Influence of micro meteorological factors on flowering in vanilla

Abstract

Investigations on “Influence of micro meteorological factors on flowering in vanilla” were carried out at the Department of Plantation Crops and Spices, College of Horticulture, Kerala Agricultural University during 2005-2007. The objective of the study was to find out the effect of soil moisture stress and micro - meteorological factors on flowering in vanilla. The studies were carried out in five year old vanilla plants maintained in Department of Plantation Crops and Spices farm and in a selected farmer’s field at Thrissur district.

Moisture stress was induced in vanilla gardens by withholding irrigation at four levels viz. one month, 1½ month, two months and 2½ months. The influence of soil moisture stress on flowering in vanilla and the changes in physiological and biochemical parameters in vanilla due to moisture stress and influence of micro meteorological parameters on flowering in vanilla were studied in the present investigations. Soil moisture stress induced flowering in vanilla. Maximum flowering of 80 per cent was observed in plants stressed for moisture for a period of one month followed by 60 per cent flowering in 1½ month stress period. Hence soil moisture stress for a period of 1-1½ month during November-December is sufficient to induce flowering in vanilla. Soil moisture stress altered various physiological and biochemical parameters in vanilla. Leaf thickness, relative leaf water content, membrane stability, soluble protein and total chlorophyll content decreased due to soil moisture stress. The content of epicuticular wax, total free amino acids, accumulation of proline, activity of peroxidase enzyme, total sugar content and K concentration in tissues increased due to stress. The changes in physiological and biochemical parameters were more pronounced as the intensity of stress increased.

The micro-meteorological parameters of the garden also influenced flowering in vanilla. Flower opening in vanilla was found positively correlated with maximum temperature and negatively with relative humidity and minimum temperature. Flower opening showed highly significant positive correlation with light received from North and South directions and percentage of light infiltration. Soil moisture stress for a period of 1-1 ½ month during November- December is sufficient to induce flowering in vanilla. Changes in physiological parameters due to moisture stress could be used to visually assess the extent of moisture stress in the garden. The biochemical parameters recorded at ideal stress period could be used as indices to assess the extent of moisture stress in plants more precisely in high tech / precision farming systems. Manipulation of microclimate with respect to temperature, light and relative humidity is essential for getting proper flowering in vanilla.