Response To NaCl Stress Of Different Clones Of Catalpa Bungei

Catalpa bungei belongs to Bignoniaceae family, which is the unique precious timber species and the famous landscaping tree species in China. At present, a number of research on C. bungei has been carried out in past twenty years, including main biological characteristics, germplasm resourses, propagation techniques, planting technology and so on. However, the effect of salt stress on C. bungei clones has not been reported. In this study, With the controlled experiment and grads of salt stress,physiological characteristics, ion content and ultrastructure of vegetative organs of cutting seedling of 9 clones of C. bungei were studied in 6 salinity(NaCl) treatments,the salinity concentration was 0,0.1%,0.2%,0.25%,0.3%,0.4%. The main conclusion were as follows:The chlorophyll content of different clones increased first and then decreased during experiment, and decreased with increasing the salinity gradient. Salt stress affecting seedling photosynthesis and growth, and that more severity to height growth than the diameter growth. The relative electrical conductivity of different clones increased at the initial stress and then decreased, membrane systems were also severely injured at the initial stress, then with SOD activity increased, reducing reactive oxygen species injury to the membrane system and the injured degree decreased. The clones with strong salt tolerance within a certain degree salt stress by increasing proline, soluble sugar and soluble protein content, decreased cell water loss; when the salt concentration over this range, these materials synthesis was inhibited and their content decreased. Under the low salt stress, proline, soluble sugar, soluble protein synthesis of the poor salt tolerance clones were inhibited, their content were significantly lower than the control, plants were severely injured.The strong salt tolerance clone 02-2-5, the moderate clone YQ1 and poor clone 07-1 were selected to study photosynthesis and root characteristics, we found that the daily average net photosynthetic rate was maximum for strong salt tolerance clones, and the average amplitude reduction was minimum, the result was opposite for poor salt tolerance clone. With the increasing salt concentration, the fine root and coarse root length, surface area, volume and root activity all decreased for the three clones. The order of salt stress impact on the three clones of root activity was 07-1>YQ1> 02-2-5.Vegetative organ inorganic ions distribution and leaf ultrastructure were studied for the clone 02-2-5, and found that the roots of C. bungei clones with distinct functions to resist salt to stop the upward transport Na+, high salt concentration will destroy the root structure, can not stop Na+ delivery, and thus affect the normal development of C. bungei. Overall, the first victims under salt stress was the chloroplast, chloroplast shape became round and internal structure gradually blurred with the increasing salt concentration, and then leading to degradation of the chloroplast. Under the control, 0.1% and 0.2% salt concentration, leaf cell membrane system remained intact almost, and membrane systems have been damaged and disintegrated for 0.3% and 0.4% salt treatment.Comprehensive analysis showed that the seedling height, collar diameter, proline, soluble porte, SOD activity, the relative electrical conductivity, the net photosynthetic rate and root activity can be used effective to index to evaluation salt tolerance of C. bungei clones.Under 0.1% salt concentration, all clones seedling height and collar diameter growth were differently inhibited, the membrane systems injury was serious, as a whole, the salt tolerance of C. bungei was poor. According to analysis of membership function of fuzzy mathematics method to the 9 clones, the salt tolerance of different clones followed by: 02-2-5> 9-1 > 2-2-3> YQ1> 02> 1-3-36> 02-2-2> 07-1> 14-6. The clones 02-2-5, 9-1 and 2-2-3 with strong salt tolerance grew well within 0.25% salt concentration, and the growth were inhibited over 0.25% salt concentration. Under 0.2% or 0.1% salt concentration, the growth of clones 07-1, 02-2-2 and 14-6 was significantly affected.