The Physiological Ecology of Cardamom (Elettaria cardamomum M) in Cardamom Agroforestry System

Abstract

Since 1895 cardamom has been cultivated in the cardamom hills of Western Ghats, India, which form a part of global biodiversity hot spots. These tropical forests in the last couple of decades have been subjected for severe periodical shade lopping and selective felling for maximizing cardamom production. Photosynthesis, transpiration, leaf temperature and leaf relative humidity was studied in response to change in intercepted light condition in each month during the year 2007. The light interception significantly varied from one month to another and increasing trend was noticed from January ( close to 48 I¼ Iµi m-2 s-1) up to the month of May ( close to100 I¼ Iµi m-2 s-1 ) and thereafter decreasing trend followed until December (50 I¼ Iµi m-2 s-1 ). Increased light interception increased photosynthesis, transpiration and leaf temperature. Photosynthesis rate was maximum (close to 7 I¼ mol CO2 m-2 s-1) in the month of August in which month the interception of light was 77 I¼ Iµi m-2 s-1. Increasing light interception beyond 77 I¼ Iµi m-2 s-1 did not increase photosynthetic rate of the crop. The highest transpiration rate of 59 I¼ mol H2O m-2 s-1 was observed when the light interception and leaf temperatures were 100 I¼ Iµi m-2 s-1, 33.4 ÂoC respectively. Summer months have recorded higher transpiration rate than those of monsoon months. Results showed good correlation between light interception and the rates of photosynthesis, transpiration, as well as leaf temperature.