifty bush pepper plants of Panniyur 1 maintained in pots. The plants were observed from March 2018 to March 2019 for studying the floral morphology, floral phenology, agents of pollination and breeding system.
The floral morphology revealed light green (149 B ) colour in 52 % and dark green colour (140 A) in 48 % of the observed flowers as per the Royal Horticulture Society Colour Charts. The odour of the flower was slightly minty during the first five minutes and then increased to strong minty after 30 minutes and became light minty six hours after keeping in closed containers. Presence of nectar was noticed on the black pepper flowers. Anthesis started from 4-5 pm and was maximum between 6-7 pm and extended upto 12 midnight. The flower size was maximum (1.53 x 1.34 mm) on fifth day of stigma receptivity. The number of flowers in a spike varied from 48 to 98 flowers depending on the length of spike. The number of anthers in each flower was four and anther dehiscence was longitudinal. The anther dehiscence occurred from 11 am and continued till 4 pm and was maximum at 2-3 pm. The number of pollen grains was counted using haemocytometer and it varied from 5,00,000 – 7,00,000 pollen grains per inflorescence. The pollen morphology studied using Scanning Electron Microscope (SEM) revealed monosulcate pollen grains with mean polar diameter of 10.414 µm and mean equatorial diameter of 7.803 µm having an exine thickness of 924.8 nm. The stigma was 4 lobed, wet type and papillate. The duration of stigma receptivity was for 7 days with peak stigma receptivity was on fifth day of anthesis. Pollen was available in an inflorescence from 9 to 12 days from the first day of anthesis depending on length of spike and was available throughout the year in a plant. The longevity of flowers varied from 14 to15 days. Pollen fertility studies by Acetocarmine test revealed that 91% of the pollen were fertile. The pollen viability by 2,3,5-triphenyl tetrazolium chloride (TTC) stain and iodine potassium iodide (IKI) stain was 91.03% and 92.4% respectively. In vitro germination in Brewbakers medium showed highest pollen germination at 5% sucrose. In vivo germination was done through diaminobenzidine (DAB) test and aniline blue fluorescence method for 6 h and 24 h respectively and imaged through fluorescent microscopy. The cross and longitudinal section of the immature spikes revealed the emergence of ovary and stamens. Flower emergence duration ranged from 19 to 20 days. Flowering frequency in black pepper was maximum in the month of July and the flowering intensity was maximum in the fifth day of anthesis. The anthesis period in an inflorescence varied from 9 to 12 days depending on length of spike and was noticed throughout the year in a plant. Duration of spiking was 26.84 days while spiking extended for 259.5 days in a plant population. The fruit is a drupe and the mean period taken from fertilization to maturity was 150-175 days.
The percentage of fruit set with rain water in field grown pepper was 92.76% and that for pot grown bush pepper was 92.90%. The percentage of fruit set by experiments on wind pollination resulted in 77.67% with wind alone and 92% with wind and geitonogamy in field grown black pepper plants and 59.39% with simulated wind and 96% with wind and geitonogamy in pot grown bush pepper plants. The floral biology of the black pepper revealed numerous pollen with very small grain size and pendulous spike supporting the characteristics of wind pollinated plant. Presence of dew was observed from June to December and the dew collected from the inflorescence showed the presence of pollen grains which suggests the role of dew also in the pollination of pepper. Three different floral visitors of the black pepper spike were and black ant, yellow crazy and pollu beetle visting day and night. However the role of insects in pollination could not be confirmed, but collection of nectar was noticed by black ant and yellow crazy ant while visiting the flowers. Studies on breeding system revealed high fruit set in geitonogamy followed by autogamy, open pollination and xenogamy. However no fruit set was noticed due to apomixis. The study on pollination biology of black pepper revealed the floral biology, phenology and the role of rain followed by wind and dew in pollination and supported geitonogamy, autogamy, open pollination and xenogamy.