Influence of light intensity on photosynthesis, capsule yield, essential oil and insect pest incidence of small cardamom (Elettaria cardamomum (L.) Maton)

Abstract

Elettaria cardamomum (L.) Maton (Small cardamom) is a widely used high value spice with various medicinal properties. Differences in the availability of solar radiation can cause modifications in the structure and function of small cardamom plants through altered source and sink capacities. The objective of the present study was to evaluate the effects of varying levels of light intensity on growth, physiological characteristics, yield, chemical quality and pest incidence of small cardamom (variety Appangala-1) under full sunlight and two shading conditions (75 % shade, 50 % shade). The experiment was performed during 2016-2018 at the Regional Station, ICAR-Indian Institute of Spices Research, Appangala, Karnataka. The experimental data revealed that the plant samples under 50 % shade produced more physiologically active tillers and higher capsule setting as well as yield per plant than those of other plant samples kept under 75 % shade and full sunlight condition. The highest photosynthetic rate, stomatal conductance, transpiration rate, chlorophyll fluorescence and lowest canopy temperature were observed on plants exposed to 75 % shade. Oleoresin content was higher in plant samples under full sunlight as compared with those under shade condition. But no significant difference was observed in essential oil concentrate ion in capsules. The percentage contribution of 1,8-cineole and α-terpinyl acetate that are considered the major constituents of essential oil are different under different illumination conditions. The concentration of α-terpinyl acetate and 1,8-cineol was highest respectively under full sunlight and 75 % shaded levels. Increased borer damage on shoots (Conogethes punctiferalis Guen.) was noticed for 75 % shade level. Significant difference was not noticed on the incidence of thrips and borers irrespective of shade levels. Plants under 50 % shade registered higher capsule yield besides having physiologically more active tillers and essential oil constituents and would be hence optimum for increased yield and growth of small cardamom.