Study On The Relationship Between Salt-stress And β-carotene Metabolism In Processing Tomato Leaves

The area of saline-alkali soil in Xinjiang was wide and becoming heavier year by year, salt stresscould not only affect the plant growth, development and yield, and even affect its secondary metabolism. Inorder to discuss the effects of the growth and pigment metabolism of processing tomato under salt stress,two local cultivars (shihong305, ligeer87-5) and one commercial cultivar (LA2711) which used as a salttolerant varieties were chose as materials. The effect of Four levels of salinity(0,50,100,150mM NaCl)on seed germination, seedling growth and physiological characteristics were studied, we also used HPLCand RT-PCR to test the content of β-carotene under different stage and the expression of key enemies forthe molecular mechanism of β-carotene. The main results were as follows:1. By the test of the germination rate, relative germination rate, germination potential, germination index,germination vigor, hypocotyl length, radicle fresh weight and so on under different salt concentration, thenevaluated the salt-tolerance among the3cultivars by the rate of decline of test indicators with the increaseof salt concentration and the salt tolerance of the cultivars at germination stage level was:shihong305>ligeer87-5>LA2711.2.Among the growth index, salt stress had more significant effect on plant height, fresh and dry weight ofup and under ground, and lower salt concentration (50mM NaCl) could promote the growth of tomatoseedlings, but higher salt stress (150mM NaCl) could make each test index decreased significantly. Withthe increasing of NaCl concentration, soluble sugar and proline content in the seedlings leaves wereincreased, and in the150mM NaCl concentration the increase was most obvious. The measure ofchlorophyll content showed that, the content was increased under50mM NaCl treatment, then decreasedgradually along with the salt stress increased, chlorophyll a has relatively lower effect compare withchlorophyll b, and the change of chlorophyll content was different in different stress treatment time.After careful comparison, that level of salt-tolerance of the3cultivars seedlings was correlated with thegermination period.3. The content of β-carotene in seedling leaves could be changed along with the time of salt treatmentbased on the test of β-carotene content of different time.And regular change of shihong305was morequickly then the ligeer87-5and LA2711, this illustrated that the one which had higher salt-tolerance couldadjust itself to adapt the changed environment in a shorter time. On the determination of older leaves showthat the β-carotene content changed more little than the youngs, it can be explained by that the effect of saltstress on tomato leaf pigment metabolism mainly concentrated in the young tissues. The difference of β-carotene content change of the3cultivars which could be related to the tomato’s genotype and their abilityof salt tolerance.4. The expression of key enzymes (Psy2, Pds, Lyc-β) of β-carotene metabolism under different salt stressfurther revealed that salt stress could affect the metabolism of β-carotene synthesis by regulating the expression of lycopene cyclase gene，and change of Lyc-β was highly corelated to the β-carotenemetabolism.The salt tolerance of local cultivars of Xinjiang was stronger than the commercial cultivar (LA2711) atgermination stage and seedling stage, this might be related to the long-term adaption of local varieties toXinjiang special environment; the changeβ-carotene content in the leaves of3processing tomatoescultivars was related to the concentration and time of salt stress, and salt salt stress could affect the contentβ-carotene by regulated the expression of key enzymes of carotene metabolism; Further study should betook to explore the mechanism of relation among the salt stress, pigment metabolism of leaves, the growthand physiological characteristics of processing tomato.