Seedling Barley Adaptation under Hypoxia and High Ambient Temperature

Abstract

Barley (Hordeum vulgare L.) production in Thailand is often limited by transient waterlogging. Under this condition, there is inadequate soil oxygen supply which can affect the physiological processes of barley. Physiological and morphological responses of barley seedlings to hypoxic pre-treatment and high air temperature levels were investigated. This study was conducted at Lampang Agricultural Research and Training Center, Thailand in 1999. Different waterlogged adaptation of barley genotypes; Samoeng 1, FNBLS#140 and BRBRF9629, were grown in plant growth chambers which varied in diurnal air temperature; 25/15, 30/15, and 40/15๐C (day/night temperature). All barley seedlings were subjected to aerated (as control) and stagnant agar nutrient solution (as hypoxia). Hypoxic pre-treatment were exposed two times and interrupted with recovery period for 7 days. The results showed that the nodal roots/plant increased under the 1st hypoxia and had a greater value as air temperature increased. But those decreased under the 2nd hypoxia with 40/15๐C. The ability of nodal root formation was greatly affected by high temperature compared with hypoxic condition. ADH activity of all genotypes sharply increased under hypoxia with 40/15๐C. Leaf chlorophyll fluorescence under hypoxia decreased with increasing temperature. Photosynthetic rate under the 2nd hypoxia was lower than the 1st hypoxia. The shoot dry matter of FNBLS #140 and BRBRF 9629 under the 2nd hypoxia and high temperature decreased greater than Samoeng 1. While the root dry matter of all genotypes increased under the 2nd hypoxia with 25-30 /15๐C. Only Samoeng 1 had sufficiently ADH activity and well photosynthetic adaptation under hypoxia and high temperature conditions.