Physiological And Biochemical Characteristics Under Salt Stress And Isolation Of Salt Stress Regulated Genes In Tomato

Salinity soils are of widespread occurrence in arid and semi-arid areas in the world and contribute to low production of crop. In China, the food and vegetable production were also severely affected by salt soils. In this research, a salt-tolerant cultivar LA2711 and a salt-sensitive cultivar ZS-5 were tested. Their physiological and biological characters under salt stress during germination and seedling stage were studied. Further more, to better understand the molecular basis of plant responses to salt stress, suppression subtractive hybridization (SSH) and microarray approaches were combined to identify the potential important or novel genes involved in salt tolerance. The results showed that:1. Salt-tolerant LA2711 performed better than salt-sensitive ZS-5 during seed germination stage under different salt treatments. The germination rate of LA2711 was not reduced until 100 mM salt stress, whereas the germination rate of ZS-5 decreased with only 50mM salt treatment. Although both cultivars exhibited delayed germination under salt stress, LA2711 reached 50% germination rate faster than ZS-5. With the increase of salt stress, the fresh weight, number of lateral roots, hypocotyl length and cotyledon length of the seedlings of the two cultivars decreased, but LA2711 decreased less than ZS-5. The radical length of treated seedlings of LA2711 was longer than that of controlled seedlings; as for ZS-5 seedlings, the radical length of which germinated at 100mM or more salt was shorter than that of controlled ones.2. Salt stress imposed different influences on the physiological and biochemical characteristics of LA2711 and ZS-5 in the seedling stage. Firstly, LA2711 maintained higher net CO₂ assimilation, Stomatal conductance, transpiration and CO₂ carboxylation efficiency than ZS-5 did under salt stress. Secondly, the ion partition was quite different between LA2711 and ZS-5 after salt treatment. After being treated by sodium chloride, the young leaves of LA2711 accumulated more Na⁺ than that of ZS-5, and ZS-5 accumulated more Na⁺ in mature leaves. The K⁺ concentration increased in the roots of ZS-5 while it increased in the leaves of LA2711 under the treatment. The Ca²⁺ content decreased in both cultivars, however the Ca(2+) content of LA2711 decreased less than that of ZS-5. The Mg(2+) concentration in the roots of LA2711 increased significantly, on the contrast, it decreased in the roots of ZS-5. Thirdly, after salt stress, the POD activity in the roots of LA2711 was quite higher than that in the roots of ZS-5, and the activity of SOD and CAT was similar between the two cultivars. Fourthly, the proline content increased...