Very often planters resort to spraying of black pepper vines with water to increase production through effective pollination. In fact, during estate visits we have seen workers deployed for sprinkling water, during the spike development stage.
The above practice is based on a myth that pollination in black pepper is through rain water. Some literature also mention that water is the medium of pollen dispersal in black pepper. Lack of proper scientific studies would have paved the way for this belief.
Detailed scientific studies conducted at the Indian Institute of Spices Research, Calicut have helped to elucidate the pollination mechanism in black pepper. The role of rain water in pollen dispersal, the role of insects as pollinating agents and the ability of self pollination in black pepper were investigated using bush pepper of three black pepper varieties viz., Karimunda, Panniyur-I and Aimpirian.
The result of the study was very interesting. In all the 3 varieties the result was alike. About 86-95 per cent selfing (self pollination) was observed in the varieties when the spikes of the varieties were protected from water or insects by enclosing them in polythene bags. Research studies conducted at Kerala Agriculture University, Thrissur also support this finding that rain water is not essential for pollination in pepper.
Then how pollination (selfing) is effected in a plant like black pepper where protogyny (maturing of female part prior to male part) is very common ? It is simple. The pollen grains from the anther lobes of the top-most flowers in a spike fall downwards, once dehiscence takes place. The pendant nature of the spike and the chronological order of maturity of the flowers in the spike are very handy for the downward movement of the pollen grains and fertilization. The receptive stigma in the lower part of the spike will be waiting for the pollen grains. (The male part in the flower is represented by two white anther sacs on either side of the female part, the stigma, in the pepper flower. There will be many such flowers in a single spike).
Once pollen grain falls on the stigma, fertilization takes place. Pollen grain can remain viable even up to 5 days after the opening of the flowers. Stigma receptivity also last for a few days. In short, pollination in black pepper is through selfing (geitonogamy). ( A thin film of water sometimes, help to disperse the glutinous mass of pollen grains in cultivars like ‘Karimunda’). Apomixis also may be playing a role. The profuse spiking of bush peppers kept as indoor plants or in roofed sheds itself tells that rain water is not essential for pollination in pepper – simple logic ! Now the questions still remain ? Will spraying of water increase black pepper yield ? Not as a mean of pollen dispersal but since water alleviate stress and rejuvenates the plant it may indirectly help to get better yield.