Salt tolerance threshold is an important factor for screening salt tolerant plants in the selection process. The objectives of present study were to determine the salt tolerance threshold and to evaluate the 32 accessions of Andrographis paniculata for salt tolerance. Two experiments were carried out for this purpose. In first experiment, 40-day-old seedlings were grown at different salinity levels (control, 4, 8, 12 and 16 dSm-1) on Hoagland medium and compared at various exposure times (0, 5, 10, 15 and 20 days). The results indicated that salinity, exposure time and their interactions had significant effect on the morphologic and agronomic traits. The relative growth rate (RGR) during exposure time was significantly decreased in two stages. The initial decrease happened five days after salt exposure, mainly due to osmotic stress, while the secondary reduce occurred 15 days after salt exposure because of ion stress. The results revealed no significant differences among accessions based on salt tolerance index in first ten days. All the studied morphological traits were decreased with increasing salinity levels. Finally, it was realized that 12 dSm-1 salinity for a period of 15 days can be considered as the salt tolerance threshold for A. paniculata seedlings. In the second experiment 32 different accessions were evaluated under salinity stress. All measured Agro-morphological traits; chlorophyll content, K+ and Ca2+ content were significantly decreased with increasing salinity levels, while proline and Na+ content increased. Under salinity stress, tolerant accessions could accumulate higher proline, K+ and Ca2+, and lower Na+ content than sensitive accessions. Consequently, the results suggest that proline, Na+, K+ and Ca2+ are the most effective indicators for salinity tolerance screening in A. paniculata.
کلید واژگان :Andrographis paniculata, Ion content, Proline, Salinity stress, Salt tolerance, Salt tolerance threshold
ارزش ریالی : 600000 ریال
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