Physiological Responses Of Carthamus Tinctorius L. To Salt Stress And It Remission Effect Via Application Of Exogenous ALA

In this article, a hydroponic experiment was conducted to use medicinal safflower (Carthamus tinctorius L.Space No.l) as the experimental materials in the greenhouse of Nanjing Agricultural University. We studied the physiological and biochemical responses of medicinal safflower seedlings in different NaCl concentrations and measured its experimental parameters such as growth index, biomass accumulation, osmoregulation substances, antioxidant systems and ion distribution. On this basis, the influence of exogenous ALA on the osmotic adjustment substances and antioxidant enzyme systems of medicinal safflower seedlings under salt stress was also investigated. Meanwhile, we studied the influence of exogenous ALA on secondary metabolite flavone and ion distribution under salt stress. The main results were listed as follows:1. Under hydroponic conditions, low salt concentration did not affect the growth of safflower seedlings, suggesting that safflower seedlings showed good adaptability to weak salt stress.When the salt concentration was higher than 100 mM, apparent salt stress occurred on safflower seedlings. To maintain normal osmosis, the physiological responses of salt stress to safflower seedlings exsited as follows:growth inhibited, biomass decreased photosynthetic pigments declined andsoluble sugar and protein increased. Meanwhile exogenous ALA could ease the injury of safflower by salt stress, promote the growth rate of safflower seedling, increase the biomass, and accumulate the osmoregulation substance effectively.2. Salt stress largely resulted in the damage to antioxidant system of safflower seedlings; however, this damage could be recovered through self-regulation of antioxidant systems. The combination functions of antioxidant enzymes were lied in cleanning up the active oxygen during the early stage of salt Stress. With the time duration,, the function of CAT in cleanning up active oxygen appeared more powerful than SOD when salt concentration reached 50 mM. Under the salt stress of 150mM, the capacity of SOD showed a significant decrease in cleanning up free radicals as well as CAT. Meanwhile, exogenous ALA played a very active role in the influence of salt stress on safflower.30 mg·L-1 egenous ALA showed a relatively poor effect on the activity of SOD than 15 mg·L-1, indicating that a good effect was exsited in terms of increasing antioxidant enzyme activities. However, the accumulation of flavanoid was also suppressed visibly.3. Salt stress has an important effect on ion distribution of the safflowers. During the early plant growth stage, most of Na+ accumulated in the root, but imidiately transported to stems and leaves with the time duration. Salt stress caused the accumulation of K+, Ca2+ and Mg2+ and increased the K+/Na+ ratio in the roots in order to keep the normal growth of safflower seedlings under salt stress, exogenous ALA could improve the ability of root system chelate Na+ further, and ease the effect of Na+ on the growth of stems, reduce the loss of K+ in organs under salt stress, boost absorptive and storage capacity,which plays a most important role in stems. Meanwhile, exogenous ALA could improve the root’s absorptive and storage capacity of Ca2+ and Mg2+ in the safflower seedlings under salt stress to curb diffusion of Na+ from outside to roots, add the accumulation of K+, and promote Mg2+ transport to leaves.