Response of selected forestry and agroforestry tree seedling to water stress

Abstract

An experiment was conducted at the College of Forestry, Kerala Agricultural University, Vellanikkara, Thrissur during the period from 1994 to 1995 with seedlings of Acacia mangium Willd., Ailanthus triphysa (Dennst.) Alston., Pterocarpus marsupium Roxb., Swietenia macrophylla King and Tectona grandis L.F. to study the response of the species to water stress. The results showed that the growth characteristics and Physiological behaviour of all the five species were adversely affected due to water stress. Among the five species studied S. macrophylla was the most sensitive species and did not show much adaptations to tolerate water stress. Eventhough A. mangium showed adaptations like quick closure of stomata, thick cuticle and low chloroplast disintegration when exposed to water stress, growth characteristics were found to be adversely affected due to water stress. So the species has to be tested for its water stress tolerance in a long term experiment. Pterocarpus marsupium was also found to be sensitive to water stress and all the growth characters were adversely affected. However, it showed relatively high net photosynthesis and relative growth rate. Ailanthus triphysa was the least sensitive species to water stress. Considering the relative growth rate and net photosynthesis, A. triphysa and P. marsupium are rated to perform well under dry situations. Among the five species studied T. grandis seedlings showed symptoms of permanent wilting when the water stress was increased from moderate (~ 5 Bar SMT) to severe (~ 10 Bar SMT) levels. Other species did not show permanent wilting even when the plants were not watered for nine days condinuously (S3). Growth characteristics in T. grandis was not much affected due to mild (S1) levels of water stress eventhough the plants wilted and dried under severe water stress (S3).